Author Topic: 45-70 Case Rim Chamber Recess Dimension? (Read 1831 times)

David I. · « **on:** February 28, 2010, 11:48:58 AM »

I have some brand new Starline 45-70 cases and the rim measures an average of .065" thick. The recess cut in the chamber for the rim is about .074" deep, leaving the case about .009" recessed below the barrel face. My barrel locks up nice and tight to the standing breech. Is this built in headspace of approx. .009" correct and what I should expect to see? I don't know how much head space I should have maximum for the 45-70, nor do I have any "go/no-go" gauges. The gun is a brand new H&R BC and I'm just checking a few things on it. I know the least amount of headspace the better....but I'd like to know the maximum. I'm not real happy with the .009"+ dimension, but if it's within spec than OK. From what I've been able to find so far, modern 45-70 brass rims measure either .062" or .066" thick. Please advise, thanks, David.

cwlongshot · « **Reply #1 on:** February 28, 2010, 11:54:20 AM »

Have you shot it yet?

Don't go trying to fix things that aint broke..

CW

quickdtoo · « **Reply #2 on:** February 28, 2010, 11:55:48 AM »

That's not a new issue, there have been a few H&R 45-70s with deep rim cuts, if it won't fire, H&R needs to replace the barrel or you can do what I did on my SS Ultra Hunter by modifying the extractor to hold the cartridge to zero headspace, but if it proves to be a problem, H&R will replace the barrel at no cost to you, just call and explain the problem and ask them to cover return shipping. See if it will fire a primed case(no powder or bullet) before making a range trip.

Tim

jather · « **Reply #3 on:** February 28, 2010, 11:59:33 AM »

the extra space isn't much for helping accuracy, is it? much less excessive headspace/safety issues? jather...

David I. · « **Reply #4 on:** February 28, 2010, 12:36:39 PM »

Thanks Tim for the info. I will try what you said to see if it fires off some primers.....once I get some primers! Just for the record in reply to cwlongshot, I'm not trying to fix anything yet....I'm just checking some things, especially since there have been some other issues with my gun., there is absolutely nothing wrong with checking some things and asking questions. I'd still like to know if there is a maximum headspace dimension for the 45-70, which may be just for my knowledge. I really don't care to get into a debate as to why I ask some of the questions I do, therefore I won't....other than to say a lot of my questions are to gain knowledge for many reasons. Isn't that one of the purposes of this forum? Thanks again Tim for the info, I appreciate it.

cwlongshot · « **Reply #5 on:** February 28, 2010, 12:46:05 PM »

Far be it for me or anyone to pu-pu anyone with a question. Nothing could be farther from reality!! As a matter of a fact, I'm a firm believer in the antage, we ALL learn something new everyday, the day we stop learning is the day we meet our maker!!!

Please, if my response lead you to believe I didn't think you should be asking questions, you read me wrongly!

All I meant was, don't get all caught up in the "could b's". (This or that could be and problem...)
Now, from your post, I got the impression that you had yet to fire the rifle. Am I correct? If so, clean the barrel really good and go have some fun shooting it. If a problem arises, post up and let us know and we will all do our best to help you out. If you have read any of my posts here, you would see I do offer help...

CW

quickdtoo · « **Reply #6 on:** February 28, 2010, 01:36:15 PM »

David, SAAMI defines maximum excess head space as anything over .006", so your barrel seems to me to fit the definition spec as excess. I just measured rims on some Starline and Rem brass, they're right at .065" - .066" thick, so it's not the brass.

Tim

trotterlg · « **Reply #7 on:** February 28, 2010, 01:57:19 PM »

Rim thickness for a 45-70 is max of .070, this is the SAAMI specification. In reality I have never seen a rim on a cartridge that was as thick as the specification, so any rim cut to SAAMI spec will probably end up with about .005 to .006 headspace on it. H&R cuts a little extra, remember you will probably not be able to latch up the rifle it the case head is over the breach unlike a bolt gun where you can just squish the round into the chamber. When I cut the rims I try to cut them to about .002 or so more than a real rim is, this has always worked out for me. Larry

quickdtoo · « **Reply #8 on:** February 28, 2010, 02:03:28 PM »

This didn't use to be a problem on ejector barrels, the ejector spring would hold the rim against the breech face or close enough that it worked fine regardless of the rim cut depth, at least one of my ejector 45-70 barrels has a deep rim cut, but it's never been a problem.

Tim

David I. · « **Reply #9 on:** February 28, 2010, 02:28:21 PM »

Thanks Tim for the specs, I really do appreciate it. I'm always concerned about headspace for many reasons, including safety as the number one reason. Obviously even with a new gun things can sometimes be out of spec. Will my gun shoot fine?, probably. Will the excessive headspace cause any problems now or down the road?, not sure. I won't be shooting any real heavy loads, but that's not the point in my mind. Right is right and wrong is wrong......excessive is excessive. At this point in time I'm not sure what I'm going to do. Eventually I will be shooting it and looking very closely at the brass and primers, that's if it fires just primers first! My measurement of .009"+ seemed excessive to me and it's one of the reasons I asked my question., it's a detail I didn't care to just ignore. I may contact H&R and ask some questions as to what their specs are for headspace and see what they say. It's very possible my excessive headspace IS a problem and may be out of spec, which would only get worse in time. If the headspace my gun has is within H&R's specs I'll be happy.....but I have a feeling if SAAMI states a max of .006", my gun probably needs help. All of the above reasons and then some are why I look into things when I notice something not right or what seems excessive. Besides a possible safety issue, I payed good money for something I expect to atleast be within spec. Thanks again Tim for answering my question.

David I. · « **Reply #10 on:** February 28, 2010, 02:30:04 PM »

Thanks trotterlg for the info.

quickdtoo · « **Reply #11 on:** February 28, 2010, 02:52:04 PM »

My SS Ultra Hunter would even fire when I took it to the range the first time, I didn't measure the excess head space, but it was enough to cause a problem. I wanted to shoot it before I sent it back to H&R, if it was a good shooter, I'd repair it myself and not worry about what replacement barrel I got after returning it, that's if they had a replacement, this was when it was first available. I modifying the extractor so it held the round against the breech face. This is the result of the second range trip.

Tim

Slufoot · « **Reply #12 on:** February 28, 2010, 03:12:44 PM »

Quote from: quickdtoo on February 28, 2010, 01:36:15 PM

David, SAAMI defines maximum excess head space as anything over .006",

Quote from: trotterlg on February 28, 2010, 01:57:19 PM

Rim thickness for a 45-70 is max of .070, this is the SAAMI specification.

According to the SAAMI specs as listed by Tim & Larry your chamber should be in tolerance. A max rim thickness of .070" and a max excess headspace of .006" would mean the rim recess could be cut up to .076" deep and be at the maximum of the SAAMI specs.

I personally would rather have it tighter as Larry likes to cut them, but your chamber should be fine and not cause you any problems.

GOOD SHOOTING!
Slufoot

David I. · « **Reply #13 on:** February 28, 2010, 04:03:16 PM »

Thanks Tim and slufoot for the great info. It's unfortunate in my opinion that todays brass is .062,.065-.066 and not closer to the original .070" rim thickness. As I see it, this creates problems when things aren't truely standardized. Some guns will really end up having rather excessive headspace, and even though it doesn't seem to cause too many problems it's still not a good situation. As I said, my gun's rim recess is cut to .074" deep and if that's within spec than OK.....I wish it was not quite that deep but like you say it will probably be OK. Out of curiousity it would be interesting to know if .070" brass can even be found any more! Another curiousity is I wonder how many H&R/NEF 45-70 guns out there have rim recesses cut to .074"....in other words what the average depth is for these guns? My gun was made in 2007 if that matters. I may still call H&R to see if I can get their specs on this, but like some of you said...they probably went with a max rim thickness of .070" and can then add up to .006" if they wish,in my case they added .004".

trotterlg · « **Reply #14 on:** February 28, 2010, 04:36:02 PM »

There is a fix for it if it really bothers you. Take a small center punch and punch the face of the rim cut on the barrel all the way around, probably about 20 punches. That will probably hold the brass up about .004 more than it is now. It is kind of ugly however, but it gets the job done. Larry

mitch132 · « **Reply #15 on:** February 28, 2010, 04:37:50 PM »

You may find this link helpful. Cartridge and chamber specs for the 45-70 Gov.

http://www.leverguns.com/dimensions/images/4570.jpg

David I. · « **Reply #16 on:** March 01, 2010, 04:02:27 AM »

Thanks trotterlg and mitch132 for the helpful, respectful and considerate info to my legitimate question. What bothers me is that my actual headspace is .009"-.010" using brass with a .065" thick rim (common modern brass size). This headspace won't get any less in time, probably more. It bothers me for various reasons but most importantly for safety and accuracy reasons. If most other H&R/NEF 45-70's have approx. a .074" deep rim cut and haven't experienced any negative results, then I won't be concerned. It would be interesting to know what some other peoples rim cuts measure in depth. I may call H&R, I may ask Tim more about his mod to the extractor, I may try trotterlg's mod.....I haven't decided yet. At any rate, I really appreciate all the info. I still feel it's unfortunate that todays brass is made to about .065" thick rim when apparently rim cuts by H&R are made in relation to the original 45-70 rim thickness of .070" (I understand why they do). I realize there may always be some old .070" brass out there, but it doesn't seem to be made that thick anymore. Other than cost savings, I wonder why the brass manufacturers changed to .065", or were allowed to for that matter. But, as I said, if .009"-.010" of headspace doesn't cause any problems then I won't worry. I guess putting it more simply.....I want to make sure that my rim cut depth of .074" isn't out of the ordinary for the H&R/NEF.

trotterlg · « **Reply #17 on:** March 01, 2010, 05:46:30 AM »

You will never get one with a rim cut less than .070 from any manufacturer, that is SAAMI Spec, the lawyers would never let them sell soemthing that is not in specification no matter what the real world facts are. Larry

kite · « **Reply #18 on:** March 01, 2010, 07:09:00 AM »

Quote from: mitch132 on February 28, 2010, 04:37:50 PM

You may find this link helpful. Cartridge and chamber specs for the 45-70 Gov.

http://www.leverguns.com/dimensions/images/4570.jpg

If I'm reading this right a max rim cut of 0.077" paired up with a max case rim of 0.070" would still leave 0.007" 'play', eh?

David I. · « **Reply #19 on:** March 01, 2010, 12:36:54 PM »

I hear yah Larry, I understand what you're saying "legally". According to the drawing that mitch132 linked, the cartridge rim thickness should be .070" with a tolerance of up to -.010". I do have another question: Is that SAAMI spec of .006" max headspace specific for the 45-70? If I'm reading the drawing correctly (link from mitch132), "kite's" comment reagarding .007" would be correct for headspace IF the brass is .070". If the brass is something less than .070" then the headspace increases. Which brings me back to the brass.... According to the drawing the thinnest the brass rim can be is .060", so worst scenario would be a headspace of .017"!!! This would be with a case that has a .060" thick rim and a chamber with a rim cut .077" deep. Unfortunately none of this equates to the max headspace of .006" or .007". I'm not sure whos drawing it is., is it a SAAMI drawing? Anyway, this may all be very interesting but I would still like to know what other H&R/NEF guns out there measure for a rim cut depth.

mitch132 · « **Reply #20 on:** March 01, 2010, 12:41:00 PM »

@ kite: Or worst case, a 0.077" max chamber rim paired with a 0.060" min cartridge rim. 0.017" "play" or better yet "slop."

My BC rim depth measures 0.073" - 0.074" depending on how I place the calipers.

My Starline brass has a 0.063" - 0.065" thickness rim.

It has fired first time, every time since I have owned it.

The drawing is from http://www.leverguns.com/dimensions/ with this caption on the first page:

"Cartridge & Chamber Dimensions are established by the Sporting Arms & Ammunition Manufacturers Institute and they hold the copyright to them. All dimensions shown here are used by permission. www.saami.org"

David I. · « **Reply #21 on:** March 01, 2010, 03:16:09 PM »

Thanks mitch132 for the great reply. Your info is not only the type of info I was looking for at this point, but also very good news. Apparently the max headspace of .006"-.007" is not something that needs to be strictly held to with the 45-70, atleast not with mild to moderate loads. Of course I would much prefer to have less than the approx. .010" headspace I have, but atleast I know your gun (and hopefully others out there) is very similar to mine and shoots well and your brass doesn't show any signs of undo stress. I may decrease my headspace with a mod and I may not, but for now this is as far as I need to carry this....unless others would like to chime in regarding what their rim cut depth measures. This has been very interesting, I do enjoy research and gathering info, I guess that's why I have a technical background amoung other things. I enjoy research and gathering facts, but I also enjoy doing the "hands on work", but most of all I enjoy hunting and shooting with the gun I have worked on and made even better. I want to thank all of you that helped, I truely appreciate it. To repeat myself, I would still enjoy hearing from others as to their guns rim cut depth. Also, FYI, in regards to one of my previous threads on front sight height.....to save money,time, and a slight "skew" problem, I have successfully shortened my front Lyman globe sight from .584" to approx. .494", it was a pretty easy fix actually and even my knit picking eye can hardly tell it was shortened.