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

[CATTLEMAN]

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!

[Wayne S]

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

[nhrifle]

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.

[felix]

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=0O9wU...ature=youtu.be ... felix

[Jailer]

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.

[CATTLEMAN]

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.

[nhrifle]

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.

[Artful]

One Solution

Dual adjustable gas ports on 300 Whisper barrel

[bmiller]

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.

[CATTLEMAN]

Just an update:

I am running an adjustable gas block, but I have it full open as I need more gas not less.

I did finally get the rifle to cycle and lock open on the last round with 4227 and the NOE 247 but I had to go supersonic to do it. I am sure it is super but I haven't shot it over a chronograph yet.

I shortened the buffer spring and lightened the buffer and worked up the load .2 grains at a time until it ran.

With the load that cycles and locks open there were no pressure signs and the accuracy was so-so.

I need to work on the load to try and improve the accuracy: bullet fit, crimp, charge weight etc. As I suspected the recoil is very similar to a 44 magnum out of a lever action carbine.

When I can get some other powders I am going to try to find a subsonic load that will run acceptably.

I suspect that what I really need is a pistol length gas system. I may look into modifying or replacing the barrel as time allows.

I also loaded and shot some 135 grain GC boolits that were designed for the AK. They were loud but the recoil was a lot lower and they easily cycled.

The quest continues...

[x101airborne]

I am running an 11 inch upper on a form 1 SBR lower with the pistol length gas system. My sub load is the NOE 247 over 5 grains of red dot. No crack, cycles ok as long as the weapon is clean, and locks open on the last round. Only other mod I did was to get a JP enterprises capture rod recoil system. It replaces the buffer and spring and works a lot more slick.

[CATTLEMAN]

x101airborne -- Pistol length gas seems like the way to go ...

If you don't mind me asking:

Which lube are you using?

What kind of accuracy are you getting?

Are the boolits plain base or gas checked?

Are you sizing them and if so to what diameter?

I hate to admit it but I haven't slugged the bore on this one yet.

My first set of the 247 NOE boolits were: ww, sorted +/- 1 grain, lubed with Jake's red, gas checked and sized 309 cause that was what was already set up in the sizer. The accuracy was so-so about 1.5 inches for 6 shots (two 3 shot groups on the same target loaded separately) at 25 yards. I used the pistol range since I was in a hurry and primarily there to find a load that would cycle.

I am considering turning the case necks slightly and sizing the next set to 311. The throat I am working with is large enough to allow boolit release at 311 without turning based on the fired cases.

I think I can get some 1680 within the next couple of weeks...

I have a jar of boolits already cast and weight sorted but not processed as I try to find the optimal load.

[x101airborne]

Sure.
My lube is just plain ole 45/45/10 tumble lube. Alox would probably work as well
My alloy is 50/50 pure/WW air cooled. Boolits are plain base and sized to .311. I did not slug my barrel either, I know, I know. I just sized some boolits to .309 and .311 and tried both. They shot about the same, so I focused on powder charge to improve accuracy. I am seating about .005 off the lands for smooth lockup. I tried several powders to get here and Red Dot worked for me about as well as anything.
Just not a lot of thump for hogs.

[Paulinski]

I was under the impression that pistol length gas system is neede for reliable cycling of subsonic loads...

I have 16" LMT MRP barrel that I have tried 220gr SMK J words with 10.8gr of AA1680 (cycles and locks on empty). As soon as it will warm up I will be casting with the NOE mould and workin up a load...

[sparky45]

I am running an 11 inch upper on a form 1 SBR lower with the pistol length gas system. My sub load is the NOE 247 over 5 grains of red dot. No crack, cycles ok as long as the weapon is clean, and locks open on the last round. Only other mod I did was to get a JP enterprises capture rod recoil system. It replaces the buffer and spring and works a lot more slick.

Airborne; has your load been tested in a carbine length (16") barrel yet?

[Gunnut 45/454]

Now you have an out of spec buffer spring! Never cut the spring to get an AR to function! If you use the data provided below you should be able to get full Function in your AR! If these loads will not do it then you have a gas problem NOT A SPRING PROBLEM! You could try a lighter buffer! Is your gas key tight-no broken screws? No gas leak in the tube?

Another question do you keep your BCG lubed well (as in WET)?

220 GR. SIE HPBT IMR IMR 4198 .308" 2.260" 11.5 1036 25,300 CUP
220 GR. SIE HPBT Hodgdon H4198 .308" 2.260" 11.5 1068 25,600 CUP
220 GR. SIE HPBT IMR IMR 4227 .308" 2.260" 10.5 1014 28,800 CUP
220 GR. SIE HPBT Winchester 296 .308" 2.260" 9.9 1050 29,700 CUP
220 GR. SIE HPBT Hodgdon H110 .308" 2.260" 9.9 1050 29,700 CUP
220 GR. SIE HPBT Hodgdon Lil'Gun .308" 2.260" 9.0 1077 31,100 CUP
230 GR. BER TACT IMR IMR 4227 .308" 2.260" 10.2 1065 37,100 CUP
230 GR. BER TACT Winchester 296 .308" 2.260" 9.5 1085 34,500 CUP
230 GR. BER TACT Hodgdon H110 .308" 2.260" 9.5 1085 34,500 CUP
230 GR. BER TACT Hodgdon Lil'Gun .308" 2.260" 8.7 1077 28,900 CUP


(Click on any icon below to return to that product)

[Don1955]

I have a cmmg upper in 300BO. I only use 4227 with J bullets untill I can get some cast boolits and then will only use 4227 with them also. I had some cycle problems at first in this 16 inch upper but it proved to be break in of the BCG. Keep it wet the first 300rnds. I never could get bluedot to cycle reliably but 15.0 of 4227 with the old WW2 tracers seated to the crimp grove work well. 17 grs. expanded primer pockets after 3 reloads so I cut back to save on brass in these componet scarce times. 4227 should work when you get the BCG broke in and I will be trying the heavyer cast soon. Keep us posted on you progress.

[CATTLEMAN]

Another update:

I appreciate all the suggestions and comments. Yes, if I had it to do over again, I would have opted for carbine barrel with a pistol length gas system with traditional rifling (assuming a barrel with those specs is made, I haven't been able to find one listed anywhere). But I have a carbine length gas system and am having fun trying to make it work.

To clarify, the gun runs fine with jacketed supersonic loads. I am trying to make it do one thing well: run subsonic NOE 247 boolits (preferably plain base) without a can as I want really inexpensive low recoil ammo that cycles and locks back without a suppressor. I was limited to 4227. The 4227 powder was what I had on hand that appeared to fit my goals, and I would still like to use it.

But I now have more powder options as I was finally able to get some 1680.

As for the out of spec spring, they are cheap and I have spare springs so it isn't a cause for concern. Come to think of it my buffer is now out of spec also. Actually I might be out of spec as well, I'll leave that for others to determine.

I made it to the range but ran out of light before I could get any more testing done, the RO came by with some guidance on shooting after dusk.

Anyone have any experience with reduced weight bolt carriers as mentioned above? I have already reduced the buffer weight and wonder if a low mass bolt carrier may be another way to improve cycling with subsonics without a can.

My bolt carrier is recently assembled, it was lubed with pure molybdenum disulphide (did I spell that correctly?) when assembled as was the interior of the upper receiver. The key is very tight, adequately staked and shows no signs of leakage. Since the BCG was assembled it has twice been R&Red (field stripped, wiped down and liberally sprayed with CLP). There is a small trace of leakage where the gas tube exits the gas block with the leakage showing on the tube, but I doubt it is enough to create / offset the cycling issues.

I hope to get back to the range soon with some boolits sized 311 and / or some 1680 loads.

The quest continues...