223 AR15

[KeithB]

The OD of 1/8-27 male straight pipe thread ranges from .390 to .397 according to Machinery's Handbook. The OD of 1/8 pipe before cutting tapered pipe threads is .405. I never realized that 27 tpi was that unusual since every piece of equipment I've run for years has it.

I looked in Table 3 Unified Screw Threads in MH and found listings for the following: 1/4-27 UNS, 5/16-27 UNS, 3/8-27 UNS, .390-27 UNS, 7/16-27 UNS, 1/2-27 UNS, 9/16-27 UNS, 5/8-27 UNS, 3/4-27 UNS, 7/8-27 UNS, and 1-27 UNS. I could not find any standard 27 pitch threads larger than 1".

 

[freebullet]

Brad

I have the mp75gr. You are welcome to borrow the mold if you'd like.

The 19 gr Varget is solid advice.

Pure lino leaves wild antimony wash for me. May use a scooch to further harden range scrap.

 

[Ian]

Pure lino leaves wild antimony wash for me.

Bingo. That's why it's no good for HV, among other things.

 

[300BLK]

By crimping into the middle band I can avoid "jumping a throat gap". I'll have to try it both ways and see what the rifle likes.

I seated a bullet in a case trimmed to 1.755" so that the mouth was close to the top of the middle band. Even though my seater was just floating so as to not crimp, I detected a little misalignment. The dummy was chambered and left the bullet in the throat when extracted. When I checked the bullet, I could clearly see interference partway around the front band. The mechanical fit didn't seem robust enough to survive cycling, so I'll try taper crimping into the bottom of the front band.

 

[Ian]

Seating so the bullet touches any part of the barrel directly when chambered is a recipe for malfunctions in an AR-15. Do your work at the loading bench so the bullet finds and holds center without any training wheels. Guys that never load for autos don't know what "fun" they're missing.