300blk 208gr

Moorvogi · Mar 1, 2015

I managed to pick up some powder. (IMR4198) and looking at the manufacture site, they don't list a starting load amount. They show a MAX of 11gr.

I want it to cycle in an ar15 (carbine gas system) but never like pushing the max as it just.. sounds more than I need/want.

The question is, does anyone know what to do in this case? I was thinking of taking it down to 9gr, then testing in 1/2 gr steps till it cycles consistently and stabilizes.

I don't want to go TOO low though...

iH8DemLibz · Mar 1, 2015

What are your reloading manuals suggesting as a starting load?

Moorvogi · Mar 1, 2015

iH8DemLibz said:
What are your reloading manuals suggesting as a starting load?

I have 2 manuals (lyman and hornady). Neither one list that powder, which is why I went to the manufacture of powder.

Magnumite · Mar 1, 2015

10% off max load is typically a safe starting load. There is usually a notation to that effect on the website. That would put you at 9.9 grains starting.

Pretty narrow range, that is heavy for caliber bullet. What are the expected velocities?

iH8DemLibz · Mar 1, 2015

Moorvogi said:
I have 2 manuals (lyman and hornady). Neither one list that powder, which is why I went to the manufacture of powder.

No harm in trying 9 grains.

Either it will cycle or it won't.

Getting cycling and stabilization to mesh may prove difficult.

You will have a very small window between cycling and not cycling.

Stabilization will have to be what it is.

smdub · Mar 1, 2015

Almost no one lists starting load for 300blk subsonic, just a "max". If you look at the pressure on hodgdons website for the 208gr in your powder: 11gr equals 20,200cup. **WAY** under the pressure limit of the barrel. Most 300blk sub loads don't stress the barrel at all. The max is usually somewhere around the max you can get into the case w/ a huge bullet. I load 1680 w/ 220gr SMKs. Im pretty sure the "max" load is compressed when you seat the bullet to the suggested OAL. I don't think there is any harm in starting at the max load for THIS application.

Edit: max saami pressure for the 300blk is 55ksi. cup and psi are roughly equivalent, so the max load is nearly a THIRD the pressure a load can safely exert. Mouse farts

Broncolou · Mar 1, 2015

Gonna be tough without tinkering with the gun to get it to cycle. I'd just wait for some 1680....... I have kicked myself in the nuts with other powders. I'm not saying it can't/wont work, but it will take a bunch of trial and error.

Here is 81 pages of info.......
http://www.ar15.com/forums/t_6_42/385765_300_Blackout_Master_Thread.html
Good luck!

Marauder · Mar 2, 2015

Hodgdon start point for (SUBS) is listed as max as the starting point then reduce. I could see it confusing to a newb.

Sticky · Mar 2, 2015

Moorvogi said:
I managed to pick up some powder. (IMR4198) and looking at the manufacture site, they don't list a starting load amount. They show a MAX of 11gr.

I want it to cycle in an ar15 (carbine gas system) but never like pushing the max as it just.. sounds more than I need/want.

The question is, does anyone know what to do in this case? I was thinking of taking it down to 9gr, then testing in 1/2 gr steps till it cycles consistently and stabilizes.

I don't want to go TOO low though...

Loading subs is done backwards from loading normal ammo... start with the max load listed and slowly work your way down. If you go too low, you may stick a boolit in the barrel, thus you start with the listed max and work down (I use a chrono to ensure my velocities are matching up to load data specs and to verify that I am actually getting subsonic velocities). Usually in my experience, the max loads will be above subsonic velocities and you have to work down a grain or two to get subsonic speeds.

If it doesn't cycle at the max listed load, then you probably need a different powder (read AA1680).

Moorvogi · Mar 2, 2015

Ahhh. Starting at max n going DOWN. Yes. I'm use to going min and working up.

The silver lining in it not cycling is.... You can find you brass easier!

Thanks for clearing up the "work down".

Pushrod · Mar 2, 2015

Sticky said:
Loading subs is done backwards from loading normal ammo... start with the max load listed and slowly work your way down. If you go too low, you may stick a boolit in the barrel, thus you start with the listed max and work down (I use a chrono to ensure my velocities are matching up to load data specs and to verify that I am actually getting subsonic velocities). Usually in my experience, the max loads will be above subsonic velocities and you have to work down a grain or two to get subsonic speeds.

If it doesn't cycle at the max listed load, then you probably need a different powder (read AA1680).

Pretty much this! IMR 4198 is a good powder for heavy subsonics and should work for you with the 208 grain Amax. I wouldn't go any lighter on the bullets with that powder though. 4198 sweet spot is beneath a 220 grain or better projectile.

Jmorrismetal · Mar 2, 2015

I tried a load out the other day 10.7 H110 with the 208 @ 2.230" going 1200fps out of an 8.5" barrel.

Might be able to use it as a data point.

LAW683 · Mar 2, 2015

Jmorrismetal said:
I tried a load out the other day 10.7 H110 with the 208 @ 2.230" going 1200fps out of an 8.5" barrel.

Might be able to use it as a data point.

Was this with or without a suppressor ?

Jmorrismetal · Mar 3, 2015

Without, I always make sure a load fires a stable bullet before firing them through a suppressor.

Signo · Mar 3, 2015

I use this combo extensively.

208 Amax
10.5g IMR 4198
COAL 2.230
KVB 223 Primers
Converted LC cases sized in RCBS Small Base Die

My rifle is 9 inch AAC upper with pistol length gas and 1/7 twist.I get BHO on last round and it cycles perfect with or without my 762SDN6. I had a few go super on a really cold day a few weeks back, but my Dillon throws powder a little inconsistent sometimes, so it might of been a hotter load. I dont have a Crono so I am not sure about exact speed. (Its on my list of things to get)

Carbine length gas system is going to change things a little but you should get a good starting point. This load was worked up from a thread on 300 blktalk on alternate powders.

I am currently working on a load using 4198 and Nosler 190g custom competitions, early testing has been successful with this combo also. This combo is a little tighter window on powder charge to stay subsonic.

If you work on this combo you should have pretty easy success.

300blk 208gr

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