Question about weird accuracy loss, SVT40

Zedbra said:
My Zeiss shook loose inside on my K31 with under 6 months of use - so it isn't Burris, some rifles just shake the mounts harder than others. Anyways, this has nothing to do with the OP's issue.
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Good info ..Thanks. So was the Zeiss damaged and fix/replace under warranty?
 
milsurpo said:
I've had individual SVT's that simply wouldn't group but never one that had accuracy fall off after a mere 20 or 30 shots. Part of the challenge with SVT's is that there was never a "National Match" version with associated accurizing tips like, for example, the Garand. You have to start with proper bedding as the refurb SVT's are all over the page in fit. You have two choices- either go for solid up-pressure at the forend tip (as in the earliest SVT 40's) or fully floated at the tip (as I see in some refurbs but more importantly in the '43 Bulgarian light refurbs I've owned). In the first type the barrel is supported by a metal ring in the lower guard and the Soviets concluded that the biggest problem was the lower guard (which just slips over the wood) being loose and moving after initial shots. You can try shimming the guard to make it really snug but the front end cannot be in contact with the flange under the gas block when cold or heating and lengthening of the barrel will alter the POI (same thing applies to Garand guards). I've seen improved accuracy with 5-7lb up pressure. Shims under the rear of the receiver are the easiest way to increase up-pressure. My best luck with accurizing came with fully floating the barrel at the front. This can be done by sanding if your rifle has the later lower guard without the barrel support ring but the best approach is to inlet the top of the upper rear deck of the stock to let the receiver sit down a bit lower which rotates the barrel up. This is how it was done by the factory on my "43's. Group sizes with my $200 Lever Christmas special gun dropped from 6" to 2" by floating. Note that many of the refurbs come with really marginal bedding- receiver free to move front to rear or side to side. It seems logical to tighten things up but it won't always improve accuracy. Can progressive heavy fouling (of bore and/ or gas system affect accuracy? I really don't know but I have observed POI of 5 shot groups changing dramatically (almost a foot) as I've changed the regulator setting which is pretty weird. The fact that SVT Sniper production was halted in favour of the PU probably tells us that the Soviets couldn't come up with any practical "fixes" for the accuracy issues.

milsurpo
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Thank you for this! I have been searching for a detailed explanation.

I had heard soldiers would put 1/8" birch strips under the front handguard ring to generate up pressure. So I put shims using 3 strips cut from a coke can in that spot. Did it a month ago and then General Winter arrived so I am just waiting for some semi warm weather to try this and see if accuracy improves.

Lee Enfield with its skinny barrel also likes up pressure.
 
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GUB said:
Scope loosens inside under recoil.. I'm having that with a Burris now.. Sent it back ..told it is fine
will not be going back on my K31
Burris is junk only good for a .22 maybe!!
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Some of the Burris is now made in the Philippines.
 
GUB said:
Scope loosens inside under recoil.. I'm having that with a Burris now.. Sent it back ..told it is fine
will not be going back on my K31
Burris is junk only good for a .22 maybe!!
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The only two scope failures I ever have were Burris optics. One was a scout scope of unknown history it's reticle became lose and the other was a 2-7 compact that IIRC was possibly made in the Philippines (maybe?) in partnership with Nikon. Lost its nitrogen seal.
Both repaired very quickly, but I don't trust them.
 
1 . once your accuracy drops off . try cleaning your rifle at the range, and shooting it after it cools down. check the muzzle brake for crud build up .
2. once you start shooting the heat could be drying out your stock causing it to warp . is the humidity different where you store it than out side. (basement)
3. try a recoil pad.
4. does the outside temperature change the issue . summer vs winter.
 
Likely heat...causing barrel to whip. I've had my notched SVT40 and after a couple of mags it loses accuracy. POI strings vertically on the target but not so much horizontally.
 
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