300Blk - Hornady 190gr Sub-X Bullets - Reloading (2024)

I finally found the Hornady 30cal 190gr Sub-X bullet in stock for my 9in 300blk AR suppressed, and I want to build a subsonic load for it (sub 1100 fts). Below I will list what I'm starting with, but if anyone has any experience, please post below.

Brass - LC once fired, Starline new

Primers - CCI 450

Powders -
Accurate 1680 - 11.8gr, 12.2gr
CFE BLK - 12.4gr, 12.8gr

COL - 2.070

I have the Hornady reloading book that recommended the 2.070 COL. The velocities are based on a 16in barrel, and because I'm 9in, I started loads reporting 1100fps and went up.

I've used ACC 1680 on 300blk rounds before. I really like it but I did find out this summer (I live in Phoenix) that it is not temp stable at all. I left my loaded ammo in the 120 degree garage for a day and they shot 100fps faster than the the ones I kept inside. This matters when you are trying to keep a round subsonic. I know a lot of people sh*t on CFE BLK, but I have actually had really good experience with it in another 300blk round I made. Much more temp stable and got single digit SD.

I've also learned that COL is tricky with subsonic rounds. Obviously you want the round to be as long as possible to stabilize the bullet, but to leave and air gap with the powder makes velocities hard to control.

I'll post my results when I have them. I would appreciate any of your tips or experiences.

Matthias86 said:

Had anyone noticed these Sub-X Bullets not being completely uniform??...Seating these to a uniform COL was a pain in the ass.

Click to expand...

I believe it’s due to the flex tip. I ran into the same issue with the ftx in my 45-70. They want you to buy their flex top seater

I found better SD with a regular small rifle primer rather than magnums.

Also I’ve had poor results with body shots on medium game with all subsonic bullets except Maker bullets. The SUB X hasn’t expanded reliably for me. Plus the energy on target is less than a 220-240 grain bullet.

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So I shot my first round with the sub-x. I was at an indoor range so didn't really care about accuracy. I had my chronograph and wanted to make sure everything cycled okay.

Accurate 1680 11gr - Ave 1066 fps, SD 18.2
CFE BLK 12.4gr - Ave 1054 fps, SD 16

Everything cycled wonderfully. I think the standard deviation is due to the discrepancy in seeding depth.

So I loaded another set. First of all, I bought the FTX seating stem and it destroyed the top of the bullet. If anyone knows what I am supposed to get, please tell me. My Hornady dies came with the stem to seat the A-Tip and that actually worked out well with very little damage if I lubed the case mouth. I was able to seat 20 rounds with a +/- .003 discrepancy in COAL, which I'm very happy with compared to my last batch. I go to the range again tomorrow and will post my new results.