312-185 in 300BLK Subsonic?

[petroid]

Searched around and didn't find much about this boolit in the BLK. My AR feeds the 309-170FN fine and I've killed a couple deer with it this year. I don't have the scratch for a NOE 311-247 or I'd be all over it. The 309-230-R works fine but for a little more thump I thought about trying to get a subsonic load worked up with a RN or FN boolit.

With my alloy the 309-170FN drops at 179gr. With Alox and GC they are 184gr. I can almost but not quite get this load to cycle subsonic with IMR4227 and Reloader 7. Ejects but won't pick up next round. I cast up some 312-185 today and they weigh 190gr as cast. With GC and lube they should be about 195. I made up a dummy round and it has to be 1.960" to chamber without jamming into the lands. This puts the GC below the neck. That's not a problem but it leaves lube grooves exposed to powder too. I haven't loaded any yet but just wondering if anyone else has tried this. I could ream out one cavity of the mold to remove the GC shank. This may add a little more mass as well. Thoughts?

[Moonie]

Generally subs won't cycle, even with the correct powder, until the weight gets to 200gr+. If I were you I'd try H4895, it creates lots of gas volume, if it won't cycle at subsonic speeds nothing will.

[petroid]

Function tested a few. At 195gr with lube and GC they cycle at 10gr of imr4227. On the verge of supersonic though and no last shot hold open. 10.5gr is definitely supersonic. Gonna try some reloader7 next. Dont have any 4895. Got a little 1680 to try too

[petroid]

Round 2 of function testing. 11.0gr Reloader7 will cycle but no last shot hold open. Still subsonic. Decided to test expansion. Line up four gallon milk jugs and one Drano jug. Went through all four milk jugs and clipped the bottom of the drano jug. 30 caliber holes all the way through. Guess my alloy is too hard for this speed.

[Jupiter7]

H4895 ain't gonna do it, too slow. Velocity will be low and action will be extremely dirty. Would expect 100% case fill before you really got anything out of it.

[petroid]

Even Reloader 7 is too slow really. Lots of unburned powder. I just tried it because it does keep the pressure up later in the cycle. Gonna try the 1680 next, but also I'll have to soften up the alloy. May file a flat on the nose too to assist expansion.

[petroid]

Tried some 1680. 10.5gr is subsonic and LSHO. Will test groups and expansion when I get some casted up softer.

[Moonie]

H4895 ain't gonna do it, too slow. Velocity will be low and action will be extremely dirty. Would expect 100% case fill before you really got anything out of it.

That has not been my experience in the real world. On paper yes, it appears to slow and you would expect lots of unburned powder. In reality there is little unburned powder and the velocity is not bad and the volume of gas will run a gas gun better than most other powders.

Jupiter7, have you tried H4895 in the 300BO?

[petroid]

That has not been my experience in the real world. On paper yes, it appears to slow and you would expect lots of unburned powder. In reality there is little unburned powder and the velocity is not bad and the volume of gas will run a gas gun better than most other powders.

Jupiter7, have you tried H4895 in the 300BO?

I can see how that could work as H4895 is recommended for reduced loads it would stand to reason that it would burn consistently at low charge weights. But I haven't tried it

[geargnasher]

Reloder 7 also has by far the best SD numbers with heavy, subsonic cast, and is one of the few I found that will cycle carbine-length gas systems reliably. AA1680 had SD swings of more than 30 FPS each way in my AR, and groups were terrible. Hope you have better luck with it than I did. IMR 4198 works but is not as good as Reloder 7 in my rifle. Tried many others and I always keep coming back to Reloder 7 and every couple hundred rounds blow the little yellow mummies out of the action, upper, and barrel extension with compressed air.

Anneal the tips of the Lee 230-grainers and they should mushroom nicely.

Gear

[Moonie]

The reason I gave up on H4895 was the high SD numbers, I switched to RL-7, but this thread was about trying to get 185gr to run subsonic in an AR, I don't think you will be able to do it reliably if H4895 won't.

[minmax]

"Little yellow mummies" ?

[petroid]

"Little yellow mummies" ?

I believe he's referring to kernels of unburned powder lol

[petroid]

Though they present a challenge when aiming at a distance with a red dot sight, squirrels are no match for a 195 gr bullet at about 1000fps