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gas port size

kfreeze said:
I've never needed that. I always run a low mass bcg, lighter recoil spring and good click adjustable gas block and adjust it just open enough that the bcg stays back on an empty mag, then they run nice with almost no recoil. I've never seen the need to mess with all of the buffers and such that people like to mess with.
Click to expand...
i don't have any silencers, so that's out of the equation............i like to be able to use (as a standard for reliability) standard weight buffers (rifle or carbine), standard pressure springs (regardless of flat or round), full mass bcg and non-adjustable gas blocks.................from there going with a lite weight carrier and lower weight buffer is more easily done by adding an adjustable gas block...... less reciprocating mass does make less recoil felt or not...............having the gas port properly sized to do so is key..............i don't care to use a h2 or h3 just to combat op issues and the use of +2 isn't the answer like proof barrels and a few other rely on....................that's their excuse for their op and popped primers answer...........i don't mind fine tuning with adjustable gas blocks as it is needed for handloading variances........don't want to reload that can make accuracy worse just to make it reliable for non agb's.
 
ARlife4me said:
i don't have any silencers, so that's out of the equation............i like to be able to use (as a standard for reliability) standard weight buffers (rifle or carbine), standard pressure springs (regardless of flat or round), full mass bcg and non-adjustable gas blocks.................from there going with a lite weight carrier and lower weight buffer is more easily done by adding an adjustable gas block...... less reciprocating mass does make less recoil felt or not...............having the gas port properly sized to do so is key..............i don't care to use a h2 or h3 just to combat op issues and the use of +2 isn't the answer like proof barrels and a few other rely on....................that's their excuse for their op and popped primers answer...........i don't mind fine tuning with adjustable gas blocks as it is needed for handloading variances........don't want to reload that can make accuracy worse just to make it reliable for non agb's.
Click to expand...
The standard for reliability only works for the standard 5.56 and 7.62 rounds and milspec ammo though since that is what it was designed to use. I don't run much of that stuff. I had to learn to make it all work. The gentleman at x-caliber barrels was really helpful when I was first learning how to make odd stuff run good. He said that when you go away from milspec, it's kind of a guessing game that leads to most stuff being over gassed for reliability, becuas they test a few things to set gas port size. And in my case (204 ar barrel at the time) he said that the load must have been a little lighter than what they tested, because it wouldn't fully lock back on an empty mag. He also told me that since I was running an adjustable gas block that he would have the gas port opened up an extra .010" to ensure that I would always have enough gas. And that in the future to call in barrel orders and ask for the extra if I was using adjustable blocks. Short dwell times of high velocity stuff can really mess with stuff too. That guy was really helpful and knowledgable. I was really glad I made a phone call from what he explained to me.
 
kfreeze said:
The standard for reliability only works for the standard 5.56 and 7.62 rounds and milspec ammo though since that is what it was designed to use. I don't run much of that stuff. I had to learn to make it all work. The gentleman at x-caliber barrels was really helpful when I was first learning how to make odd stuff run good. He said that when you go away from milspec, it's kind of a guessing game that leads to most stuff being over gassed for reliability, becuas they test a few things to set gas port size. And in my case (204 ar barrel at the time) he said that the load must have been a little lighter than what they tested, because it wouldn't fully lock back on an empty mag. He also told me that since I was running an adjustable gas block that he would have the gas port opened up an extra .010" to ensure that I would always have enough gas. And that in the future to call in barrel orders and ask for the extra if I was using adjustable blocks. Short dwell times of high velocity stuff can really mess with stuff too. That guy was really helpful and knowledgable. I was really glad I made a phone call from what he explained to me.
Click to expand...
i've talked with someone at x-cal also and when ordering ar's there is a place to choose adjustable and not for gas port sizing. my 7saum from them port size was close to .100+/- with the pin set i have. difficult to have a "1 size fits all" for anything in the ar10 platform as you can go from 22 to 50cal..........that's a big range! cartridge and caliber make a difference on port size as some could be the same at the same distance. i might talk with x-cal on monday or this week as see what or how much difference there is (for example) between 260rem and 6.5creed on port size as 1 has more case volume and has less max pressure.
 
ARlife4me said:
i've talked with someone at x-cal also and when ordering ar's there is a place to choose adjustable and not for gas port sizing. my 7saum from them port size was close to .100+/- with the pin set i have. difficult to have a "1 size fits all" for anything in the ar10 platform as you can go from 22 to 50cal..........that's a big range! cartridge and caliber make a difference on port size as some could be the same at the same distance. i might talk with x-cal on monday or this week as see what or how much difference there is (for example) between 260rem and 6.5creed on port size as 1 has more case volume and has less max pressure.
Click to expand...
There is definately a range. Haha. And then throw in different gas system lengths to adjust it even more. I was surprised to see my 20" 204 barrel come from APF with a mid length gas system. But it runs perfect.
 
Your other option is to open the port and add an adjustable gas block. I had to do this with my 450 Bushmaster. It is helpful when you change bullet weights.
 
Zen Archery said:
27" barrel, wildcat caliber w/ +2 gas. Smith started with #42, .0935, knowing it would be under gassed. I was using a super fast powder and we weren't sure if it needed a narrow or wider port to cycle properly.

I worked up to a #38, .1015 to get system to cycle properly without adjustable gas block.

Long story short most +2 systems need a minimal of #39, .0995. Measure yours and if it's .0995 and under gassed, go up to #38. If it's over gassed at .0995 get an adjustable gas block and tune it down.

As you know there is a wide relationship between barrel length, powder selection, buffer, and buffer spring. Fix what you can fix without drilling. If you have to drill yourself it's super easy.

FINALLY BE SURE GAS BLOCK PORT AND GAS TUBE PORT IS PROPER DIAMETER! That's another story for another time. 🤦🤣

Included chart for reference.
View attachment 480060
Click to expand...
I thought if it were over gassed, you could increase buffer weight?
 
ARlife4me said:
increasing buffer weight can help for an "improper" sized port no matter gas system length.
Click to expand...
I tried the heavier buffer weight but I cannot tell if everything is proper. I found that the adjustable gas block allows me to set it properly and some have multiple detents for changes like bullet weights and suppressors. That being said, I have only needed this adjustment on my 450 Bushmaster. I really recommend this option for the larger calibers.
 

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