phexAnex

First round locked back like a champ and ejected at about 3:30 at 8', followed by a huge smile on my face. No issues at all over the 20 rounds I ran through it. Thanks again for the help.

I was leaning towards a chisel and file...Picked up a cobalt bit and dowel; decided to play hooky after a canceled meeting. the shank on the bit was about 0.0945 so the hole is probably closer to 0.096 with the very little play I feel It was shockingly painless. Slow, with the weight of the drill, and a little cutting oil. Didn't see any burs on the inside when I shined a light thru the gas port while looking thru the business end of the barrel. Thanks everyone for the direction and laughs. I'll chime in this weekend if I get some range time even though it's Easter.

Appreciate the chime in 98Z5V. JTALLEN83- After some more reading I am going to use a hand reamer. The prospect of a broken bit and fishing it out of the barrel from holding my drill doesn't sit well. Found a decently priced hand reamer on eBay for $20.

Everything I have heard from Criterion has been great so I didn't even want to take the gas block off and check, but I am glad I did. The idea of a dowel came to mind, didn't think of the cutting oil. I pulled up their site again and looked at the specs. Diameter choice possibly to help with suppressor? "Gas hole tuned for proper function with and without suppressor" https://criterionbarrels.com/products/large-frame-ar/dpms-pattern-308-hybrid-barrel-rifle-gas-nitride/?v=00dc5da36527

Firstly, I have to say that this forum is full of extremely insightful information, which I had found it months ago. I am not the kind of person who asks for help as searching and reading I find what I need/think i need to make an informed decision, but this Aero M5 is driving me up the wall. Have put over 100 rounds through it testing different ammo, m80 ball, reloads with 175gr SMK looking for an accurate load since I had single shot M5 ☹. Thinking it was over gassed based on what I was reading online I installed an adjustable gas block and ran it at different settings, no dice. Different Magpul magazines, AR Stoner mags, still not locking back or stripping another round. Took some slow-motion video with my cell phone and I am definitely not over gassed, the BCG wasn't going back all of the way. Yesterday I loaded 10 of the SMK’s with 42.5 and 43 grains of IMR4064 since the slow motion video showed the BCG was not traveling back enough. Add more powder, get more gas see what happens. Good thing was that this was the first time that every round ejected and they fell neatly in a pile at around 4 o’clock. Hand full of times it locked back but not on the bolt face, on the BCG body. This was confirming i was still under gassed and I needed to read more. BTW, I have been lubing the BCG up to the point where it is dripping through the seams between the upper and lower. Spent a few hours this morning reading and found this forum and the post below. Criterion 18" 1:10 port dia (in) 0.077 Gas Journal (in) 0.749 Rifle gas tube length (in) 15.125 Aero M5 .308 Rifle Buffer Kit Buffer Weight (oz) 5.36 Buffer Length (in) 5.29 Buffer Spring Length (in) 12.44 Buffer Spring Coils (no) 41 buffer tube depth (in) 9.687 Gas Block JP Adjustable BCG/Bolt AERO M5 Am I on the right path saying that the port if undersized? I was able to insert snuggly a 5/64th bit which I measured as 0.077 with a caliper and it should be closer to 0.096 inches. I have never had to drill a barrel and that makes me a bit nervous, so I figured I would apply the age old adage of measure twice, cut once by asking for confirmation. If there is something else I would appreciate the input.