Reloading .300 AAC Blackout using .223/5.56 Cases

[jwh20]

HOWTO: Reloading .300 AAC Blackout using .223/5.56 Cases

Over the weekend I took my first foray into .300 AAC Blackout reloading and also my first try at converting .223/5.56 cases into .300 BLK.

I've written it all up here:

.300 AAC Blackout Reloading

Please let me know if I've left anything important out or have made any glaring errors. I'd be interested in anyone else's experience with this round as well.

Enjoy!

(I updated the PDF file with a few more pictures and some corrections after proofreading it a bit more.)

 

[william]

Really nice write up. I've been thinking about getting an 300blk upper to use with my suppressor. I was curious about reloading them. I was going to ask Andrew at Profire the other day, but it was too busy in there. I'm glad to see they make 300blk dies...I heard at a gunshow you had to use 7.62x39 dies and a .223 base. Which didn't make sense to me. Now I know

 

[jwh20]

Really nice write up. I've been thinking about getting an 300blk upper to use with my suppressor. I was curious about reloading them. I was going to ask Andrew at Profire the other day, but it was too busy in there. I'm glad to see they make 300blk dies...I heard at a gunshow you had to use 7.62x39 dies and a .223 base. Which didn't make sense to me. Now I know

Be sure it's a .30 cal. suppressor or you'll be really sad! I started out with a .300 BLK barrel and decided right away that I needed a complete rifle. Hence the CMMG AR-15 in .300 BLK.

I don't see how a 7.62x39 die will do the trick as that case is larger than the .300 BLK case but quite a bit. I suppose it would work if you only sized it down far enough for the neck. That would be really tricky but if you lacked a .300 BLK reloading die that would be all you could do. But I think you'd be better off ordering a custom-made reloading die of having a machine shop modify one.

 

[gopurdue02]

very nice write-up.

 

[william]

Be sure it's a .30 cal. suppressor or you'll be really sad! I started out with a .300 BLK barrel and decided right away that I needed a complete rifle. Hence the CMMG AR-15 in .300 BLK.

I don't see how a 7.62x39 die will do the trick as that case is larger than the .300 BLK case but quite a bit. I suppose it would work if you only sized it down far enough for the neck. That would be really tricky but if you lacked a .300 BLK reloading die that would be all you could do. But I think you'd be better off ordering a custom-made reloading die of having a machine shop modify one.

I have a 30 cal gemtech quicksand. I like shooting it best with some subsonic 308 loads I work up. So quiet... makes it a lot of fun. I was looking for something else like that to play with that I could get to cycle a semi auto. I've heard that 300 blk fits what I'm looking for.

You don't have to worry about me trying to load it with 7.62x39 dies. That sounded pretty stupid to me. I was just a conversation I was listening in on. I'll do it right or not at all.

 

[BKExpress]

Excellent article! Thanks for sharing!

 

[jwh20]

Excellent article! Thanks for sharing!

You're welcome. As I mentioned in the original posting, please feel free to add any experiences of your own with loading this round.

From what I've been able to tell, there are not that many folks here reloading .300 BLK yet, but as familiarity with it grows, I expect it to become more popular.

 

[BKExpress]

You're welcome. As I mentioned in the original posting, please feel free to add any experiences of your own with loading this round.

From what I've been able to tell, there are not that many folks here reloading .300 BLK yet, but as familiarity with it grows, I expect it to become more popular.

.300 BLK is most likely my next pick up to add to the collection. I will keep you posted.

 

[Slow Hand]

Good article! I have made a few cases myself. I tried a small abrasive wheel in my drill press but it spun too slow and grabbed a few cases out of my hands, sending them flying across the garage!! I ended up using tubing cutters (what can I saw; I'm a plumber!). After that, it's the same procedure, size, trim, etc.

I basically have two loads I shoot, a Speer 125 TNT load that approximates 7.62x39, and a heavy, 200-230 subsonic load for suppressed use. I've used a few heavy cast bullets and awhile back bought a lee mold specifically designed for .300 blk in AR's. it seems to hoot pretty well. I have a 16" AR (soon to be chopped down an put on a pistol then SBR lower) and a Stevens 200 action fit with a 16" .300 barrel. The boltgun is about like shooting a suppressed .22!!

I have had very good luck with the AR cycling most all of my loads. Last October I had the chance to stretch it out some. We were shooting at some previously perforated propane tanks at 300 yards. I was shooting from the bench but could have a round in te air by the time we heard the previous shot thunk steel at 300 yards!! That was a fun day!

I shot a good number of subsonic .308's but now that I have my .300, it doesn't happen anymore!

 

[Slow Hand]

I forgot to mention, after the first few cases I sent a big box of hem to Utah to a guy who converted them for me. I still had to run them through the sizing die and debur them, but it was worth the money to not have to mess with cutting them down.

 

[JonProphet]

Let me offer you a tip. I had a problem with my .300 loads. Andrew answered my question, w/o even me asking. Basically, my gas tube was getting plugged. Turns out you can't shoot H110 in cold weather. It doesn't burn completely.

-JD-

 

[jwh20]

Let me offer you a tip. I had a problem with my .300 loads. Andrew answered my question, w/o even me asking. Basically, my gas tube was getting plugged. Turns out you can't shoot H110 in cold weather. It doesn't burn completely.

-JD-

I read that in a couple of threads regarding H110 but others said they had no issues. I'm sure it's one of those things where a combination of factors including cold make for less than optimal results.

I didn't experience anything that would indicate incomplete burning on my .300 BLK loads but then the temperature was in the lower 60's.

These days, of course, you take whatever powder you can find and H110 was on the shelf.

I am curious, however, what did you find worked for you? I'm not too worried about cold weather shooting right now in the middle of May (although today, 5/11, makes me wonder) but a few months from now I may be more concerned about that.

Thanks for the comments though, I'm by no means an expert on .300 BLK reloading, rather I'm trying to learn all I can.

 

[JonProphet]

I was shooting and it was 30 degrees or something. I also had some issues with alignment of the tube and block. Got that sorted and h110 seems like a good supersonic load. I haven't done any testing for accuracy yet.

 

[Slow Hand]

H110 needs to be loaded near max for complete burn. That's the rule in magnum pistol cartridges; I'm sure it carries over to the .300 blk.

For powder I'm happy with Lil Gun for supers and AA1680 for subs.

 

[jwh20]

H110 needs to be loaded near max for complete burn. That's the rule in magnum pistol cartridges; I'm sure it carries over to the .300 blk.

For powder I'm happy with Lil Gun for supers and AA1680 for subs.

With the 165 gr bullets there was not much free space left in the case. I found of 180 gr bullets in my box of reloading supplies and I was going to try them also. I read a couple of postings where folks were trying to get subsonic with 180 gr. projectiles but I don't see any point in doing that now since I don't have a supressor.

I'm watching out for some alternate powders to try some other combinations and Lil Gun was on my list.

 

[Sean]

I bought a case cutoff jig from a guy on 300blktalk it made processing brass a snap.

300BlkTalk • View topic - Case cut off tool *soldout can preorder annodized*

 

[jblomenberg16]

Good article! I have made a few cases myself. I tried a small abrasive wheel in my drill press but it spun too slow and grabbed a few cases out of my hands, sending them flying across the garage!! I ended up using tubing cutters (what can I saw; I'm a plumber!). After that, it's the same procedure, size, trim, etc.

I basically have two loads I shoot, a Speer 125 TNT load that approximates 7.62x39, and a heavy, 200-230 subsonic load for suppressed use. I've used a few heavy cast bullets and awhile back bought a lee mold specifically designed for .300 blk in AR's. it seems to hoot pretty well. I have a 16" AR (soon to be chopped down an put on a pistol then SBR lower) and a Stevens 200 action fit with a 16" .300 barrel. The boltgun is about like shooting a suppressed .22!!

I have had very good luck with the AR cycling most all of my loads. Last October I had the chance to stretch it out some. We were shooting at some previously perforated propane tanks at 300 yards. I was shooting from the bench but could have a round in te air by the time we heard the previous shot thunk steel at 300 yards!! That was a fun day!

I shot a good number of subsonic .308's but now that I have my .300, it doesn't happen anymore!

The 125's are great in the .300BLK, and I'm really starting to like the 110's as well. A little more velocity which means a bit more expansion at close range, and a little longer range above the min expansion velocity.

 

[shibumiseeker]

The 125's are great in the .300BLK, and I'm really starting to like the 110's as well. A little more velocity which means a bit more expansion at close range, and a little longer range above the min expansion velocity.

I've been shooting cast 155s and have a pretty sweet load for them and it's some cheap shooting.


Oh, and for those who have been posting it with a "." it's 300BLK or 300 AAC Blackout, there is no ".". Just my peeve

 

[jblomenberg16]

I've been shooting cast 155s and have a pretty sweet load for them and it's some cheap shooting.


Oh, and for those who have been posting it with a "." it's 300BLK or 300 AAC Blackout, there is no ".". Just my peeve

Good point...get so used to the "." with .223, .308, 7.62, etc. Bad habit.

 

[Slow Hand]

With the 165 gr bullets there was not much free space left in the case. I found of 180 gr bullets in my box of reloading supplies and I was going to try them also. I read a couple of postings where folks were trying to get subsonic with 180 gr. projectiles but I don't see any point in doing that now since I don't have a supressor.

I'm watching out for some alternate powders to try some other combinations and Lil Gun was on my list.

I think I tried some180's and they were borderline subsonic when loaded to function my AR. I've got between 1 and 200 rounds I need to pull down. They were loaded with a 210 gr cast round nose. They were supersonic and won't cycle my AR! Worst of both worlds! I'll pull them down and reclaim the components. Other than those two loads, I've had very good luck getting my Ar to cycle.