Rebarreling Mosin Nagant

Discussion in 'Technical Questions & Information' started by Mosin_Nagant_Fan, Oct 18, 2008.

  1. Mosin_Nagant_Fan

    Mosin_Nagant_Fan Active Member

    Joined:
    Jan 18, 2007
    Messages:
    1,842
    Location:
    Montgomery, AL
    I recently got a M91/30 barrel in very good shape, only minor, superficial, pitting. I was thinking about getting a Mosin with a bad barrel and try to rebarrel it with the barrel (or have someone do it for me). Number matching doesn't matter to me since not all Mosins have matching numbers.

    I really want to do this because 1.) I like doing stuff with my hands 2.) I like building stuff (i.e. building computers).
  2. LDBennett

    LDBennett Well-Known Member

    Joined:
    Dec 20, 2003
    Messages:
    6,920
    Location:
    Hesperia, CA
    Mosin_Nagant_Fan said:

    "I really want to do this because 1.) I like doing stuff with my hands 2.) I like building stuff (i.e. building computers)."

    ME TOO! But......

    When I retired about 12 years ago I bought a lathe sized to be able to re-barrel guns. I had picked up a Ruger Model 77 in 243 in a distressed condition (mild surface rust that disappeared when treated with 0000 steel wool and Hoppe's) with the intent of re-barreling it. My caliber of choice was 6mm Bench Rest.

    To make a long store shorter, I was sucessful, but it was absolutely no cake walk. I picked up every book I could find on rebarreling guns only to find that it was a precision task at the very limits of my cheapy Chinese lathe. I managed but the precision required was beyond my initial belief. And the looseness of my Chinese lathe/mill was unbelievable. And finally I'm an engineer not a machinist! I have had to learn how to machine parts by trial and error, mostly error.

    So I suggest you read every book on how to do it so you can appreciate what is required. AGI makes a video on rebarreling modern guns and one on rebarreling a Mauser. I have the first video and it covers the subject well and all it has to say would cover a Mosin Nagant, at least from the view point of fitting a barrel blank to the receiver. Now you have to worry about contouring the outside of the barrel to fit the rest of the gun. My Ruger did not need any barrel contouring. It took me a year to make the tooling and get up the nerve to start the actual barreling which took several days on the lathe.

    The biggest problem I had was threading the barrel blank since the threading had to be done up to a shoulder that seated against the receiver. My lathe had no threads counter or fast stop brake. I could not disengage the saddle as that would have got the cutter out of sync with the threads. I had to stop the barrel from turning with my hands after timing the turn off of the lathe motor, back the cutter out and move the cutter back with the saddle still engaged and the motor running backwards. Later someone suggested running the cutter on the backside of the barrel and running the lathe backwards so that the cut was from the shoulder and out...DUH.... I did say I'm not a machinist, didn't I.

    Anyway, know what you are getting into before starting, unlike what I did. The lathe has not gone to waste as, for that same 12 year period, I made tons of parts for our vintage racing motorcycles. I would never take on a re-barreling project again on this lathe and probably not on a better lathe (which is absolutley NOT in my future).

    Some of these surplus arms have barrels that look terrible and some that look great. But looks are not the whole picture. Some crummy looking guns with pitted barrels shoot really good and some that have nice shinny barrels may have a shot out throat which leads to bullets sideways on the target. I have had both examples! Shoot the gun first before deciding that it really needs a new barrel. You may be surprised. We (me and my son-in-law who has a huge collection of surplus arms) have also found that the original sights are often the limit on accuracy. My Mosin-Nagant has a period scope and mount on it and that bettered the accuracy significantly. The scope moved that particular gun from just shooting OK to being pretty accurate (out to 600 yds!). Its another story but I would never put a scope mount on one of these guns again as there is more to it than meets the eye and $100 for a good gunsmith who does it all the time is money well spent.

    LDBennett
  3. Mosin_Nagant_Fan

    Mosin_Nagant_Fan Active Member

    Joined:
    Jan 18, 2007
    Messages:
    1,842
    Location:
    Montgomery, AL
    I will agree with you about testing out my next gun before I try rebarreling it, I may just use this barrel to practice recrowning and I will try to find books on both topics, since I may still try out rebarreling in the future.
  4. LDBennett

    LDBennett Well-Known Member

    Joined:
    Dec 20, 2003
    Messages:
    6,920
    Location:
    Hesperia, CA
    Re-crowning is actually easy and accurate if done the easy way.

    The biggest problem is getting the crown concentric with the bore. You need either a piloted cutter that runs a pilot in the bore or use an crown that is center independent. The pilot of of a piloted cutter must 1). be accurately made, 2) fit the bore tightly, and 3) not mar the bore when it revolves. I think it easier to use a center independent crown profile. And what would that be? A 90 degree crown. That is, a crown that is cut 90 degees to the bore centerline. Any other angle or profile has a center that has to be put on the bore's centerline.

    Testing and physics show no advantage to the 11 degree crown or rolled edge crowns over the 90 degree crown. There is nothing magic about the 11 degree crown regardless of the common belief that it makes a difference. Science disagrees as does testing.

    The easiest way is to but the barrel in a three jaw self centering chuck in the lathe. While the bore may not be on the same centerline as the outside of the barrel and you would normally have to use a four jaw independently adjustable chuck, for the 90 degeree crown it makes no difference and the barrel being on the centerline of the bore is not important. When you pull the cutter across the end of the bore it is automatically at 90 degerees and since such cut has no center, the cut is perfectly at 90 degrees and completely uniform around the end of the barrel. This assumes you lathe is setup accurately and not damaged.

    I make my crowns recessed 90 degree cuts and with the Brownell's crown sherical lapping tool and grinding paste I chamfer the bore to crown cut. The lap is self centering and the chamfer goes from the top of the lands to just below the bottom of the groves. The chamfer is done to remove the burr created by the lathe cutter. No matter how fine the cut with the lathe cutter, there is always a burr where the cutter pulls metal from the land and into the groove so the lapping chamfer eliminates the burr.

    Sorry to be so technical but info like this is not easily found. It took me years to figue this out as few books tell you why crowns are made as they are. Most only show you how.

    LDBennett
Similar Threads
Forum Title Date
Technical Questions & Information rebarreling a 1903 Springfield Jul 28, 2005
Technical Questions & Information 45-70 Mosin Nagant conversion questions Nov 15, 2014
Technical Questions & Information mosin nagant slugged barrel vs ammo Jun 7, 2014
Technical Questions & Information Mosin Rear Sight Leaf Spring Mar 13, 2014
Technical Questions & Information Mosin M44 barrel bands Mar 6, 2014

Share This Page