5.56x45 NATO in a .223 rifle (sort of long)

[Liam]

I reload my buddy's .223 ammo from our varmint trips for him. Nothing fancy. I neck size or full length size each time with my Lee .223 Remington dies, trim to length, usually load 55 gr bullets and only use one of two different powders he buys (IMR 4064 and Varget). If it's stuff he fired through his .223 CZ bolt rifle, I usually neck-size only and label BOLDLY the boxes to be fired in CZ ONLY (and indicate how many reloads the brass has gone through). His other rifle is an AR variant with a Wylde chamber. So, that gun gets full length sized every time. It has, so far, fired all my .223 reloads without issue. Up until now he has only supplied me fired .223 brass. His last batch of 75 rounds was a mix of 5.56 and .223, but I didn't note the headstamp until I had full-length sized all the brass with my .223 Lee dies. The brass may now be the same on the outside as my normal .223 brass, but on the inside there is less volume due to more brass (or, so I have read). Thinking about holding back a half grain or so from the load with these 5.56 brass pieces. Does this seem reasonable? And, if so, should the 5.56 headstamped brass be designated to fire in one of these rifles only? In my thinking, I would lean towards the AR for firing these since the Wylde chamber can handle higher pressure rounds. Or, do I tell him to stick to .223 ammo purchases from here on out and scrap the brass (40 pieces). I feel I have created .223 profile brass that has a built-in chance of having higher internal pressure when fired than is normal for a .223.

I know I'll get wrist-slapped for this, but the education will be worth it.

[m1ashooter]

As long as you are sizing them in your 223 die and loading to 223 specs then I don't think you have any problems.

[S.A. Boggs]

If you are neck sizing his brass for the exact same rifle I see no problem, nor is their a problem with the military/commercial loading of the same amount. He will get a different point of impact due to pressure differences. My question is are you using a headspace gauge to set your sizing die when you full length resize? There is not much area to play with and I have found that Lee rifle dies usually size on the long side. I have some 5.56 dating 1964.
Sam

[Liam]

I got lucky, I guess, S.A. Boggs. My Lee dies size correctly, as I use Wilson cartridge case gages to verify my final sizing and trimming results. I have a Wilson gage for every caliber I reload (7 of them). I have also compared my results to some factory rounds just for peace of mind.

[emmagee1917]

40 pieces of brass worth about .10 per = $4.00 . How much is all this worry costing you ?
Chris

[Sunray]

"...sizing them in your .223 die..." No such thing as a 5.56NATO die. There's no 5.56NATO load data either.
Before there was an internet, .223 Rem and 5.56NATO(which is just a military standards designation) were the same thing. The cases still are. The only difference between .223 and 5.56NATO is the pressure. The 5.56NATO's being higher.
NATO has their own testing methods. The U.S. military follows SAAMI's method. That puts U.S. made 5.56NATO ammo at 55,114 psi. SAAMI max pressure spec for .223 Rem is 55,000 PSI. NATO says all ammo must test to 125% of the max of 62,366 psi which is 77,958 psi. The latter being a test max, not an operational max. Whole thing is about where the test sensor is on the case during the test.
The Wylde chamber just has a longer throat than a regular .223 chamber. The case is the same length. No need to worry about the higher pressure of 5.56NATO. No need to worry about using commercial .223 either.

[Liam]

This is the first instance where my buddy has brought me 5.56-marked brass, emmagee1917. We've been shooting over 10 years together. I suspect he has located a cheap source. If this is going to be a regular thing, I just wanted to get the scoop on the differences now. And I think I have. Also, I envy your brass source @ .10 per!

[S.A. Boggs]

I got lucky, I guess, S.A. Boggs. My Lee dies size correctly, as I use Wilson cartridge case gages to verify my final sizing and trimming results. I have a Wilson gage for every caliber I reload (7 of them). I have also compared my results to some factory rounds just for peace of mind.

You are one of the few who have posted here that do this, most don't understand the importance of doing this.
Sam

[emmagee1917]

Down around here , you can get 55 gr GI for .35 delivered . Most people don't bother to reload it . Once fired brass is available at .10 per . You can go to the outdoor ranges and pick up all you want .
Chris

[Clark Howard]

To answer your question, I faced the same question reloading for a friend. I warned him of my concerns when he picked up the ammo. He shot it all in his AR, then returned the brass to me. He could not discern any difference in firing, and the fired brass gave no sign of excess pressure. Any difference in case capacity is inconsequential. Regards, Clark