Loading 5.56

[tbcollins]

Just finished building my AR-15. It's chambered for 5.56. Would rather be able to load 5.56 rounds vice .223 rounds. Sure this has all been discussed before. Haven't looked everywhere, but seems really difficult to find new 5.56 brass. Is it possible to load to 5.56 specs in .223 brass? If I understand correctly only real difference is 5.56 uses small rifle magnum primers and powder slightly different. Would the pressure decrease integrity of .223 brass? Help, Info and suggestions appreciated.

[jumbopanda]

"U.S. military specifications for M193 Ball ammunition require a 55
grain bullet at a muzzle velocity of 3,250 q 40 fps from a 20
inch test barrel measured 15 feet from the muzzle."

"NATO specifications for SS109 (U.S. M855) Ball require a 61.7 grain
(q 1.5 grains) with a hardened steel penetrator at a velocity of 3,025 fps
(q 40 fps) from a 20 inch barrel 25 meters from the muzzle."

My reloading manual has data for .223 loads that exceeds M193 and SS109 performance, and I would assume that the data listed here is safe for any .223 brass.

[ocabj]

If you want Lake City or WCC brass, it's pretty easy to come by.

Grafs sells brand new, unprimed LC brass.

[mstlaurent]

Natchez has new Lake City for about $0.13 per. That's dang cheap.

http://www.natchezss.com/product.cfm?contentID=productDetail&prodID=fa556upb2000&src=tpSlrByr2

[Boots]

From what I understand, the only difference between military brass (5.56) and civilian (.223) is that military has slightly thicker walls and the primers are crimped. And the primer cups are a bit "harder".

[ocabj]

From what I understand, the only difference between military brass (5.56) and civilian (.223) is that military has slightly thicker walls and the primers are crimped. And the primer cups are a bit "harder".

Unprimed brass can't have crimped primer pockets. The pockets are crimped after the primers are seated. Buying new unprimed LC brass will be the same as any other brass with regards to primer pockets.

And generally, LC is thicker than most brass. But Lapua brass is definitely thicker than LC.

[Boots]

Unprimed brass can't have crimped primer pockets. The pockets are crimped after the primers are seated. Buying new unprimed LC brass will be the same as any other brass with regards to primer pockets.

Correct.. again, I should have clarified that. I overlooked the fact that the OP was referring to "new" brass.

[sonnyt650]

I don't know of any 5.56 loads and so I don't know that much about it (I do however use military/magnum primers because of those cold San Jose mornings ), though as indicated Lake City brass is made specifically for military weapons and is available new. I suspect .223 brass can be used though it can't be reloaded as often because the likelihood of case head separation increases as the case wall thins, and .223 brass already has a head start over 5.56 brass.

As far as the load itself I'd stick to the .223 loads but seat the bullet out further for accuracy. Early on I tried to determine how long I could seat the bullets before hitting the lands, but it turns out more important for me is loading from the magazine. I load even the light 52 grain bullets just shy of the 2.26" maximum OAL hoping to get better accuracy than if the bullets were seated closer to the Hornady minimum 2.230" for these bullets.

[ireload]

I would caution you against loading to 5.56 spec. That's 10,000 psi more than the SAAMI maximum level.

It will be more wear and tear on brass and rifle.

The use of magnun primer is dependant on the selected powder for the load.

I have a 5.56 chamber and rarely fire 5.56 ammo. You can improve the terminal ballistic by using premium bullets.

[diginit]

MilSpec = 26.8g Win 748. Fills the case...
Example:
7th Edition Hornady manual shows a 55 grain #2265 SP with COL 2.200", for Win
748 the MAX load is 26.4 grain which gives 3200 fps. 23.8 is Min.
26.8 is dangerous with this bullet!
00.1g makes alot of difference in a high pressure load. ALWAYS start low and work up. Do not just copy other loads unless you like explosions 5" from your face.
There is really no need to push a 55g bullet to 3250 fps. It will not increase accuracy. It depends on what your gun likes. Every one is different. I get 1.5" groups of 10 at 100 with 26.2g of 748 at 2900 fps with a 55g speer SP at 2.220 in a 16" Bushy carbine,1/9 twist. Every bullet brand is different also. So use load data from the manufacturer of the bullet you are loading and work up.

As for primers. CCI #41 are made for AR's. They have a harder cup to resist slamfires in a semi auto under rapid fire and are my preference. But I have had good results with CCI #400's and Win S.R.P.'s also. You don't have to use a magnum primer.
If you change to a different brand of primer or bullet, It is best to work up a new load rather that use the charge from your last workup. Change a component, Work up a new load.
I recently learned that ANY change, even in crimp tension requires a new work up to be safe.

The only difference between 223 and 5.56 cases is in the shoulder and powder capacity. The first time you fire a 223 case in a NATO chamber, it will conform to the chamber and if you only neck size, Rather than FL size. It will be a 5.56 case. The NATO chamber will handle both rounds and can handle 60,000 C.U.P
As will a 223 Wilde chamber. Don't fire a 5.56 (NATO) rnd. in a .223 (SAAMI) chamber as the powder charge creates excessive pressure and 60,000 C.U.P. will blow the breech.

Keep reading, doing searches, and asking questions.