300 BLK Newbie - SLR 5" Subs

[AK49]

Hey all, newbie to the forum here from Alaska, also new to supressors and to the 300 BLK caliber. I've been handloading other calibers for years, just about ready to start slinging powder for this project. Just introducing myself and have a few questions of course

The pistol is a 5" SLR barrel 1:6 twist behind a Rugged Radiant 7.62 supressor.

For the short barrel specifically with Berrys plated 220 gr, I haven't been able to find much detail as far as subsonic loads - I have a number of load data manuals and starting points for Lil Gun, VV N110 and N120 (cannot find A1680 locally) but not sure what adjustments I should be looking at. Is it common to drop some weight in powder initially vs what we would be loading with 8-10" barrels?

For instance, my data notes 8-10 gr Lil Gun, 8-10 gr N110 and 9.5-10.5 gr N120. Do you short barrel guys start in those normal ranges?

I have access to CFE BLK powder also but the others should keep me busy for a while. Also have H110 which I run through 458 SOCOM loads.

And how important is it to ladder test without the supressor installed, vs installed?

But at least I finally found small rifle primers locally, that took a while..

Glad to be here!

[ShootNstuff]

When loading subs, take off your can and check for stability first. Load a ladder and start high and work your way down to your lowest charge. I shoot into white poster board and look for clean holes, no keyholing. NOTE: you may not get the bolt locking back with the can off, so don’t worry about that yet.

Then when stability is confirmed, put the can back on and shoot through a chrony. Start high and work down until you reach the speed you want. I load 1 round at a time to check for bolt hold open.

When you have a fully functioning series of loads in the subsonic range, you can shoot your loads for groups and tweak from there.

That’s the basic process I do.

I don’t have a 1/6 but two 1/5 twist barrels and have had Berry’s bullets frag coming out of the barrel and Berry’s recommends no faster than a 1/7 twist for their plated bullets. I have also had cavity back 195gr MKZ expand as it leaves the barrel. All this will show up in your stability testing phase, which is why it’s important to shoot with can off first. I learned the hard way by making assumptions, and that resulted in destroying the core of one of my cans… I mean, who would think that petals would expand just from twist… now I know.

I spoke to the owner and Cavity Back is now redesigning their bullet to work with 1/5.

[AK49]

Appreciate the info! Interesting on the Berry's fragging, will definitely keep an eye out for that, and ditch the can initially. What length barrel on 1:5 were giving you those issues?

[ShootNstuff]

6” and 6.25”

[Demphna2]

Out of the powders you mentioned, I would try N110. 8-10 gr range seems pretty good, that's what I started with on my 6.5" barrel.

If you don't have it already, download Gordon's Reloading Tool. It's just like quickload, but free. It'll give you an idea of where to start, what velocities you'll see, what muzzle pressures you'll have, etc. Just like with any of these programs though, shit data in gives shit data out.