AERO .308 Short Stroke Specifics & Symptoms:

[SgtDog0311]

I did read the links. I am concerned about finding sharp bits without ordering and waiting. Home Depot or Ace doesn’t inspire confidence with Chinese products..

Btw, while ‘Survivalshop’ gives these number from Tactical Machining:
DPMS LR-308 Style Rifle
18" rifle 0.308. 0.096
I did find in the links where some posters referred to ranges with minimum and maximum.

Ref: “supposed to be 0.0890" mimimum to 0.0960" max, actually drilled at 0.0760". Drilled it out to the minimum 0.0890" and it "kinda-sorta" worked most of the time, went back and drilled to 0.0960" and now it works like a champ”.

And another anecdotal case given, the poster, 1911popo, got good performance at .0930.

If I find bits tomorrow I plan on giving it a try. I’m gonna get as close to .0960 as I can without going over. I’ll bring calipers when I go shopping.

[dpete]

When you go to the hardware store (not Loew's, Home Depot, etc.) a real hardware store, ask for numbered drill bits for drilling steel. They are measured in decimals of inches (.0890", .0960" etc.) #41 = .0960". #42 = .0935". #43 = .0890". There are metric and fractional (3/32") sizes in between those but you have the idea of what needs to be done. A good titanium or cobalt coated bit will last you many years of drilling through steel in the future.

[rpoL98]

if it's a Faxon barrel, you need an Armalite AR-10 gas tube. If it's an Aero or BA barrel, then it's the AR-15 gas tube. They are different. wasn't sure what brand of barrel.

[SgtDog0311]

Gas tube length:
Per 98Z5V - gas tube should END in the middle of the cam pin cutout, in the upper receiver. Short of using caliper to measure I’m as close to center as my eye can discern. If I knew how to post a picture I would. Hope to get to the port today. I’ll post how drilling goes.

[dpete]

Gas tube length:
Per 98Z5V - gas tube should END in the middle of the cam pin cutout, in the upper receiver. Short of using caliper to measure I’m as close to center as my eye can discern. If I knew how to post a picture I would. Hope to get to the port today. I’ll post how drilling goes.

Eyeballing to the center of the campin cutout is good enough. 1/2 way is perfect, short is not good (the gas key recieves gas from the tube for less time), a tad long is ok. No need to pull out a caliper.
Gas tube length in 308 ARs is just one thing that builders have to be aware of and make sure to get right. No Milspec bites azz otherwise. AR15 builders don't even have to think about it. Milspec measurements are pretty much set in stone.

[SgtDog0311]

Well crap, Milwaukee 3/32” (.0938) is the closet I can find in Titanium. They have the wire #’d bits in Irwin but they are neither Cobalt or Titanium.

I’m gonna buy a #43 (.0890) for a step-up from the existing hole and a #41 (.0960) for final pass, just in case you fellas think they are good for a one-use application.

Stop me if that’s a bad idea due to hardness mismatch. Or if stepping up from existing .0770 (best I can measure) to the .0960 should just be made in one step.

[dpete]

The Irwins will do just fine. Just keep the port hole and the bit oiled as you drill and go slow using light pressure. The bigger hole cannot be drilled crooked, the bits will want to follow down the original hole.

[SgtDog0311]

Thank you! Last question. In steps be best or all at once? Think I just found cobalt so got the option once their truck comes in this afternoon.
(Btw, I realize the “last question” are just famous last words{:-)

[dpete]

Your talking about less than .02" in drilling up. All at once should work just fine. Oil it up, go slow, and if your concerned about plunging too deep put a dowel inside the barrel.

[grizzman]

Was this barrel purchased new? What does the manufacturer have to say about the port size?