I am installing a bull barrel on a Mosin ,I hand tightened the receiver then torqued it another eighth of a turn checked the headspace with a PTG headspace gauge ,go gauge, I cannot close the bolt should I get a chamber reamer and go from there? My other question is can the extractor cut be done on my drill press with a end mill bit or other tool?
Mosin Nagant new barrel
- Thread starter Robert E
- Start date
dakota.potts
New member
Did you ream the barrel yourself?
There is a possibility it was not reamed to full depth or the rim cut was insufficient. You may have bought one that was intentionally short chambered to fit with whatever rifle you would put it on. You may have not reamed it deep enough or alternately may need to go a little deeper for proper headspace considering the amount of torque on the barrel.
How far does the bolt attempt to close without significant resistance? Do you also have a no go or field gauge. I would definitely recommend one or both or seeing if you can borrow them
There is a possibility it was not reamed to full depth or the rim cut was insufficient. You may have bought one that was intentionally short chambered to fit with whatever rifle you would put it on. You may have not reamed it deep enough or alternately may need to go a little deeper for proper headspace considering the amount of torque on the barrel.
How far does the bolt attempt to close without significant resistance? Do you also have a no go or field gauge. I would definitely recommend one or both or seeing if you can borrow them
What'd you use for a receiver wrench? Just curious.
This an unfinished barrel or a pre-chambered one? Unfinished means you get to finish ream it until the bolt closes on the Go, but not the No-Go. Pre-chambered means the barrel doesn't quite fit and it'll need a bit of turning.
If the barrel isn't a .311" ID you're going to have grief loading for it too. Expander button will be too big. Easily fixed though. Expander buttons are usually interchangeable. Depends on your dies, of course. Also assumes your still using 7.62 x 54.
This an unfinished barrel or a pre-chambered one? Unfinished means you get to finish ream it until the bolt closes on the Go, but not the No-Go. Pre-chambered means the barrel doesn't quite fit and it'll need a bit of turning.
If the barrel isn't a .311" ID you're going to have grief loading for it too. Expander button will be too big. Easily fixed though. Expander buttons are usually interchangeable. Depends on your dies, of course. Also assumes your still using 7.62 x 54.
When rebarreling a Mosin you should set the shank to fit the receiver to proper depth and cut the relief for the extractor before you cut the chamber. You should be able to close the bolt on the new barrel without any chamber cut at all.
Then you cut the chamber and set the headspace. I do them with .003" headspace.
I do not have a mill myself, so I have to cut the extractor relief with a die grinder and hand chisels, but I can do one in about 20 minutes.
Then you cut the chamber and set the headspace. I do them with .003" headspace.
I do not have a mill myself, so I have to cut the extractor relief with a die grinder and hand chisels, but I can do one in about 20 minutes.
Oh boy...where do I start?
Lemme guess...McGowan? I have three of their "prefits" in here now ( I don't know anywhere else you could obtain a bull barrel in .311, that would be threaded to fit the MN receiver).
You apparently didn't realize these require gunsmithing (McGowan states this)- either professional, or hobbyist with a lathe- to install.
You're in over your head, if you even need to ask these questions- no offense, this isn't a Savage project.
Assuming still you have a McGowan, it's fully chambered (at least, it's supposed to be. I had one that wasn't and needed to be reamed a few thou).
Headspaces off the rim. Even if the chamber needed to be deepened, that has nothing to do with the bolt not closing on the go gauge. There could be NO chamber cut (as Wyosmith alluded to), it's all off the breech.
Now the odd part...McGowans are supposed to be short-shouldered, meaning the shoulder gets set back on a lathe to headspace. Last couple I got, were very close to spec- not sure why. I'd rather have 20 thou to turn off than 2 or 3.
Anyway, if headspace is too tight the breech needs to be set back, and the chamber reamed back to depth.
I hesitate to even ask...but you did remove the extractor from the bolthead, right?
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Yes,
I made a headspace gauge that is headspace plus one thread turn.
This allows me to check headspace with the extractor still on the bolt head.
Or
Mosin bolt heads measure much the same on the Granite surface plate, and you could have a spare bolt head with the extractor removed.
The reason the mosin extractor design is so narrow is so the bolt can rotate 90 degrees and still have the extractor relief cut is small enough so the case rim still has more than 180 degrees of support to stand up to the firing pin.
I helped rebarrel this rifle that shot an antelope last week.
The rifle was purchased in the 1960s for $9.95.
It now has a surplus springfield barrel. We used a floating pilot to fit the 308 groove barrel.
I made a headspace gauge that is headspace plus one thread turn.
This allows me to check headspace with the extractor still on the bolt head.
Or
Mosin bolt heads measure much the same on the Granite surface plate, and you could have a spare bolt head with the extractor removed.
The reason the mosin extractor design is so narrow is so the bolt can rotate 90 degrees and still have the extractor relief cut is small enough so the case rim still has more than 180 degrees of support to stand up to the firing pin.
I helped rebarrel this rifle that shot an antelope last week.
The rifle was purchased in the 1960s for $9.95.
It now has a surplus springfield barrel. We used a floating pilot to fit the 308 groove barrel.
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Interesting idea with a shimmed .0625 heavy disc for a gauge, but
I don't follow the relevance of the height from base of bolthead to it's face.
The critical dimension is from the back of the locking lugs to the boltface, and I find significant variation there. If I'm looking to pick up- or lose- a couple thou of headspace I dig into the box 'o boltheads.
I don't follow the relevance of the height from base of bolthead to it's face.
The critical dimension is from the back of the locking lugs to the boltface, and I find significant variation there. If I'm looking to pick up- or lose- a couple thou of headspace I dig into the box 'o boltheads.
Gunplummer
New member
That works fine. I used to set two blocks on top of the 1-2-3 blocks and use a depth mic. I made quite a few Arisaka bolts that way.
Aha!
Shimmed em up off the lugs on 123 blocks off the plate....figured you weren't measuring off the base but didn't know how you were holding them. Just gave me an idea...bore out a faced-off aluminum "tube" and just drop in and measure. I should take a couple hours one day to do that and measure/sort/label them.
Shimmed em up off the lugs on 123 blocks off the plate....figured you weren't measuring off the base but didn't know how you were holding them. Just gave me an idea...bore out a faced-off aluminum "tube" and just drop in and measure. I should take a couple hours one day to do that and measure/sort/label them.
Gunplummer
New member
No, they are not the same material. Arisakas bolts are 4140. At the time, I had no way to reliably case harden high power bolts. Even the Moisin bolt heads I made were 4140. I thought it was better to mix materials than to make up something that may or may not be up to it.