Gunsmithing Mosin Nagant Headspace?
Re: Mosin Nagant Headspace?
Sent you what I believe to be a CIP print from PTG.
Sent you what I believe to be a CIP print from PTG.
Re: Mosin Nagant Headspace?
Chances are good that rifle's chamber is looser than a french whore. Both of my 91/30's shoot OK with milsurp "blammo" and pretty dandy with handloads and once fired, neck sized only brass.
Mine also head space on the rim. This was done for a fool proof combat weapon. My dad has one of the Finnish sniper versions and it was built to headspace on the shoulder.
If you want it to really shoot, take it apart, cut the chamber back a few thou and have it set to space on the rim, but only just barely.
Chances are good that rifle's chamber is looser than a french whore. Both of my 91/30's shoot OK with milsurp "blammo" and pretty dandy with handloads and once fired, neck sized only brass.
Mine also head space on the rim. This was done for a fool proof combat weapon. My dad has one of the Finnish sniper versions and it was built to headspace on the shoulder.
If you want it to really shoot, take it apart, cut the chamber back a few thou and have it set to space on the rim, but only just barely.
Re: Mosin Nagant Headspace?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JLM</div><div class="ubbcode-body">He already blew one shoulder out with what looks to be Yugo surplus ammo. That one grew .058 upon firing
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Sounds like it would be a good time to have the bolt checked too.
Many of those rifles have Action A with Bolt B with Stock C, etc.
They were built to crap-ass standards during the war because of the stress of the wartime production. It's possible that the bolt is too short. I've seen it several times when a barrel stub is just a little short, so they cut the chamber a little deeper, let it headspace wherever it pleases and sent it off to the front.
The life expectancy of the soldier is so much shorter than the rifle that there's a good chance it would be in the mud under 3 dead bodies before firing 20 rounds.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JLM</div><div class="ubbcode-body">He already blew one shoulder out with what looks to be Yugo surplus ammo. That one grew .058 upon firing
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Sounds like it would be a good time to have the bolt checked too.
Many of those rifles have Action A with Bolt B with Stock C, etc.
They were built to crap-ass standards during the war because of the stress of the wartime production. It's possible that the bolt is too short. I've seen it several times when a barrel stub is just a little short, so they cut the chamber a little deeper, let it headspace wherever it pleases and sent it off to the front.
The life expectancy of the soldier is so much shorter than the rifle that there's a good chance it would be in the mud under 3 dead bodies before firing 20 rounds.
Re: Mosin Nagant Headspace?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JLM</div><div class="ubbcode-body">bohem, everything is serialized and all serials match. It's a Russian Arsenal rifle.
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Still check the bolt. When the arsenals refinish them the sometimes get mixed up, to make things match they are restamped. One of mine is "all matching numbers" but the cleanliness and alignment of the original S/N on the reciever is WAY below the standard used to refinish them. It looks crooked and not stamped to an even depth but the numbers on the bolt and stock are clean, straight and even.
I have a Turk Mauser that is "all matching" also but from the suspicious beautiful new finish on it I doubt highly that it's all original.
Barring a "short bolt" issue it might just need to have the barrel removed and trimmed 0.045" to get it to headspace on the rim. If you want to make it shoot and are willing to go to that distance, then take 60 thou off the face and get the chamber checked to headspace on the shoulder.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JLM</div><div class="ubbcode-body">bohem, everything is serialized and all serials match. It's a Russian Arsenal rifle.
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Still check the bolt. When the arsenals refinish them the sometimes get mixed up, to make things match they are restamped. One of mine is "all matching numbers" but the cleanliness and alignment of the original S/N on the reciever is WAY below the standard used to refinish them. It looks crooked and not stamped to an even depth but the numbers on the bolt and stock are clean, straight and even.
I have a Turk Mauser that is "all matching" also but from the suspicious beautiful new finish on it I doubt highly that it's all original.
Barring a "short bolt" issue it might just need to have the barrel removed and trimmed 0.045" to get it to headspace on the rim. If you want to make it shoot and are willing to go to that distance, then take 60 thou off the face and get the chamber checked to headspace on the shoulder.
Re: Mosin Nagant Headspace?
Okay thanks for your help again.
How do you gauge the bolt to see if the length is right?
I've never dealt with rimmed carts before, and after looking at the gauges it appears as if the 'headspace' is between the end of the rim and the end of the chamber, and NOT to the shoulder.
Nonetheless it seems (to me anyway) that if the chamber is still too long your brass has to stretch somewhere and the potential for it to split somewhere is there.
I have the one case that blew out .058 longer and it has a crack on the shoulder itself. Thought that was weird, you'd think it would head sep first but.....
Thank you sir
Okay thanks for your help again.
How do you gauge the bolt to see if the length is right?
I've never dealt with rimmed carts before, and after looking at the gauges it appears as if the 'headspace' is between the end of the rim and the end of the chamber, and NOT to the shoulder.
Nonetheless it seems (to me anyway) that if the chamber is still too long your brass has to stretch somewhere and the potential for it to split somewhere is there.
I have the one case that blew out .058 longer and it has a crack on the shoulder itself. Thought that was weird, you'd think it would head sep first but.....
Thank you sir
Re: Mosin Nagant Headspace?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JLM</div><div class="ubbcode-body">Okay thanks for your help again.
How do you gauge the bolt to see if the length is right?
<span style="font-weight: bold">
I've done it by taking a sheet of paper (which generally has a very stable thickness through the sheet) and putting slips of paper on a shell base, continuing to build it up until the bolt closure gets very difficult.
Take it apart and measure the final crushed thickness of the paper, this will get you an idea of how far off the bolt might be.</span>
I've never dealt with rimmed carts before, and after looking at the gauges it appears as if the 'headspace' is between the end of the rim and the end of the chamber, and NOT to the shoulder.
<span style="font-weight: bold">
Correct, those were built to space on the rim, like many rimmed cartridge rifles are. A very easy way to improve accuracy is to set back the barrel so it spaces on the neck before the rim, but only just BARELY maybe under 10 thousandths</span>
Nonetheless it seems (to me anyway) that if the chamber is still too long your brass has to stretch somewhere and the potential for it to split somewhere is there.
<span style="font-weight: bold">Yes, it certainly sounds like this is the problem. You might have a proper bolt length and a bad chamber. Wartime production being what it was in Russia, there's a good chance they just said "screw it" and sent it to the line. I've taken corrosive surplus ammo from wartime, pulled the bullets and dumped the powder and bullets into new cases with non-corrosive primers. Doing this I found a couple pieces of grass seed in the powder. "Floor sweepings" was the way a CR fellow rationalized it to me. I've seen it in Turkish 8mm ammo too.</span>
I have the one case that blew out .058 longer and it has a crack on the shoulder itself. Thought that was weird, you'd think it would head sep first but.....
<span style="font-weight: bold">Try cutting one of those cases in half and take a look how thick the web on case head is, for the suplus ammo I wouldn't be surprised to find out that it's very thick so that crappy MG's can shoot it without sticking a separated case in the chamber.</span>
Thank you sir
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I'll send my dad a link on this thread and get his take on it, he's worked on a number of MN's over the past few years, he might be able to diagnose it immediately. He's a pretty decent 'smith and likes to tinker with CR rifles, so he maybe be able to offer you a cheap solution if the "extra long" chamber is the issue at hand.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JLM</div><div class="ubbcode-body">Okay thanks for your help again.
How do you gauge the bolt to see if the length is right?
<span style="font-weight: bold">
I've done it by taking a sheet of paper (which generally has a very stable thickness through the sheet) and putting slips of paper on a shell base, continuing to build it up until the bolt closure gets very difficult.
Take it apart and measure the final crushed thickness of the paper, this will get you an idea of how far off the bolt might be.</span>
I've never dealt with rimmed carts before, and after looking at the gauges it appears as if the 'headspace' is between the end of the rim and the end of the chamber, and NOT to the shoulder.
<span style="font-weight: bold">
Correct, those were built to space on the rim, like many rimmed cartridge rifles are. A very easy way to improve accuracy is to set back the barrel so it spaces on the neck before the rim, but only just BARELY maybe under 10 thousandths</span>
Nonetheless it seems (to me anyway) that if the chamber is still too long your brass has to stretch somewhere and the potential for it to split somewhere is there.
<span style="font-weight: bold">Yes, it certainly sounds like this is the problem. You might have a proper bolt length and a bad chamber. Wartime production being what it was in Russia, there's a good chance they just said "screw it" and sent it to the line. I've taken corrosive surplus ammo from wartime, pulled the bullets and dumped the powder and bullets into new cases with non-corrosive primers. Doing this I found a couple pieces of grass seed in the powder. "Floor sweepings" was the way a CR fellow rationalized it to me. I've seen it in Turkish 8mm ammo too.</span>
I have the one case that blew out .058 longer and it has a crack on the shoulder itself. Thought that was weird, you'd think it would head sep first but.....
<span style="font-weight: bold">Try cutting one of those cases in half and take a look how thick the web on case head is, for the suplus ammo I wouldn't be surprised to find out that it's very thick so that crappy MG's can shoot it without sticking a separated case in the chamber.</span>
Thank you sir
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I'll send my dad a link on this thread and get his take on it, he's worked on a number of MN's over the past few years, he might be able to diagnose it immediately. He's a pretty decent 'smith and likes to tinker with CR rifles, so he maybe be able to offer you a cheap solution if the "extra long" chamber is the issue at hand.
Re: Mosin Nagant Headspace?
actually all rimmed cartridges headspace off of the rim no matter if it's a lever action or bolt.
actually all rimmed cartridges headspace off of the rim no matter if it's a lever action or bolt.
Re: Mosin Nagant Headspace?
True, unless they've been specifically setup not to. The Finnish MN91/30 of my father's collection spaces from the shoulder. It also has a shimmed barrel, it was worked for sniper applications.
I have a Marlin 336 in 30-30 that I pulled the barrel off and nipped a total of 7 thou from the barrel stub and it now spaces on the shoulder, accuracy with hand loads tightened it from a 1" to a 3/4" rifle on a nice day. Far better than I need for shooting deer, but I wanted to try it out.
True, unless they've been specifically setup not to. The Finnish MN91/30 of my father's collection spaces from the shoulder. It also has a shimmed barrel, it was worked for sniper applications.
I have a Marlin 336 in 30-30 that I pulled the barrel off and nipped a total of 7 thou from the barrel stub and it now spaces on the shoulder, accuracy with hand loads tightened it from a 1" to a 3/4" rifle on a nice day. Far better than I need for shooting deer, but I wanted to try it out.
Re: Mosin Nagant Headspace?
Here's my dad's reply:
<span style="font-style: italic">Do a chamber cast and compare to a cartridge. Worn from excessive use ? Not sure how that would be so bad, but anything's possible with these weapons.
Check lockup lugs on bolt head for severe wear.
Should be able to chamber a cartridge and close bolt. Obviously he can. Then put a piece of paper between bolt face and cartridge. Should not be able to close.
If it the paper test it's a chamber issue. Casting it with wax or lead will give you a good idea how excessively large it really is.</span>
Second Reply:<span style="font-style: italic">Its almost impossible to screw up headspacing on a rimmed cartridge because they headspace on the rim, unless something else is *very* wrong. If chamber cast shows chamber is correct length, without even looking at it, I'd bet its the lugs that are messed up. Now if the bolt lugs are OK, I'd be really worried that the lugs inside the receiver are on their way to that big demilling operation in the sky.</span>
Here's my dad's reply:
<span style="font-style: italic">Do a chamber cast and compare to a cartridge. Worn from excessive use ? Not sure how that would be so bad, but anything's possible with these weapons.
Check lockup lugs on bolt head for severe wear.
Should be able to chamber a cartridge and close bolt. Obviously he can. Then put a piece of paper between bolt face and cartridge. Should not be able to close.
If it the paper test it's a chamber issue. Casting it with wax or lead will give you a good idea how excessively large it really is.</span>
Second Reply:<span style="font-style: italic">Its almost impossible to screw up headspacing on a rimmed cartridge because they headspace on the rim, unless something else is *very* wrong. If chamber cast shows chamber is correct length, without even looking at it, I'd bet its the lugs that are messed up. Now if the bolt lugs are OK, I'd be really worried that the lugs inside the receiver are on their way to that big demilling operation in the sky.</span>
Re: Mosin Nagant Headspace?
Okay, well actually have two rifles to deal with
In the M44 I was NOT able to close the bolt on one thickness of paper.
In the 91/30 I had to MONT down on it to get it to close on the 3rd piece of paper. The combined thickness of the three came out around .016.
I really appreciate your help. Do you have any idea of the dims on the FIELD and NO-GO gauges?
Looks like the M44 is okay headspace wise anyway?
Okay, well actually have two rifles to deal with
In the M44 I was NOT able to close the bolt on one thickness of paper.
In the 91/30 I had to MONT down on it to get it to close on the 3rd piece of paper. The combined thickness of the three came out around .016.
I really appreciate your help. Do you have any idea of the dims on the FIELD and NO-GO gauges?
Looks like the M44 is okay headspace wise anyway?
Re: Mosin Nagant Headspace?
Looks like the M44 is GTG on the bolt length and headspace. The chamber is too long if this is the rifle that stretches the brass .050+
The 91/30 is 10 thou out of headspace (too much clearance).
I don't know what the field and NG gage are, I'll ask and see what "my 'smith" says LOL
Can you wax cast the chamber in the M44? Pack a piece of paper patch into the throat, spritz with WD or something slick and just cast it full of wax. Then lightly push on the paper from the muzzle end with a cleaning rod (careful on the crown) and it should pop right out.
You can take chamber dimensions off of that.
Looks like the M44 is GTG on the bolt length and headspace. The chamber is too long if this is the rifle that stretches the brass .050+
The 91/30 is 10 thou out of headspace (too much clearance).
I don't know what the field and NG gage are, I'll ask and see what "my 'smith" says LOL
Can you wax cast the chamber in the M44? Pack a piece of paper patch into the throat, spritz with WD or something slick and just cast it full of wax. Then lightly push on the paper from the muzzle end with a cleaning rod (careful on the crown) and it should pop right out.
You can take chamber dimensions off of that.
Re: Mosin Nagant Headspace?
Here's my dad's reply
<span style="font-style: italic">
Typically you need .002" to .003" or the bolt closes with difficulty. The .308 spec is something like .003" to .008" for go/nogo and 0.009 for field gage. He was out of spec by about double. The strength of the action save him but accuracy will probably be poor. If the headspace isn't addressed then hot loads should be avoided. Sounds like the M44 is good.</span>
I asked about the M44 stretching the brass.
<span style="font-style: italic">Examine the bolt head, see if it needs to be replaced. If its OK, do a chamber cast. if that's OK, the receiver is bad.</span>
Here's my dad's reply
<span style="font-style: italic">
Typically you need .002" to .003" or the bolt closes with difficulty. The .308 spec is something like .003" to .008" for go/nogo and 0.009 for field gage. He was out of spec by about double. The strength of the action save him but accuracy will probably be poor. If the headspace isn't addressed then hot loads should be avoided. Sounds like the M44 is good.</span>
I asked about the M44 stretching the brass.
<span style="font-style: italic">Examine the bolt head, see if it needs to be replaced. If its OK, do a chamber cast. if that's OK, the receiver is bad.</span>
Re: Mosin Nagant Headspace?
So here's the reason that you didn't see a case head separation in either rifle. I didn't even think of this.
The correct headspace would hold the case into the chamber so that the head is supported, it's pretty hard to separate a case head that way. You'd see a split shoulder first.
Even the rifle that's double the tolerance is still only 9 thou out of tolerance and with the thick webs that the military cases have, you would split a neck first.
The chamber casting will tell you for sure.
Are the primers backing out or looking excessively flattened (indicating a "reseated primer") on the rifle that's out of head space?
So here's the reason that you didn't see a case head separation in either rifle. I didn't even think of this.
The correct headspace would hold the case into the chamber so that the head is supported, it's pretty hard to separate a case head that way. You'd see a split shoulder first.
Even the rifle that's double the tolerance is still only 9 thou out of tolerance and with the thick webs that the military cases have, you would split a neck first.
The chamber casting will tell you for sure.
Are the primers backing out or looking excessively flattened (indicating a "reseated primer") on the rifle that's out of head space?
Re: Mosin Nagant Headspace?
Will report back tonight when I get over to my bud's and can get hands on the rifles.
It was the M44 oddly enough that had the split shoulder. Everything thru the 91/30 was GTG.
So, if I read you right (and your Dad, tell HIM thanks too by the way) .016 of paper is thicker than a NO-GO?
Will report back tonight when I get over to my bud's and can get hands on the rifles.
It was the M44 oddly enough that had the split shoulder. Everything thru the 91/30 was GTG.
So, if I read you right (and your Dad, tell HIM thanks too by the way) .016 of paper is thicker than a NO-GO?
Re: Mosin Nagant Headspace?
Nagant stuff:
headspace gauge
http://www.geocities.com/yankeeengineers/instruct.html
7.62x54R
http://7.62x54r.net
Better to check the headspace. Most of us in our younger days would just shoot. Luck runs out from time to time.
Nagant stuff:
headspace gauge
http://www.geocities.com/yankeeengineers/instruct.html
7.62x54R
http://7.62x54r.net
Better to check the headspace. Most of us in our younger days would just shoot. Luck runs out from time to time.
Re: Mosin Nagant Headspace?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JLM</div><div class="ubbcode-body">Will report back tonight when I get over to my bud's and can get hands on the rifles.
It was the M44 oddly enough that had the split shoulder. Everything thru the 91/30 was GTG.
So, if I read you right (and your Dad, tell HIM thanks too by the way) .016 of paper is thicker than a NO-GO?
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Since the M44 has the proper headspace and what we both suspect is a very deep chamber, it makes sense that the brass is stretching like crazy and splitting necks/shoulders. The case head is properly supported so it's not going to grow or split before the blown shoulder will.
The 0.016" headspace on the MN91/30 is minimum 7 thou over tolerance so what I'd expect you to see is some very flat primers. The thing saving you from wearing it is that action is very strong. Metal does let go though, so I'd suggest you get a new bolt-head from Numrich and/or check the receiver lugs for damage from abusive hot loads.
I didn't check the links, but it seems that 303 has sent you some decent info to work from too.
My dad said his go to method for casting a chamber is to melt sulfur and pour it into the chamber, it's hard/strong enough to be able to take good measurements from.
1) Do it outside
2) Don't breathe it
3) Shower afterward
4) Clean the rifle VERY well once you get a good casting
I've done it with wax, but I guess he doesn't like using that method for whatever reason. I don't like smelling like a coke plant after casting a chamber on an old rifle.
EDIT: He just emailed me again and said he'd rather that you cast it and pack it up well, then ship it to him. He can take the measurements and look for issues. Send a couple pieces of the fired brass and 1 unfired case (pull the powder and bullet for ORM-D reasons) so he can get a good idea of the bigger picture.
No charge on that, he doesn't wanna see someone wear a rifle over it.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JLM</div><div class="ubbcode-body">Will report back tonight when I get over to my bud's and can get hands on the rifles.
It was the M44 oddly enough that had the split shoulder. Everything thru the 91/30 was GTG.
So, if I read you right (and your Dad, tell HIM thanks too by the way) .016 of paper is thicker than a NO-GO?
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Since the M44 has the proper headspace and what we both suspect is a very deep chamber, it makes sense that the brass is stretching like crazy and splitting necks/shoulders. The case head is properly supported so it's not going to grow or split before the blown shoulder will.
The 0.016" headspace on the MN91/30 is minimum 7 thou over tolerance so what I'd expect you to see is some very flat primers. The thing saving you from wearing it is that action is very strong. Metal does let go though, so I'd suggest you get a new bolt-head from Numrich and/or check the receiver lugs for damage from abusive hot loads.
I didn't check the links, but it seems that 303 has sent you some decent info to work from too.
My dad said his go to method for casting a chamber is to melt sulfur and pour it into the chamber, it's hard/strong enough to be able to take good measurements from.
1) Do it outside
2) Don't breathe it
3) Shower afterward
4) Clean the rifle VERY well once you get a good casting
I've done it with wax, but I guess he doesn't like using that method for whatever reason. I don't like smelling like a coke plant after casting a chamber on an old rifle.
EDIT: He just emailed me again and said he'd rather that you cast it and pack it up well, then ship it to him. He can take the measurements and look for issues. Send a couple pieces of the fired brass and 1 unfired case (pull the powder and bullet for ORM-D reasons) so he can get a good idea of the bigger picture.
No charge on that, he doesn't wanna see someone wear a rifle over it.
Re: Mosin Nagant Headspace?
The only Finn 91/30 snipers I have seen were put together by Century Arms. Got any pics? And I have had over 15 Finns and none have ever been headspaced on the shoulder. I just sold my last M39. It was a unissued no maker 1969 year. I even had the arsenal tag. It was HS on the rim like all of the others. They just have a better chamber than the Russians. I still have a few rds of Finnish ammo left that will be sold shortly.
The only Finn 91/30 snipers I have seen were put together by Century Arms. Got any pics? And I have had over 15 Finns and none have ever been headspaced on the shoulder. I just sold my last M39. It was a unissued no maker 1969 year. I even had the arsenal tag. It was HS on the rim like all of the others. They just have a better chamber than the Russians. I still have a few rds of Finnish ammo left that will be sold shortly.
Re: Mosin Nagant Headspace?
This was imported by a company in MD, the guy isn't a bulk importer like Century, he specializes in documented strange stuff.
I will ask my dad for a few pictures if he gets a chance, it's the only Finnish sniper that I've ever gotten to handle, mostly because I haven't tried very hard. I figured they were all like this, I assume that's not the case?
This was imported by a company in MD, the guy isn't a bulk importer like Century, he specializes in documented strange stuff.
I will ask my dad for a few pictures if he gets a chance, it's the only Finnish sniper that I've ever gotten to handle, mostly because I haven't tried very hard. I figured they were all like this, I assume that's not the case?
