300 blackout subsonic load test

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Walther shooter
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300 blackout subsonic load test

Post by Walther shooter »

I started loading for my 300 BO today. I got a box of 208gr Hornady Amax bullets. Cut my cases down and trimmed to length. I went to the Hodgdon website and got data from them for using H110 powder. 9.5 grains of powder, SRP and seated the bullet to 2.258-2.260. Gonna go test them tomorrow in my AR. 16" barrel with pistol length gas system. Their site says 1080 fps. Gonna shoot them without the suppressor, in case something goes wrong, which I doubt it will. Taking the chronograph also.
Anyone else try this load?
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dellet
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Re: 300 blackout subsonic load test

Post by dellet »

You might consider shortening the length, it will probably feed easier and lower the velocity spreads.

I would also probably load some down to 8.8 grains. I would not be surprised if 9.5 goes super.

They may not cycle or lock back without the suppressor, so check stability without, test with the suppressor before giving up. New assemblies can be tight for a few hundred rounds.

Have fun and report back.
300 Blackout, not just for sub-sonics.
Walther shooter
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Re: 300 blackout subsonic load test

Post by Walther shooter »

So I thought I'd post my findings.
16" AR pistol gas system.
208gr Amax
9.5gr of H110
CCI 400 srp
LC converted cases
Odin Works MOAB Suppressor
Bolt licked back on every round. Cases ejected at 3 O'clock, about three feet away. Stripped next round from Colt 20rd magazine.
No signs of pressure on cases.

Rounds 1-4 were unsuppressed
1) 1160fps
2) 1039fps
3) 1098fps
4) 1083fps
Average velocity 1095fps

Rounds 5-9 were suppressed
5) 1091fps
6) 1105fps
7) 1108fps
8) 1087fps
9) 1177fps
Average suppressed velocity 1114fps

I think I will drop to 9.5gr of H110 next
Walther shooter
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Posts: 7
Joined: Tue Nov 10, 2020 10:17 pm

Re: 300 blackout subsonic load test

Post by Walther shooter »

Walther shooter wrote: Sat Nov 14, 2020 5:02 pm So I thought I'd post my findings.
16" AR pistol gas system.
208gr Amax
9.5gr of H110
CCI 400 srp
LC converted cases
Odin Works MOAB Suppressor
Bolt locked back on every round. Cases ejected at 3 O'clock, about three feet away. Stripped next round from Colt 20rd magazine.
No signs of pressure on cases.
Cycled both suppressed and unsuppressed.

Rounds 1-4 were unsuppressed
1) 1160fps
2) 1039fps
3) 1098fps
4) 1083fps
Average velocity 1095fps

Rounds 5-9 were suppressed
5) 1091fps
6) 1105fps
7) 1108fps
8) 1087fps
9) 1177fps
Average suppressed velocity 1114fps

I think I will drop to 9.2gr of H110 next
Chris melone
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Re: 300 blackout subsonic load test

Post by Chris melone »

Walther shooter wrote: Sat Nov 14, 2020 5:04 pm
Walther shooter wrote: Sat Nov 14, 2020 5:02 pm So I thought I'd post my findings.
16" AR pistol gas system.
208gr Amax
9.5gr of H110
CCI 400 srp
LC converted cases
Odin Works MOAB Suppressor
Bolt locked back on every round. Cases ejected at 3 O'clock, about three feet away. Stripped next round from Colt 20rd magazine.
No signs of pressure on cases.
Cycled both suppressed and unsuppressed.

Rounds 1-4 were unsuppressed
1) 1160fps
2) 1039fps
3) 1098fps
4) 1083fps
Average velocity 1095fps

Rounds 5-9 were suppressed
5) 1091fps
6) 1105fps
7) 1108fps
8) 1087fps
9) 1177fps
Average suppressed velocity 1114fps

I think I will drop to 9.2gr of H110 next
Weird that you had a round on each string that was high. Are you loading powder manually or with some sort of powder drop? Looks good though
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Walkers Bay
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Re: 300 blackout subsonic load test

Post by Walkers Bay »

That load combo was exactly what I had in mind, going to watch your progress
I would have to have a look at my book but the last 208gr subs were for the post card challenge. From memory it was with 2205 Adi.
You might be lucky and have a rifle that cycles subs well from new.
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