.300 ACC Blackout Casing Question

[Click_Here]

Im going to have to go dig up some GFL's I got. I havent had a problem with those... IK 21 on the other hand, i have to thank for making sure I now have a handful of spare decapping pins.

 

[unwashed]

I'm with the crowd to just buy the brass at this point. I converted many during the shortage but now would just buy it. I may still convert a few, just to stay in practice.

 

[MFInc]

I have alot of already converted 300 brass, Just have to remove the crmp on most. I have more 5.56 brass than I will ever convert so still trying to decide what to do withthose, as I don't want to process all that. Hello Starline!

 

[n2omike]

I just bought re-done Lake City and Starline brass... along with Berrys plated 220 grain bullets.
However, I've been shooting my 9mm AR more than anything. Loading 9mm with RMR 147 grain FMJ RN is cheap and easy. 3.8 grains of HP38/W231 at 1.14" OAL shoots great in both the pistol and carbine, and is still subsonic in both.

Getting the itch to shoot the 300BO more. Found that 10.5 grains of 4227 behind the 220 grain bullet works great subsonic, has consistent velocities and is also the most accurate of what I've tried with my 10.5" barrel. Some powders didn't have consistent velocities and accuracy until they were supersonic. H110/W296 for example.

This is a test target. 50 yards off a bench with a Palmetto State Armory 300BO with a 10.5" barrel.
10.5 grains of 4227 behind a 220 grain Berrys plated bullet shot really well. 7X scope.
Average velocities for 4227 and 2400 were around 1100 fps, Lil Gun was around 1060 and VV120 was only 950 fps. If the 4227 didn't work as well as it did, some further testing with a stronger charge of VV120 could be in order... as each group had one velocity flyer, as well as one group flyer.

 

[rsrocket1]

Yesterday's range test with the Lee C309-170-F gas checked and lubed with beeswax/Vaseline using 19.0g CFE BLK and Federal 5.56 chopped down brass using the HF chop saw.
50 yards off sandbags using a 16" Ruger American Ranch Rifle. Groups and velocities were similar with my BCA 16" upper (1700 fps). My experience says brass makes a difference for 100 yard precision .223/5.56 but chopped down brass tends to be fine for 50 yard 300 BLK ammo.

 

[Bcwitt]

Ive got half a mind to just ream the chamber neck to accomodate the formed cases. I can not think of any issues? Ream the chamber once vs ream necks forever. Seems logical.

 

[Walkalong]

The wise man has spoken.

Way way back in the day, I converted 1,000's of .223
Chop, deburr, size, trim, deburr....
Only brass that was too thick to chamber after conversion was S&B.

Fast forward to modern times.... Just buy it.

I ended up (even though my chambers neck was generous), culling thick necked converted cases.

 

[kcofohio]

Since you're building an "upper" and depending on the barrel you choose you might be able to get away without neck turning, AR 300 blk chambers are generally more forgiving. I've converted thousands of 223/556 cases to .300 BLK but stuck to the following brass without issues. PSO, PMC (Large Font), LC (Any), R-P, GFL.

My process. Cut to a length where I will not need to trim after sizing, Chamfer/Debur, Tumble, Resize/Form to 300 BLK, Tumble again to get the lube off.

I have found LC, FC, A USA, GECO, & Perfecta are ones that have converted with the right wall thickness and that fit the Lyman's case gage.

I use a vertical band saw that has a fence. And a small vise with vee cuts vertically and horizontally that are to hold round pieces. The case headstamp sits on a plate bottom and acts as a positive stop. Once the length is set, the cutting goes pretty quick. I have done a couple hundred at least this way.