SVT-40 Correct adjustment & questions...

sean69

sean69

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Just got me a nice SVT-40 & was wondering about the correct adjustment of the gas cylinder... I've done a little research and found out to start the adjustment nut at 1.1 & work up until the rifle ejects the casing about 2 meters & leaves the bolt open... ok - makes sense... BUT:

1. How tight is the piston rod supposed to be in the gas lug? If you look at the picture I still have 1 or 2 threads exposed when it is all the way up to the adjustment nut. If it's too tight, you cannot move the nut. Too loose & won't it allow the adjustment nut to move around, getting worse & worse as you go?

2. looking at the piston head, there is a groove cut in it, is there supposed to be a gasket of some type on that? The tolerance between the piston & cylinder is quite large. [see pic below]

Basically when I finally get this thing out to the range, will I have to be disassembling the fore-stock every time I need to adjust the gas setting to make sure the piston is tightened down properly?

svt-40.jpg


Oh, & I guess it would be bad form not to post a full size pic including toes ;)

1943, Tula, fantastic condition, note the AVT type stock... an added bonus!
svt-40-002.jpg


-thanks
-sean
 
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No gasket in that groove.

You should tighten the piston until you cannot move the adjusted nut. The whole idea is that the piston holds it in place so it cant loose its place or rotate and block the gas port.
 
First the part you call the piston rod is in fact the gas tube:) The gas tube must be tight, not to strip the thread but very snug so will not get loose upon firing because if the tube get loose, the regulator will come out of adjusment and can lead to malfunctions. There's no seal of any kind on the groove in the gas tube. To set the regulator, loosen the gas tube and turn the regulator. With a svt gas adjustment tool, you can turn the regulator without loosening the gas tube but if you have only your fingers, loosening the tube will make adjustment easier. Start with 1.2 setting and move up until rifle cycle reliably without sending the empty case in the next country:p Usually with military ammo 1.3-1.5 setting is perfect. If you fire heaver bullet than 150gr, the setting may have to be lower to be easy on the rifle. Very nice SVT you got btw:)
Joce
 
"First the part you call the piston rod is in fact the gas tube" - Ha!, yes, that would be correct - duly noted.

Thanks for the info guys, I thought I was going to have to find some kind of odd 70 year old gasket.

Guess I'll have to internet me an adjustment tool...

-sean
 
Svt1940 gave ya the best advice, and P&S Militaria have tools for sale I believe. I have the same year Svt and I have mine on 1.5 and I shoot 203gr MFS. Make sure the piston is good and tight or it'll work loose and cause fte's which are a pain you know where, and make sure the little etched lines on the gas settings match up. Happy shooting.
 
RMXC51 said:
Also, that is a Naval SVT stock, used by Russian Naval Infantry (their Marines, elite troops).
Click to expand...

You're sure on that? that's the right hand cutout for the full auto selection, semi is the other side [i.e. it's notched on both sides]
 
You seem to be missing the piston ring (for lack of a better term). Mine has a compression ring in the grove you were asking about. I have tried in vain to find a diagram of the sytem but to no avail. My rifle shoots at a 1.2 setting but I would bet that without the ring it will still shoot okay at a higher setting.
 
points said:
You seem to be missing the piston ring (for lack of a better term). Mine has a compression ring in the grove you were asking about. I have tried in vain to find a diagram of the sytem but to no avail. My rifle shoots at a 1.2 setting but I would bet that without the ring it will still shoot okay at a higher setting.
Click to expand...

Hmm interesting, but yes - sounds like people are shooting without the ring just fine... I suppose I could check here: https://www.buymilsurp.com looks like they have a manual with parts diagram ...
 
svt1940 said:
None of my Tokarev have a ring on the gas tube and work perfectly.
Joce
Click to expand...

Thanks, yea - I think I'm gonna not worry about the ring ...

say, you don't happen to have a spare sight tool ? I can find the gas tool easily enough, but no luck on the sight tool.... [or will an sks/ak sight tool work?] [I've seen a full kit listed for $175.00 ... but that's ridiculous - no way I will pay that! ]
 
sean69 said:
Thanks, yea - I think I'm gonna not worry about the ring ...

say, you don't happen to have a spare sight tool ? I can find the gas tool easily enough, but no luck on the sight tool.... [or will an sks/ak sight tool work?] [I've seen a full kit listed for $175.00 ... but that's ridiculous - no way I will pay that! ]
Click to expand...
I never tried but a SKS sight tool might work but a cheap and effective solution is to take a bolt,(i took a 5/16bolt,grinded a bit so the bolt can go thru the sight hood and cut a notch so the front sight post can be adjusted. To adjust windage, you can use a sks sight tool, a C clamp or even a brass punch.
Joce
 
svt1940 said:
I never tried but a SKS sight tool might work but a cheap and effective solution is to take a bolt,(i took a 5/16bolt,grinded a bit so the bolt can go thru the sight hood and cut a notch so the front sight post can be adjusted. To adjust windage, you can use a sks sight tool, a C clamp or even a brass punch.
Joce
Click to expand...

I like the DIY approach... never considered I don't need the actual tools ... a $3 steel clamp from crappy tire, just grind a slot into one of the jaws... & I'll bet I can find/rig some sort of t-key arrangement that I can cut a slot into for the sight. [like an old spring wound clock key, that'll have some character!]

thanks!
 
I only have one SVT 40 and it has a compression ring. I naturally assumed that they all did. I can't find a diagram or parts listing and after a long hunt have only found a couple of references to a stainless ring. I wonder if it was just something the Russians decided was not needed.
 
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points said:
I only have one SVT 40 and it has a copression ring. I naturally assumed that they all did. I can't find a diagram or parts listing and after a long hunt have only found a couple of references to a stainless ring. I wonder if it was just something the Russians decided was not needed.
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Or possibly [my guess] rotted away from all the corrosive ammo they were using, if there ever was in fact one there. Maybe it could have been a design flaw/fix? with the gasket you would be trapping more gas perhaps on some rifles with the gasket you would not be able to set the gas port low enough??

Purely guessing...
 
svt1940 said:
Usually with military ammo 1.3-1.5 setting is perfect. If you fire heaver bullet than 150gr, the setting may have to be lower to be easy on the rifle. Very nice SVT you got btw:)
Joce
Click to expand...

I bought my first Tokarev last month... I haven't tried it yet but I too was wondering what should be a good gas port setting to begin.
If I shoot surplus ammo, a good *starting setting* will be 1.3, right ???
Surplus ammo bullets weigh around 147 grains if I'm not mistaken...

heavier bullets = lower setting
lighter bullets = higher setting

:adult:
 
ben777lemay said:
I bought my first Tokarev last month... I haven't tried it yet but I too was wondering what should be a good gas port setting to begin.
If I shoot surplus ammo, a good *starting setting* will be 1.3, right ???
Surplus ammo bullets weigh around 147 grains if I'm not mistaken...

heavier bullets = lower setting
lighter bullets = higher setting

:adult:
Click to expand...
Yes 1.3 will be a good start for military ammo. Somes rifles can even work at 1.2 setting but mine require 1.3 and 1.5 in winter to operate reliably. Yes the milsurp ammo we find here are supposed to be 148 gr.
Joce
 
Put about 40 rounds through it today, it was a little grouchy to start with but after 3 rounds and 3 adjustments, it started purring with a gas setting of 1.3 .... ~however~ nearing the end the gas tube was not tightened enough so t started working itself loose and I got problems with extraction, it required a bit of wood [read as small log laying nearby] to get the bolt open again.

I think the tool would be a good investment. [or maybe I'll just make some copper jaws for a small vise grip :) ]

Thanks for all the advice guys...

-sean
 
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