300BLK Boolits & Gas System

[nitrohuck]

Hey all,

Finally "building" my first AR (okay, not building it myself, but customizing each part and having someone else assemble :p ) and it is going to be in 300BLK.

This round is a dream round for me, the day I found out about it and started studying it I knew it would be the perfect round for me given that I already cast .30Cal boolits and brass can be made easily from .223, it is a range scrubs paradise! I am a poor twenty something year old, so $0.10/round is quite appealing.

I believe my research has answered most all of my questions, but I still have one very important one that is still unanswered that I figured I would turn to you guys for wisdom on:

Will a 16" barrel fitted w/ a carbine gas system fully and reliably function with loads of RL-7 (~17grs) pushing the LEE 155 C312???

I understand this load DOES work for many out there, however I need to be sure it will work in a 16" barrel w/ carbine system. Also, from what I understand the optimum port size is roughly .110" is that correct?

I know for a fact I have RL-7 at my disposal, not so much for Lil'gun and H110 (If I see em I'll snag em, but the LGS has RL-7 for sure) and really am not excited on the idea of having a bolt-action AR...

Assuming this load will push out the 155's, I can then of course assume heavier boolits will work just as well, but I need to make sure I can operate the rifle with the bare minimum boolit weight that I forsee myself using with this rifle.

[prsman23]

I've got some made up from 16.0 in .2 gr increments up to 17. 17 pretty much fills the case. I'd start low and work up. What works in one may or may not work in yours. I'd say 17 is about as far as you want to go. If anyone here has specific experience with this load I'm all ears too. I'm hopefully going to shoot them Sunday.

[KYShooter73]

.....No.

That's the safe assumption. Mine has given me fits. Reliability = blown primers and pockets. I wish I could have a do-over and get a pistol length gas system. Mine runs ok after boring out the gas port. I'm still less than a 1 gn range between functioning an blowing primers.

[blikseme300]

Yes.

Both of my AR-15's in 300blk are 16" carbines. I have no idea what the gas port sizes are but cycling is perfect. SOTA arms HBAR and AR-Stoner light weight stainless barrels used. The perfect mix for me is the Lee boolit and RL7. I load 17.7gn under this boolit and is accurate and works well on feral hogs.

I use Hornady GC's and size to .310 and use TAC#1 as lube.

[blikseme300]

.....No.

That's the safe assumption. Mine has given me fits. Reliability = blown primers and pockets. I wish I could have a do-over and get a pistol length gas system. Mine runs ok after boring out the gas port. I'm still less than a 1 gn range between functioning an blowing primers.

What brass and powder did you use? I ask because when I started reloading for the 300blk I did not realize that not all .223 brass have the same wall thickness. Blown primers where giving me the fits until I found hints on the Whisper threads that clued me in. The blown primers were from when I used PMC brass and the walls are thicker than other head stamps. I now only use LC brass and no problems.

Another problem some run into is the use of M-16 BCG's. These are heavier than AR-15 BCG's and need a bigger push to cycle reliably. I ran into this when developing loads for cast in .223. Switched BCG and cycling is fine.

[blikseme300]

.....No.

That's the safe assumption. Mine has given me fits. Reliability = blown primers and pockets. I wish I could have a do-over and get a pistol length gas system. Mine runs ok after boring out the gas port. I'm still less than a 1 gn range between functioning an blowing primers.

What brass and powder did you use? I ask because when I started reloading for the 300blk I did not realize that not all .223 brass have the same wall thickness. Blown primers where giving me the fits until I found hints on the Whisper threads that clued me in. The blown primers were from when I used PMC brass and the walls are thicker than other head stamps. I now only use LC brass and no problems.

Another problem some run into is the use of M-16 BCG's. These are heavier than AR-15 BCG's and need a bigger push to cycle reliably. I ran into this when developing loads for cast in .223. Switched BCG and cycling is fine.

[Jupiter7]

When designed, 300 aac blackout was developed to work in a standard m4 with a barrel change only. If your gun is properly gassed(.110 gas port is good, .111 better), and doesn't run from reloads, it's not the gun. Lots of people are doing things that simply aren't needed. Then again there is no real continuity between manufacturers. Can't speak to the RL7, never used it. Of course as reloaders and caster, we tend to "try" more stuff than the general shooting community. I have had great luck with a1680 5744, h110 and lil gun. I will say that a pistol gas system is still not a fix all, I've seen a few guns that wouldn't cycle subs no matter what. As above, stay away from foreign or pmc brass. I only convert RP, Winchester and Federal. I've also had good luck out of middle-weights 170-180gr in cast with 13-14.5gr charges of lil gun and h110, get around 1700fps.

[KYShooter73]

My barrel is a CMMG carbine length, load is currently 15.8 gn of Lil'gun. Mixed head stamp. I start blowing primers out at 16.0 gn. BCG is Wilson Combat m16 type. Standard buffer and spring. I have some Win 296 to try, but haven't had the opportunity yet. The scrap bucket shows a mix of FC, LC's, Pmc, and RP all blown. The gas port is properly aligned. Running "wet" operates fine for a few rounds. Everything but the barrel is top end components. I expect it to run many hundred rounds without a hiccup. Right now, that is not the case. I can't say I have ever made it through a full mag without malfunction.

[blikseme300]

KYShooter73

My experiences with Lil Gun, H110 & Win296 was not good under cast with poor cycling, blown primers and leading. Lil Gun worked OK under Sierra 125gn bullets but the reason to getting a rifle in 300blk was for CB's. I did research and tested a number of slower powders and found that they worked better than the faster types such as Lil Gun and H110 under the Lee 155gn boolit. Reloder7 and Reloder10x yielded best results and stayed with RL7 as I have a good local source for this.

The dwell under the curve of the powder burn is what ensures sufficient gas pressure to cycle the action and this is why fast pistol type powders work in bolt guns in this caliber but won't cycle gas guns.

Don't give up on your rifle as I have been there with frustration getting my AR-15 in .223 to shoot well with CB's. A combination of things with a new rifle caused this but I worked through it and now have a much better understanding of this rifle platform and it is a pleasure to shoot.

Bliksem
Edinburg, TX

[garym1a2]

I have very good results with IMR4227 (15.0grs) and that lee boolit. Functions great in two 16 inch carbine gas systems. One barrel a Wilson and the other a Midway AR-stoner. I average 1720 fps with this load.
I only get reliable feeding with 30 round Pmags, this short round did not work with my steel mags nor my 20 round pmags.
P.S make sure to get M4 feed ramps for upper and barrel.

[Jupiter7]

My barrel is a CMMG carbine length, load is currently 15.8 gn of Lil'gun. Mixed head stamp. I start blowing primers out at 16.0 gn. BCG is Wilson Combat m16 type. Standard buffer and spring. I have some Win 296 to try, but haven't had the opportunity yet. The scrap bucket shows a mix of FC, LC's, Pmc, and RP all blown. The gas port is properly aligned. Running "wet" operates fine for a few rounds. Everything but the barrel is top end
components. I expect it to run many hundred rounds without a hiccup. Right now, that is not the case. I can't say I have ever made it through a full mag without malfunction.

In all honesty, it may be your CMMG barrel causing fits. They state that "may or may not run subsonic" on their descriptions on midway. I'd pull it and measure gas port. They also recommend not shooting supersonic through their pistol gassed barrels(not sure what's that about). If 15grs lil gun or h110 isnt running, something is wrong.

Garym1a2,
As to mags, I've found that only mags with anti tilt followers work. The few older 20's I have won't feed subs, neither will a new 10 rounder. Pmags, lancer, d&h and tangodown mags have worked well. A bud of mine only uses slightly rib modified thermold master caster 20's.

[oldpapps]

nitrohuck,

Take these babblings from an old fat man for what they are worth, very little. But.....
Any combination of bullet - primer - propellant that will push the bullet out the barrel is a step in the right direction, for a single shot. However, an auto feeder requires ample pressure for an appropriate amount of time to get the job done.

I would never say that your choice of 'AL7' will not work as there is no reason the right mix shouldn't. I just don't think you will be happy with the very narrow pressure spread with a powder this fast and AL7 has a much faster burn rate than any of the more accepted preferred propellants for the Black.

Further more, I would never say you should conform to a set of powders (my preferred Black powder is Olin 630, try to find some of that). I'm just saying that I think you would be better served with a, shall we say, more versatile pressure range producing powder.

I also understand the current 'run' on most all components and the spotty and limited availabilities. May I suggest that you keep your eyes open at your LGS and be open to 'other' powders. Think: 296/H110, Lt'Gun, N110, 2400. These are all known to function well in a carbine gas system with the .300 AAC Blackout and there are others. (Of the ones I listed, for lead in the 150-160 range, Lt'Gun and 2400 are my choice. N110 is too $. 296/H110 are not known to act well with reduced charges, although I have never pressed my luck with them, I have always been happy with my results.)

Good luck with your quest.

Load with care,

OSOK

[nitrohuck]

Thanks so much everyone for the responses thus far.

I've had a nice little development in my endeavor: The vendor (MAS Defense) says they will happily open up gas ports to my desired diameter.

This makes me much more comfortable in going with a carbine system, but now that I have the option to open it up, how far should I open it???

Jupiter says .111" in his post above. This seems to be congruent with many other's experiences from what I have read, but now that I have the option to choose my exact diameter, should I go even bigger?? Would a .120" be way too large? .115"?

I plan on ordering this today, thanks again for all the help


Oldpapps, what was your load with 2400 that cycled your AR? You would be the very first person I have heard of that has gotten 2400 to work for them, and since I have it around I would be interested in hearing more from ya!

[nitrohuck]

Just purchased my MAS Defense 16"bbl complete upper with carbine gas - LINK (http://www.shop.masdefense.com/16-300-BLACKOUT-BARRELED-UPPER-TROY-BATTLERAIL-ALPHA-15-163TBA15BU.htm)

I asked them to open up the gas port to .111", they told me it would be no problem and will drill it out to spec.

At the end of the day it seems people CAN get performance with cast boolits out of a 16" carbine gas 300BLK barrel, but the big "X factor" is gas port size, as many of the barrels come from the manufacturers with undersized ports. Now that MAS Defense has said that they will customize this for me, it takes a lot of the gamble out of this scenario.

Can't wait to load up rounds and shoot it... alas I've blown all my money on a rifle and now must wait another paycheck to buy the, ahem, batteries to make it run...