done

[Fl0und3rz]

I've heard that the pressures are higher in the military 5.56 ammo to make sure they cycle the action in an AR type gun in battle.  I load for accuracy, and that's usually about the middle of the load table.  Even loads at the bottom of the load table have never failed to cycle in my AR rifles. 

That's a good point of reference.  What are the specs of the rifle?  With tolerances (or possible out of spec parts) at the buffer, buffer spring, bolt, carrier, key, gas tube and gas port stacking in the wrong direction, a weak load - speculating - might provide insufficient pressure to cycle the AR.

I'd like to say that mine have been 100% reliable with 45-55 grain bullets with mid to lower end loads, but that is not the case for me, and it was exacerbated at lower temperatures (e.g., a load that cycled reliably in mid-day, mid-summer heat failed to cycle in early morning temperatures). With M193 level loads tested concurrently, they cycle fine. Just another data point.

[Heredoggydoggy]

Another thing to check is that your collapsible buttstock tube isn't screwed in too far-it needs to be screwed in JUST far enough to hold the spring/detent from coming out.  One turn further, and your bolt might not go back far enough.  They are a simple rifle in operation, but there are a few subtle things that can cause them to be finicky....

[Brownie28]

I use 26 gr varget with 60gr hornadySP and get Awesome groups.
I always FL resize and check case length.

lC brass, win SR primers, varget, hdy SP , loaded to .010 under mag length and I get this

[Hilltop123]

I use 26 gr varget with 60gr hornadySP and get Awesome groups.
I always FL resize and check case length.

lC brass, win SR primers, varget, hdy SP , loaded to .010 under mag length and I get this

Barrel specs.? Just curious..

[Blacklab]

Have you chronyed you load? Nice group btw 

[Brownie28]

Don't have a chrony so I'm not sure of velocity but if I remember correctly that's towards the high end of the charge weight. Rifle is a RRA lower with NM 2 stage trigger, YHM upper with 18" CMMG .556 barrel 1:8 twist cheap $10 walmart see through rings and a bushnell trophy XLT 3x9 scope. Groups were at 100 off sand bags

This is Marie laveu

[fowl smacker]

I have some Sierra 107 grain bullets, some Speer 85 grainers, and Barnes 62 grain Varmint Grenades, but haven't tried any of them yet.  You can get the barrel in 1 in 10 or 1 in 9 twist.  I specified 1 in 9, so it should stabilize the heavier bullets OK.  If it does, I may snap up the Berger VLDs at the gun shop...

So far, the 58 grain Hornadys with IMR 8208 XBR powder seems to be the ticket!

I would not use the heavier bullets with a 1 in 9" twist, max bullet weight for that twist should be 73 gr.  You would want a 1 in 7" or faster for anything 90gr and up.
I've reloaded a lot for my AR's both 1 in 9 and 1 in 7.  I highly recommend the Lee fl die for the AR platform.  You also want to stay a couple grains lighter on the powder from max load on a bolt action .223. My best load for 1 in 9" is 55gr Hornady vmax pushed by 24.6 gr of varget, and my best for 1 in 7" twist is a 69gr sierra match king hpbt (not a hunting round) pushed by 25.3 gr of varget.  Hope this helps.

[Heredoggydoggy]

I have some Sierra 107 grain bullets, some Speer 85 grainers, and Barnes 62 grain Varmint Grenades, but haven't tried any of them yet.  You can get the barrel in 1 in 10 or 1 in 9 twist.  I specified 1 in 9, so it should stabilize the heavier bullets OK.  If it does, I may snap up the Berger VLDs at the gun shop...

So far, the 58 grain Hornadys with IMR 8208 XBR powder seems to be the ticket!

I would not use the heavier bullets with a 1 in 9" twist, max bullet weight for that twist should be 73 gr.  You would want a 1 in 7" or faster for anything 90gr and up.
I've reloaded a lot for my AR's both 1 in 9 and 1 in 7.  I highly recommend the Lee fl die for the AR platform.  You also want to stay a couple grains lighter on the powder from max load on a bolt action .223. My best load for 1 in 9" is 55gr Hornady vmax pushed by 24.6 gr of varget, and my best for 1 in 7" twist is a 69gr sierra match king hpbt (not a hunting round) pushed by 25.3 gr of varget.  Hope this helps.

This is a 6.8SPC necked down to 6mm.  Standard load for the 6.8SPC is 110-115 grain bullets.  I agree with the .223 info.

[Jekemi]

Lots of good comments here. I would watch www.ultimatereloader.com video's on reloading for the .223. Some of the best information available.