30blk ar question

[seabreeze133]

Am interested in a 300 BLK upper for my DPMS 5.56 slick side D I and wonder if anyone has tried the conversion and has had success w/cast boolits?

Or would a piston rifle work better?

Thoughts please.

seabreeze

[petroid]

Lots of people use cast in 300BLK. I like to powder coat. Seems to prevent head buildup on my bolt. Lots of molds to choose from

[reed1911]

Lots shooting case in the .300BLK as stated above, however, if you are shooting suppressed you may want to contact the maker and verify that cast will not void the warr. Many do not recommend cast through them.

[kencha]

As far as DI vs piston, the 300BLK can be finicky to get to run due to the large range of differences in pressures/dwell/etc when you're trying to run ammo ranging from subsonic to supersonic.

A piston may only complicate matters.

They can be made to run, but you're probably looking at fiddling with the gas port size, buffer weight, and spring.

So it depends upon what you're wanting. Subs only? Supersonic only? Suppressed or not? All of the above? Barrel length? Gas system length? Building your own, or off-the-shelf?

Currently, I run piston in 5.56 but DI in my other calibers, although I have considered piston in the 300BLK too. The problem is, the piston system I like is not available in a pistol-length, which is what I'd need. I don't feel that I'm missing much.

I haven't shot cast yet in my 300BLK. Waiting for my mold. There is a ton of information here and elsewhere on cast in the blackout, though. Eventually, leading of the gas system may be a problem. I can imagine a piston (depending upon which design) will only make that matter more troublesome too.

I'd probably recommend going DI. You can always try a piston later if you still feel the need.

[arjacobson]

I have shot thousands of cast rounds through my 300blk. I use lees 155 mold with aluminum gaschecks. Lil gun for powder. Cycles great and is very accurate.. I am a firm believer in annealing the brass after forming. I have heard of some guys having accuracy problems with reformed brass that hasn't been annealed??? Love my 300blk!!

[ryokox3]

I also have done well with cast in the blackout, however on a 300 blackout specific board there is a good amount of talk about why a piston is not the best choice in that caliber.