Stresses on a Handi frame.

[trotterlg]

For a while I have been thinking out the stresses on a Handi frame when it is fired.  All started when I was looking at the numbers of the pounds of thrust generated by different cartridges for which SB1 and SB2 frames were used for.  After thinking about this for some time, I think that what makes the difference mostly, is if it is a straight walled cartridge or not. Think about this:  What does the pressure in the barrel have to act on when the cartridge is fired?  It pushes back on the standing breach, it pushes forward on the bullet, and it pushes out against the chamber walls.  In a straight walled cartridge, there is nothing for the pressure to push forward against in the barrel.  As far as I can figure, the only forward thrust on the barrel comes from the friction of the bullet sliding down the barrel and some load from the frame being kicked back by the recoil and the barrel having to follow it.  The pressure in the cartridge has near zero to do with how much load it on the hinge pin in the frame.  Think about the old open top revolvers where nothing tied the top of the barrel to the frame.  Now when you get to bottleneck cases every thing changes.  With a bottleneck case there is the shoulder area for the pressure to push the barrel forward with, this is the difference in area of the bore and the case diameter at the breach, the taper of the case including the shoulder of the case provides the area for the pressure to act against, so there is load applied to the hinge pin depending on this area and pressure.  The reason the 30-30 got away with being used on the older frames was because of the very minimal taper and shoulder area of that cartridge, once they decided to do 30-06 and 308’s they had to make a frame that could take more load at the frame hinge pin because these shaped cartridges generated loads that were not present in the old straight walled stuff including the shotguns.  I would say that, at the hinge pin, there is not a significant load generated by any of the straight walled cartridges.  Is there something I have missed here, the only place I can figure any load is on the breach face of the frame and the rear of the bullet.  Larry

[quickdtoo]

I agree, Marshall Stanton has said the same thing about straight walled cases, the pressure is pretty much equal on the case walls and standing breech, not true in bottlenecked cases. It's also the reason why straight walled case growth is minimal compared to bottlenecked case growth.

Tim

http://shootersforum.com/showthread.htm?t=2137&highlight=.375+win

[S.E.Ak]

I believe the most force comes at the point where the water table meets the standing breach. Thats where cracks first appear on SXS guns and I believe it holds true for H&R's

[v8r]

That sounds like a fairly sound theory to me.Makes sense to me anyway.

[billy_56081]

I can tell you from experience that straight walled cartridges have basically no forward thrust. When I made my 357 stub barrel I loaded a 38 round in the barrel, held is in the stub and fired it. I could feel no noticable forward thrust on the barrel.

[AtlLaw]

Interesting thought.  Never really gave it much consideration except when I see bits in movies where people are ducking bullets flying around from cartridges exploding in a fire...    Overcoming bullet inertia might figure in there somewhere with friction don't you think?   

[billy_56081]

Forward thrust on a bottlenecked cartridge in a handi can be seen in the forces that stretch the case longer when fired with a fairly warm load. When I fire some top end loads in my 243 I definitley have to full length resize or I will have trouble getting all rounds to fit on the next firing. I have even considered a small base die for mine.

[Blackhawker]

Newton's Third Law:  For every action, there is an equal and opposite reaction.

I'm no expert at gun designs etc but the way I see it is that every time a round is fired, regardless of cartridge shape, a bullet moves forward and a cartridge is moved backward at an equal pressure (hence the third law).  Every time a cartridge is literally hammered into the standing breach, the breach face is moved backward ever so slightly with violent force.  The face of the breach, being connected to the rest of the frame forces the entire frame backward and away from the barrel (where the explosion has occurred), hence the reason why we, the shooters, are pushed backward.  While that frame is pushed backward, the only place the frame makes contact with the barrel is on the hinge pin.  Eventually something will give in...be it the hinge on the barrel, the pin, or the opening in which the hing pin is mounted. 

If you don't believe this, then tell me that you would willingly take a rod, stick it down your barrel and hammer a flat faced object against your breach face over and over and over again with an excess of 40,000 lbs of force on it and nothing will happen.  Eventually something will give in.

And if you say, "well the barrel moves with the frame and there is no opposing force".....OK, that's like saying that your arm moves with your body because they are connected.  If someone or something jerked on your arm with 40,000 lbs of force, yes, your body will move in the direction in which your arm was pulled but I'll tell you, eventually your arm will certainly dislocate from the socket. 
Ok, that's a rough example but I think you see the picture I'm trying to paint here.

[S.E.Ak]

On break open gun you get the lever/pivot motion involved plus barrel whip the all rifles have

[gcrank1]

Just speculating, but once the breech pressure is maxed at the standing breech isnt the load (mostly) equally distributed between said point and the hinge pin?

[trotterlg]

I don't think so, there is nothing for the pressure to push on except the breach and the rear of the bullet, there is no area on the barrel for the pressure to act on.  Larry

[S.E.Ak]

I delt mostly will old shotguns but it holds fairly true with rifles. Pressure peeks at 9" to 11" from the standing breach. The watertable of break open guns have a few thousanths gap between the watertable and barrel. This gap closes when the gun is fired. The muzzel end moves upward and from the cross pin back moves down (pivot point). On SXS guns the right tubes moves right and up with the back end moveing left and down. The result is seen on old Ithaca Flues models in 20ga that develope a crack on the left side of the reciver where the watertable meets the standing breach. The reason most cracks are found on the left side is because the right barrel gets fired much more than the left in hunting if you can shoot.

[bikerbeans]

What about the latch on a break open gun?  When you don't have good engagement on the latch/latch shelf the barrel pops open when you shoot so there is force again latch from the barrel trying to rotate around the pivot pin which is transmitted into the receiver.  When one starts shooting high pressure (Ruger #1 type) loads does this start to do bad things to the latch and or latch assembly?

thanks

BB

PS:  I always enjoy reading these type of threads as I end of learning more about shooting and guns.

[Mac11700]

I delt mostly will old shotguns but it holds fairly true with rifles. Pressure peeks at 9" to 11" from the standing breach. The watertable of break open guns have a few thousanths gap between the watertable and barrel. This gap closes when the gun is fired. The muzzel end moves upward and from the cross pin back moves down (pivot point). On SXS guns the right tubes moves right and up with the back end moveing left and down. The result is seen on old Ithaca Flues models in 20ga that develope a crack on the left side of the reciver where the watertable meets the standing breach. The reason most cracks are found on the left side is because the right barrel gets fired much more than the left in hunting if you can shoot.

A lot of this equation is true,but a lot has been left out as well.

On a Handi,straight walled case or bottle neck,there are forces acting on the Handi's weakest parts,and that is where it locks up. The tolerances with it's moving parts and being a friction fit lock up is what causes the flex..not that the action itself is stretching or flexing. This has been discussed here a long time ago,and something I verified with Gordan at NEF while he was C/S director.

While it is true under most circumstances a straight walled case will have less effect on the lock up due to it's large bearing surface and subsequent cling factor in the chamber,they can never the less be driven past their intended pressure curve and wreck havoc on these actions just as any bottle necked cartridge can. Each cartridge has an ideal pressure curve which also includes it's own dwell time. This dwell time is the time it takes for the powder to completely burn inside the cartridge and forward into the throat and barrel and it goes hand in hand with how much back thrust is applied to the chamber walls. Bottle neck cartridges with their shoulders have a longer dwell time than straight walled cartridges,here's why.. Think of bottle neck cartridges as squeezing a garden hose while filling a bucket.You have more pressure and velocity of the water coming out,but it won't fill the bucket any faster than just allowing the water to flow freely without squeezing it..The shoulder of the bottle neck is the squeezing down of the hose,hence Newtons laws are readily seen and felt in the hand,much more easily than in firing the different types of cartridges in this rifle since those times are in nanoseconds and milliseconds and one would need a very fast camera to capture this happening.

While the frames of Handi's are very strong,they aren't being subjected to the same back thrust as that of a bolt action or falling block action where the barrel and action lock up is solid..nor is the frame strong enough to actually incur the standing breech to move rearward repeatedly(flexing as some call it) ,because you would see stress cracks forming at the junction of it's side and breech wall very quickly if this happened.The internal workings on this rifle was designed to compress and give enough to allow the rifle to work without this happening,this is after all a friction fit lock up..not a solid lock up as a bolt gun.The barrel and chamber moving is what people are seeing with their cases..not the breech wall flexing rearward.One other thing that has to be taken into account is the compression of the hinge pin and barrel lug. These too effect the "flex" of the rifles action since it is allowing some movement of it.When the mating isn't perfect or the metal is softer the forces applied in this area directly influence each firing of the rifle.These forces are not acting in a straight line as those of other types of rifle actions because of the design.There is not only downward pressure being exhorted but forward and rearward forces coming into play,and since the initial back thrust is in milliseconds it is difficult to measure exactly how much true back thrust is applied on this type of action since it isn't static as other actions are,even those of some shotgun type actions which has a Greener locking bolt that slides across the locking lugs instead of a radius surface that the Handi has that moves up and down.

Mac

[NFG]

Yes...Bikerbeans...when things go bad the innards get munched...I've broken one latch already on my 45-120 with what I thought was a too vigorous load   when the barrel popped open.  The real cause I found out afterwards was too little engagement of the latch on the lug shelf...only about 0.080" of the total 0.170" width of the shelf.  After I cleaned up everything and mading sure I got full engagement, the same load worked fine...it just slapped me into next week...720 gr bullets can REALLY get your attention.

I'm finally getting around to putting in a new latch spring as related in the FAQ's and bedding the barrel to the frame rails.

ANY loads that get into the upper pressure ranges can cause problems depending on you well you have "tuned" your shooter, and REALLY in the sh** if your shooter is factory as is.  Following all the information given in the FAQ's on barrel fitting and accurizing will put you well ahead of the curve.  This is a simple and relatively easy to tune toy, but they all NEED to be tuned to get the best out of them.

Listen to Mac11700 as to the forces...Newton and Boyle are crawling all over this toy...you need to understand a bit of physics to see the big AND little picture.

All those litle extra movements are what cause cases to stretch as the barrel moves one way and the case the other...that is why you have to FL resize in the NEF...the shoulder gets moved forward just enough to cause problems if you don't FL resize...the same thing happens in T/C's and rear lug bolt actions to a smaller extent.

Luck

[NFG]

Some bits of information about case head "thrust" and case size.

The 12GaFH uses a reworked 50 BMG case with a head dia of ~.800"...it has an area of ~.503 sq in. High pressure 12 Ga mag rounds run at about 15KPSI and puts ~7500 ft lbs of pressure on the standing breach...the 12GaFH is loaded to roughly the same pressures so generate similar breach pressure.

A 10 ga has a case head ~ .860", area ~.580 sq in and can run 15KPSI or slightly above and puts ~8500 PLUS psi on the standing breach.

A 30-06, .470 ", ~.173 sq in puts about 7000 psi against the breach, at 40KPSI

The 585 HE has a case head of ~.637, area ~ .319 sq in and the loads developed for the NEF cause nary a problem.

The point is...as long as you keep the standing breach pressures relative, equal, approximate...etc., to the design limits you won't have any problems no matter WHAT the size of the case head happens to be...

Exceep ANY design limits and you get into trouble.

Luck

[trotterlg]

My point is that, in a straight walled case, there is nothing for the chamber pressure to push against in the barrel.  It may be hard to imagine, but think that you are a tiny person in the case in place of the powder.  When the primer goes bang, you have to push on everything you can push on.  You push on the breach with your feet and the base of the bullet with your hands, you can also push on the walls of the case, but there is nothing to push on that will move the barrel forward, just straight sides of the case.  With a bottelneck case, there is a sholder you can push on, this then pushes the barrel forward causing stress on the hinge pin and latch and latch shelf, which does not happen with a straight walled cartridge.  This is the difference in how a straight and bottelneck case load a H&R frame.  This is very simplified, but I believe it is sound physics, there are other accelerations to take into account, but it seems consistant with how H&R is using their frames with loadings from straight walled cases going on SB1 frames.  Larry

[Mac11700]

My point is that, in a straight walled case, there is nothing for the chamber pressure to push against in the barrel.  It may be hard to imagine, but think that you are a tiny person in the case in place of the powder.  When the primer goes bang, you have to push on everything you can push on.  You push on the breach with your feet and the base of the bullet with your hands, you can also push on the walls of the case, but there is nothing to push on that will move the barrel forward, just straight sides of the case.  With a bottelneck case, there is a sholder you can push on, this then pushes the barrel forward causing stress on the hinge pin and latch and latch shelf, which does not happen with a straight walled cartridge.  This is the difference in how a straight and bottelneck case load a H&R frame.  This is very simplified, but I believe it is sound physics, there are other accelerations to take into account, but it seems consistant with how H&R is using their frames with loadings from straight walled cases going on SB1 frames.  Larry

While this may seem simple Larry,there is indeed something to push against on the barrel.Newtons laws are still in effect,For every action there is a equal and opposite reaction.If you have 40kpsi that produces 15,000 psi reward thrust,you will achieve the same forward thrust to the hinge pin,and since the hinge pin is attatched to not only the barrel but the chamber..ergo these forces are acting on the same.

One other factor you are not accounting for is if the chamber is off the x axis of the bore.If it is,then there will be additional stress/pressure from the twist of the projectile crashing into the lands.While some may argue this won't amount to much,we are talking in miliseconds here for the pressure to be able to spike,and if things are not perfect with the entire rifle,the results won't be satisfactory...and this is for any cartridge,bottle neck or straight walled.Look at almost any Handi barrel and see how abrupt of a leade they have.Most are at 10 to 14 degrees of leade angle instead of 1-2 degrees.While this may seem inconsiquintial to a bolt gun with it's fully locking bolt..in a Handi it matters more since it isn't fully locked in battery but is utilizing a friction fit with a radius locking latch.Impart additional stresses twisting to the barrel..the pressure rearward will increase...looks at what else happens.

This is my main reason for telling folks that want to rechamber by hand to be careful or let someone with the proper tools to do it for them.Also,many times the chambers them selves are out of the x-axis of the bore for the donor barrel.Unless cutting a large enough chamber to completely clean up the original screw up,then there will be problems with the new.

Now..if one does have a perfectly diemensioned chamber that is in line perfect to the bore,and they have a very tight fitted barrel with no slop in the lock up links/pins,one can have exceptional accurate handi. I know this since I have had some.These always sem to do better than those that don't across the board consistantly...accuracy..and velocity wise,and these rifles don't allow the brass to stretch excessively or be out of round from shot to shot even when being pushed to their respective limits and beyond nearly as much as one that isn't in spec.

Mac

[trotterlg]

Because the bullet moves forward, out of the barrel, you need to subtract all the energy that is put into the bullet, that number is the foot pounds of energy at the muzzel, there is very little energy left to impart stress in the frame after the energy in the bullet is deducted.  Larry

[gcrank1]

And deduct a nominal amount expended in the rotational forces used climbing the rifling? But, since the peak pressure occures in the lower 9ish inches of the breech, and the bullet has not exited the muzzle, is deducting the muzzle energy the right factor? It may effectively be, as the inertial force of the launched projectile is still acting, but the foot pounds of energy vary with the square of the velocity(?) and the velo and 'start pressures' in the breech are not what they are at the muzzle.

[NFG]

It is the peak pressure acting on the stationary bullet milliseconds after ignition that causes all the ruckus...this is a tube with one end closed with a moveable object(a bullet) and the other end close with a pressure transfering device(a case).  There are specific "tube" formulas to calculate the instantanious pressures in the system.  As the bullet progresses down the barrel the pressure is continually reduced even though it is still burning continuously and producing gas until consumed fully and it is expanding to fill the bore...a little bit of differential calculus or a Kinetic energy formula can give you the bullet energy number at various points along the length of the barrel.  

I don't think the muzzle energy has anything to do with pressure on the standing breach at the moment of ignition...or I have a big problem with trying to use foot lbs of muzzle energy in the equation, two separate and distinct things are happening...that muzzle eneregy number is calculater AFTER the bullet leaves the muzzle or it can be calculated at any point that you know the bullet velocity...it has nothing to do with pressure generated by burning gas, THAT pressure is generated at the time of ignition BEFORE the bullet starts moving...THERE IS NO KINETIC ENERGY(energy produced by motion) AT THAT POINT...IT IS ALL POTENTIAL ENERGY(energy contained in the stationary object prior to motion) UNTIL AFTER the bullet starts moving...THEN the velocity is converted into kinetic energy...I know the bullet starts moving BEFORE the powder is completely burned...lets keep it simple.  You're talking about overcoming the bullet inertia at the point of ignition and the amount of pressure transfered to the standing breach and other points on the frame...basically all 3 of Newtons laws acting in concert at different points in time...and the energy produced by the velocity and mass of a moving object at another point.

How much peak pressure is produced depends on a lot of factors...powder burning rate, friction of the type of bullet metal, bullet size in relation to the bore/groove, powder burn rate, the weight(mass) of the bullet and so forth.  All of these factors are at work at the moment of ignition, and all of them have a basis in physics..which I'm still struggling to try to understand fully.

People are starting to play fast and loose with a lot of factors they really don't know a lot about,  mixing apples with oranges again....like the metallurgy of the frame, hinge pin, barrel etc.  NO ONE but NEF knows the exact formula of the metals or the "hardness".  It doesn't matter WHAT the metal is called....1132, 4340, "ductile iron"...all those metal formulas have a range of tensile, compression, shear, etc strengths and can range from 45KPSI to 250KPSI for each designation.  People, as usual, are lumping that information together without due understanding of all the facts...a dangerous thing to do.

As already alluded to, there CANNOT be any generalized answer to JUST WHERE, WHEN AND HOW MUCH pressure is exerted on WHAT part during the whole process without some very sophisticated measuring devices... and even then WHAT does it all mean? ...and just HOW useful is it to the average reloader.

It has been my experience with the NEF that the case will stick in the chamber or the action will lock up  before you get into very much trouble...with the exception of the exceptions...you can definitely become coyote bait by EXCEEDING DESIGN PRRSSURES WITH THE LARGE DIAMETER CASES...

But in doing so you have broken ALL THE SAFETY RULES of reloading...START LOW AND WORK UP SLOWLY AND ....DON'T EXCEED DESIGN LIMITS.

I will use one more example...the 585 HE,  I have one in my hot little hand that measures 0.633 at the  base.  Loaded to 15KPSI it will generate 4720psi which we assumed to be pushing against the standing breach.  Due to the straight wall, strenght and thickness of the case it can be loaded to much, MUCH higher pressures without harming the NEF or putting too much more pressure on the breach.

Compare that to what the 30-06 does at 40,000 psi in my previous post.

Jack up the pressure in the 585 HE to 40KPSI and things change...the breach is now seeing 12,488 psi.!!!  I'm not too sure just how well the NEF would handle this amount of case thrust OR how the pressures would be distributed...nor does anyone else until it has been tested and THEN ONLY for that specific rifle.  Another rifle firing the same load might come apart.

Conjecture and opinion are great when tasting wines or how you like your steak, but in relation to the NEF frame I tend to think specific information from NEF should rule and the rest is just smoke and mirrors and walking TOO close to the edge of the unknown.

Luck

[gcrank1]

Thanx!, I find that a thoughtful and well worded expanation of a very complex issue.
FWIW, I've noticed, that when I have had a 'pop open', with a straight or bottlenecked case, that the felt recoil seems noticably less. At the same time, I have not, thankfully, had a case exit the breech, in fact, there hasnt been enough tip open to trigger the ejector.

[trotterlg]

I am not talking about pressure of any kind, only the forward thrust on the barrel, which I contend is minimal with a straight walled case and much more with a bottelneck case.  There is no area for the pressure to act on to push the barrel forward if there is no sholder in the chamber.  Larry

[quickdtoo]

I'll share two incidents of over pressure that have severely tested SB2 frames, one is documented here on GBO, and I think the other will soon be posted by the owner. The first was several years ago when a member was at the range shooting his 243 Win H&R, his friend somehow loaded a 7.62x39 round in it without his knowledge and sent a round down range, the resulting over pressure locked up the action and he ended up sending it in to H&R for repair. H&R reported the underlug damaged but the frame was fine, they fitted another barrel and returned it to the member. The pressure generated by pushing a .30 cal bullet thru a .243" bore had to be substantial to say the least!!

http://www.gboreloaded.com/forums/index.php/topic,70638.msg433117.html#msg433117

The other incident happened after a member had a case stick in his 223 Handi, he used a brass rod in the bore to knock the stuck case out. Apparently the brass rod was still in the bore when he fired the next round because he hasn't been able to find the brass rod since!  The resulting pressure blew the trigger guard out of the frame, he ended up with plastic bits in his trigger hand, but fortunately no loss of body parts. He has since used the barrel on another frame without any problems, I recently converted it to a modified extractor and shortened and recrowned the barrel for him, he should be posting a range report as soon as he can get out to shoot it.

Tim

[NFG]

I see where you're going, Larry...and I think you're right to a large extent...what pushes the barrel forward in a straight walled chamber is the push from the case head by the pressures trying to push the bullet out the barrel AND the pressure ON the case head....while with a bottlenecked case you ALSO have an additional push on the shoulder AND the push from the case head/bullet action/reaction.  You can calculate the vectors the same way you calculate the pressure on the case head...take the area of the shoulder and shoulder/case wall angle and plug it into a vector formula...that should give a ball park number  to add/subtract from the other numbers.

But here again I haven't read ANY definitive, objective, empirical information where the actual forces were measured in ANY receiver other than a few engineering treatises on bolt lugs...that doesn't mean there hasn't been something published somewhere.  As I simplistically stated the forces are going in many different directions and they are very hard to calculate OR measure.

There is no doubt in my mind the NEF is a strong action, the lug is softer than the hinge pin and the receiver and it is a simple but well designed receiver...I wasn't dissing the NEF, just pointing out some of the posible weak areas.  I have subjected my 45-120 to some hairy, well over pressure loads and it hasn't complained yet nor can I find any evidence of cracks, permanent deflections or other problem areas that would cause me to go after it with oxy/acetyl torch.  I've done the same with my 12Ga USH rechambered to 12GaFH, but I hit recoil ending loads well before I hit the pressure limits...1500 gr of ejecta(powder, wads and bullet) up near 1900 fs even WITH a MB gives a whole new meaning to "Do that Honey and I will slap you into next year.

The problem with that long barrel and additional weight of the muzzle brake is the torque/moment forces are increased by the additional weight and lever arm.

If you want an eye opener study the T/C blow-up picture closely...it looks to me like the barrel was pluged right where the splits stopped or close to it, but what interested me was HOW the "frame rails" and bottom section was peeled apart....right at the junction of the standing breach and "frame rails".  I would really like to see that disintegration in slow motion to see actually WHERE the ruptue started and how it propagated.  I have several thoughts about the whys, but again that is conjecture on my part and doesn't belong on the web.

There is never just ONE reason for things to go sour...Murphy always has his nose stuck in the pie and jumping to conclusions only muddies the already totally opaque waters.

Luck

[NFG]

One last observation and more food for thought...a comparison between the 500 S&W and a 30-06 case(I used a cylindrical case of 2.5" x .470" no taper)

The dimensions of the 500 S&W are 1.65" x .515"(I averaged the taper) or ~2.67 sq in(C=D x Pi x L)...splitting the case wall and flattened the brass so to speak...I didn't include the area of the ends to keep it simple. Taking the square inch area and multiplying by 50000 psi I come up with ~133500 total pounds in the chamber area.

A 30-06, 2.5" x .47" works out to be ~3.69 sq in and ~184500 pounds.

The base area of the 500 S&W is (.530/2)* x Pi(A=Pi x r squared) or .221 sq in x 50000 lbs = ~11050 psi
The base area of the 30-06 is (.47/2)* x Pi or .174 x 50000 lbs = ~8700 psi.

You can see that although the 500 S&W has MORE theoretical/calculated pressure against the standing breach it also has LESS total system pressure.  Without an actual pressure reading on the standing breach AT the point the case pushes against it, all we are doing is trying to use "educated" guesses to deduce something that, in all probability is not quite right nor not quite wrong.

I'm just guessing there is some meaning in this information, I see it as a way to visualize what is going on and where the danger areas are...and for those that keep bandying there is some way to extrapolate significant information from the pressure ratings of the 500 S&W into something meaningful, you are just waving the apples to orange flag again.  The fact that the NEF can handle the pressures gives more imputus to the already know fact that the receiver is very strong..

You might use that pressure figure as an upper limit for another straight walled wildcat case application if you were careful when you started working up loads.  I'm not uncomfortable doing it...and I've used similar thinking when developing possible wilcats for projects.

It would really be nice to know the pressure ratings for the various components...i.e., barrel, receiver, lug  and hinge pin steels, but I think that would be hard to get...maybe Tim could.

Luck

[quickdtoo]

I think Gordon shared some proof pressures with Mac at one time, but he'd have to post those, I dunno if they were for publication or not. IMO, the frame itself is very strong, unfortunately the action leaves a bit to be desired, specifically the size on the latch frame pin, I think it's the weak link in the lock up, if it were increased in size or was supported better closer to the latch itself, the action wouldn't be so springy and you would get as much case growth and internal action movement with warm loads.

Tim

[S.E.Ak]

note my comments were about results with shotguns and they for sure fire straight wall cases. I believe no matter the rounds type its the ejecta hitting the forcing cone or rifling with the pressure behind it giving forward thrust.

[Mac11700]

I think Gordon shared some proof pressures with Mac at one time, but he'd have to post those, I dunno if they were for publication or not. IMO, the frame itself is very strong, unfortunately the action leaves a bit to be desired, specifically the size on the latch frame pin, I think it's the weak link in the lock up, if it were increased in size or was supported better closer to the latch itself, the action wouldn't be so springy and you would get as much case growth and internal action movement with warm loads.

Tim

Your correct Quick..Gordon did share this information with me,and,no it isn't for publication.I will say it is much higher than any factory pressures from any cartridge they have a option for..but not as high as what Remington has for their model 700 bolt gun..but that data may not be correct now..

The weak link (no pun intended) is the lock work of the handi rifle & frame. It always has been,and it is also part of the design to be so.This was implimented when the cast iron frames were being used for a limited number of centerfire cartridges. Also,most all of these early centerfires had extremely long throats.This too was a built in safty mechinism for them,and is still in use today.Then as now, the company doesn't warrent for people who reload,so staying within factory available pressure ranges is a moot issue to them.

A couple things to bear in mind when trying to calculate just how much case thrust is being applied.
1) Case slope..
2) Burn rate

In a properly chambered rifle,a cartridge that has little slope angle to it, (straight walled or bottle neck) produces substantionally less back thrust than one that has a great deal of slope to it.The more bearing surface it has that doesn't have to over expand to fill the chamber,the more cling it has.This is due to the cling factor of the brass. This is one of the reasons Ackley and other improved cartridges do not readily show over pressure signs,even though many are running them that way.One of the big problems with our little rifles,is mis aligned chambers and out of spec'd chambers..either from the factory or when being rechambered.Also this is one of the main reasons for brass that over expands and must be full length resized just to fit back into the chamber.

The 9" of burn is an approximation..not a rule written in stone,espcially for the reloader.While most factory loading will come in around this length not all loadings will.Being able to vary the load density and powder burn rates by utilizing much slower powders will dictate just how far down the tube the powder will actually burn,as well as what type of primer is being utilized.This too will effect what back thrust is occuring.There is also some secondary detonations occuring with certain loads.


The time tested rules of reloading are there for all of us to ultilize.If one elects to experiment,then it is that persons responsibility to ensure his and others safety.This is also the reason for everyone to err on the side of caution when attempting to turn a 7lb SB1 Handi rifle into a elephant gun. While the frame is strong,it is not as strong as a Ruger #1 or #3 nor is it as strong as a bolt action rifle even the rear lock up type like the 788 Remington.. So using these type of loads on a daily basis isn't really recommended as some here seem to think they are,no matter what mathmatical formula they want to give to prove they can,so as NFG stated unless you have acess to a strain gaged equiped Handi..you are just guessing what the pressures are.Even if we did have a strain gauge equiped handi..with the variances that these rifles have, each rifle will give a different result,because each is different and each has it's own limits,and that is a fact we all have to deal with.

I don't have a problem with running hot loads through mine,but as a responsible reloader I understand the dangers and have reached those levels safely and slowly by working up my loads in very small incriments and chrongraphing each load.What is and what I consider safe in my rifles may or may not be safe in anyone elses..

Mac

[bikerbeans]

Mac, Tim and others,

So i get this right I will try and summarize what I have read that seems important to me.  The most probable failure from shooting high pressure loads in a H&R single shot is with the locking mechanism, either a pop open or maybe something a little more extreme.  Repeated high pressure loads may (can?) result in failure of the latch system.  

My question is what is the worst case scenario for a latch system failure?  An empty brass being propelled rearward into the shooter?  Brass rupturing and spewing hot gases & brass particules into the shooter? Something else?

I guess the last question is which GBO member is going to design/build the Magnum Handi latch system?

thanks, as always I enjoy reading and learning from the GBO membership.

BB