SB1 frame, facts or fictions.

[jackddavis]

Yesterday, I read all I could find on the SB1 frame and the differences between the SB1 and the SB2 frames. I've come to the conclusion that there are a lot of thoughts, facts and/or myths surrounding them. The H&R website isn't much help in sorting out the facts from the fictions.
 
Without getting into the technical aspects, I'm wondering if anyone has ever had a problem with the SB1 frame and, if so, what were the problems and what caused them? Details and pictures welcome.

[quickdtoo]

The biggest problem I've had and seen reported here with SB1 shotgun frames is caused by the large firing pin and hole in the standing breech causing primer issues with the 22 Hornet and pistol cartridges (357mag/max and 44mag), other than that which is commonly reported,  MtJerry unknowingly fitted a 270 barrel to an SB1 frame which promptly caused issues with mild 270 handloads, barrel release was real hard to press and primers were bulged(his words), he checked with Raynor and learned the frame was originally a factory 45-410 Survivor.

Tim

[jackddavis]

Thanks, Tim. I've been searching again this morning for reports of catastrophic failures with the SB1 frame and can find nothing. Either they don't happen, or they are not reported or posted. I have found reports of folks using them for rifle cartridges without problems.
 
I don't plan anything like this, but must admit the warnings about catastrophic failures with loads up to 48K CUP (.357 Maxi) have me wondering. I've not had any cratering of primers either, but my firing pin hole seems to have good tolerances. It is oval shaped, but needs to be due to the angle it strikes at. When protruded, it fills the hole nicely. I'm using SRP's with heavy loads.
 
Looking at the frame, it seems to me that if it were to fail, it would likely be at the hinge pin. You'd end up with barrel in one hand and the stock/frame in the other. Not a good thing, but I can't find any postings where that has ever happened. Perhaps it has, but was never posted. I suppose the latch could fail, but I suspect that is the same on both frames. I doubt that the breech face would ever fail before the hinge pin area. At least that seems logical to me.
 
My SB1 is obviously cast alloy of some kind. This is easily seen with the barrel removed. You can see the mold seam and rough cast surface in the bottom between the breech and the hinge pin. Cast "iron" is all inclusive and doesn't accurately describe the material used to cast the frame. The actual alloy is a mystery to me. I've read that it is the same alloy as the SB2 frame, just not heat treated. I wonder if that is correct. Does the SB2 frame look the same in that area? Is it also cast? Or is it machined from a forged block?
 
There are a number of rifle cartridges with equal or lower pressures than the .357 mag. or .44 mag. (30.30, 35 Rem., 45 Colt, etc.), but H&R won't put any of these barrels on the SB1 frame. Strange. I suppose if I were to want to ream mine out, I'd choose the .35 Remington over the .357 Maximum (due to case scarcity), but that is probably not a DIY job.

[quickdtoo]

We've been over this very same subject many, many times before, too many IMO, some of those discussions are in the FAQs.  SB2 frames(rifle and 10ga shotgun) are heat treated, investment cast alloy steel, SB1 frames are ductile cast iron, this info comes direct from the H&R Brand manager, I have several hundred emails from him from 2007-2010, this was the subject of more than one of them that related to previous discussions.

Breech thrust can be calculated using a simple formula, use the external case head diameter for a ball park comparison, actual breech thrust is dependent on the internal case head area and the pressure. I use the hydraulic cylinder calculator since it uses the same formula, just add the cylinder diameter(case head diameter) and pressure in PSI, the other fields don't apply and aren't needed.

http://www.riflebarrels.com/articles/custom_actions/bolt_lug_strength.htm

http://www.baumhydraulics.com/calculators/cyl_calc.htm

Probably the biggest reason H&R doesn't offer some of the other low pressure chamberings on SB1 frames is because they have no incentive to do the testing that is required to do so, the SB1 357mag and 44mags were tested to take advantage of the Indiana pistol cartridge deer season market, there's no such market for the Hornet or other low pressure chambering, in fact the Horney has been dropped from the H&R lineup for 2012 entirely, same for the 45 Colt which was dropped in 2008, can't say there's any market incentive for the 30-30 since they sell pretty well on SB2 as they are! 

FWIW, 40kpsi which is the SAAMI MAP for the 357Maxi(not kcup) in a small case round like the 357mag produces a ball park breech thrust of ~4500lbs, a high pressure round like the 30-06 with a SAAMI MAP of 60kpsi produces over 10,000lbs pressure on the breech face, expecting an SB1 to last very long at those levels of stress would be asking a lot of the material they're made of, it may work for a while, but eventually it will fail. The 357Maxi is considered a low pressure round and shouldn't be a problem tho, it has less breech thrust than a 44mag at 36kpsi (5900lbs) which just happens to be factory available on SB1 frames also. 

Tim


Let me add that the only frame failures I've seen reported here were on SB2, a 243 with a cracked breech face, two other failures, most likely due to overloads, where the trigger guard blew out, one on a 270Win/5744 double charge, and one other I think on a 223, but I don't remember for sure. I know of another 223 that blew the trigger guard out due to an obstructed bore, the owner routinely used a short brass rod to drop down the barrel to remove stuck brass, he thinks he left the rod in the bore because he had just used it and the trigger gaurd blew out next shot, the brass rod was MIA, so he thinks that's the cause.

[jackddavis]

Thanks for a very informative post, Tim. Scouring the internet for this very subject, I've encountered the term "cast iron" relating to the SB1 frame, but never with the descriptive term "ductile" included. As I'm sure you are aware, there are many forms (alloys) of "cast iron" and when one thinks of cast iron, one thinks "brittle". Not a good word around breeches or chambers IMO. Adding the word "ductile" probably negates any possibility of failure around the hinge pin. At least it would take much more to crack it there using ductile iron.
 
In one post,  in another forum, a poster says he has a letter from H&R stating that the cast metal in both the SB1 and SB2 are identical, but the SB2 is "tempered". I'm not sure this is true, but ductile iron can be tempered and is much stronger when it is quenched. You say they told you it (SB2) is cast steel (the difference is the amount of carbon in the alloy). Steel is 2%or less carbon and iron is 2.1% or more carbon. Both statements make sense, so I'm unsure which is correct.
 
None of this matters in the scheme of things as far as I'm concerned. What I was worried about is the term" cast iron" and whether the SB1 could fail without showing any of the normal signs of excess pressure. The word "ductile" cleared it up for me.
 
For those interested, this article and the included chart tells of the different cast iron alloys.
 
http://en.wikipedia.org/wiki/Cast_iron
 

[abolt-fan]

Tim,
Reading your responses I took note of your comments on testing SB1 frames with low pressure rifle rounds.  I only worked for H&R for about 6 months before they moved.  One of the last projects I was working (shooting, testing) on was this very project.  The plan was to test with the goal of putting low pressure and small case head rifle cartridges on SB1 frames.  I was told this was to explore being able to produce rifles in these type cartridges using the cheaper to manufacture SB1 frames.

SB1 frames were made with hardened steel disk fitted to the breech face.  These frames were then fitted with 45-70 barrels.  I started the test with four of these guns with the plan to put 1,000 rds. through each gun checking every 20 rds. for cracks, stretching and breech face damage.  I had gotten up to 500 rds. on these four guns with no problems or damage when Remington announced the move to Illion.

After the announcement many of the projects in the works were cancelled or set aside, this being one of them.  I would guess that nothing more was ever done on this project.

Robert.

[jackddavis]

Interesting, Robert. On the my rifles breech face pictured above, I assume the small bright ring is caused by the primers and the larger ring is the disc you mention? Or is it just caused by the cartridge base? Did all SB1 frames have the hardened disk or just those you were testing?

[abolt-fan]

Jack,

The cartridge base.  As far as I know, no other frames were fitted with the steel disk but the ones we were testing.

[quickdtoo]

Thanks for the info Robert. 

Tim