My Build, with gas port size questions..

[Christopher67]

MY Build

1. Aero M5 Upper/Lower/15" Enhanced M-LOK Handguard

2. Aero M5 .308 Lower Parts Kit, Minus FCG/Pistol Grip - LaRue Tactical MBT-2S Straight Bow Trigger

3. Ballistic Advantage 16" 308 Win BA Hanson Profile Midlength (.750") AR 308 Barrel w/ Lo Pro, Premium Black Series + .308 Complete Bolt Carrier Group, Phosphate

4. Aero Precision AR15/AR10 Enhanced Carbine Buffer Tube + Heavybuffer CAR-10 Buffer 5.5 ounces + .308 Carbine Buffer Spring

 

 

Do the Ballistic Advantage .308 barrels typically come under gassed(ordered my barrel this past Saturday)?

 

Any help or advice would be greatly appreciated.

[Albroswift]

Limited experience, but had to drill up a 308 and a 6.5 Creedmore BA. Post the port diameter when the barrel shows up. Numbered drill bit set is ideal for determining size of port. I would expect around 0.079 would run about right with your setup, lots of experts here so might get some other advice on that. Also watch for gas tubes, 12-1/16" (Large frame carbine) is usually correct, 11-3/4" (ar15 midlength) usually a little short. But not always. Both the 6.5 and the 308 BA's I messed with took 12-1/16"

Gas tube should hit center of cam cut out. This is a 12-1/16 in an Anderson AM10 Carbine. Just right. Came with a 11-3/4"

 

[Christopher67]

@Albroswift

 

Thank you, my barrel shipped today.

 

I have a couple of mid-length ar15 gas tubes.

 

I will post the port size when it gets here.

Edited September 18 by Christopher67

[Christopher67]

1/16 drill bit fits with a little wiggle room, bit measures 0.062

5/64 drill bit is to big and won't fit, bit measures 0.077

 

Below is my Aero Precision AR15/AR10 Enhanced Carbine Buffer Tube + Heavybuffer CAR-10 Buffer 5.5 ounces + .308 Carbine Buffer Spring

 

 

[Christopher67]

What drill bit would you recommend to open up the gas port?

[Albroswift]

Have you shot it with current configuration?

The 0.077 would be close, I used the numbered bit that equates to 0.079 (don't remember which one that is) on 3 different .308's, one with Carbine Gas / 18" barrel and the other 2 with 12-1/2" barrels and different custom length gas tubes.  All 3 have AGB's but run close to all the way open. Ran one with 7" buffer tube and short buffer / tailhook tube. Orange spring.

Another option would be to get a numbered set of bits, and sneak up on the correct size with a fixed AGB, more range trips but eliminate the AGB. I would also get an orange sprinco spring if it was me running the short buffer.

[Christopher67]

3 hours ago, Albroswift said:

Have you shot it with current configuration?

The 0.077 would be close, I used the numbered bit that equates to 0.079 (don't remember which one that is) on 3 different .308's, one with Carbine Gas / 18" barrel and the other 2 with 12-1/2" barrels and different custom length gas tubes.  All 3 have AGB's but run close to all the way open. Ran one with 7" buffer tube and short buffer / tailhook tube. Orange spring.

Another option would be to get a numbered set of bits, and sneak up on the correct size with a fixed AGB, more range trips but eliminate the AGB. I would also get an orange sprinco spring if it was me running the short buffer.

 

 

My gas tube & Midwest industries .308 reaction rod won't be here till tomorrow, won't get to shoot it till the following weekend.

 

But yea the 0.077-5/64 drill bit won't fit, so its off to get a numbered set of bits today.

 

Thanks you

[Christopher67]

Any numbered sets that you would recommend ?

Edited October 4 by Christopher67

[Armed Eye Doc]

21 hours ago, Christopher67 said:

Any numbered sets that you would recommend ?

Looking at the above conversation chart, you need a #47 to get to almost 0.079 or #46 to go a little bigger. 

You can get individual numbered bits at many hardware stores.  Unless you want an entire set, you don't really need all of them.  Just be sure to get the Cobalt bits.

Edited October 5 by Armed Eye Doc

[Albroswift]

I like the cobalt as well, stay sharp longer, but maybe just a little more brittle. Just go easy. Some barrels have a hard outer coating as well as the bore. you can slide a wood dowel in the barrel if you prefer for punch through. I have bought Maxtool, Uxcell, topline cobalt's off amazon all good. 

I have a mill so it is real easy, but most of the brothers here use a cordless drill with success. 

 

 

[Christopher67]

Ok i bought this numbered drill bit set https://www.harborfreight.com/titanium-m2-high-speed-steel-drill-bit-set-115-piece-61543.html

 

The #50 drill bit .070 fit, #48 .076 & #49 .073 were to big.

 

I don't have a drill press, so i would have to do it by hand.

 

What vise jaws would work best, any recommendations?

 

Thanks everyone. 👍

[Armed Eye Doc]

7 hours ago, Christopher67 said:

Ok i bought this numbered drill bit set https://www.harborfreight.com/titanium-m2-high-speed-steel-drill-bit-set-115-piece-61543.html

 

The #50 drill bit .070 fit, #48 .076 & #49 .073 were to big.

 

I don't have a drill press, so i would have to do it by hand.

 

What vise jaws would work best, any recommendations?

 

Thanks everyone. 👍

Those are ok for measurements, but I would still recommend Cobalt bits.  I have used similar HF bits on other metal and did not have good luck, especially with the smaller bits.  However, I did not have a pilot hole.  With those, I would go up the next size that doesn't fit even if you have to drill more than one time.  You just want to be sure not to break the bit in the hole.  Be sure to use some oil to keep the drill cool.

I used a drill press as well with an AR upper vise.  But have heard of plenty of people using a handheld drill.

[Christopher67]

20 minutes ago, Armed Eye Doc said:

Those are ok for measurements, but I would still recommend Cobalt bits.  I have used similar HF bits on other metal and did not have good luck, especially with the smaller bits.  However, I did not have a pilot hole.  With those, I would go up the next size that doesn't fit even if you have to drill more than one time.  You just want to be sure not to break the bit in the hole.  Be sure to use some oil to keep the drill cool.

I used a drill press as well with an AR upper vise.  But have heard of plenty of people using a handheld drill.

 

I have some tap magic

[Rsquared]

Yes. Oil and patience. Remember to let the drill bit do all the work. Like Doc said, the last thing you want is to have the drill bit break off in the hole.

[Albroswift]

One thing about the less expensive bits, the shank is undersized compared to the hole called out or drilled, so once you find a snug fit you need to measure with the digital or dial caliper. Then order quality bits next sizes up. my bet you will end up running wit a 48, 47, or 2mm. If you are patient you could start small and test each size. 

[Christopher67]

IF you're going to buy a quality #47 & #48 drill bit, who makes a quality drill bit?

[sagebrush]

I use Irwin bits and get them at ace hardware store. have used them on several barrel drilling jobs, no problems. lube, go slow, let the bit pull itself through. let the pilot hole guide you

[Cunuckgaucho]

I like SKF and Walter drill bits but again unless you plan on drilling a lot of holes Irwin,Milwaukee,DeWalt bits with lots of oil,going easy will do the job. 

Probably not common in your neck of the woods( semi rare here) I have a drill set(2 boxes) from 1-10mm in 0.1 incriments( 4thou) which covers not only the metric sizes but 

fractional to 3/8",number drills and letter drills up to W.

FYI a 5/64 drill bit is pretty much half way between a #47 and #48 drill bit

a #47= 2mm

a #48= 1.9mm

[Christopher67]

Good choice?

 

https://www.homedepot.com/p/Milwaukee-5-64-in-Cobalt-Red-Helix-Drill-Bit-48-89-2302/205879027#overlay

 

 

Thanks.

[Armed Eye Doc]

That should work.

[Christopher67]

32 minutes ago, Armed Eye Doc said:

That should work.

 

Thank you 👍