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Post by mss47150 on Oct 18, 2016 11:58:15 GMT -8
I have the BHW 18" match/heavy barrel in rifle length and bought the Superlative Arms piston kit for it. I was told I needed to bore out the gas port to accommodate for the increased need for gas pressure to fully operate the piston. Can anyone help on what size/drill bit size to use to get the appropriate gas port size for it? Thanks in advance.
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Post by GLSHOOTER on Oct 18, 2016 18:26:55 GMT -8
Welcome to the board. The best method is mount the system and shoot it. Most of these barrels tend to be over gassed slightly so drilling it will not be needed.
Let us know how it runs and pictures are always nice.
Greg
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Post by peabody on Oct 18, 2016 20:33:35 GMT -8
I agree with Greg. Try it with the factory gas port first. I have two piston uppers that I had custom built by Black Rifle Arms using their CAPS design. One is a carbine length and the other is a mid gas. With a rifle length barrel, you might be losing enough of the gas impulse to warrant drilling it out some. But it's best to try it without modification first, especially considering you have a screw adjustment, vice the 4-port design on the type I have (which can be rotated on the fly to support a suppressor or to open up to the larger port if you get a good bit of carbon fouling). Someone at Superlative should be able to tell you what port size works best for your specific caliber and gas tube length. Both of those factors will determine the ideal port opening on the barrel. If they can't, give it a go as-is, then proceed to open the port by a few thousandths at a time until you can dial in the adjustment to get your casings ejecting and the bolt locking on the empty mag (per their instruction). Though I haven't drilled a gas port, I've heard that you can protect the bore using a wooden dowel or a sacrificial brass rod to keep your bit from gouging the far side of the bore upon breaking through while drilling. That said, I love (LOVE) my piston uppers! They're both bastard soviet calibers (7.62x39 carbine and 5.45x39 mid) that are taboo to the AR purists. But they're both great uppers. And the beauty of it is that having the piston system eliminates the chamber fouling one gets from shooting surplus or Tula-grade ammo. Seriously - I can shoot a few hundred rounds of 7n6 (corrosive) and have less carbon on the bolt and chamber than firing one round of 5.56 on a direct impingement upper. No joke. However, the piston system adds weight and may degrade accuracy to some extent. But when your shooting crap ammo with minute-of-man accuracy, who cares!  |
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Post by mss47150 on Oct 19, 2016 5:24:55 GMT -8
I suppose trial and error is the best way to do it after all. I've been looking once in awhile for a good video to watch about it as I learn through visual imagery best. Any suggestions would be appreciated. I keep putting off going to the range but I really need to. Clowns aren't going to intimidate themselves.
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Post by GLSHOOTER on Oct 19, 2016 9:56:54 GMT -8
I suppose trial and error is the best way to do it after all. I've been looking once in awhile for a good video to watch about it as I learn through visual imagery best. Any suggestions would be appreciated. I keep putting off going to the range but I really need to. Clowns aren't going to intimidate themselves. With luck the first trial is all you'll need. If not drilling one is easy. Greg |
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Post by RockNRollMullet on Oct 20, 2016 12:46:53 GMT -8
I have Superlative Arms piston kit on 16" BHW Lightweight Mid Length and it works good. If you adjust gas block 4.5 turns is all way open. After 4.5 turns is bleed off. I had local gunsmith install it and they put gas block against barrel shoulder so I had to move gas block off shoulder to get it to lock back on last round. Syrac has youtube video for Pistion Installation
SYRAC ORDNANCE - Piston Installation - Official Video
Superlative Arms AR-15 Piston Kit Field Test: Effect on Muzzle Velocity and Sound Suppression
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