Originally Posted By -Obsessed-:
My advice is atay away from LilGun with 300 BLK. Its a nightmare if you get a lot that burns hot. It will literally vaporize the base of your bullet and deposit copper drips all in the action, on the bolt, etc.

Took me 2 years to chase that down to the powder.

Originally Posted By Kalashnikov762:

Just the reason I'm here.  Was that from subs or SS?

Originally Posted By -Obsessed-:


Subs. Did it with every sub projectile I used, from 190gr up to 245gr.

Shame as I had a ton of it and it is oretty quiet.

Originally Posted By DVCNick:
As someone who's loaded about 10k rounds of 300blk (not a lot, but not nothing):

-180gr bullets:  Probably not the best for this cartridge.  You can probably make them run, but they are really heavy for supers, and really light for subs.  I like the 110 to 125gr best for supers, maybe 147s on sale; they will also work for blasting ammo. 220gr for subs, 200gr on sale.  Some commercial subs are 190gr; I have not tried them.  I think you might have trouble trying to get 180s to run as subs especially if your gun is set up to run both sub/supers.

-This thread is the first time I've ever heard that you are supposed to use magnum primers.  I've never used a magnum primer in 300blk.  I tried some pistol primers in subs once when primers were scarce; they fired and functioned fine, but they were Federals and I was getting the occasional double/slamfire in an AR from the floating firing pin impact.... so I would definitely not recommend pistol primers.

-In DI ARs, the only powder I've ever got to function consistently with subs is AA1680.  I've tried H110, Lil Gun, and neither are even close to cycling a DI AR for me with 220gr subs.  I've done a little bit of testing with N120, so far so good, but need to get a larger sample size when I get back around to it.  In my Spear LTs, setting them to high gas and with a can, they work so far with H110 or Lil Gun subs.  I bought the Lil gun to try with subs; personally I haven't noticed it running any hotter or had any other problems with it in the little bit I've used it, other than it not able to run a DI AR with subs.  My current plan is to eventually burn it up in subs for the Rattler since it will run that gun on high gas (so far).

-I use H110 all the time with supers.

-If you find "Xtreme" headstamp 300blk brass, 100% chuck it in the trash.  It has WAY less internal volume than other headstamps, and in my opinion, is flat out dangerous if you put a normal supersonic charge in it.  If you load it with subs, it won't be dangerous, but will turn your subs into supers when you aren't expecting it.

-I also chuck any 223 converted brass that isn't Lake City.  I've had one too many other headstamps with an overly thick neck that didn't want to chamber, to the point I don't bother with converted brass unless it's LC, which I know works.  Overall, 300blk is common enough now that the vast majority of brass you come across will likely be manufactured 300blk and not converted 223.

-Get 300blk dedicated mags; they are more forgiving of different ogive profiles/OALs than 223 mags.

There is a huge variation in ammo, bullet weights, powders, barrels, etc... so more than any other cartridge, "YMMV" really applies here.  So learn what you can on the internet, use it as a guide, but if any variable in your system is different, you might get a significantly different result than the guy on the internet did.

Originally Posted By GHPorter:
I'll echo DVCNick's point about 180 grain bullets.  I've had lots of success with 147-150gr FMJs in supersonic loads.  My experience has been that these are definitely supers, and adding only 30 grains of bullet weight probably wouldn't make it particularly easy to keep those bullets subsonic.

Obsessed's point about Lil Gun in subs is something I've seen mentioned in many places.  It is just great for supers, but not a good fit for subs.  Check your load data sources for specifically subsonic loads to find which powders work best in that velocity range.

I've never used magnum primers with any powder for 300 Blackout.  Some loading manuals have a basic philosophy that "certain powders" "must" be ignited with magnum primers.  I prefer to verify that mandate before I spend extra money on magnum primers.

Originally Posted By DVCNick:
As someone who's loaded about 10k rounds of 300blk (not a lot, but not nothing):

-180gr bullets:  Probably not the best for this cartridge.  You can probably make them run, but they are really heavy for supers, and really light for subs.  I like the 110 to 125gr best for supers, maybe 147s on sale; they will also work for blasting ammo. 220gr for subs, 200gr on sale.  Some commercial subs are 190gr; I have not tried them.  I think you might have trouble trying to get 180s to run as subs especially if your gun is set up to run both sub/supers.

-This thread is the first time I've ever heard that you are supposed to use magnum primers.  I've never used a magnum primer in 300blk.  I tried some pistol primers in subs once when primers were scarce; they fired and functioned fine, but they were Federals and I was getting the occasional double/slamfire in an AR from the floating firing pin impact.... so I would definitely not recommend pistol primers.

-In DI ARs, the only powder I've ever got to function consistently with subs is AA1680.  I've tried H110, Lil Gun, and neither are even close to cycling a DI AR for me with 220gr subs.  I've done a little bit of testing with N120, so far so good, but need to get a larger sample size when I get back around to it.  In my Spear LTs, setting them to high gas and with a can, they work so far with H110 or Lil Gun subs.  I bought the Lil gun to try with subs; personally I haven't noticed it running any hotter or had any other problems with it in the little bit I've used it, other than it not able to run a DI AR with subs.  My current plan is to eventually burn it up in subs for the Rattler since it will run that gun on high gas (so far).

-I use H110 all the time with supers.

-If you find "Xtreme" headstamp 300blk brass, 100% chuck it in the trash.  It has WAY less internal volume than other headstamps, and in my opinion, is flat out dangerous if you put a normal supersonic charge in it.  If you load it with subs, it won't be dangerous, but will turn your subs into supers when you aren't expecting it.

-I also chuck any 223 converted brass that isn't Lake City.  I've had one too many other headstamps with an overly thick neck that didn't want to chamber, to the point I don't bother with converted brass unless it's LC, which I know works.  Overall, 300blk is common enough now that the vast majority of brass you come across will likely be manufactured 300blk and not converted 223.

-Get 300blk dedicated mags; they are more forgiving of different ogive profiles/OALs than 223 mags.

There is a huge variation in ammo, bullet weights, powders, barrels, etc... so more than any other cartridge, "YMMV" really applies here.  So learn what you can on the internet, use it as a guide, but if any variable in your system is different, you might get a significantly different result than the guy on the internet did.

Originally Posted By DVCNick:
As someone who's loaded about 10k rounds of 300blk (not a lot, but not nothing):

-180gr bullets:  Probably not the best for this cartridge.  You can probably make them run, but they are really heavy for supers, and really light for subs.  I like the 110 to 125gr best for supers, maybe 147s on sale; they will also work for blasting ammo. 220gr for subs, 200gr on sale.  Some commercial subs are 190gr; I have not tried them.  I think you might have trouble trying to get 180s to run as subs especially if your gun is set up to run both

Originally Posted By Kalashnikov762:


I did my first test today and 9.5 of 1680 pushed my 180's at 850fps. Brand new upper cycled perfectly.  Working up will be a breeze if 180s are cycling.