300 blackout cast bullet loads for ar-15

[gatorshooter]

My plain water quinch GC WW lee 170fp work fine at 14.5 gr of h110. Lock back bolt too. Tried 1 coat of dry tumble HF red powder coat. Bullets look great. Gc and lubed anyway with lbt blue lube. In lyman lubrisizer. Now they will not allow bolt to fully close. Very hard to extract loaded round. Good thing i crimped bullet. Tried seating coated bullet deeper still not functioning 100%. Obtw sota arms 16" full float upper carb. Length gas. No high pressure signs. Running stock m4 buffer and lower. Will test for accuracy after get function correctly. So far accuracy looks promising.

[TreeKiller]

Check the nose diameter did you bump them up in the sizer?. Had that trouble with Lee 160gr and the 65gr NATO in the 223. Baking the PC made the boolits soft.

[gatorshooter]

May have to get the lee push through sizer...ill keep playing with it for now.

[gatorshooter]

Sized the bullet deeper in sizer without lube and seated gc. Then seated it deeper in case to top groove. Inserts and extracts easily now in chamber. Test fired no high pressure signs. tried 15 gr h110. All ok so far. Pulled bolt after about 30 rds fired of plain hard cast and found leading behind gas rings on tapered part of bolt this had to be scraped off to remove. Will load up a few more and see what they yield off the bench.

[popper]

I use the 31-165C in 308 & 300BO. PC'd, no GC, 1750 (308 1.5 MOA), 1680 (BO) no problem. Haven't tried faster in 308 but BO was a full load of Re7. No crimp or lube grooves to get in the way, nose is .297 PC makes it .300 so it fits seated long. Sand ~ 0.005 off the ribs in the 10 rnd Pmag so the mag doesn't bulge. COAL 1.95 fits mag fine, sized 0.310. BO pretty much vertical stringing @ 50, got ~ 100 jacketed through it so time to try 100. Unsized it fills the throat and I don't see any land markings yet. Using PPU, Hornady, LC, Rem brass - no problems in a diamondback bbl.

[fredj338]

At 15-1600 you will need gas checks for a 30 cal.

How about cast hard, epoxy paint coating, no gc @ 1500-1600fps?

[HMC710]

I'm running the Lee 230 5R and love it. It's actually designed to fit the BO chamber and it works as designed. No fuss, no muss, & 7.5gr of Lil Gun.

[Mark-II]

I'm running the Lee 230 5R and love it. It's actually designed to fit the BO chamber and it works as designed. No fuss, no muss, & 7.5gr of Lil Gun.

Could you give some details as to bullet prep and OAL? I've got a blackout upper on its way, along with that very mould. I'm curious as to whether it needs sizing, since its a TL design. I was just going to cast it from range scrap, which seems a touch softer than WW, since that's the only lead I've got at the moment.

I've got to track down some lil gun. In the meantime I'm wondering if the likes of RL7 or 2400 are worth playing with in the AR15 with that bullet

I also have some RCBS 165-sil that I use in my m1a clone available to try.

[Moonie]

RL7 is a great powder to use, 2400 might be a little fast to cycle the action.

[Jailer]

RL7 is a great powder to use, 2400 is too fast to cycle the action.

There, fixed it for ya.

[popper]

So how low can you safely go with Rx7 or 4227? Any problems at 10 gr or so? Not much load data in that range.

[BearBear]

This is a long thread with many discussing how they've used lead bullets for the 300 Blackout. I am about to get a 300 blackout but have been advised that one can't use lead bullets because the lead fouls the gas operating system. Is this advice wrong?

[Moonie]

I've run nothing but cast in our 2 300BO uppers, no issues with fouling. I also use cast in 5.56 and 6.8SPC uppers, no fouling issues at all between them.

People make assumptions based on ignorance and hearsay, we shine the light on this and have done it quite well.

[HMC710]

Built two more 10" uppers to go along with the 16" for some comparisons. My goto boolit has been the Lee 230 5R so I cast up about 100 of the gems, tumble lubed, and seated 10 of them to crimp groove over 8gr of Lil Gun. Much to my surprise, I was getting keyholing at 50 yards with about an 8" spread. Brought back to 25 yards and still got some key holing. One thing I did notice was a very large amount of smoke when firing these loads and clean up afterwards revealed a lot of leading. I didn't chrono these loads but the J220's were 1010fps. My lead is a bit soft, but didn't have the issue before. I tumble lubed the batch again, will clean the barrels up and try again....

[rongaudier]

Quick progress report on my custom boolit load for .300 BO. Quick rundown, I have am running a Hardened Arms 8.25" upper that worked fine with several brands of factory ammo. My boolit is a 160gr spire point and is PC with red HF paint and aluminum gas checks. I first ran it in my 30-06 bolt action at around 2200 fps and had pretty decent results. I finally got some powder for the .300 BO and loaded up a few rounds to try out. My powder for now is 4227 and ran 14.8 grains of it today. Well there are some issues in my AR. First off, I was having trouble getting it to feed. Next was the problem of it not wanting to go into battery. I attribute that to having the boolit set too far out. Unfortunately, the radius of the ogive requires that I set the boolit back pretty far and have now settled on a COAL of 1.89". I also had pretty inconsistent bolt lock back. I'm thinking setting the boolit back will take care of the not going into battery issues, and I'm going to try upping the powder charge to 15.8 gr. Hopefully that will give me more consistent bolt lock back. Not too sure about the feeding issue though. Is the short COAL the culprit? Here's a video of my first session.

[Sticky]

Are you sizing those and if so, to what diameter?

The bolt lock back in the one that was shown on video didn't occur since you didn't have an empty mag in the rifle to engage the bolt lock, I assume you tried it with only a single round in the mag to check for lockback, otherwise you won't get it, regardless of your ammo.

FWIW, my testing with the 300 using subs is to load a single round in the mag first, fire and check for bolt lockback, then load 3 rounds, fire all three, checking feed, cycling and bolt lockback on the final round... Then I load the mag up and continue to test the loads.

I primarily load for subsonics, just started casting, so I have a lot to learn there, but have cast some lee 3092305R's to test for sub loads in the blackout. I have had awesome success loading subs with AA1680, it is my go to powder for subsonics in the 300. Almost every load I have tested with jboolits have cycled my 10.5" pistol, down to about 800fps with several boolits, but as you said, those jboolits are pricey for loading subs, thus my quest to cast for it..

Good luck with your testing! Anxious to see how you make out with it!

[rongaudier]

Are you sizing those and if so, to what diameter?

The bolt lock back in the one that was shown on video didn't occur since you didn't have an empty mag in the rifle to engage the bolt lock, I assume you tried it with only a single round in the mag to check for lockback, otherwise you won't get it, regardless of your ammo.

FWIW, my testing with the 300 using subs is to load a single round in the mag first, fire and check for bolt lockback, then load 3 rounds, fire all three, checking feed, cycling and bolt lockback on the final round... Then I load the mag up and continue to test the loads.

I primarily load for subsonics, just started casting, so I have a lot to learn there, but have cast some lee 3092305R's to test for sub loads in the blackout. I have had awesome success loading subs with AA1680, it is my go to powder for subsonics in the 300. Almost every load I have tested with jboolits have cycled my 10.5" pistol, down to about 800fps with several boolits, but as you said, those jboolits are pricey for loading subs, thus my quest to cast for it..

Good luck with your testing! Anxious to see how you make out with it!

Yes the boolits are sized to .309. I figured that thing out about the bolt lock back after watching the video again. I've loaded up another batch with 15.8 gr 4227 and the bullet seated a little deeper. I think I have hit the max powder load without compressing. I'll take it out and try it again.

[Sticky]

You may also want to try sizing larger, if you can. Many are shooting 300's at .311, or thereabouts. I have a .311 die coming today for the 309230's, hope to be trying them out here shortly. My mold drops them at about .311, but after coating, they are a tad larger, may even try some with Hi-Tek and no sizing, since it's a pretty thin coating after curing.

I ran some through the .309 sizer to try out in my AR308, anxious to try that out too!

[Greg Skinner]

Ron,I am running the same Hardened Arms 8 1/2" upper and have experimented with 4 different cast boolit designs. I have the Lee 150 fp, the Lee 170 fp, the Accurate 31-150B and the Accurate 31-235A. I power coat everything and I don't use gas checks. I size .309 and have used Lil Gun,IMR4227 and IMR4198. The super loads using Lil Gun and 4227 have all functioned fine, fed OK and locked back. OAL is 1.89 for the Lee bullets and 2.01 for the 31-150B. I've used only a 10 round Magpul mag and don't usually load more than 6 or 7 at a time. The mag will not seat with the bolt closed, but if I insert it with the bolt open, it functions fine with no problem either picking up the round or ejecting it. These boolits, especially the Lee are just too fat to allow the mag to seat when the bolt is closed, even if I seat them deeper. I suspect that filing the ridges in the mag might help, but so far it has not been enough of a problem to warrant that action.

I tried the 235 gr as subs with both 4227 and 4198. They functioned OK with the 4227 but would not lock back on the last shot. Function with 4198 was perfect. I think I seated them 2.15. The problem with them is that the bore ride portion of the nose is not great enough diameter, even when powder coated, and they appear to be tipping before getting out of the barrel. They are obviously not entering the target totally straight on, although they aren't grouping terribly at 50 yds - about 2", m-o-m for sure.

Accuracy with the 150 grain supers is not great - best groups are about 1" - 1 1/4" at 50yds, 1600-1700 fps, so it is still a work in progress, but Jacketed accuracy is not a great deal better, averaging at best 1" at 50 yds.

The Blk seems to be fairly sensitive to variations of any sort so part of the challenge is figuring out how to be totally consistent in re-loading technique. I haven't tried annealing the brass but I do trim between each firing and use a Lyman "M" die for the cast boolit reloads. The seating depth seems to be fairly critical, also - lots of room for experimenting. Maybe I need to try sizing .311 next to see if that would tighten groups any. Or maybe get a gauge to check for run-out.

[rongaudier]

Greg,
Great info. Hey if I could get 1" groups at 50 yards with this gun I'd be tickled pink. If you watched the video you could see I was having problems getting the mag to seat. Glad to see I'm not the only one. In the future I'll keep the bolt locked back for mag insertion. I'm going for round two tomorrow with the bullets seated a little deeper (should cure my not going into battery problem). I've also upped the powder charge slightly. I think I'm pretty close to the max powder charge (about 15.8 gr) without starting to compress.
I'm also gonna take a closer look at that pmag and see about trimming it a bit as you suggest. Quick edit: I went ahead and filed those ribs on the pmags a little. Let's keep our fingers crossed for tomorrow.