AR 300 BLK and Lee 300blk mold

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  • Last Post 16 May 2015
JDNC posted this 12 May 2015

I have just completed a AR UPPER IN 300BLK, and would also like any info regarding cast bullets in this platform.  I have ordered the Lee 300BLK mold. I do plan on using a supressor and really have concerns about the use of gas checks.  In the past I've seen evidence of checks coming off at the muzzle (stuck in my start screen) and would hate for this to happen inside a supressor. I have a 16” pistol port (port size 0.1065") barrel with adjustable gas block so I hope I will have some control with cycling.  I plan on using this bullet subsonic velocities and without GC's.  What powders do you suggest?  I have on hand..IMR4227, 5744, Lil Gun, IMR8208, H4895, IMR4895, H335, H322, and Benchmark to name a few.  I also have PuffLon on hand. Any suggestions would really be appreciated,JD

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358156hp posted this 12 May 2015

Is your suppressor a sealed unit, or can you disassemble it for cleaning? If you cannot disassemble it, I'd suggest one of the epoxy type bullet coatings or possibly powdercoating. If you get a bullet lube buildup in the can, it may burn out, but if there's lead in with it, it's almost impossible to get any lead out.

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JDNC posted this 12 May 2015

Can will be closed. I've coated some bullets but haven't shot any. I'm worried about the bore ride section on the Lee mold. If casting too hard it might be too large and nearly impossibly with the added PC. Guess I'll have to wait for the mold.

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onondaga posted this 13 May 2015

http://castbulletassoc.org/view_user.php?id=885>JDNC

Instead of placing a lot of conditions on your project that make it nearly impossible to start. Consider starting with what is working already.

The Lee bullet is successful in your application. It will cast big enough to be sized for your rifle. 45:45:10 tumble lube once before and once after size works well when no check is used. Nose on my bullets is .301” in #2 alloy. I fire this bullet sized .312” subsonic with H TiteGroup in 7.62X39.

Gary

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JDNC posted this 14 May 2015

Mold should be here today.  I'm going to do a chamber cast and then cast some bullets.  I hope I'm lucky as for the bore ride dia. of the bullet, at least where I can adjust within alloy within constraints.  I've recently been testing to see what fast powders I have on hand that will cycle the AR action.  As this is a pistol port 16” with adjustable gas block I think I'll be able have a larger selection to choose from hopefully.  Of course I've generally used slower powders for decades for cast rifle bullets, so it's going to be challenging, at (least for this old bird) playing with the AR-15 300 blk.  I'll will post my findings when I get this project started.  I also think it's going to a different animal with the back pressure of a Supressor, but Im still waiting on that animal.  Thanks to all for your imput, and please keep it coming. Thanks, JD

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JDNC posted this 14 May 2015

I might add, I also swage 30 caliber and have been testing with 205 gr but this is too expensive at today's jacket and wire prices.  I have 30 cal moods but not anything I care to try, so I'm eager to get the Lee mold.  I think the heavier bullet will help in cycling the action not to mention a more efficient burning of powder.  I'll see, I'm just scratching my head now waiting on the mold.:P

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onondaga posted this 14 May 2015

http://www.castbulletassoc.org/view_user.php?id=885>JDNC

THe Lee 300 AAC mold is NOT an easy to use beginner mold and was very challenging for me to get working well. The long bullet and high weight is hard to cast well. It takes trials with different pot temperatures and casting speeds. I do best at 625 F using #2 alloy and dropping bullets 3 times a minute. Any cooler or slower and I will get poor fill out and shiny undersize bullets. Get your heat and speed up to get them to drop slightly frosty for best fill out. It ain't an easy mold to work with!!!!!! GAry

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358156hp posted this 14 May 2015

The plan to wait and see what you have to work with when the mould comes in is a wise move. One guy I know powdercoats his bullets for use with the suppressor, then drops the coated bullets in cold water to compensate for any potential loss of hardness from the baking process. He uses a PID to control the baking temperature, thereby controlling the finished bullet hardness. Then the bullets will be sized (if needed) immediately upon drying. We haven't determined if sizing oven hardened PC bullets will work-soften them, as can happen with uncoated bullets. I supposed you could always size the noses too, if it becomes necessary although it would be a pain to do. Anyway, this is where we are with our adventures with 300BO ARs. Another option would be to do epoxy coating, similar to the HITECH procedure. Let me know if you don't already that information and I'll get it for you.

Bob

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JDNC posted this 16 May 2015

Well, I got the mold and personally I didn't find it to tempermental but it does like high temps.  Long story short, 9.5grs IMR4227 and this bullet cast with lyman#2 powder coated and sized 0.311” put 7 or 8 (I can't remember) in 1” with my fouler shot going dead on. Should have shot the fouler for group as I didn't think of the powder coat.  This all at 100 yards. I first tried 20:1 that I had in my furnace powdere coated and sized 0.309” and it shot over 9” with egg shaped holes in the target.  Got lazy, and haven't done a chamber cast yet.  I was thinking that at sub velocities I wouldn't have to use hard cast but I think the faster twist demands it.  BTW, 8'pitch maybe right on the edge as for stabilizing this long bullet at these velocities.  This load gave me 1100 fps.  I tried LilGun but it smoked up my necks.  I had no cycling problems with either powder with this 16” pistol port barrel and never had to adjust my gas block from my previous adjustment. JD

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JDNC posted this 16 May 2015

358156hp wrote: The plan to wait and see what you have to work with when the mould comes in is a wise move. One guy I know powdercoats his bullets for use with the suppressor, then drops the coated bullets in cold water to compensate for any potential loss of hardness from the baking process. He uses a PID to control the baking temperature, thereby controlling the finished bullet hardness. Then the bullets will be sized (if needed) immediately upon drying. We haven't determined if sizing oven hardened PC bullets will work-soften them, as can happen with uncoated bullets. I supposed you could always size the noses too, if it becomes necessary although it would be a pain to do. Anyway, this is where we are with our adventures with 300BO ARs. Another option would be to do epoxy coating, similar to the HITECH procedure. Let me know if you don't already that information and I'll get it for you.

BobThanks Bob, I'm new to the powder coat thing and I'll admit I really thought it was a young person's thing making their bullets pretty more than anything else. BUT after yesterday I'm a believer due to the 8 shot group I got.  I never probably would have even considered PC if I had not built the Blackout.  I saw somewhere how a guy was dropping buckshot in his mold heating until it melted then casting hard alloy.  Then he reheated the mold over a flame until his sprues got soft then cooled and proceeded as normal.  I tried this on another 30 cal mold last year and it worked perfectly leaving a perfect tip.  I was using wheel weights so I just water dropped.  They shot good too!JD

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