300 blackout subsonic, hollow points, and expansion

So im hoping to put together some powder coated subsonic 300 blackout cast boolit loads for an AR, and am interested in something like the NOE 247gr hollowpoint mold. Im fairly new to casting so im still learning, but I do know that subsonic bullets tend to have a hard time expanding unless specially designed to do so. I was wondering a few things:

a) what lead hardness will allow a 30 cal 247gr hollowpoint to expand properly in a person or animal, assuming that its even possible? (these are hunting and defense rounds)
b) Will said hardness cause the boolit to get chewed to hell in an AR action?
c) Is hollowpoint the best bet for this task? worried that round/spitzer bullet will pass right through (TwangNBang did a video shooting ballistics gel with the spitzer tip NOE 247gr, and it went clean through 2 gel blocks without the slightest hint of tumble or expansion), and worried that any flat nose wont cycle reliably on the feed lips.
d) am i expecting too much out of these cast boolits and resort to machined expansion rounds like the Lehighs or Maker REX's?

Thanks for the tips!

Honestly, if I were to use cast hp's in a 300 blackout, I'd use pure lead. That will give you the best chance at opening.

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You're looking to find a tough combination of things within the AR platform. Now, with a bolt gun I think you may have a bit better odds.

I think soft are going to get tore up/hung up in an AR. And, nothing says you'll get much expansion.

I think the guys running cast in ARs are running them hard to get them to function well and they gave up on expansion. Could look at something with a large meplat (works in a bolt) but not sure that will run in an AR either.

Throw in the challenges some have getting ARs to run with subs (depending on barrel length and gas system/openings) and you have a lot of work/time ahead of you possibly to get that to work just right.

I would go with off the shelf in this case to possibly get some expansion and reliable feeding.

I'm a 300 guy but use the subs in a bolt gun and supers in the AR.

Check out this group buy thread. Lots of good info starts several pages in after the molds were delivered. They were offered as solids or hollow point. I did not look at his shop, but the mold may be available from M&P. He sometimes stocks them after a group buy.

https://castboolits.gunloads.com/sho...+.300+Blackout

Sub-sonic defeats the expansion of a hollow point . You are going to have to do a delicate balancing act between Boolit Hardness - Hollow Point Size - Velocity .
The fact that the ammo must feed in a semi-auto complicates the matter .

I would choose a BO dedicated mould and have it made to cast a solid point , small hollow and large hollow (NOE type pins) with replaceable pins . Then it's a matter of testing what hardness / velocity / hollow point works best.

If the alloy hardness is soft enough you won't need a lot of fps ... a gas check would help with leading of the softer alloy or powder coat it .
Good Luck ...You can do it !
Gary

Try pure lead boolits with a hollow point and s2 ogive. And work up to an alloy that cycles.

Shoot ballistic gel at 25 yards and add small bits of harder lead into the mix until you start cycling the gun reliably.

You will need to powder coat at least 2 coats and test what sizes shoot best for accuracy.

My BCA upper liked them sized down to 308 and needed a harder alloy

My stag sbr upper liked 310. And works fine on straight lead.


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I wouldn’t shoot pure lead in a NON muzzleloader. A ml uses a patch to protect the bore from the lead and engrave the rifling into the boolit. Now you might be able to pc your lead boolits to make them work. Experiment and see what happens but a super soft bullet is not going to act like a high speed hp would, it’s going to fold in on itself. A solid lead bullet will flatten and expand. I’ve killed many deer with ml lead bullets that flattened out with deadly results. Good luck.

My results with soft hollow points in an AR has been disappointing. The feed ramps distort the nose resulting in poor accuracy.

Sounds like you are working to opposite ends of the results. The subsonic projectiles need larger diameter, or more weight for the diameter and a larger meplat to increase their performance, not a softer projectile.
I use 230g very hard cast, 70-20-10 alloy, water dropped, with a double powder coat in my sub sonic 30cal ARs. the penetration is very good.
But in the BO it ain’t a big hog or bear gun.

A single shot or bolt action rifle would make goal easier to achieve .

I fooled around with hollow point is 9mm Luge for a long time . What I discovered was a soft truncated cone boolit mushroomed "more better" than any hollow point and would feed w/o distorting the hollow point . I gave up the HP and use a alloy 50-50 lead & COWW (bhn 8 ) 124 gr. TC GC , the gas check lets me drive the boolit to velocity that allows expansion of the soft boolit .
I wouldn't use pure lead but 1 part Tin with 20 - 30 - or 40 parts lead would make a alloy that will mushroom without a hollow point .
Good Luck with experiment ...keep us posted .
Gary

I've researched this a good deal. The only way you are going to get reliable expansion from subsonic, is to pony up and get some of the Lehigh Defense projectiles. They are the only ones I've seen that accomplish this goal. Pure lead is never going to work. The violence of a AR action is going to bend and bent the bullet.