Need Loading Data & Relevant Issues for Subsonic Loads for 300BLK

[Capt Mike]

I have tried hard to research old threads here, so please be kind as I post this. I am working up a subsonic load for my AAC 300 Blackout AR carbine and as I researched this I kept coming up on new issues. Here is the rifle I have: 300 Blackout upper by AAC w/16” barrel (not slugged); YHM Titanium Suppressor. Reloading supplies: 220 gr Sierra MKHPBT & Lee 230 cast bullets (powder coated) w/gas checks & without (GC are Hornady & sized to .309), sizing dies .308, .309, .311. H110 & Lil Gun powders (I do not have any A1680 and cannot find any right now) & formed 5.56 cases.
I want to shoot this rifle suppressed but read in one thread that the cast bullets are BT (they are .311 tapered to .286 – gas checked to .309) and that could be a sealing issue. Also a thread mentioned that it was not wise to shoot gas checks through a suppressor. The whole point of buying this mold was to be able to shoot suppressed as inexpensively as possible. The idea behind the powder coating is to keep the fouling down in the gas system and suppressor.
I called AAC in Lawrenceville, GA and the rep there said shooting cast through their uppers would void the warrenty; no big deal there, but good to know. After a little explaining where I was with this project (liability keeps them from recommending any hand loads in their products) and that I did not have any A1680 he said the Hornady “manual” recommended a starting point of 6.5 grains of Lil Gun with a Hornady 225 jacketed bullet for a velocity of somewhere around 1100 fps(maybe a little less).
So with all this said, could we discuss the variables and issues concerning the hand loading of mostly the Lee 230 cast boolet? What are known proven loads and what are inherent problems with using GC’s, suppressors & powder coating in an AR type rifle.

[Jailer]

Powder coated bullets shouldn't be an issue. I'd try them without gas checks as you could possibly suffer a baffle strike especially with a non gas check design mold such as the Lee.

I didn't see where you mentioned if you had a pistol length gas system or carbine. If it's a carbine length, good luck getting it to cycle with lilgun. You said you couldn't find 1680, so see if you can find some 4198 or Reloder 7 they should provide enough gas volume with subs to cycle. Hogdon does list a charge of 9.9gr of H110 for the Sierra 220 gr bullet but I don't know if H110 will provide enough gas volume to reliably cycle your action or not.

[felix]

The lot of RL7 that I have will not cycle a carbine gas return with a 200 boolit. Only the 680's work as advertised, at around 11-12 grains based upon lot characteristics. Maybe a short cut 4198 might work, but I don't have any to play with. I am quite sure a normal cut version of 4198 won't work because of case volume constraints, so I never even tried. The most accurate boolit by far is the 311299 form. Must gently file the follower guides towards the mouth to be a little more rounded within the magazine for positive cartridge pick up. Using the Magpul mags, and the filing action is light enough to permit no changes in feeding genuine 223's. ... felix

I will try harder soon when the weather changes. Double base powders generate enough gas for the job provided they are slow enough, but ignite fast enough. A very, very tricky circumstance because the range of acceptance is so narrow for keeping things subsonic. Using a 231 to push a 335 is on the agenda when things cool down around here. ... felix

[Jailer]

Accurate also lists 10.7gr of 5744 for the 220 sierra so there is another less popular powder option for you.

I do like my AR's but subs are why I love my 300blk bolt gun, I can run any powder I want.

[Capt Mike]

Jailer, I am assuming I have a carbine length gas system as this is a stock unit produced by AAC with a 16" barrel & I do have a pound of 4198. Looks like another vote for baffle strike by a GC. I am using the H110 for my 125 Sierra supersonic loads with good results. However, I could not get it to work reliably with the 155 cast boolets. At 15 grains the H110 would cycle the bolt and pick up a round, but would not lock the bolt back on the last round. Also had minor pressure problems. At 15.5 grains of H110, I blew 3 out of six primers and discontinued that load.

Felix, I think you are right about the case volume and 4198, but I will run a test and see. I have 11 or 12 Magpul mags so if I need to modify one I guess I can.

[Capt Mike]

Jailer, I agree with the bolt gun, they are my favorites, but I have one of these black ones so I would like for it to work.

[Jupiter7]

Sounds like a different mold may be in order. I've gotten lil gun to cycle subsonic, but at about 8grs. Most do not have luck with it as subsonic powder.

[Capt Mike]

JUpiter7, are you talking about 4198, H110 or Lil Gun?

[Jailer]

Sounds like your gas port is a bit on the small side if it won't cycle reliably with 15gr of H110 and the Lee 155. This isn't the first time I've read of cycling difficulties with AAC uppers and some safe loads with the Lee 155. My Daniel Defense and my buddies home built AR stoner barreled upper run perfectly fine with that combination.

Try switching to a slower powder and see if that helps and if not you may have to open up your gas port a bit.

[Jupiter7]

JUpiter7, are you talking about 4198, H110 or Lil Gun?

Lil gun, pistol gas length, 10" barrel, .95 gas port, functions maybe 80% of the time. I'd agree that something is amiss if your having issues at 15grs h110 with lee 155. Buddy of mines dpms upper will not cycle factory Remington subs until drilling out gas port to .11. Same rounds cycled in my pistol.

[Pirate69]

While I do not personally own a 300 BLK, I am casting and loads ammo for a friend. I am using the Lee TL309-230-5R mold and 10.0 grains of H110. In his upper, they are running fine.

[Doubleg]

Just got a Core15 300 BO 16" upper, dies, sizers, and a ton of lead to run subs. However I'm following these posts from one end to the other trying to see where someone has come up with the right boolit mold or mold modification that really works in the AR platform. I also want to find a boolit mold that will work well for supersonic loads too. I'm not a patient man but this endeavor has made me exercise self control..... Anyone got an accurate working combo for the AR system yet? Anyone?

[Jupiter7]

Just got a Core15 300 BO 16" upper, dies, sizers, and a ton of lead to run subs. However I'm following these posts from one end to the other trying to see where someone has come up with the right boolit mold or mold modification that really works in the AR platform. I also want to find a boolit mold that will work well for supersonic loads too. I'm not a patient man but this endeavor has made me exercise self control..... Anyone got an accurate
working combo for the AR system yet? Anyone?

A lot of questions there. For supers, most have found the lee 312-155 to be more than adequate at 1800fps +\- from a 16" AR, feed well, reasonably accurate. The subsonic mold is a different story, lots of choices. Personally I don't run subs anymore, but heavy supers, 245gr boolit at 1250fps. The mold is accurate 310-240e, mine feeds fine with anti tilt followers, others have had problems. I don't like the lee 230gr blackout mold(midway exclusive), the boattail on a cast boolit is a non starter.

As you're a new member, do you cast?

[fastglock]

I love the LEE 230 in my 300BLK's. Only if its powder coated

[leadman]

I have a 300 Whisper Contender carbine barrel so won't be able to comment on function. I have the Lee 230gr and do not recommend this boolit at all. Might be ok for 50 yard plinking.
The one I use for longer ranges is a 314299 sized to .310". This is the same style boolit as the 311299 recommended earlier.

I do have a friend with a 308 Win AR that is using my Saeco 120gr RN GC boolit at 2700 fps and moa groups at 100 yards. He is going to try longer ranges to see how the accuracy holds up when he gets time. Function in his gun is good so this might be a candidate for a 300 BO.
I use the Hi-Tek coating on my boolits and they are very clean shooting. At subsonic velocities the gas check would probably not be needed but this would be "try it and see" situation.

Hodgdon has loading data on their website.

[Moonie]

I have had good luck cycling wise with H4895 and the 245/247gr however the SD was very high with it. I have not had luck even with supersonic loads of H110/W296 behind a 245/247gr. I haven't tried the RL7 that I have yet.

[Capt Mike]

I gave up trying to get a good cast load to cycle in my AAC upper. I bought a Remington 700 in 300 BLK and really like it. It shoots subs (you can actually hear them hit a 50 yard target) and supers both great and no I'll see what kind of load I can work up for subsonic cast. As I mentioned, I have the Lee 230 mold and a Lee 155 grain mold. That's all I have right now so that is what I will use. I have been loading Sierra 220 grn MKHPBT's with 11.2 grns of A1680. How will that work as a starting point for the Lee 230?

[Jumbopanda]

I gave up trying to get a good cast load to cycle in my AAC upper. I bought a Remington 700 in 300 BLK and really like it. It shoots subs (you can actually hear them hit a 50 yard target) and supers both great and no I'll see what kind of load I can work up for subsonic cast. As I mentioned, I have the Lee 230 mold and a Lee 155 grain mold. That's all I have right now so that is what I will use. I have been loading Sierra 220 grn MKHPBT's with 11.2 grns of A1680. How will that work as a starting point for the Lee 230?

One interesting thing I have found is that my 200gr cast boolits will never cycle in my AAC 16" upper if they are tumble lubed, but will cycle reliably if they are coated with Hi-Tek. This is using the same powder charge and crimp.

[Capt Mike]

Now that I have the paperwork back on my can I will try the upper again. Maybe the heaver boolets or a lesser load for the 155 will work. It's always fun to try to make things work!

[Jupiter7]

While I do not personally own a 300 BLK, I am casting and loads ammo for a friend. I am using the Lee TL309-230-5R mold and 10.0 grains of H110. In his upper, they are running fine.

Pretty sure that load is supersonic. I'd guess upwards of 1200fps. I've downloaded h110(disclaimer: not suggested by manufacturer for well known pressure spikes, position sensitive), crazy numbers on the chrono and the ES was in the 200fps range. Not conducive to good accuracy.

[HURK]

Hello all, just joined and this is my first post. I am currently casting a batch of Lee TL309-230-5R and will be coating with Hi-tek system. I have shells all ready and now searching for a good load for this. I am going to a gun show this weekend with the intent on buying powder. I have seen on this site that LIL gun and H110 is a choice for some of these loads but have been reading different reviews? I have built a AR to shoot the 300 AAC with a 16" barrel, Carbine. Could use some info. I will be also purchasing some 150 Gr jacketed bullets with the intent of hopefully using same powder as the 230 gr that I have cast. Thanks

[Jailer]

I gave up trying to get a good cast load to cycle in my AAC upper. I bought a Remington 700 in 300 BLK and really like it. It shoots subs (you can actually hear them hit a 50 yard target) and supers both great and no I'll see what kind of load I can work up for subsonic cast. As I mentioned, I have the Lee 230 mold and a Lee 155 grain mold. That's all I have right now so that is what I will use. I have been loading Sierra 220 grn MKHPBT's with 11.2 grns of A1680. How will that work as a starting point for the Lee 230?

I run the Lee 312-155-2R tumble lubed, no gas check sized to .310 over 4.8gr of W231 in my bolt gun. It's very accurate and consistently cronos right at 1080 FPS.


Now that I have the paperwork back on my can I will try the upper again. Maybe the heaver boolets or a lesser load for the 155 will work. It's always fun to try to make things work!

There's a good chance that you'll have better luck with a can attached. The can kind of acts like a barrel extension giving you gas pressure in the barrel for a longer period as well as providing more back pressure. If you've ever had gas in the face from shooting an AR with a can on you'll know what I'm talking about.