please help a noob

[Crocks and Socks]

ok i have been lurking and reading here for the last few weeks and can not for the life of me figure out what i am doing wrong in regards to my cast bullets for 300 black out. i am using this lee mold. and tumble lubing with bayou bullets hi tek lube system.

http://www.midwayusa.com/product/938...5-ogive-radius

i have cast a few bullets and ran them through my .309 sizing die and loaded them up with 8.6 grains of imr 4227 and have shot them through my chrony and am hitting 1050 fps. the problem i am having is that i can not get my ar-15 to cycle these rounds. i have even stepped up to 12 grains and hit 1550 fps and still no cycling. i have a load worked up for sierra match kings 220 gr and they cycle fine in my gun and anyone elses. i thought that maybe i was loosing gas around my projectile so i found a buddy of mine that had an old 30-06 mold that cast 245 grain .312 projectiles and he sized them down to .311 for me and i tried them and still had the same results, the ar would eject a spent casing but wouldnt allow the bolt to come back far enough to pick up the next round.

here is where i need the advice from some of you guys that have been there and done it. i have been messing with this for about 3 weeks and have tried everything i know to do and am about to loose hope. im hoping that someone here could steer me in the right direction as i surely have no clue.

my first question is i am wanting to make a slug to slug my barrel and mic it. will soft sheet lead work for the slug? or will i need to order some barrel slugs from somewhere?

next question is upon slugging the barrel and getting an exact diameter how many thousands over my bore diameter do i cast my bullets?

third question is could it be possible that even though my bullets have been sized to 311 that when i am seating them in the case that my case could be smaller and is actually resizing the lead as i push it in the case? if this is a possibility where could i find a new decaping sizing pin that would expand the necks of my cases further than what comes stock in a set of lee dies?

also i am using cut down 223 cases to form my 300 blk brass.

any help would be greatly appreciated.

[Harter66]

Ok socks,
Your not leaking gas by if your not leading.
Nominal sizing is .001-2 over groove dia,its likely w/that Lee sizer your closer to .310 anyway. Slugging the bbl is always a good idea and will confirm your numbers. You're probably not ''doing'' anything ''wrong''. Here's why ,Ive a 32 Rem, data says full tilt w/a max load under a 321dia 170gr jacket it will clock 2100fps w/a Lee PB 325-170 sized .323 it clocks 2100 , 2 gr under the start load. I'm working a 7x6.8Rem the serria 120 23gr RL10x clocks 2230 a PP'd 27-130 FP at 131gr clocks 2250 on 22gr. Cast are slicker and operate at lower pressure (faster for the same charge) .
My best guess is a powder that will carry either higher pressure or greater volume to the gas port may be needed. W/that have you checked the gas port? Is it clear?

For apples and oranges I used IMR4350 in a 22'' s k s w/200gr boolit . 1800fps single feed 1200 at every mag length. It would cycle down under 1100fps though that was not my goal then. I know there's 300 data in here someplace.

[Crocks and Socks]

my gas ports are clean and i have tried these loads in 4 different ar's to make sure it wasnt the weapons fault. i have found load data here from others that have suggested loading with imr 4227 as well as h110 and lil gun. i have tried all three of those powders and still no joy. my mic'd bullets are micing at .309 and the ones i got from my buddy last night mic'd out at .311. i am begining to wonder if a powder such as unique like i load my 45 acp with will give me the pressure i need to get my gun to cycle? any input?

[Harter66]

The best I had w/Unique in the x39 was a crushed case mouth .

This 1 is not really a cartridge or platform I've worked in , but I think you will do better w/a fast rifle powder and 100% case volume. I could ask about gas tubes and buffers but I know very little about their relationships and parts swapping for function. Apoligies for not having more help. Someone w/more AR know how will be along.

[StratsMan]

Crock...

Pistol powders may not be your best bet in your rifle. As stated earlier, fast rifle powders are likely to carry more pressure to your vent, which is apparently what you need. AA1680 comes to mind, and is used for many 300AAC loads with heavy boolits.

You've covered the boolit diameter testing, and you stated that your vent is clear, but did you check the diameter of the vent hole??? If the barrel was built with the same size vent that is used when chambered for 223, then you'll need to keep your pressure high at the vent or you may not get the action to cycle reliably at sub-sonic pressures. If the vent hole is substantially larger than a 223 barrel (mine is), then it's much easier to get the action to work with sub-sonic loads. A lot of guys make sure the vent hole is well oversize, then put an adjustable gas block on the barrel. Open it for sub-sonic, and close it down for higher pressure loads...

And you can always increase the size of the vent if it's too small...

[runfiverun]

you just don't have enough gas volume to operate the gun fully.
nothing more nothing less.

[Crocks and Socks]

my rifle is a spikes tactical 300 blk with wilson combat barrel. the gun functions flawlessly with fmj projectiles both subsonically and supersonic. when using the cast bullets i cant get it to cycle no matter how fast i push them

[burr7870]

I have not fired j-words subsonic from my 300 whisper but my AR will cycle subsonic with the Lee bullet you are using at 9.5 grains of AA1680. Unfortunately it is still not that quiet with this powder w/o a can. You did not say whether you have a pistol port or carbine port. Mine has the carbine port and from what I read is harder to get to cycle with subs.

The other thing that helped my AR cycle is clean and lube the bolt with a dry lubricant.

[Crocks and Socks]

i have a carbine length gas port on my barrel. im not sure if i have any aa1680 laying around but i do have some varget that i load my 243 wssm with i wonder if i can get it to work, i know its a fast burning powder

[runfiverun]

varget is similar to 4064 in burn rate.
you'll need about 18-19 grs of it to function the rifle.

[Crocks and Socks]

runfiverun thank you very much for the help. i will try varget tomorrow afternoon and will report back. i would like to thank everyone who has chimed in here with advice, it is greatly appreciated.

[Crocks and Socks]

still no joy runfiverun the varget did not do the trick. also i could only fill the 300 aac case to 10 grains with varget and only hit 740 fps and the case would not eject.

[runfiverun]

okay you know what is too slow and too fast.
get more in the middle and use some volume.
the 1680 and rl-7 area is going to be more where you need to be.
4227 might work also.

[Crocks and Socks]

run five i havent been able to locate any 1680 or rl 7 but i have seen where a few folks are saying 5744 was working for them. i have sourced some of it and should be able to pick it up tomorrow. what charge would you start with?

[runfiverun]

I have no idea on the 5744 I have never used it.
I would have to pick the closest in burn rate and modify that data.
if there is data showing for a step faster powder I would start with it and go from there.

[Moonie]

Pistol powders don't normally work very well with carbine length gas systems for subsonic, it's a gas volume thing. 1680 is about the fastest you will have luck with. I couldn't get H110/W296 to cycle 100% at subsonic velocities in either of our 300 BO uppers. I did have some luck with cycling using H4895 but the SD was rather high. I've read RL-7 will work but I haven't tried it yet. My current load of choice is the Lee 155-.312 boolit in front of 15.3gr of H110/W296 @1800. My next attempts with both the 230 Lee and my 245 Accurate will be supersonic velocities rather than subsonic, I do not have a can and don't really have a need for subs.

[Crocks and Socks]

i was able to get my gun running without hiccups with 10.2 grains of reloader 7. they were mostly running at 1050 fps but had ranges of up to 60 fps under and 30 fps faster. all bullets made perfect lil round holes in the paper so it seems i have it worked out.
thanks to everyone here for the help. it is greatly appreciated