gas ports under sized?

[hochst04 7]

ok i just took my gas block off since it was not.shooting cheap ammo. its a 3 port gas system. i measured the ports with a kit of drill bits that determine size. my ports where .70 that was a nice tight fit. so i then took the 3/32 and that was to big. now im told they should be 3/32 is this correct? so if thats the case my ports are under sized? and i should drill them to 3/32 ? any one know why they have a hard time drilling.these to the right size? thanks please tell me what i should do. thanks

[evlblkwpnz 3,418]

Lots of opinion on this subject. The Saiga 12 in this video has 4 ports at .093". I'm not saying that port sizing will please everyone here, but.... well, I'll let you be the judge of whether it runs ok

 

[gunfun 3,931]

The consensus of most builders is 4@ .078 or 3 at .093... And get rid of any obvious friction issues.

 

4 at .093 will definitely run, but it gunks up your gas block much faster according to most users.

 

depending on the arrangement, you might consider adding a 4th hole if there is room.

[bitters 6]

I guess the Russians have trouble drilling the ports because they are drunk and/or don't care. Hence the term "Vodka special".

[evlblkwpnz 3,418]

There are a few things that can be done to minimize fouling with larger port sizings. Increase the angle, remove the burrs inside the barrel, and run bulk ammo other than Federal (notorious for fouling). If all else is done like I do it , the weapon has the potential to flawlessly go to 200+ rounds of Winchester Universal as fast as you can insert and dump MD-20s, all while using unmodified factory springs, regulator, and puck (200 rounds in a couple on minutes). Beyond that, lockup dimensions begin to change drastically due to the heat, factory handguards will begin to melt, the thin walls of the gas block will begin to expand and change how well the puck seals in it, and shot cups may melt on their way through the barrel and the molten plastic will blow into the ports, no matter what sizing of .070" or larger. If insane Winchester Universal/MD-20 mag-dumping reliability isn't what you desire, then less port surface area will probably be fine, but do not expect to get 100 out of 100 reliability with winchester universal and MD-20s without increased port surface area, unless you want to run weaker springs, less tension on the drum spring which can lead to feed issues during rapid fire, and compromise the weapon's ability to function as intended with buckshot and slugs. Lonestar Arms is Legendary for reliability and runs more port surface area in his gas operated Saiga 12 conversions. I have seen as many as 6 ports in a LSA S12 with about a 16" barrel. The VEPR 12s have 5 ports at approximately .080", FWIW. I suppose MOLOT can join LSA and I in the "gas happy" demonized category when it comes to port sizing/number combos on these gas operated weapons.

 

Many will disagree, but it doesn't make much sense to me that a gas operated weapon in which the gas system was designed to fire buck and slugs in an 8 round stick mag would not need increased port surface area to 100% reliably run cheap bulk birdshot in a much more restrictive 20 round drum. I find fault in that premise, but everyone has an opinion.... and this one is mine

 

evl....

[operator1391 9]

^^^ evlblkwpnz is the man , he got me up and running

[hochst04 7]

im going to drill out my 3 ports this weekend with a 3/32 bit. just hoping the angle wont be hard to get right. and i can get the gas block on after i open that up 2.

[gunfun 3,931]

FWIW one of mine has 5@.078" but I started small and stepped up. Factory springs and whatnot. I know the argument will never end, but as a strainer more small ports with a 30* angle is better IMO.

 

I can say that with my cousin's gun, his didn't run the Winchester until 4 @ .093, but the fouling increased observably. My other one runs every thing fine with 4 unmodified ports that are smaller than .093" If any thing, it is on the snappy side. That's part of why I think every gun should be addressed individually, there is so much variance in friction and what-not, the port size necessary to function will vary.

 

I agree that the winchester burns cleaner, but the federal is better in all other aspects. The more durable hulls feed more reliably, and I have got a couple Winchester shells that came with only the anvil part of the primer. In any case, I think a gas gun should be tuned to run both while held loosely. It ain't a blow-back.

[evlblkwpnz 3,418]

GF,

I too believe that multiple smaller than .093" ports are superior when it comes to fouling. However, we have a lot of people here that want to perform work on their own weapons and many barely have enough mechanical aptitude to get the gas block off, much less successfully drill multiple new ports that will end up inside of the port orifice of the gas block. I am dumbing it down with the 4 @ .093" suggestion as it is fairly easy to do successfully. It should be noted that smaller ports will clog more easily with extended use of weaker loads. Really, it is a "pick your poison" type situation.

 

My 8" SBS runs the cleanest and it has four ports at about .070". It is a very impressive machine with all loads that I have tried. I let someone demo it recently with Federal Multi-purpose and the gentleman said it reminded him of the recoil impulse of his .22 magnum rifle. The guy is a regular at the shop and I have never seen him smile like that. He tried to buy it from me, but it has some prototype parts in it that I just can't let go. With the second term of obama, they may never come to market and will likely die with me. Very good ideas though.