Lilgun load data for what its worth.
 

For what its worth.

8.5 grn lilgun 240 grn smk

ar15 with 2 different uppers

m1s 16 inch barrel with pistol and carbine gas blocks, Bowers 9mm can:
pistol gas block open - 995 / 1012 full cycle and picked up next round
carbine gas block open - 980 / 965 bolt only came back about 1 inch and stopped.
Overall very little sound except for the action noise.

tp555 10 inch barrel with pistol gas block, aa 7.62 sd can:
1150/1155 full cycle and picked up next round.
Loud crack about 25 ft out from the muzzle but you could still hear the bullet hit the target.

8.2 grn lilgun 240 grn smk

tp555 10 inch barrel with pistol gas block, aa 7.62 sd can:
1006/1034 full cycle and picked up next round.
Much less noise than the 8.5 grn load out of this barrel but not as quite as the 16 inch barrel even with the 8.5 grn load. Not sure if its the suppressor or the extra barrel that makes a difference.

300/221 reloading issues
 

I have loaded aproximately 50 rounds for my new Remington 700 based 300/221 fireball. The brass was all newly formed (mixed headstamp) and fired for the first time with a suggested starting load of 10.7 gr of H110 with a 200gr Sierra MK. This data is from the Sierra loading mauual. I fired about forty of these with little to no issues and then BOOM. Powder residue and the report of the rifle back in my face. Now the bolt of the rifle opened smoothly. I quickly found that the primer was blown and flattened and stuck to the bolt face. The gas pressure has totally screwed my extractor. Now I am asking those of you who have a 300 Whisper or 300/221 fireball...... What the hell?On the bright side of things, the new barrel/rifle is starting to break in and it is shooting rather well but I am a little gun shy after this incident. What gives? Is this SEE incident or what? Why after 40 or so rounds with no issues did this happen? Please share your ideas? Low and slow is my goal as I plan to add a suppressor to this rifle soon.

Thanks,
Jerryr

Possible double charge or bullet jammed into the lands?

Neck wall too thick?

I have a Noveske 16" Barrel on a home made upper. I Cerrosafe cast the chamber and the neck is .336" on the casting. Ejected brass is .334" I made brass from Federal 223 brass. When I got to measuring it I discovered the necks were generally to thick, epecially near the shoulder. I decided to neck turn all of it to .011 wall. that gives me a .330 OD with a .308 bullet loaded in it. I was quite amazed at what was happening when I turned the brass. I used the neck turning atachment for my Forster Case Trimmer with a 3,000 rpm air drill driving it. The brass fit the 30 cal mandrell very tight after it was sized. Lubrication is obviously required. What I observed was that many cases were only thinned on one side until very close to the shoulder. On others the cutter started trimming right at the mouth of the case. Obviously the was a lot of variability in the thickness of the case necks. I think that turning the case necks was quite worthwhile. My first loads had an Extreme Spread of 23 fps on the Pact Chronograph for 10 shots. Groups were sub 1 inch at 100 yards for 10 shots. I think case neck thickness is a very big problem for this cartridge when using converted .223 brass. Several of the first dummy cartridges I prepared would not chamber in my AR. Those that would sometimes showed marks on the neck near the shoulder. They were obviously very tight.

Spook's 10.5" AR barrel (great barrel if you are on the market for one) with 1 in 8 Twist and pistol length gas system Subsonic loads:

Hoser's Lake City Brass
220 Grain Sierra Matchking
CCI Small Rifle Primer
8.5 grains of 2400
Seated to 2.13" (if memory serves) - just go to where they feed in standard AR mags which is a little less than a quarter inch from the front of the mag for mine.

I also get great results from the same above with
175 Grain Sierra Matchking or M80 military bullets (147 grain)
and 7.5 grains of 2400

All of these loads are subsonic and cycle my action with M16 type Bolt Carrier Group and standard carbine buffer and spring.
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8.3 gns of AA9 and 8.7 gns of N110 work well in my 10.5" ar with a Thunderbeast suppressor. I'm getting between 975 and 1025 fps.