I had a partial case head separation using a 1.8oz buffer

[LRRPF52]

More testing today - different powder (SW Match Rifle) but same 123 ELD-M bullets. I did two 5-round group/es tests and lo and behold I got a ringed Starline (new) on one of the cases in the second groups. At that point, I lost trust on this barrel. I'm going to contact Odin Works and see if I can send it to them for evaluation. BTW, when the gas block was off, I measured the gas port at around .076-.080? Hard to get an accurate measurement with my old RCBS caliper. Again - I closed the gas on this barrel and slowly (? turn) opened until I got a lock on last round. I feel like the gas is controlled, and this was with the Monster bolt and H3 buffer. Fun stuff. I think I'm going to order a 16" monster barrel in the mean time...

.076” is too large for CLGS 12” 6.5 Grendel suppressed.

.076” is too large for 10.3” 5.56 NATO suppressed.

I think the SOCOM spec for 10.3” guns is .070/.071” since they are pretty much run suppressed all the time.

Even with my Faxon group buy barrels ported at .068”, they need to be choked fully with the Bootleg carriers suppressed.

One thing I did notice was that the 12” with .068” port, unsuppressed, with Maxim PDW tiny 2.9oz buffer and short/stiffer spring, would not cycle factory 90gr TNT 100%, with the Bootleg carrier on the fully-open position (no choke).

As soon as I attached the Ultra 5 suppressor, it cycled like a raped ape with factory 90gr TNT, as if they were all designed to work optimally with each other in that configuration.

It’s asking a lot to run a wide range of factory ammunition weights and powder combos, especially tiny, short bullets that need to be punted out with fast-burning powders and still have enough port pressure to reliably cycle the action, then load up 120-129gr with medium-slow powders and hit the port with anything close to that pressure and gas flow rate.

To graph it out, it would look like this:

Light, short bullets like 85gr Sierra and 90gr TNT, fast powder..............larger port, lighter buffer, moderate spring weight
Long, high SD bullets like 123gr ELD-M, 123gr SMK, 123gr Scenar, medium-slow powder.........smaller port, H or H2 buffer, standard or heavier spring

Add a suppressor and you might need to buffer and spring-up a bit even behind the 90gr TNT.

There are a lot of factors in this, as the above assumes a Mil-Std spec M16 carrier with correct 3-bore inner diameters, correct upper receiver ID and coating, gas tube seal to the block, actual Mil-Std action spring, correct bolt, etc.