Any difference in reliability of suppressed AR when using 5.56 vs .223?

Depends on your specific rifle and suppressor. If your gun is really overgassed to begin with shooting lower pressure .223 will help that to a degree.

Not in my experience

You’re on a roll today

Trying to become an educated consumer.
Plus my team in the ncaa bracket is already out.

A few years back someone told me in order to have a reliable AR-15 with a can you must use a piston conversion.

So I blew off the piston idea and started using my SF mini on a 17 inch barreled (rifle gas) OBR.  I have since gone through 2 barrels in about 6-7K rounds each and am on barrel #3.

I think I cleaned the bolt carrier and receiver a few times, maybe once a 1,000 rounds.  And that was just a wipe down and check for broken or unusual wear.  Pretty much I just added oil, kept it wet and ran it.

This was with a somewhat warm reload using lots of Varget and Hornady 55 FMJs.

I dont remember the last time I had a malfunction.

Another top end is a 16 inch chambered in 223 Ackley with a Thunderbeast 223 Ultra 7.  Rifle length gas with a JP sidecharger upper.  Not one single issue there either.  Not fireforming or using Ackley ammo.

I guess pistons were not the answer for me.

I also shot some 556 green tip ammo through them.  Still worked perfect.

Blue Devil nation baby!

5.56 and .223 are chamberings

Semantics aside the rounds are identical for all intent and purposes. Factory 5.56 tends to be hotter/higher pressure

There are differences between SAAMI spec'd .223 chambers and true 5.56 NATO military chambers. The ammo might look the same at first glance but there are differences.  Rule of thumb, .223 and 5.56 spec ammo is ok to shoot through the military spec chambers.  If your barrel is a bonafide .223 chamber stick to the commercially loaded stuff only.

Maybe I'm misunderstanding but most freeloaders would probably prefer a .223 chamber in a bolt or precision gun.

Why would loading .223 be an issue?

With the 5.56 being a higher pressure round than .223 I was not sure if any of the "pressure" translate to reliability and if the .223 would be slightly under powered, but based on my other thread, the use of a suppressor inherently increases the pressure which was different from my original thinking.

The 5.56 will theoretically be more reliable, unless it is severely overgassed and starts outrunning the magazine. The key for good reliability would be to adjust your gas system until .223 is reliable, and then just know that 5.56 may be slightly overgassed.

I'd much rather have my rifle capable of running any ammunition, rather than having to rely on higher pressure ammunition only.

It's like having a semi-auto .22 that won't run standard velocity ammo...

By freeloader I believe you meant handloader?



My response was to your comment about for all practical purposes and intent they were the same.  That is simply not true. That picture hopefully clears it up.  As far as the original posters question, shooting either NATO or SAAMI spec'd ammo through a can marked 5.56 is perfectly fine.  OP as long as your barrel is clearly marked 5.56 NATO you will be good to go.  If it is marked .223 Remington you would be wise to check with the manufacturer first that it is in fact a commercial chamber. Add in the additional back pressure a can will introduce and you can see why that makes it even more of a bad idea to do so.

I'm not sure what you think you're clearing up?

I said 5.56 and .223 are chambers, as the picture you've just posted shows

The ammunition is identical in most ways (brass and bullets) except one is typically loaded hotter.

The shorter leade of most .223 chambers could potentially cause an overpressure situation with a hot 5.56 round. You reload both rounds with the same dies, brass, bullets and powders.

You stated both were the same.  They are not.  The brass isn't either.

I think I see what Effenpig is getting at. Saying to stick with commercially loaded ammo only is a bit ambiguous, as it could be taken as saying to avoid using reloads in a .223 chamber. I do agree that one should not use any 5.56 labeled ammunition in a .223 chamber, which includes the majority of military surplus ammunition, and to make sure any commercial ammo you purchase is properly labeled as .223 Remington. (One exception is the Ruger Mini-14, which is labeled .223 Rem, but is actually a 5.56 chamber.)

I believe Effenpig was simply saying that reloading for .223 is just fine, which I also agree with. There's no harm in using reloads as long as they are properly loaded to .223 specifications. One can use all of the same components to load .223 & 5.56, including powder, so one must check their load data very carefully. The two biggest factors are seating depth and powder charge, both of which can severely affect pressure, so of course it's the reloader's responsibility to stay within safe pressure ranges for the intended chambering.

No harm I agree if the reloader understands that 5.56 brass has thicker walls and will be a smaller case volume and adjusts the powder charge accordingly.  Just saying they use the same components simply isn't accurate.  Anyway.  Off my soap box now.  Hopefully the OP has gotten the information he needed. There's plenty of information out there explaining the differences between the two if one wants to go read up on it.

Two (Among the largest) US manufacturer's top level people have told me privately that all their barrels marked only .223 have always actually been 5.56 chambers.

Actually, tests have shown that to be true for 7.62 NATO brass, but not true for 5.56 brass. Lake City brass actually seems to have the highest case capacity of most .223/5.56 brass. Odd, isn't it?