300 BLK 245 gr MBC question

[wheelman]

So I have around 250 of these left and was thinking i should load them for general purpose AR rounds around the farm. No need for subs so i am trying to get the most out of the round without asking for trouble either in the pressure or leading department.

The projectile is a 245 gr Missouri with their new hytech coating.

I am using IMR 4198.

Have nosed around more than once and have only found a couple of usable references to this combination in a supersonic load as most are looking to go the other way.

My last load was 12.7 grains giving 1280 fps and cycled ok. 11.7 gr was running around 1200 fps but would not allow the pick up of the next round so chamber would be empty. No pressure signs on any cases that I can notice but I am no expert..
Gun is the AR that JD put together for the auction.

I get the feeling that i am starting to compress at 12.7 as my bullet is seating just a snuff higher that at 11.7 and my eye tells me i am there.

My next disk setting will put me around 13.5 grains. Anyone see a problem with this load? I do not have any experience compressing loads.

I assume at some point the bullet will not seat and that is max compression/load?

The 12.7 gr was at 2.11 oal and the 11.7 gr was at just under 2 oal.

I know we have a few that play with this round. Marcus? Rumbler? others?

[Rumbler]

Wheelman,

I have absolutely ZERO experience with the IMR 4198 in 300BLK. Closest I have gotten is AA 1680, and that is about four steps faster. I use that powder for the 230gr Berger Tactical (BTJHP) with excellent results.


I can see your rationale for using a slower powder with the 245gr, I just have not loaded a bullet that heavy . . . yet. Hopefully Marcus can help.

Did you check the 300BLK "load catalogue"?

http://www.300blktalk.com/forum/viewtopic.php?f=141&t=81567

[wheelman]

The next faster powder i have in stock is H 110 and i am not going there. Too many stories about detonation with heavy bullets. I am not that experienced and i like my hands.

Well documented that 4198 is a bit slow for this caliber and probably at the limit of usable powders with respect to burn rate...

I may just go try and make one up at 13.5 to see if i can even get it to seat. Any general words of wisdom regarding compression?

[wheelman]

And I did nose around the recipe pages of the blackout forums but again - most were looking for the upper end of subsonic. Could not find where someone that was going in my direction.

[wheelman]

So the next disk up drops at around 13.3 gr. I tightened the bullet seat a snuff and made up a round. OAL at 2.12.

Clearly compressing holding the bullet next to the charged case.

Stopping here awaiting thoughts.

[Rumbler]

It has been my experience that compressed loads MUST be approached in little bitty increments. Pressures go through the roof very quickly as the level of compression increases.

Now way on earth I would jump from 12.7 to 13.3 in one step even though that is obviously (only) a .6 grain increment.

[marcus6176]

I know out of a 9" barrel getting around 1015 8.9 gr of imr 4198. But the bolt would only lock back was with a suppressor. I ran into a lot of problem with those projectiles. In other wors they suck. They cause a lot leading in the barrel. My advice is to melt those down and use this mold I have for 198gr and it is working really well for sub work. I have two molds for super if you ever want to try them out.

[marcus6176]

Don't use h110 for that heavy of a bullet. You could use lil gun, but I still recommend to melt them down. I had a load for thoses with imr 4198, it the page went missing. Uncoated OAL OF 2.120, coated OAL 2.048