300 blackout with NOE 247 and 4227 ... how much is to much?

I am working with the 247 grain NOE boolit in an AR-15 chambered in 300 blackout. I have problems getting the action to cycle. The rifle has a 16 inch barrel with a .120+ carbine length gas port. I have clipped a few coils off the buffer spring and am considering lightening the buffer. I now have decent ejection but it still short cycles. I have mated the gas block and gas port as well as verified the gas tube to gas block fit.

I can go super sonic as I am not running a can and can run gas checks if necessary to get reliable cycling.

I am using 4227 cause I like it and I can't find any 1680 for sale right now due to the panic.

The load data I can find for 4227 stops at sub sonic levels with pressures well below other listed supersonic loads, so I assume I can go higher on the powder charge without getting excessive pressures.

Does anyone have any idea what a max load of 4227 using this case / boolit?

Does anyone have quick load? Would it give me this type of information?

Any insight, tips or suggestions would be appreciated.

If you don't want to post load data please feel free to PM me with it.

Thanks in advance!

I think your problem lies in the burning rate of 4227 and your gas port. I say " think " as I read of a simular problem with a 223 AR. Anyway, do a search for "gas ports" & "gas blocks".
On the other hand, since you are limited to 4227, do the step test, load in .3 gn.steps till you see signs of pressure or your weapon cycles

IHMSA # 566 "time sure flies when you're having FUN"

That gas port size should allow proper function easily. I opened mine to .110" and have no problems when the right powder is used. I have never used 4227 so I will defer to the experience of others and assume its pressure curve is not suitable. So far the powders that work for me are H110, Lilgun (very good), AA5744 (very very good), and Reloader 7 (probably my favorite especially for heavies). It's all about gas volume and port pressure in this cartridge. I have had loads with some of the faster powders that were bordering on very high pressure and all I was getting was short stroking. But with the right powder, it runs like a champ and is alot of fun to shoot.

Wilson's combat makes a variable takeoff valve block. I have this gadget on order. The addition of the "can" will help smooth out "early" pressure curves. Last resort is playing with the springs because that affects the Lower's function and would make the gun less interchangeable. ... felix

Colt is bringing out a gun actually meant for caliber interchange. It's the 2100 dollar AR version, new this year. http://www.youtube.com/watch?v=0O9wUV8ozmk&feature=youtu.be ... felix

Last edited by felix; 03-09-2013 at 08:25 AM.

Leave the coils on the buffer alone. What buffer are you currently running?

I'd follow Wayne S advice and work up looking for signs of pressure.

You may just have to switch to a different powder with a burn rate that is a better match for your gun.

I appreciate all the ideas!

I am current running a carbine buffer. I need to weigh it and a spare that I have and see if any improvements can be made.

nhrifle -- were your reloader 7 heavy bullet loads sub or super sonic? Were the bullets cast or J's?

Once the panic settles down I will have some more powder options but powder and loaded ammo is difficult to find in this area at this time.

I plan to continue to work up loads in small increments as suggested, but would like some idea of where to stop. Waiting for cratered, flattened, loose or blown primers has always made me slightly nervous.

However this plays out I am planning to keep the buffer and spring dedicated to this upper as they probably will not be suitable for use with others after I tinker with them.

Will quick load give me the data that I am seeking? I have been considering buying a copy for years and just never got around to it.

Last edited by CATTLEMAN; 03-09-2013 at 10:41 PM. Reason: spelling

I've gotten a sonic crakc from every load I have tried so far that cycles the action. Once I get some 1680 (impossible to find around here) I will get some subs worked out.

One Solution

Dual adjustable gas ports on 300 Whisper barrel

My Synrac Ordinance adjustable gas block works great, adjusts easily, and fits under a free float tube. They have detents to keep adjustment with no loctite. They were about $100.

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Abbreviations used in Reloading
Pointed Soft Point "Core Lokt"

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