Reloading 5.56 brass.

I just read an article in Human Events warning against firing 5.56 ammo in rifles chambered for .223 Remington. Apparently the "danger" is the chamber leade in the two different rifles. In guns chambered for 5.56 the leade is greater, allowing for the supposed longer length of the 5.56 brass. If you fire a 5.56 cartridge in a .223 rifle, the bullet engages the rifling upon being chambered, causing higher pressures when it's fired.
Here's the problem I'm encountering. I came across a large batch of surplus 5.56 brass. I resized, decrimped the primer pocket and trimmed to .223 specs using a Lee case trimmer. I then reloaded the brass using the starting load of 23.4 grs of AA 2230 powder for a 55 gr FMJBT bullet. I fired about 100 rds and noticed very flattened primers.
I'm at a loss. I thought trimming would eliminate excessive length as a problem. Any ideas?
Also, I'm firing this ammo out of a standard Colt AR-15. Since Colt also manufactures the M-16, aren't all the parts essentially the same (except for the selective fire components)? It would seem a AR-15 could safely fire 5.56 as well as .223 Rem. Where did I go wrong? BTW, the article stated that both .223 and 5.56 brass has the same wall thickness, so that's not the problem.

Two things here. First off, by trimming back, you limited seating bullet depth. Second, the case walls may be thicker allowing less powder. A combination of both or just one can raise pressure.

A 5.56 should fire in a Colt without concern. By trimming, you actually increased the bullet seating depth and lessened powder room to burn.

Another thing to consider is that " free boreing" or seating the bullet so that it just contacts the lands and grooves is not necassarily going to cause excessive pressure. As a matter of fact, that is a technique used to get maximum accuracy from a rifle.


Here's another thing; if you are not using the exact same components listed in the manuel, it could cause pressure issues. I would back it off a grain and try it again .

This is where a chrono earns it's keep. Invest in one.

trim brass to what to book says for 223/556

some brass may have less case capacity then others. i load lots of mixed brass, and load many above book max... no issues in my guns

To tell you the truth I first started loading with Lee dies and had problems with cases jamming in my AR15's and buddies M16,I was trimming cases to specs and adjusting crimp die up and down and still couldn't get them to run 100%,then I bought a set of RCBS small base 223 dies and haven't had a problem with FTF FTE since, and as long as cases are within specs haven't trimmed any in a long time.I load mine with 21.5 grains Reloader 7 55 grn fmj and haven't had any problems according to load data should be getting 2900 fps but really need to chrony them

my H-Bar runs when full length sizer is used, even range PU brass runs fine. my friends auto--is finiky,

the value of my time when re-loading is seldom an issue. but for that...stock up on a good sale and the fun factor is restored.

loading a 1/1000 off the lands is for extream accuracy; 300 +yards. my H-bar to 600 yards with 69gr BTHP or 71 gr hand feed ammo.
the zombies will win but for othr items --like an sks and....some claymores.

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Another thing to consider is that " free boreing" or seating the bullet so that it just contacts the lands and grooves is not necassarily going to cause excessive pressure. As a matter of fact, that is a technique used to get maximum accuracy from a rifle.

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Not quite.

Seating the bullet to the lands does two things.

One, it forces the bullet to enter into the rifling as square and concentric as possible, eliminating any deviation from the bullet to the bore.
Two, because the bullet is loaded to the lands, the start pressure is increased, so it is reccomended to reduce loads at least 10%.

Free bore has nothing to do with that. Free bore is a technique used to make a hot loaded bullet start with a lower pressure and the free bore is supposed to guide the bullet into the rifleing. In fact, Weatherby is about the only one that even uses that technique.

Years ago Remington did a limited run of .300 Weatherby Magnums and they freebored the rifles just like Weatherby did. A friend of mine had one and he never was sastified with the way it shot. Yes, it was about 200 fps faster than my .300 Win mag, and my rifle shot circles around his. If freebore proved to be that great a thing, every maker would have adopted it and that hasnt happened either, in fact Weatherby rifles are noted for mediocre accuracy. Sure they'll do for hunting but how many have you ever seen at a Benchrest or Long Range match? Not many.


As for any auto loader, whether it be an AR or a Remington 7400, you always use small base dies or the rifles will not feed due to the increased size of the case.

On a bolt action, you want to neck size so that the case is tensioned enough to hold the bullet firmly and the fired case fits the chamber perfectly having been fired in that chamber prieviously.