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Old September 5, 2014, 03:57 AM   #1
Jack Package
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Join Date: August 8, 2014
Location: Dry Wells Arizona ;)
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SVT40 gas system setting

Okay I am not sure if this is bad or not but I will never shoot corrosive ammo in my 1940 Tula SVT40. I usually shoot 174 grain silver bear with the gas setting at 1.5. Is that bad? Will i eventually put to much stress on the gas system and mess it up? The brass usually land about 5-7 yards away which to me seems a little far for a semi-auto. I also have abosluty no idea how the gas setting works even tho i have searched the interwebs for it. Any help would be greatly appreciated.
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Old September 5, 2014, 08:46 AM   #2
GBExpat
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Quote:
Originally Posted by Jack Package
I also have abosluty no idea how the gas setting works even tho i have searched the interwebs for it.
You shouldn't need the internet to discover how the gas system works ... you have an SVT-40 in your possession. Take it apart and study the function of the 3 key components. You are going to be amazed at the simplicity ... maybe

If your brass is landing that far away, odds are that the port setting is too high and your receiver is taking more of a beating than it should. Try 1.1 and 1.3.

Once you study the gas system components you will see that these numbers relate to the size of the gas port opening. They may reference the hole sizes in mm but I have never checked that.

1.1 = least gas
1.7 = most gas

You should choose the lowest number that will work the action reliably with the ammo you are using ... and, unless the chamber is screwed up, that should have your brass landing right ... there.


EDIT: What kinda humidity do you run in a place named "Dry Wells"? If it is a desert community, you have little to worry about vis-a-vis shooting ammo with corrosive primers. The stuff that makes them "corrosive" is in the primer compound and depends upon attracting water vapor from the air to start a rustfest. Extremely low humidity = no rustfest.
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Last edited by GBExpat; September 5, 2014 at 08:52 AM. Reason: Thoughts on chlorate-primered ammo in the desert
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Old September 5, 2014, 09:47 AM   #3
Jack Package
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Dry Wells is a Fallout reference truth is I live in south Texas so it can be 98% humidity one day then bone dry the other but usually is about 20-50% humidity these past few weeks.
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Old September 5, 2014, 05:36 PM   #4
elwoodm
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i have a 41 tula and the gas ports should measure 1.1 .043 1.2 .0465 1.3 .050 1.5 .0550 1.7 .067. be sure to check both recoil springs for any damage. i got 2 sets from mil surp in florida a while back cause mine were bent up from somebody not knowing how to put the rifle back together. check the hole diameter on the gas adj to make sure its not bigger than it should be from not cleaning properly. if ok set on 1.3 or 1.5. most guns were set on 1.3 but that hole could be enlarged bigger than 1.5 from corrosive ammo. use the smaller of the two. clean everything like you should and corrosive ammo is not a problem. try some 150gr stuff and make sure you clean the flutes on the chamber well.
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Old September 5, 2014, 06:03 PM   #5
Field Tester
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Quote:
Originally Posted by Jack Package View Post
Dry Wells is a Fallout reference truth is I live in south Texas so it can be 98% humidity one day then bone dry the other but usually is about 20-50% humidity these past few weeks.
I believe he lives among those Twisted Hairs types. Or are you a Legion man?
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Old September 5, 2014, 07:39 PM   #6
Jack Package
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Field tester... I like you Legion for life but anyway I set the gas to 1.2 and the shells went about 1 yard away from me so i am guessing thats good. I dont like messing with the gas system to much because I dont have a tool and have to gently turn the crap out of the nut with pliers. I always clean my SVT after I shoot it to.
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Old September 7, 2014, 09:12 PM   #7
elwoodm
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been a little busy but you don't need a tool to change gas settings. the piston that holds the gas adj. needs to be taken off with a 5/16 inch wrench. this will allow you to pull the gas adj. out to clean the ports. pipe cleaners work good for this.put the adj. back in on the 1.3 or 1.5 setting and screw the piston back in to hold the adj. tight. oil the piston and adj. to prevent rust. also clean the cup that goes over the piston and oil it. take care of it you are saving a piece of history. my cases might go 2 feet forward and to the left after it fires.
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