Need help loading a AR-15 carbine

[sixpac1961]

Quick Load data atttached.

I have been reloading for a standard AR-15,Colt) 20" barrel with no problems for several years. The 60 Gr Hornady Spire Point is accurage at low pressure,34,000 psi) with 24.5 gr of BLC-2.

I shot this same load in my Olympic Arms 11" barrel AR-15 w/ retractable butt-stock and it cycled just fine - the problem is the amount of powder burned is low,76%) and I have powder residue all over the weapon.

I have worked up some loads with a 55 gr Hornady FMJBT and Accurate 2015 as it is faster burning and I can get most of the powder to burn. I started with 21 gr and loaded to 23 grains as it gives acceptable pressures based on QL. ,I am trying to duplicate a lower pressure version of a PMC round - H322, 27 grn - but its at 69,000 psi based on QL)

My problem is that the bolt does not fully cycle even with 23 gr of Accurate 2015. This leads to jamming and improper feeding. I do note that the spring rate between the STD AR and the Carbine are different, with the greater spring rate being the Carbine. I thought this was the cause of the bolt not fully cycling. I thought I had to increase the pressure to fully cycle the bolt but I proved this wrong by firing the lower pressure,34,000 PSI) STD AR-15 load with BLC-2 which cycled the action.

What am I missing?

I would like to work up a load that stays below 46,000 psi so I can safely reuse my brass.

Any insight would be appreciated as I cannot easliy find the PMC ammo I used to fire.

Scott

 

[ronemus]

You'll need a faster powder to burn well in the short barrel with light bullets - probably 4198, N-133, RL-7, etc. I'd recommend looking at pistol loads for .223 as they'll be more relevant; I know the Hornady manual has them, but I don't have it to hand. Short-barrelled ARs are finicky about their loads, but you can probably get recommended loads from whoever built it for you. You may be unnecessarily limiting pressure, as I've reloaded brass 8 times,and still counting) with warm loads,~55k psi, SAAMI max.) in my spacegun. The gas system on your rifle may not let you reduce your load much and still function reliably.

 

[Spotcheck_Billy]

It's not so much the pressure as it is the duration of burn in your direct impingement gas action. Try H335 and H4895. If you continue to have problems you might seriously consider a carrier weight system like the one David Tubb markets.

BTW, I have an 11.5" carbine. Works great with the two powders I've mentioned. What you want to do is to duplicate USGI Ball loads M193 or M855) as closely as possible and don't worry about the psi. They shouldn't be hard on your brass as long as your chamber is properly polished. Lake City brass seems to last the longest on my carbine.

 

[constructor]

+1 on the 25gr-335 and 25gr 4895, 27.5gr-748 is another good one with 55fmjs.
4198 would not cycle my colt and was very dirty.