My new single shot AR upper

[BillB]

I have mostly cheapo drills but a great Mitutoyo tool to measure them with so using the shanks as my pin gauges ( yes yes I know, they're not pin gauges) I found one drill that measures. 055" and it is a very near perfect slip fit. Believe me, that gasport is either .055" or extremely close to that.
Clint, I tried to send you a PM seeking your advice regarding the specifics you normally ask for when ordering one of your gasblocks or tubes. I wanted to get your suggestion because I'll just set up my press and give the barrel a properly sized gasport.
I bought this barrel as a beater build and I'm not wanting to go through all of the hassle and aggravation of an RMAthen waiting and then getting a barrel back with no explanation of what I waited on, I'll just do it myself.
Above you said the gp should be at least .062", is that for using only 5.56 pressure brass cased ammo and warm handloads, non suppressed? I have both the Vltor A5 setup I can use (A1 or 2 buffers and Sorinco green)or a Sprinco white spring and H1,2, or 3 available as well. Obviously I seek your advice because you know gas management and certainly steered me down the right road twice before and those worked beautifully.

[BillB]

Well, having neither the time nor the desire to send the barrel back to BA I set up the drill press and chucked in a 1/16" cobalt bit, set the speed to 3100 rpm, inserted a steel cleaning rod and put the barrel in my machinist vice, leveled it and plumbed everything as close as I could and lowered the bit. As soon as I saw movement of the cleaning rod I removed the bit
Checked the bore with my borescope and saw a beautiful, clean and crisp new, larger gasport . It looked great.

I reassembled the gun and rechecked gasblock/gasport alignment from inside with the borescope and finished the reassembly. I took my spring and buffer assortment, some 233 pressure ammo along with full 556 pressure loads and some hot handloads as well and headed to the range.

First 4 or 5 rounds of 224 went perfectly. Chamfering and ejection were as normal with the brass landing at a solid 4 Oclock position. Joy. Loaded 5 more and the second round wasnt pickedbup or chambered. I pulled the charging handle and loaded it manually and all subsequent round behaved normally and ejection again and still at 4 Oclock.
M855 cycled flawlessly with no issues at all and still the brass could be collected in a little neat pile at about 4 Oclock. Spring was a fresh Sprinco white and an H2 buffer. Recoil impulse was not what I'm used to or was expecting, it was really pleasant and I'll say soft. Really not what I was expecting. I think I pretty much got lucky and nailed the sizing with whatever size that bit is. My caliper said .061" at the shank.

I continued on with 90 more rounds of m855 and 180 rounds of a 62gr Trophy Bear Claw over 23.8gr of 8208xbr in LC brass and a CCI41 primer, not a single problem and I'm quite happy with my little build so far. I zeroed it in 6 rounds, just the optic not the irons but I'll get to that next trip.

[Disciple]

Nice work.