Customized Mosin Nagant not holding zero

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cm_machinist

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Hey guys.

I'm having issues with sighting in my Mosin. It's a customized 1891/30 with a round receiver. What I did to it was I replaced the wood stock with an Archangel stock, shortened the barrel to 22" and threaded on a muzzle brake, installed a JMECK scope mount and attached a Harris bipod to the stock. My scope is a Vortex Diamondback 4-12x40 AO. Not that it would have any effect on functionality, but I also made a bent bolt handle.

What happens is I can shoot 100 yards, and get 1" groupings. But after I shoot a few rounds, then my shots seem to go all over the place. Upwards of 6" away from the initial points of impact.

I'm not the best shot in the world by any means but I know I'm more steady than that.

I have a few ideas of what my problem could be, but I just wanted to hear some opinions on the matter.

1) Heat of the barrel after a few shots.
2) Rigidity of the JMECK mount. (I had issues last autumn with my mount but I contacted the manufacturer who helped me out and examined photos of my mount. He said it appeared everything was installed correctly)
3) The barrel tensioner on the Archangel stock not being utilized properly.

I loctited the screws on my mount with Loctite Purple. I used a Wheeler FAT wrench to torque them to the right spec. I'm starting to doubt the reliability of the JMECK mount. I got it because I heard good reviews about it. I'm starting to look at the Rock Solid Mount, now that it's available through a Canadian retailer. What are your guys' thoughts on the matter?

Thanks
 
My first guess would be heat. After a few shots the barrel is heating up, possibly touching your barrel tensioner differently, etc. Next time you're out take a few shots, let it cool for a bit while you shoot something else, then come back and see if it's throwing them all around, or if it's closer to what you had on the first few shots.
 
I was shooting MFS 185gr full metal jacket. The barrel gets quite hot after only a few shots. I'm wondering if the receiver is expanding just enough from the heat to shift my mount.
 
Doesn't the AA stock have a screw/function to go from free floating barrel or not free floating?
Mosins were designed with tight wrapped barrels so maybe tighten it down?
 
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I'm not sure if I should keep it free floating or not. Has anyone tried using the barrel tensioner? How much is too much pressure?
 
I couldn't get mine to hold zero either, so I went back to the irons and can shoot 2 MOA @100 and think im going to stick with that. Tried 3 different aluminum scope mounts/rings that all came loose after gun heated up.

I might look into some steel rings and weld them to the dovetail but so far I can keep it under 8" groups at 300 yards with irons so think it will get the job done for hunting which is all I really care about.
 
cm_machinist said:
Because I wanted to. Make something old look new again. And 7.62x54R is an inexpensive round.
Click to expand...

No I get that, I didn't ask why lol I just said the reason your Mosin is acting weird is because you modified it.
I have a 91/30 I cut down into a 20" barrel length, recrowned, bedded the stock, did a trigger job, opened up the rear sight notch, opened up the barrel channel to make sure there was nothing contacting it etc.
It shoots amazing now (for a Mosin). I always found the problems started when I tried to put it into something like a seperate stock or trying to "free float" the barrel yadda yadda, accuracy always got worse.
 
Does the zero return or the groups get smaller & closer to the point of aim after it cools? If so, then its a barrel pressure/bedding issue. If not, its a scope/mount issue. Most scope mounts for mosin are pure feces attached to the rifle with tiny screws & no thought of fitting to the action.

If you want a real shooter, forget the plastic, replace the barrel with a new one from a heavy 308 blank, bed a boyds & make your own mount from steel so you can get some real purchase on the receiver.
 
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