450Bushmaster.net

I was thinking about trying some subsonic load in my suppressed 450 Bushmaster AR

I saw a write up on some loads with 500gr bullets...……...I am not interested in that heavy.

Has anyone made some loads with 200 - 300 gr. bullets ?

What powder do you use and how much ?

Accuracy ?
Will the rifle cycle ?

Not a whole lot of people trying subs, unfortunately.

I have no first hand knowledge, so take my opinion for what it's worth.
Problem you might run into when trying 200-300gr subs is there is too much case capacity. Maybe 300gr will work. You will probably end up supersonic real quick. If you can find a powder that works, you will probably end up with extremely low pressures, so they will be very dirty loads, and slim chance of getting the rifle to cycle. If you run the heavier bullets, you should be able to get it run with a carbine length gas system, midlength gas I wouldn't even attempt. One member here was playing with heavier subs, and couldn't get his rifle to run with a midlength gas system.

As to powder, I would start with slower powders then normal, just to be safe. Work your way down. Then maybe try a little faster powders if that doesn't work.

Bmt85 wrote:One member here was playing with heavier subs, and couldn't get his rifle to run with a midlength gas system.

Yes, that's me. BMT85 hit it on the head. If you aren't going heavy and sub you will have lots of dirty, unburned powder and no chance of cycling due to low chamber pressure. I had to push my heavy bullets on the order of 1400 fps to cycle reliably with a midgas system, and I'm starting to read pressure signs here. I do have much higher hope for the GC bullet I'm trying out though.

The people running non-cycling or bolt action light loads subsonic generally use a fast burning powder and a filler to keep the powder packed near the primer. Running a fast powder with low case capacity is NOT recommended.

All that said, these work ups are in anticipation of my suppressor which "should" be getting approved soon. I'm assuming this will help with cycling.

I've never tried any sub-sonics in a AR-15.
Have used Hornady 250 gr HP for punching paper. Have shot in wet paper media and Cutting Edge Bullets 240 gr Handgun Raptor with a plastic tip they will expand down to 700 fps. Using 12.5 gr. of Trail Boss in a Ruger with 16" barrel average for 5 shots 986 fps at 15', at 50 yards 770 fps. Very quit for a large bore suppressed with a Hybrid. With the CEB I've shot several bucks, limiting shots to 50 yards, expansion has been very good and completely penetration on broad side shots no bases have been recovered, several blades were found in off side hide.
35 yards 920 fps +1 3/4 "
50 yards 770 fps -3/4"
100 yards -7" no velocity reading taken


I'am work with some Makers Bullets 425 gr. also. 18 gr. Enforcer 1009 fps average at 15' . I haven't done any wet paper media testing yet.
50 yards + 1 1/2"
100 yards - 2"
Makers Bullet being all copper takes up alot of powder space.