Gunboards Forums banner

Adjusting Mosin Headspace????????

31K views 37 replies 23 participants last post by  COASTIE 
#1 ·
How is it done?
 
#2 ·
Here we go again .... a RIMMED cartridge head spaces on the rim of the cartridge, the rim is what controls the headspace ... simple




There is a great feature of the board and it is called SEARCH ... each and every forum on this board has on it right side of the main topic of the forum has a neat little feature called a SEARCH FORUM ... hit the little button and type in the word or words you are looking for then hit SEARCH and all the topics that deal with that topic pop up ... there is over over 19 pages of stuff regarding the word headspace on this forum.

Patrick
 
#8 ·
Here we go again .... a RIMMED cartridge head spaces on the rim of the cartridge, the rim is what controls the headspace ... simple




There is a great feature of the board and it is called SEARCH ... each and every forum on this board has on it right side of the main topic of the forum has a neat little feature called a SEARCH FORUM ... hit the little button and type in the word or words you are looking for then hit SEARCH and all the topics that deal with that topic pop up ... there is over over 19 pages of stuff regarding the word headspace on this forum.

Patrick
Thanks, but I know about head space and the 'search' function. I hope I didn't put you through too much trouble.
ALL I wanted to know how it can be adjusted on a Mosin since I've never read of it being done.
#1 Having to time the barrel?
#2 As someone mentioned, changing the bolt head?
#3 or some other method.
 
#4 ·
The headspace on the Mosin is completely determined by the relationship between the bolt face and the rear surface of the locking lugs and the corresponding parts in the receiver/chamber. Even if the nominal tolerances are slightly out, most Mosin's pass a field gauge check, regardless of which bolt or bolt head is used. This is not absolute; there are sometimes bad ones. Ultimately, the rimmed cartridge system is the most forgiving of headspace tolerances. If the rifle you are concerned about was put together at an arsenal, and the bolt number matches, you have little to be worried about. If you need to be certain, get a field gauge.
 
#30 ·
The headspace on the Mosin is completely determined by the relationship between the bolt face and the rear surface of the locking lugs and the corresponding parts in the receiver/chamber. Even if the nominal tolerances are slightly out, most Mosin's pass a field gauge check, regardless of which bolt or bolt head is used. This is not absolute; there are sometimes bad ones. Ultimately, the rimmed cartridge system is the most forgiving of headspace tolerances. If the rifle you are concerned about was put together at an arsenal, and the bolt number matches, you have little to be worried about. If you need to be certain, get a field gauge.

Field guage only if you are using surpus and you nor potentially anyone else is reloading the brass. Field tolerance is too loose for reusing the brass IMHO. Case rupture can be a very unpleasant experience in Mosins. NO-GO is the standard I go by.
 
#12 ·
same here, out of all the ones i owned.. that was the only one ive had problems with. Its also the only 91/30 that i have seen that is counter-bored and arsenal matched. She has been through the ringer at one time, but a bolt head swap and a gauge check and she was right as rain.
 
#13 ·
Slamfire51, take a look at Okieguages (www.okieguages.com) for your guages. I have been using them just as a double-check. Don't even have to take off the extractor to use them. Additionally, I've got about a dozen Mosin's and I've never found one to fail the headspace check. Now that I've "jinxed" myself going forward......
 
#14 ·
Ron,
Thanks for the link.
I'm headed there now to ck out the gauges.

Link no good. You misspelled gauges. :)
okiegauges.com does work..
 
#16 ·
#19 · (Edited)
1886Lebel, perhaps the superawesome search function doesn't work, as surely it must have returned the wrong results. the OP did not ask what headspace was, or where the measurement datum points are. it asked how headspace was adjusted.

while the reply "use the search function" is always a choice, so is a responsive reply post. I'll do that.

OP, the headspace is adjusted by finding a bolt head of different length (back of lugs to bolt face), or screwing the barrel in if HS is too long, or cutting the chamber a bit deeper if it is too short. moving the barrel is major.

is your HS too long or too short?
 
#22 ·
Question: do the Okie gauges tell you if you are in spec for manufacturing tolerance or do they tell you if the rifle is within service tolerance (safe to fire)? I may not be posing the question correctly, but if a go-no-go field gauge (one gauge instead of three) tells you that you are OK (or not), then what would you need three gauges for?
 
#24 ·
if a go-no-go field gauge (one gauge instead of three) tells you that you are OK (or not), then what would you need three gauges for?
To the best of my knowledge, there is nobody out there that makes ONE gauge that can make all three of these measurements.

As a practical matter, if your rifle will not swallow the FIELD gauge and isn't impossibly tight (chambers factory rounds normally), you should be good to go.



I have only ever had two rifles with serious headspace issues.

One was a P14 Enfield that had the parts interchangeability problems that P14's became rather famous for. The FIELD gauge would rattle around in there, and there was so much excess hedspace that the firing pin could barely contact the primer if the case was pushed all the way forward in the chamber. The problem with this rifle was NOT receiver wear.

That rifle was fixed by finding a bolt that headspaced the rifle correctly.


The other was a 1945-dated Izhevsk M44 that somehow came to me with an all-Hungarian (02-mark on every identifiable piece) bolt.

Headspace in this rifle was tight to the point that it was very hard to close the bolt on an unfired cartridge. This was even after I cleaned the chamber to the point you could perform surgery in there (several times).

Unsized, fired, cases from this rifle would chamber EASILY in ALL my other 54R rifles.

I found a complete Izhevsk bolt for cheap at a gun show and ALL this M44's problems went away (except that it still has its Hungarian cocking piece, because it had a severe bump fire problem with the Izzy cocking piece).

I can also confirm that just swapping the bolt heads (using one of the right length) can fix a headspace problem, as I DID also try the Izhevsk bolt head with the Hungarian bolt body, and (as you would expect) that also would give me an acceptable headspace.
 
#26 ·
Bought a 1943r Izhevsk 1891/30 at the gunshow in Florida, from a local dealer. It is my second one, purchased at the gun show, and from the same dealer... First one is matching #, and shoots great.

Well, this second one was a rough built weapon. The bolt has a hand engraved number, the floor plate is a forced match, and the butt plate was new to this gun... newly engraved with the number, but no prior one...

The bolt closed without any cartridge. the bolt head was an obvious replacement, because though everything was from Izhevsk,
it was from Tula!

Stiff with a fired cartridge case, it only let the bolt handle go to the decock area, never closing... I was cautious even attempting to load a fresh cartridge.

FIRST, I made real certain the chamber was clean and free of any baked in gunk, cosmoline, residue...
Lightly sanded the lugs, (using 600 grit emory paper) until it closed, with a spent casing.
Each dozen strokes, cleaned, lightly oiled, and, I took the head, and inserted a new cartridge, with my fingers.

Finally, it all gently rotated and locked with no play! Re-assembled, it feeds the surplus Russian and Bulgarian ammo, just great!

But, the extractor face was rough, so, sanded it for about 24 strokes, and it now grabs the cartridge, and extracts it, good, too!
 
#29 ·
Couple things. One, congratulations on your new 91/30. Two, hopefully you didn't do any real damage.
Chambering a fired case, especially one fire-formed in a different chamber, tells you NOTHING. That fired case is oversized, so of course it doesn't fit. What you accomplished is to increase your headspace. Not surprising that the unfired ammo now fits fine. Had you tried to chamber an unfired round before "fixing" it, that would likely have fit fine too.

Luckily, headspace, even on the high side of acceptable, is seldom an issue w/ the Mosin Nagant. Just keep an eye on your primers for the first few rounds. If you get a full case head separation, then I guess you took off too much...
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top