Greetings from Manchester Mi, I purchased a 24" hvy ss barreled upper in 204. I always lap a new bbl. As I looked down the pipe I saw a burr. I mean .004 of .005 around the gas port. And the hole seemed to be BIG. I mean 1/8 inch or more. So out to the shop I go, patch the bbl out,& begin to lap it. OH OH, big resistance on that spot. I sent it back. They send me the same upper back, w/ a note cleaned out burr w/ a cleaning rod. Nope. same "feel" same .200" gas port mistake. They claim the 204 hole is .006 bigger than the 5.56 hole. None of my 8 ARs have a visually big gas port hole or a definite sticky spot while running a cleaning rod down it. School me on this 204 gas port. Thanks, Red
.204 Ruger AR bbl question
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Originally posted by Unclered View PostGreetings from Manchester Mi, I purchased a 24" hvy ss barreled upper in 204. I always lap a new bbl. As I looked down the pipe I saw a burr. I mean .004 of .005 around the gas port. And the hole seemed to be BIG. I mean 1/8 inch or more. So out to the shop I go, patch the bbl out,& begin to lap it. OH OH, big resistance on that spot. I sent it back. They send me the same upper back, w/ a note cleaned out burr w/ a cleaning rod. Nope. same "feel" same .200" gas port mistake. They claim the 204 hole is .006 bigger than the 5.56 hole. None of my 8 ARs have a visually big gas port hole or a definite sticky spot while running a cleaning rod down it. School me on this 204 gas port. Thanks, Red
I found this info on AR.15.com where Tony from Tromix posted this info on 20 caliber rifles. From my reading improper port location and port size cause significant issues with 20 caliber AR-15’s. I guess because of the different pressure characteristics mid length gas system is preferable on 20” 204 Ruger AR-15 barrels. On 24” barrels I believe most are running rifle length gas system.
“ I just found my notes when I was making small bore barrels 10 - 15 years ago.
204 Ruger 24" barrel, rifle gas, .101" port.
20 Vartarg 18" barrel, mid-length gas, .081" port
17 Remington 24" barrel, rifle gas, .078" port
17 Remington 20" barrel, rifle gas, .089" port
17 Mach 4 24" barrel, rifle gas, .110" port
Based on the above data, if I were to take a guess on port size for the OP's barrel, it should be about .076", unsuppressed.
On a 20" 204 Ruger, you would have to run a mid-length gas system. It would be nearly impossible to flow enough gas through any size gas port, to get it to run with a rifle length gas system. “
Tony
Here is a link to the thread on AR-15.com.
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