Is milsurp 5.56mm NATO ammo safe in hunting rifles?

Question

I've read that military surplus 5.56mm NATO ammo may be unsafe in standard bolt action hunting rifles chambered for the .223 Remington cartridge. Any truth to this? I'm checking out a Stevens model 200 for my son but want to shoot surplus and economy ammunition in it. Is there anything to be concerned about such as pressures, cartridge length, bullet weight or bullet seating depth? Will the Stevens shoot milsurp safely and without jamming the rifle?

Answer 1

NOT recommended
The primary difference between .223 Remington and 5.56x45mm is that .223 is loaded to lower pressures and velocities compared to 5.56mm. (Conversely .308 commercial has a higher standard pressure than it's 7.62x51 NATO counterpart)
.223 Remington ammunition can be safely fired in a 5.56mm chambered gun, but the reverse can be an unsafe combination. The additional pressure created by 5.56mm ammo will frequently cause over-pressure problems such as difficult extraction, flowing brass, or popped primers, but in extreme cases, could damage or destroy the rifle. Chambers cut to .223 Remington specifications have a shorter leade (throat) area as well as slightly shorter headspace dimensions compared to 5.56mm "military" chamber specs, which contributes to the pressure issues.

Military cases are made from thicker brass than commercial cases, and the NATO specification allows a higher chamber pressure. Mil-spec chambers also have a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. To address these issues, some proprietary chambers exist, such as the Wylde chamber (Rock River Arms) or the Armalite chamber, which are designed to handle both 5.56 mm and .223 equally well.

Using 5.56 mil-spec cartridges (such as the M855) in a .223-chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice. The manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56 mm ammunition

Answer 2

The above is a copy/paste from Wikipedia. It is correct however. 5.56 NATO is loaded to higher pressures than commercial .223 Remington ammuntion. It is not suggested that you use 5.56 in .223 caliber sporting rifles. This is due to the higher pressure and may cause more throat wear on your sporter.

The bullet weights (55, 62, 69, grains, etc.) are the same, as are the seating depths, but the pressures are different - and that is an important issue when it comes to the chamber and throat.

I would not use 5.56 NATO in a sporter. .223 ammo is cheap anyway - buy Remington UMC or Winchester USA .223 REM ammo - save the SS109 (etc.) 5.56 NATO for your Mini-14 or AR.

Answer 3

The .223 chamber throat is just a tad shorter than the 5.56. Chances are you probably wouldn't notice much diff if you *did* shoot it in a good quality firearm, but the shorter throat will hold the bullet tighter in the shell and it *will* crank up the chamber pressure before the bullet starts to move down the barrel.

If you plan to do it, you should take your weapon to a competent smith and have the throat lengthened. It will pay for itself in one good order of milsurp ammo.

As to "throat wear" etc associated with 5.56 ammo in .223 firearms, it simply means the milsurp ammo is pushing the rifling up the bore a bit with wear. It's eroding the throat longer with each shot. In this case, firing milsurp ammo through a .223 weapon will actually lengthen the throat and reduce pressure the more you shoot it. Sounds like a good thing....but much safer just to have the throat lengthened.

Answer 4

Course you can.