AR for long range F-class in 223

[Kings X]

Has anyone got information on installing a 30" barrel on an AR?
Is the location of the gas port critical? I am thinking of using a mid barrel port from White Oark.

 

[jscandale]

I build several a month like that. 30" barrel is no problem. You should use a +2" gas tube and port.

JS

 

[mac86951]

I build several a month like that. 30" barrel is no problem. You should use a +2" gas tube and port.

JS

+2 on that too ;-)

Over 26" barrels, we've found timing issues with rifle length gas-ports. An adjustable gas-block is almost a requirement for matches anyway, but for a 30" barrel a +2" and adjustable block should allow you the ability to tune in to any round.

-Mac

 

[rcw3]

. . .

Over 26" barrels, we've found timing issues with rifle length gas-ports. An adjustable gas-block is almost a requirement for matches anyway, but for a 30" barrel a +2" and adjustable block should allow you the ability to tune in to any round.

-Mac

With a +2" longer gas tube, IMO an adjustable gas block is of no use. The port needs to be in the .100" - .104" range to begin with for a .223 to cycle properly with a +2" extended gas port. The only thing an adjustable gas block can do is throttle back excess gas, and with a .100" - .104" gas port there will be no real excess gas, so in order for the block to work you would have to over port the barrel - now you talking of a .105"+ port in a barrel with a .224" bore size - - thats like a pothole in the road that's more than 45% the size of the car that travels over it - - not good!

Just remember, the only thing an adjustable gas block is good for is to cut back gas on an over ported rifle - - if the rifle is ported right to begin with the adjustable gas block is of no value. O.K. for something like a 300 AAC Blackout where you might run subsonic loads with a suppressor and also supersonic loads without one and you need a real aggressive gas flow for the subsonic loads but need to cut it back for the supersonic loads.

 

[jscandale]

Just remember, the only thing an adjustable gas block is good for is to cut back gas on an over ported rifle - - if the rifle is ported right to begin with the adjustable gas block is of no value. O.K. for something like a 300 AAC Blackout where you might run subsonic loads with a suppressor and also supersonic loads without one and you need a real aggressive gas flow for the subsonic loads but need to cut it back for the supersonic loads.

Precisely.

JS

 

[mac86951]

. . .

Over 26" barrels, we've found timing issues with rifle length gas-ports. An adjustable gas-block is almost a requirement for matches anyway, but for a 30" barrel a +2" and adjustable block should allow you the ability to tune in to any round.

-Mac

With a +2" longer gas tube, IMO an adjustable gas block is of no use. The port needs to be in the .100" - .104" range to begin with for a .223 to cycle properly with a +2" extended gas port. The only thing an adjustable gas block can do is throttle back excess gas, and with a .100" - .104" gas port there will be no real excess gas, so in order for the block to work you would have to over port the barrel - now you talking of a .105"+ port in a barrel with a .224" bore size - - thats like a pothole in the road that's more than 45% the size of the car that travels over it - - not good!

Just remember, the only thing an adjustable gas block is good for is to cut back gas on an over ported rifle - - if the rifle is ported right to begin with the adjustable gas block is of no value. O.K. for something like a 300 AAC Blackout where you might run subsonic loads with a suppressor and also supersonic loads without one and you need a real aggressive gas flow for the subsonic loads but need to cut it back for the supersonic loads.

Interesting Opinion. I've found that an adjustable gas block is very much needed to fully utilize a wider range of powders.

With a long barrel and +2" port, the slower powders will shine so long as the barrel is ported correctly, however, the adjustable gas block can be utilized to enable a wider range of powders, loads, bullets without an issue.

Example: My AR loves 77gr SMK and 23.5gr Varget. That is what the barrel was ported for, and it works very well. However, 75grn Hornady and IMR 8208 XBR causes AR swipe before I get to a similar velocity as the 77 SMK load. This is due to the faster burn rate of the powder.

Option #1: Shoot Varget, skip IMR8208. This is the old-school way of choosing what powder works for your rifle/bullet combo. This causes a problem, Varget is not available here, nor has been for ~13 months

Option #2: Tune the gas port for the faster burn rate powder, and develop a load with the powder you can get.

If the barrel is ported for a faster powder IE IMR8208, then switching to Varget, the adjustable gas block won't help get more powder, you are right. The adjustable block is only to fix the reverse, where the alternative would mean making the port smaller, or replacing the barrel.

Please notice that both options work, but one of them involves finding better "food" for your rifle, while another makes do with what you can get. It's up to the user to choose their path, however, I like this forum as usually people provide options to choose from.

-Mac