Svt-40 firing 2 round burst

All the most probable causes were advised (gas system, trigger unit, firing pin) so I'll add least probable one - try to change ammo. Any combloc surplus should be fine, not all SVT-40 digest Chinese and avoid commercial unless you are really know what you're doing.

P.s. noticed you replied with Barnaul. Don't shoot it. Grab Soviet or Bulrarian surplus. These are what SVT-40 was designed around.
 
Horilka said:
All the most probable causes were advised (gas system, trigger unit, firing pin) so I'll add least probable one - try to change ammo. Any combloc surplus should be fine, not all SVT-40 digest Chinese and avoid commercial unless you are really know what you're doing.
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This was the ammo, heard it was pretty good and never had any other issue with it. I knew chinese stuff was not good in svt

https://www.gotenda.com/shop/ammunition/bulk-ammo/mfsbarnaul-7-6254r-174gr-fmj-case-500/
 
There is solid discussion on GB about how commercial ammo can kill your SVT-40. I won't go into details on what's possible and what's not. However from basic troubleshooting point of view, use what rifle was designed for at this stage.
 
Horilka said:
There is solid discussion on GB about how commercial ammo can kill your SVT-40. I won't go into details on what's possible and what's not. However from basic troubleshooting point of view, use what rifle was designed for at this stage.
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I know they are sensitive to heavy ball or light ball and that heavy ball can damage the rifle. I have no idea why commercial ammo would be bad if its light ball.

I took it appart. Firing pin move freely and spring look strong enough to prevent inertia to set off a round. Sear and hammer look fine to but im no expert so i took these two pic. The finish is still all there they dont look worn out or anything.

1-B900-FBB-B108-48-BF-A9-AB-4-A99-A7-B994-DE.jpg

F73-B3663-CEA5-4-A00-B4-F6-B4-E809801-D7-A.jpg
 
M1-Garand said:
Hammer and sear look fine.
Maybe let someone else shoot it and see if the problem is still there,could be trigger control?
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Thats my next step. Im gonna bring it next time i go to the range and try to pull the trigger harder and see if it still does it. Let someone else try it is a good idea too thanks
 
gewehr76 said:
OP. You probably have weak Firing Pin spring in the bolt. Its critical that the FP stays below face of the bolt when rifle cycles. If spring of FP is weak, inertia of the bolt closing on second round allows FP to protrude past resistance of the spring and reach the primer, thus firing second round without pulling the trigger. You have to go to the source of the problem, remove FP from the bolt, clean and inspect FP channel in the bolt, inspect for abnormal wear and sand areas of FP that can cause it to bind and stay protruded past bolt face.
I had similar issue with one of my SVT when using reloads with soft primers, bursts of 3-4 rds were common. After swapping FP and spring in the bolt problem went away.
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I had the same issue - though it is odd that it is exactly 2 rounds and not the whole mag ;)

remove that third round before firing and examine for a light strike.
 
Ced1942 said:
I know they are sensitive to heavy ball or light ball and that heavy ball can damage the rifle. I have no idea why commercial ammo would be bad if its light ball.

I took it appart. Firing pin move freely and spring look strong enough to prevent inertia to set off a round. Sear and hammer look fine to but im no expert so i took these two pic. The finish is still all there they dont look worn out or anything.
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they do look un-messed with. though a visual examination of the pin and spring can't tell you much - the spring may look fine but it may not even be the correct spring! - hopefully you have access to another/someone SVT who can loan you the bolt & trigger group.

but it is odd that you get 2 round bursts and not 2/3/4/5 .... even poor trigger control isn't as consistent as that.
 
M1-Garand said:
I had the same problem in mine,taking a close look at the trigger group it became obvious that someone in the past had done
a "trigger job" on the hammer,only small groove left for the sear to engage.
Solution was to replace the hammer,problem solved,cycles perfectly on 1.2 gas setting,brass comes out with just a minute dent
on the side.
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I will add my anecdotal evidence to this theory. Had a FN49 that would very rarely fire two rounds with one trigger pull. Solution turned out to be replacing the hammer. Old hammer must have occasionally slipped and fired as the bolt closed, just not quite enough engagement. Just eye balling the parts wasn't enough to identify this problem though.
 
Take it to a gunsmith for repair or replace the trigger group components on spec.
The 1st components I would try in an old milsurp are the springs in the fire control group. Likely weak after 70 + years.
 
webman1 said:
Take it to a gunsmith for repair or replace the trigger group components on spec.
The 1st components I would try in an old milsurp are the springs in the fire control group. Likely weak after 70 + years.
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Gunsmith is not an option there is none in town.

sean69 said:
they do look un-messed with. though a visual examination of the pin and spring can't tell you much - the spring may look fine but it may not even be the correct spring! - hopefully you have access to another/someone SVT who can loan you the bolt & trigger group.

but it is odd that you get 2 round bursts and not 2/3/4/5 .... even poor trigger control isn't as consistent as that.
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I really wish i had a second SVT on hand to do as you say and switch trigger assembly buy sadly i dont and my only gun friend doesnt have one. I will check the 3rd round for a light strike next time i shoot it that is a good idea thanks. And its really consistent. I had a few time two-two round burst over one single 5rnd mag.

gewehr76 said:
Did you try any other brand of ammo? Any surplus?
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Haven’t and its a bit tricky to do. 7.62x54r can’t be bought local here and having a 20rnd box of different ammo shipped here is not the cheapest thing. We usually buy once and shoot what we ordered over summer. Ill see if i run out of pistol ammo i might have to order a big batch thAt way i could maybe get a few box of different 7.62x54r if tenda has some in stock
 
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Ced1942 said:
Haven’t and its a bit tricky to do. 7.62x54r can’t be bought local here and having a 20rnd box of different ammo shipped here is not the cheapest thing. We usually buy once and shoot what we ordered over summer. Ill see if i run out of pistol ammo i might have to order a big batch thAt way i could maybe get a few box of different 7.62x54r if tenda has some in stock
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Well that's the thing 20 rds is nothing for SVT you won't even notice it. You just dirty up the rifle. Probably get a crate of particular surplus brand at least and shoot it. Surplus has harder primers and they seated deeper in the case, this may remedy the problem.
 
gewehr76 said:
Well that's the thing 20 rds is nothing for SVT you won't even notice it. You just dirty up the rifle. Probably get a crate of particular surplus brand at least and shoot it. Surplus has harder primers and they seated deeper in the case, this may remedy the problem.
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Well 20 should be enough just to see if they just simply work like they should. I get about 5 burst over 20 round with the ammo i have atm. And this is if the firing pin actually make it fire with its momentum. If i check the next round in the chamber without firing and it doesnt have any lightstrike mark harder primer wont change a thing it mean its either user induced failure or trigger assembly
 
Ced1942 said:
Well 20 should be enough just to see if they just simply work like they should. I get about 5 burst over 20 round with the ammo i have atm. And this is if the firing pin actually make it fire with its momentum. If i check the next round in the chamber without firing and it doesnt have any lightstrike mark harder primer wont change a thing it mean its either user induced failure or trigger assembly
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Ok hopefully it will be resolve by different ammo, please keep us updated.
 
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