Gas port sizing

**blkexp98** · 03-03-12, 22:18

I am having a barrel cut shorter and will need to open up the gas port i assume. So whats the best procedure to follow to get this set right? I want to get it setup so I can shoot it suppressed and unsuppressed with as little excessive gas as possible. With that said while im opening it up id like to also take reliability into account.

So how do those of you go through the process of getting the correct gas port size?

**MarkG** · 03-04-12, 09:13

Originally Posted by blkexp98

I am having a barrel cut shorter and will need to open up the gas port i assume. So whats the best procedure to follow to get this set right? I want to get it setup so I can shoot it suppressed and unsuppressed with as little excessive gas as possible. With that said while im opening it up id like to also take reliability into account.

So how do those of you go through the process of getting the correct gas port size?

Send it to a machine shop that knows what they are doing...

**CRab** · 03-04-12, 11:15

A discussion here with a range of numbers posted...use google and search this site...there are many threads debating different issues that affect port sizing...

**blkexp98** · 03-04-12, 16:57

I read through that link among others and have a gas port range but also know each rifle is different. I don't like sending out work when its something i can probably do so thats why i want to learn the method. For all i know they would just drill the largest gas port they know works and thats not what im after. So I was trying to figure out if there was a certain procedure people used to determine they have the correct size to be reliable yet not overgassed.

I havent found a thread on actually drilling the holes per a certain rifles performance. Everything has just said this rifle used this port size and so on. Within that the same "type" barrel could have a range of port sizes. Thats why i wanted to drill my own so it would have the best size for my setup.

**Todd.K** · 03-05-12, 12:17

Originally Posted by blkexp98

So I was trying to figure out if there was a certain procedure people used to determine they have the correct size to be reliable yet not overgassed.

I test cyclic rates.

**rob_s** · 03-05-12, 12:26

If you're doing this yourself, and you're set on some certain goal, drill the smallest you think will work and go up from there to get function the way you want it.

**MarkG** · 03-05-12, 13:45

Originally Posted by blkexp98

I read through that link among others and have a gas port range but also know each rifle is different. I don't like sending out work when its something i can probably do so thats why i want to learn the method. For all i know they would just drill the largest gas port they know works and thats not what im after. So I was trying to figure out if there was a certain procedure people used to determine they have the correct size to be reliable yet not overgassed.

I havent found a thread on actually drilling the holes per a certain rifles performance. Everything has just said this rifle used this port size and so on. Within that the same "type" barrel could have a range of port sizes. Thats why i wanted to drill my own so it would have the best size for my setup.

That may be due to the fact you shouldn't use a drill to modify your gas port. Drills don't make round or clean holes.

**blkexp98** · 03-05-12, 20:09

MK18Pilot: What other options are you suggesting? Something like an EDM or drilled and then reamed? I do have some machine tool experience by the way so I'm not going to just jump in with a dremel. If you have a good method I'm all ears. I'm just trying to learn what ways people who have done it before have found to work well.

Rob_s: That was the method I had in mind. In your opinion do you think it would be best to get it where it functioned fine and then go a couple thousandths more for reliability?

Todd.K: I didn't consider cyclic rates. In my case I cant use that method but that is interesting. I assume you have different rates in mind for different type builds.