I'm looking to start reloading sub sonic 300 blackout. I have everything needed except for the small rifle magnum primers. I have small & large rifle and pistol and small pistol magnum.

I can't find small rifle magnum anywhere. Is there an alternative?

Why would you need small rifle magnum for 300 BO subs? I've only ever loaded standard small rifle primers. Haven't had the need to try it, but the small pistol primers might work as well. If I'm not mistaken the small pistol does not sit as tall as the rifle primers, and may seat too deep. If it were all you had, it's definitely worth a try.

Its what hodgdon had for the load data. I thought it was a little weird too. I assumed it took regular small rifle primers

Standard rifle primers have worked just fine with my setup. I shoot a 242 grain cast bullet, which takes 10.5 grains of 1680 to cycle unsuppressed. I can load 11.5 grains, which gets me to 1050 fps suppressed.

This is the first time I've even heard of using magnum primers.

I appreciate the help! Ill give small rifle primers a try.

What mold are you using to cast bullets? This was something else I was considering doing.

And what are your thoughts on 1680? I have a few cans of H110 laying around.

I use the NOE mold 311-247-FN. H110 is going to be a good powder for light weight bullets, It won't cycle subs.

My initial workup for subs was to find a load that would cycle suppressed and unsuppressed. Lil Gun was the first powder I tried. I finally got it working at subsonic speeds, unsuppressed, most of the time, but still had occasional hiccups. Suppressed, it occasionally broke the sound barrier.

I moved on to use 1680 and it was much easier to get the cycling at slower speeds. Suppressed, I can get it down to 700 fps and still lock the bolt back on last round. Unsuppressed, It still functions fine in the 1000 fps range.

If you're using H110 or 296, you should use magnums primers. That powder is slow burning and difficult to ignite, and every load I have ever seen for it calls for magnum primers. Consult your manual, but there should be plenty of loads out there for .300 blackout that use different powders that don't require mag primers.

Walker - I use standard SPP when loading AA1680 powder (the only powder I use for sub 300 B/O rounds) for all of my Sub-sonic 300 B/O loads and have shot at least 1300 rounds with no failures. I shoot 208-220 grain bullets in two different AR's as well as my Ruger American Rifle.....Giggle Quiet Fun......Mark

This message has been edited. Last edited by: sigarmsp226,

I really appreciate the help guys. You saved me a lot of money in trial and error.

I went a head and ordered 8# of 1680 (hopefully it works!). And ordered the NOE mold.

I'm going to powder coat the bullets. I'm assuming ill still have to size them?

Walker - I made a error in my earlier post that I need to point out...I stated that I load using Standard SPP which is incorrect - I actually use Standard Small Rifle Primers with the AA-1680 powder....My apology for this posting error....Mark

quote:

Originally posted by walker77:
I really appreciate the help guys. You saved me a lot of money in trial and error.

I went a head and ordered 8# of 1680 (hopefully it works!). And ordered the NOE mold.

I'm going to powder coat the bullets. I'm assuming ill still have to size them?

Yes. Powder coating will add to the thickness. I use the NOE bushing sizer die set, and run two or three passes to get to my final size.

For 300bo, I usually start @ .315 then .312, and finally finish out @ .310. I feel like that sizing in stages is less likely to distort the bullet in any way. I’ve been very happy with the accuracy of this bullet out to about 75 yards. Haven’t really played much with it past that, but with that heavy of a bullet I imagine it would begin to drop pretty fast.

Try some IMR 4227. 10gr with a 220 bullet @ 2.26 OAL is quiet, accurate, and locks the bolt open with my 8.3” barrel. That is with a standard SRP .

hairy2dawg, what is your OAL on those NOE bullets?

quote:

Originally posted by walker77:
hairy2dawg, what is your OAL on those NOE bullets?

2.142. That's about the maximum length on these bullets where they fit in the mag & feed well.