Trying to keep up with Norm

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space
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Post by space »

Got another Mosin M44 today. It's a 1944 Izzy. Paid $90 for it today at a gun show and was worried when I got home and swabbed the bore.

At the gun show, they have trigger locks on them so you can't take the bolt out and even if you could, there was enough cosmo in there to choke a horse.

Took a lot of time to get the bore clean and it seems to be counter bored but I'm not sure. Definitely worn but still bright with no pits. The last inch of the barrel doesn't have any rifling but if they counter bored it they used a 30.5 cal drill to do it. All of the others I have seen were drilled out pretty deep. Anyway, just got back from the range and first 3 shots were all within an inch of each other at 50 yards and 1 inch left of center so I guess she's a keeper. Time to clean her up. Think I'll try to "re-float" the shellac.

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Post by normsutton »

Space

Sounds like you got another keeper
a one inch counter bore that's not bad at all
I have some Mouser's that I had to cut 6 to 8 inches off the barrel to get good rifling

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Post by barnett3006 »

why are Mosin bores counter bored?
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Post by abwehr »

barrnett3006,

When the rifle is shot a lot like the MN and Mauser rifles, the end of the barrel get the most wear. When the rifling gets so worn that there is nothing to stabilize the bullet when it is still in the bore, the accuracy suffers bad. But if you counterbore out the worn rifling, then the rifling left still stabilizes the bullet as it leave good rifling. Result, better accuracy and keeps for having to rebarrel. Not a bad idea for combat weapons.
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Post by space »

I thought it was simply an easy way to "re-crown" the barrel.
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Post by bzinggg »

I think there are a lot of people who might appreciate knowing what's important in creating a crown; what makes a crown good, or bad.

The critical part of a barrel crown is the very innermost edge of the inside circumference of the muzzle end of the barrel. The shape of anything outside that edge has little to do with accuracy. If that edge is even, when the bullet leaves the bore, the gases that are under pressure in the bore escape evenly around the projectile base as it breaks free of it's contact with the bore. If there is even a tiny nick in this very inside edge, gas will escape at a greater volume at that location, the force of which will push the flight of the projectile off the line of the axis of the bore as it extends out toward the point of aim. To demonstrate this principle, simply turn a garden hose on full force and put your finger over the end and feel how the pressure of the water will push your finger tip around more as you slowly lighten the pressure with which you are holding your finger in place. It's a crude analogy, but effective in demonstrating the ability of uneven pressure being able to push the flight of the bullet off to one side.
Last edited by bzinggg on September 2nd, 2007, 12:20 pm, edited 1 time in total.
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Post by abwehr »

Well stated "bzinggg"! I was not aware how crital the crown was until I was reading the information in SHotgun News from Midway. The big problem is the crowning tools are expensive to only do 1-2 rifles. The military rifles were fired so much, the last 1" of rifling was gone. Counterboring back 1-2" left good rifling.
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Post by bzinggg »

Yes, I suppose one has no choice but to counterbore because of the burn-off at the muzzle on the rifling. If the rifling is still good at the muzzle, as is sometimes the case where an accidental impact caused the imperfection on the crown, one can use the old brass screw in a drill chuck method and come out with a pretty good result. I think Norm should manufacture a crowning tool of some sort we all could borrow! ;D
Last edited by bzinggg on September 2nd, 2007, 4:49 pm, edited 1 time in total.
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Post by normsutton »

To re-crown a barrel I always used this


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Post by bzinggg »

Is that a freehand sort of a thing? Or do you use it in a drill press and have some way of clamping up the barrel vertically?
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Post by normsutton »

bzinggg

Free hand

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Post by carguy »

I know I'm not the sharpest blade in the drawer but by counter-boring you are saying that you literally drill out the rifling (remains of worn rifling) at the end of the barrel until you reach sharp rifling? And by having the same rifling where there is any and then no rifling at all where you've "counter-bored" it, you enable the gases to escape evenly around the projectile and keep it straight and on target?

So as I look down the barrel from the "dangerous" end, if mine has been counter-bored it will be missing rifling (bored smooth) to some depth down the barrel? Otherwise I may see good rifling or some representation of rifling right to the barrel crown?

And finally, if rifling appears worn and uneven then counter-boring may be helpful in improving accuracy. Sticking Norm's drill bit carefully down the bore?
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Post by bzinggg »

I believe that Norm uses that bit only lightly, without counter-boring. Just for as little metal removal as possible and still get a new, consistently radiused inside edge.

I think that when a barrel is counter-bored, it is cut on a lathe to a slightly larger radius than the caliber, deep enough to reach good rifling and also leave a complete newly radiused crown inside the barrel, as it steps down to the origional caliber. In other words, that last inch or so is opened up to a larger diameter so that the projectile no longer even touches it on the way out.
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Post by carguy »

So Norm...are you simply "cleaning up" the edge actually re-crowning the barrel with that bit?

I understand counter-boring must be done within extreme tolerences and I obviously oversimplified in my scenario. I have heard the term before but honestly never quite knew what it meant.

Thanks guys and you too Bzingg... ;D
Last edited by carguy on September 2nd, 2007, 7:51 pm, edited 1 time in total.
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Post by bzinggg »

:o :(

Write this on the blackboard 1,000 times: "The crown is only that small bevel on the inside edge of the muzzle." Then, go to your room.

;D

bZ.
Last edited by bzinggg on September 2nd, 2007, 8:52 pm, edited 1 time in total.
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