Loading 300 Blk for accuracy

[DIYguy]

I was able to work up a 300 Blk load for subsonic and 220g bullets that pretty consistently give me groups under 1" at 50 yards using Lil' Gun. Trying to work up loads for supersonic and getting frustrated. Started with 150g Hornadys FMJ-BT, used QuickLoad and did multiple ladder load test still using Lil' Gun. Groups look great if they were a shot gun pattern. Was talking with JB (John Paul) and he recommended 125g SMK's and H110 for supersonic.  Found my ingredients and started over with the 125g but Hornady 125 FMJ with cannelure. Better groups but still not consistent. Done full ladders starting from 18.2 of H110 to 19.6 in .2 increments, (20) rounds per, four strings of five. Do get and occasional four shot single touching hole with a flyer but really rare. Problem is loading on the Dillon 650 I'm getting SD's from 15 to 25, some time higher.

 

Now to next option. I load my precision rifle loads on the Forester with all the prep and get SD's between 5 and 8. Those are for bolt gun and using neck tension. Black out is a gas gun so crimping at the cannelure for those loads. I'm using the three die Redding Comp set on the Dillon and with the small power bar for the subsonic loads getting very good loads. For the larger loads and large powder bar getting variance in powder drops up to .2 grains. I don't want to have to hand load my charges but thinking I may have too to get consistency. I have two single stage presses so could do seating with one press and crimp with the 2nd. I can't find a Redding crimp die for 300 Blk.

 

How are others loading 300 Blk for supersonic and what results?

I'm attaching my load results for any loading nerds to see what I've done so far.

Reloading Recipes-Rifle (PSA 300 AAC BLK) revised2_09-29-22.pdf

[DIYguy]

Side comment. The 125 bullets are not boat tail and are flat base with cannelure. As part of the seating process I chamfer the inside of the neck and then do a separate pass using the Lyman M die and do the 2nd stage, open neck to receive bullet but no bell. The Dillon does a separate seat and crimp. I have a separate tool head just for decapping and sizing prep only.

[DIYguy]

More loading nurdyness attachedSeriesData_PSA-300 #1042_09-29-22 (H110@18.8) 125g Target.pdf

[Tom Freeman]

Not crimping can help with accuracy unless your brass is the exact same length.

 

I got the best accuracy with N-110 and Berger 215 and 230 Hybrids.

[TonytheTiger]

Start by using an actual match bullet as suggested by JP.

[Joe4d]

when I was doing this in 3006 found even with slight varience in charge with a dillon 4350 produced good results... Point being maybe another powder.
Also have you tried changing the over all length ? I know you have to load for function, but may have some room to increase OAL.
havent reloaded 300 AAC, but in factory ammo the Hornady 125 ish SST poly tip, and the Winchester 150 gr poly tips group th ebest.