150gr sub load data that cycle and lock open

[Parkertk]

So, in normal fashion of trying to do things that are challenge I've been working om some 300aac loads with the intent of running short barrel(8.5") with 150gr bullets while staying subsonic. The goal is correct function with bolt locking open on last round.

So far IMR4198 and CFEBLK are working but nothing outside of those burn rates.

Anyone else have experience trying this?

I am running a lightweight BCG and low mass buffer and spring. Adjustable gas block also but not needed for the loads. Running wide open.

[ReadyAimDuck]

I use Reloader 7 for subs down to 115 grains. The 150 grain load with Reloader 7 is published by Sierra here:

https://sierrabullets.files.wordpress.c ... 052018.pdf

No problem locking bolt back on last round with a supressor. Not sure if I've tried it without. But I am bleeding off gas and my gas block is not wide open, so there's plenty of gas for lock back with a lightweight BCG, carbine buffer, and Tubbs 300 AAC spring.

[Parkertk]

What barrel length are you running?

[ReadyAimDuck]

16"

Your mileage may vary with a shorter barrel. But like I said, I also have gas left over to play with. If I had to run the gas block wide open I may caution you against trying this with a shorter barrel.

[Parkertk]

Totally agree. I've got it running consistantly down to an average velocity of 890fps with the 150 on top of 11.2 grs of the CFEBLK.

Definitely not overgassing it or stuffing the spring buffer to hard. No pressure signs and super smooth.

Will likely try some of the R7 and play with that one. Sounds promising.

Appreciate the info

[ReadyAimDuck]

No problem! Let us know how it goes.

[dellet]

With all the modifications you have done to the operating system, 150 subs should be no problem with powders as fast as H110/296 suppressed. Without a suppressor maybe 4227.

The powders you are using, with the changes you have made as likely to cause the own problems. They burn so poorly, and build up so much carbon in the operating system, that with light weight components and weak springs, there is often not enough inertia to close the bolt on a dirty chamber. It’s not a matter of if this will happen, but how many rounds before it does.

Gas port size and suppressed or not will make a difference.