Mosin Nagant lug seating issues

[Steveoknievo]

After ordering a UK59 barrel awhile back I had the local gunsmith time the barrel and slap her on, as well as having the action blueprinted and boy is it nice to have the heavy barrel.

I Cerakoted the entire barreled action and bolt myself, and after using the rifle casually at the range I took down the bolt to do a routine cleaning.

I noticed that the only half of one of the lugs appears to be seating.. Is this normal? I had a Remington 700 blueprinted from the same gunsmith and both lugs were trued during that process, so I find it strange that the lugs are not seating uniformly like the Remington. Granted, it's not a Remington but shouldn't the same theory be applied to both?

Is this normal? I have several Mosins one of which is Cerakoted and it wasn't ever trued yet both lugs seat (half of each of the lugs show wear through a coat of Cerakote.)

I'm thinking this is the case partly because the receiver on the heavy barreled Mosin did not have a bolt handle (I purchased a stripped receiver and barrel from Classic Arms about 7 months ago, no bolt handle included..) The Cerakoted lugs on the Mosin that are seating more properly I think could be doing so simply because the bolt matches that of the reciever.. Your thoughts?

 

[Wannashootit]

Re: Mosin Nagant lug seating issues

You should never have painted the contact points on the bolt lugs.

I'm guessing that you're not having a problem chambering rounds- since you Cerakoted the rear face of the lugs after you got it back from the smith?

When the smith headspaced the barrel, he used (I assume) the same bolt that wasn't painted. Adding the thickness of the paint changed your headspace (decreased it) and since the 54R headspaces off the rim I frankly would have expected at least some difficulty chambering a round if the headspace was set correctly.

I'm not convinced you really know what's going on there, until you remove ALL the paint from the rear of the lugs. Then paint some Dykem on the back of the lugs, and see what you've got then.

The thickness, and uneven wear of the paint may be indicating a "problem" where one may not exist.

Did you ask the smith if he lapped the lugs? Sure as hell should have...but from the looks of your pic they seem awfully "rough" looking...

Range report? What load are you running?

 

[0933]

Re: Mosin Nagant lug seating issues

Yes, this is somewhat normal. The Mosin Nagant utilizes a floating bolt head, and there is PLENTY of slop in the bolt for the lugs to seat when the round is fired.

Just because there is some wear on just one of the lugs doesn't mean that the other one isn't bearing it's share of the load, it just means that the one lug is scraping the receiver.

With a Mosin Nagant 'blueprinting' could very well just involve squaring the receiver face with the threads... I can almost guarantee that your smith didn't lap the lugs. If that bothers you, then you can do it your self. Just take a case, cut it in half, and stick a worn out, cut down 1911 recoil spring in the case.

I've used this little 'tool' to lap the lugs of a few Mosin's. The benefit is arguable, but it can't 'hurt'. Also there are some fairly large ramps cut into the bolt raceway's. These are there to facilitate the closing of the bolt should there be grit, and dirt in the chamber area. Because of this, you'll only be able to get about 60% contact with each lug at best.

You mentioned that this was for a rifle with a UK-59 barrel on it. Something that will help accuracy ALOT is reloading neck sized cases for it. The UK-59 barrels had chambers cut around 0.020" deeper than normal. If your smith didn't trim the chamber end of the barrel, then the shoulder is blowing out to fill the empty space. You can get Lapua cases for $0.30 a peice here .

 

[Steveoknievo]

Re: Mosin Nagant lug seating issues

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wannashootit</div><div class="ubbcode-body">You should never have painted the contact points on the bolt lugs.

I'm guessing that you're not having a problem chambering rounds- since you Cerakoted the rear face of the lugs after you got it back from the smith?

When the smith headspaced the barrel, he used (I assume) the same bolt that wasn't painted. Adding the thickness of the paint changed your headspace (decreased it) and since the 54R headspaces off the rim I frankly would have expected at least some difficulty chambering a round if the headspace was set correctly.

I'm not convinced you really know what's going on there, until you remove ALL the paint from the rear of the lugs. Then paint some Dykem on the back of the lugs, and see what you've got then.

The thickness, and uneven wear of the paint may be indicating a "problem" where one may not exist.

Did you ask the smith if he lapped the lugs? Sure as hell should have...but from the looks of your pic they seem awfully "rough" looking...

Range report? What load are you running?</div></div>


I have an extremely hard time believing that cerakoting the locking lugs will affect the headspacing at all.. Even if it did, when closing the bolt it would have simply worn off the cerakote (in places it did) and where it didn't wear off I believe is because it simply wasn't touching originally. Even IF the cerakote is .005" thicker on one lug or another I don't believe that it wouldn't get worn off in the cycling process..

My smith did not lap the bolt, I discussed it with him and he said it was making enough contact to be safe so leave it be (more or less.) I did lap them myself anyway (just to make myself feel better).

The gun is shooting about a minute and a half with army surplus corrosive ammo (I don't have anything else yet)

 

[Steveoknievo]

Re: Mosin Nagant lug seating issues

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 0933</div><div class="ubbcode-body">Yes, this is somewhat normal. The Mosin Nagant utilizes a floating bolt head, and there is PLENTY of slop in the bolt for the lugs to seat when the round is fired.

Just because there is some wear on just one of the lugs doesn't mean that the other one isn't bearing it's share of the load, it just means that the one lug is scraping the receiver.

With a Mosin Nagant 'blueprinting' could very well just involve squaring the receiver face with the threads... I can almost guarantee that your smith didn't lap the lugs. If that bothers you, then you can do it your self. Just take a case, cut it in half, and stick a worn out, cut down 1911 recoil spring in the case.

I've used this little 'tool' to lap the lugs of a few Mosin's. The benefit is arguable, but it can't 'hurt'. Also there are some fairly large ramps cut into the bolt raceway's. These are there to facilitate the closing of the bolt should there be grit, and dirt in the chamber area. Because of this, you'll only be able to get about 60% contact with each lug at best.

You mentioned that this was for a rifle with a UK-59 barrel on it. Something that will help accuracy ALOT is reloading neck sized cases for it. The UK-59 barrels had chambers cut around 0.020" deeper than normal. If your smith didn't trim the chamber end of the barrel, then the shoulder is blowing out to fill the empty space. You can get Lapua cases for $0.30 a piece here .</div></div>

WOW! Very informative post, thank you so much. My gunsmith didn't lap the lugs, i did end up doing it myself today. I got around 60% contact and I'm happy with that. The general slop in the bolt did sort of make me feel like what you stated was happening, but I still wasn't satisfied (as I'm sure you can understand) so I did lap the bolt myself. The tool you have made is a very great idea and I must say I am going to make one as I have plans for another UK59 barreled mosin in the future (I bought several of them with stripped receivers from classic arms)

As far as reloading them is concerned, I do not currently reload but I do have a starter kit en route so I plan to get started soon. When you say 0.020" deeper than normal, do you suggest that I load the bullets longer in order to compensate? (Sorry, I'm a novice in this regard hence the stupid question..)

Thanks both of you for the reply it has cleared up a lot of my questions.

 

[Steveoknievo]

Re: Mosin Nagant lug seating issues

Here are some pics I took of the lugs after lapping. I made tremendous progress relatively quickly. I wonder if this will negatively impact the headspacing now? I wouldn't think such a minimal amount of lapping would make a headspace issue appear? Then again if a coat of paint on the locking lugs will throw off headspace I'm not sure.. How much material do you reckon is taken off? 0.002" or 0.003"?

 

[0933]

Re: Mosin Nagant lug seating issues

The 7.62x54r headspaces off the rim. The rim thickness of milsurp, and newly manufactered rounds can be anywhere between 0.056" to 0.062". 62 thousandths is considered minimum headspace. The no-go gauge is 68 thousandths thick, and the Field gauge is 72 thousandths thick. Lapping the lugs probably took off a couple thousandths, so even if you had the max headspace of 0.068" you would still pass the field gauge. I'm sure your smith didn't set the headspace to the max, he probably set it closer to the min. I doubt that you would have affected the headspace in any real way. It's definitely not dangerous in any way.

As for the chamber being deep, it ties in with being a rimmed round. Rimmed rounds headspace off the rim. The rim keeps the round from dropping further into the chamber. The Russians and the Brittish stayed with rimmed rounds when they developed new rifles for the new smokeless powder. The Mauser magazine wouldn't feed rimmed cartridges reliably, so they developed a rimless cartridge, The U.S.A. went with a rimless round also because of the staggered feed magazine in the 1903. Rimless cartridges headspace off the shoulder of the case. If there is a significant amount of dirt in the chamber, you will not be able to chamber a round. Rimless cartridges on the other hand headspace off the rim... the chamber can, and often was, cut fairly larger than the outside dimensions of the case. This made the rifles more reliable because the extra space could accomodate more dirt and grit while still having enough room to chamber the round. The Brittish SMLE's are notorious for having large chambers. The Mosin Nagants didn't have quite as big chambers, but they did have more tolerances than there rimless feeding counterparts. I have a sporterized Russian Mosin Nagant and after firing a round in it, the shoulder portion of the case is about 0.008" further forward. If you measure the shoulder portion of a case fired in your UK-59 barrel and compare it to a loaded round, you'll find that the shoulder is around 0.020" further forward. If you take that case and only neck size, you are effectively making the cartridge headspace off the shoulder instead of the rim. By just neck sizing, you'll extend the life of your brass and because the case is 'filling' up the chamber, you're going to get a more consistent pressure curve.

When you do start reloading for it, I recommend the 174 grain .311" SMK and IMR 4350.

 

[Wannashootit]

Re: Mosin Nagant lug seating issues

Me, I would check the headspace if you lapped the lugs after the barrel was already headspaced, but that horse has already left the barn, as the saying goes. Lapping is most always done before headspacing, as it WILL affect headspace if any material is removed from the lugs, it's just a matter if it's enough to make a difference.

Keep in mind that a piece of cellphane tape is .001-.002 typically.

I just used a piece of it on a sized casing to headspace a new Savage barrel. Difference between go, and no-go...I like my headspace tight- better brass life because it doesn't get worked as much when sizing.

So, I don't know that the mil thickness of cured Cerakote is, depends on how thickly you applied it. Doesn't really matter, since the smith headspaced it off the bolthead before you painted it.

In any case, lugs are a "contact" part with tight tolerances, so they should not be painted...

 

[9H_Cracka]

Re: Mosin Nagant lug seating issues

The Pattern 14 Enfield and the The US Rifle, caliber .30, Model of 1917, both based off the same action/bolt/stock/magazine system, both reliably feed the 303 Brit rimmed round and the 30-06 rimless round with minor follower and bolt modifications.

The German action changes were not from necessity.

 

[Steveoknievo]

Re: Mosin Nagant lug seating issues

Maybe I'm dense here.. But I don't understand how the headspace is affected much by lapping the lugs.

My gunsmith headspaced the action with the lugs free of cerakote. I then cerakoted the entire bolt (theoretically decreasing the headspace), found that only some contact was occurring through the cerakote, and proceeded to lap the lugs to get them more uniform (increasing the headspace once again).

If the smith headspaced my action prior to being cerakoted and I lapped the lugs so only some of the cerakote is gone, I fail to see how the headpace is dramatically affected at all.. Since the lugs are back to being bare metal (for the most part)...


If I start out with 1, add 5, and then proceed to take away 5, don't I end up with 1 again? Maybe I'm over simplifying it..

I understand that it's not going to be EXACTLY what was headspaced by the gunsmith but I mean really, some folks say not to even go by the "No-Go" gauge, that I should use the field gauge instead.. My bolt will not completely close on a no-go gauge anyway (which is a good thing obviously), but I just don't see what's so extremely critical about the additional thickness cerakote creates, or the decreased cerakote from lapping?

 

[Wannashootit]

Re: Mosin Nagant lug seating issues

Like I said, smith headspaced with the un-painted bolthead...so unless you removed a lot of metal from the front face of the lugs, no harm, no foul...

I checked the Cerakote specs, and if applied correctly is only one thou thick...so you're correct, it's not a huge difference. But, if it's uneven, or worn on one lug and not on the other creating unevenness, then you're defeated the whole purpose of lapping, which is to get even contact across both lugs. In any case, it's always recommended not to paint the lugs, it's easy enough to mask them off.

Look at it like this...
Far as I know (and someone can correct me...), a "go" gauge for the 54R is .063, "no-go" is .070, so .007 is the maximum " slop" allowed from the face of the bolt, to the rim of the cartridge when seated against the chamber.

How "tight" we want to keep this, depends on the use of the rifle.
Military rifles are intended to be a bit on the loose side...don't want a tiny speck of crud to cause you to be unable to chamber a round and end up dead...
OTOH, if you're building a "precision" rifle- as you did- you want these tolerances fairly tight.
You're going to be shooting handloads, so the tighter you keep the base of the shell to the boltface, the less room it will have to expand and allow the brass to flow- increasing your brass life.

In your case, the smith should have headspaced the barrel until it just closed on the "go" gauge.

The "go" gauge is minimum SAAMI headspace- and that's what we want. Benchrest shooters with very tight chambers, custom reamed to specific ammo from their dies, may have headspace even tighter than "zero". This is inconsequential unless they try to shoot factory ammo, which might not chamber, or chamber with difficulty. But this wouldn't apply to rimmed cartridges like the 52R

Far as the field gauge....that's a matter of opinion.
The Civilian Marksmanship Program (CMP) where we can buy such goodies as the Garand, will REJECT any weapon that does not pass a no-go gauge.
Passing a field gauge merely means the weapon is safe- but it's on the margins (if it failed the no-go)- and is only going to get worse.

 

[Steveoknievo]

Re: Mosin Nagant lug seating issues

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wannashootit</div><div class="ubbcode-body">Like I said, smith headspaced with the un-painted bolthead...so unless you removed a lot of metal from the front face of the lugs, no harm, no foul...

I checked the Cerakote specs, and if applied correctly is only one thou thick...so you're correct, it's not a huge difference. But, if it's uneven, or worn on one lug and not on the other creating unevenness, then you're defeated the whole purpose of lapping, which is to get even contact across both lugs. In any case, it's always recommended not to paint the lugs, it's easy enough to mask them off.

Look at it like this...
Far as I know (and someone can correct me...), a "go" gauge for the 54R is .063, "no-go" is .070, so .007 is the maximum " slop" allowed from the face of the bolt, to the rim of the cartridge when seated against the chamber.

How "tight" we want to keep this, depends on the use of the rifle.
Military rifles are intended to be a bit on the loose side...don't want a tiny speck of crud to cause you to be unable to chamber a round and end up dead...
OTOH, if you're building a "precision" rifle- as you did- you want these tolerances fairly tight.
You're going to be shooting handloads, so the tighter you keep the base of the shell to the boltface, the less room it will have to expand and allow the brass to flow- increasing your brass life.

In your case, the smith should have headspaced the barrel until it just closed on the "go" gauge.

The "go" gauge is minimum SAAMI headspace- and that's what we want. Benchrest shooters with very tight chambers, custom reamed to specific ammo from their dies, may have headspace even tighter than "zero". This is inconsequential unless they try to shoot factory ammo, which might not chamber, or chamber with difficulty. But this wouldn't apply to rimmed cartridges like the 52R

Far as the field gauge....that's a matter of opinion.
The Civilian Marksmanship Program (CMP) where we can buy such goodies as the Garand, will REJECT any weapon that does not pass a no-go gauge.
Passing a field gauge merely means the weapon is safe- but it's on the margins (if it failed the no-go)- and is only going to get worse.

</div></div>

Lots of great info man, thank you very much. This is why I come to the Hide!

 

[Wannashootit]

Re: Mosin Nagant lug seating issues

PICS!
Finished with the build? Select a stock/mount/optic yet?
Details, man...details!

 

[Steveoknievo]

Re: Mosin Nagant lug seating issues

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wannashootit</div><div class="ubbcode-body">PICS!
Finished with the build? Select a stock/mount/optic yet?
Details, man...details!</div></div>

I did take one picture before I lapped the lugs. I took it back to the smith just to double check that everything jives and is safe (better to be on the safe side as any doubt at all is something I'm not comfortable with considering it's an explosion right next to my face...)

The picture quality sucks but I'll get better pics once I get it back from the smith. The scope was temporary, I have an HDMR with the H59 reticle that will be used.. But I cannot use it with the LT120 mount it came with because it's got the Rock Solid mount on it, and it's not a solid picatinny. I am currently making my own for it and I'm using the Rock Solid as a guide, so that will be soon as well. It's about a 1.5 MOA gun with military surplus ammo (which to me is quite good considering the fact that it's a Mosin Nagant!!)

It's sitting in an HS Precision that I bought on the cheap, as the fella who owned it before me jacked it up. He tried to put in lead weights in the front and I guess he tried prying them out of the epoxy, and broke through the bottom of the stock, so I converted it from a Remington 700 stock to a Mosin Nagant stock!