.223 vs. 5.56

[Texas by God]

There have been no weak action .223 Remington rifles ever made, so I don't- and haven't ever worried about it. I'm loading for two 7" twist and one 9" twist 5.56 ARs.
We shot a ton of 5.56 ammo of all nationalities through my brother's 700VS .223 in the 70s and 80s without even a flattened primer.

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[elmacgyver0]

I have an original Colt SP1 marked .223 that I haven't fired since I bought it.
That is back when I was about 20 years old, I am almost 72 now.
That rifle has less than 50 rounds thru it.
This is an example of an AR that you would NOT want to fire .556 ammo in.

[Tripplebeards]

The only thing I’ve read as mentioned above is 5.56 brass has thicker walls and a longer neck. Just don’t start out with a max suggested book load using military brass. I run all my brand new LC virgin brass through a RCBS 223 FL sizer die and trim all the cases before I start load testing them. So it’s a hybrid case? Lol. Never had any issues running both cases in my 223 LTR and 5.56 POF. The 5.56 factory rounds i believe have a longer OAL (besides longer case necks) could have have problems chambering in some 223’s. I shoot 5.56 rounds in my H&R heavy barrel 223 and have zero issues.

[elmacgyver0]

How about that! I must be getting senile, I just noticed I put the decimal point in the wrong place!
Well, at least I'm not President.

[Larry Gibson]

Thanks, guys. More info; these will be loaded with j's in the 55 grn. area. The purpose is plinking/practice ammo. I will advise the owner that 70 grn. j's are better suited to this twist rate. I have learned that this rifle has never been fired. Any ideas on break-in procedures?

M193 55 gr FMJ bullets, or commercial equivalent such as Hornady's, will work fine for plinking/practice in your friends 7" twist rifle and in the 9" twist also. No need to spend more for "better" bullets just to plink/practice. I shoot thousands of 55 gr fmj's in my own ARs, 7, 9 and 12" twists. The better quality fmj's (the Hornady's) will give excellent accuracy.

H335 has been my standard "go to" powder for loading 52 - 55 gr bullets in the 223/5.56 cartridge since '72. I got my M700V in '72 which was marked 223 Remington. There was none of this internet BS/myth about some difference between the cartridges back then. I had a chronograph in '74 and loaded 55 gr Hornady SXs to the same 3200 fps velocity that the M193 ammo gave out of the rifle which coincided with data from the manuals back then. I used 26.5 gr of H335 under M193 bullets, Hornady 55 gr SXs and Speer 52 gr HPs. I shot lot's of 5.56 M193 out of that rifle, lot's of that H335 load until I shot the throat out. I had the barrel set back 2" and rechambered with a standard Clymer 223 Rem finish reamer (I own it) and shot several thousand more rounds. Finally shot that barrel out completely on a PD shoot a few years back. It's now been rebuilt with a new barrel and still going strong. I've also a M70 12" twist which is a "223 Rem" on its barrel and it digests that load w/o any problems whatsoever. I've also shot out a Savage Competition 223 Rem barrel (9" twist) having shot a couple thousand M855 "Green Tip" rounds through it. That M855 runs 62,000 psi+.

I've had several early Mini-14s, ARs and other gas guns chambered in "223 rem" (as marked on the barrels and/or lower receiver) and they all shoot 5.56 just fine along with my H335 load. In the 10 and 12" twist barrels the 52 gr Speer HP was the bullet of choice for varmints. Many a coyote fell to those. If you're going to load any for hunting/varmints I suggest the Sierra 55 gr Blitz King bullet [not to be confused with the 50 gr Blitz bullet]. Load it over 26.0 gr H335 for an excellent AR load. It has a longer bearing surface and is a long bullet that needs the 7 - 9" twist to stabilize. Should be running 3000 to 3100 fps depending on barrel length. PSI runs right at 60,000.

For last 10 + years the current load manuals have dumbed down the 223 load data back to the SAAMI specified MAP of 55,000 psi. That is why you see max loads of H335 under the 55 gr bullet of 24.5 - 25.5 gr. Using my load of 26.5 gr under a 55 gr J bullet simply bumps it up to original M193 pressure levels and more importantly, velocity levels. I have pressure tested that load [military 5.56 or commercial 223 case, WSR or CCI 450 primer, 26.5 gr H335 with a 52 - 55 gr jacketed bullet] and it consistently runs 59 - 60,000 psi depending on the bullet used. Accuracy has always been excellent.

For long case life and no trimming needed I suggest the use of the standard RCBS 223 Rem X-die in regular commercial, milspec or Wilde chambers. The SB or AR X-die is not needed unless your rifle has a very tight match chamber.

Also, if you try HPs or SPs steer clear of the thin jacketed "explosive" bullets as the jackets won't hold up to the RPM generated by 3100 +/- fps in 7 - 9" twist barrels.

[Bloodman14]

Mr. Gibson, I was hoping you would chime in, thanks so much! I do believe I have enough info to start load development after I decap and FL size this brass. One question remains unanswered; can I use the cases interchangeably with the same load data? Or did I miss that answer?

[Milky Duck]

you can but your accuracy wont be quite as good as sorted brass...I personally dont bother as my rifle isnt fussy zastava mini mauser.... it will poke pretty much any 50-55grn load into same inch group,always has and hopefully always will.

[M-Tecs]

I have an original Colt SP1 marked .223 that I haven't fired since I bought it.
That is back when I was about 20 years old, I am almost 72 now.
That rifle has less than 50 rounds thru it.
This is an example of an AR that you would NOT want to fire .556 ammo in.

The Colt SP1 was made for the civilian market for 20 plus years. The .223 designation is on the lower receiver.

The barrels and chambers are the same as used on the military 5.56.

The early SP1's did not have a chromed barrel or chamber.

Barrel markings will be one of the following depending on if a rifle or carbine:

Colt Proof Marks between the FSB Legs
"12" approx 1" from the three prong or birdcage flashhider
Note: Early barrels were not chromed.

"Early" - C MP B
M = Magnetic Particle Inspected
P = Proof Fired
B = Chrome Bore
"Late" - C MP Chrome Bore

Per Colt all the SP-1 and GI chambers are the same. In the early 90's one of the members of the rifle time had a couple of SP-1's that he would not shoot M193 out of due to the .223 designation. We bet a steak dinner on it. He wrote Colt and based on their reply he bought me dinner. He also started shooting M193 out of them.

[Larry Gibson]

Mr. Gibson, I was hoping you would chime in, thanks so much! I do believe I have enough info to start load development after I decap and FL size this brass. One question remains unanswered; can I use the cases interchangeably with the same load data? Or did I miss that answer?

For milspec duplication loads for use with ARs I don't segregate cases by manufacturer or by year (lot). Never found any increase or decrease in accuracy as any variation appears to be within the variable of ammunition and rifle capability. A match AR used for 300 - 1000 yard match shooting could use the segregation as can discerning bolt actions capable of sub moa accuracy. Accuracy these days is determined 80 - 90 % by the quality of the bullet. Getting wrapped around the axle in the other minutia is most often lost because the rifle/ammunition isn't capable of making any difference.

[Der Gebirgsjager]

Just an observation-- as recently as a year ago one could buy PPU, Igman, and Wolf in boxes labeled 5.56 mm or .223 Rem. Lately it seems like it's all labeled .223 Rem.

DG

[wwmartin]

When the 223 Remington XP100 varment special came out I just had to have one . He first ammo I fed it was PMC 5.56 factory. Round #17 extracted hard and had to be preyed from the bolt and I never found the primer. I was told at the time it was because I was using 5.56 not 223. I marketed a round and found rifling marks engraving about 1/16 on the bullet. I've been feeding it cast Lyman 55gr ever since.

Bill

[Bloodman14]

Mr. Gibson, Thank you, sir! I was leaning in that direction. Carry on, gents! Interested in how far this thread might go.

[Mk42gunner]

... Accuracy these days is determined 80 - 90 % by the quality of the bullet. Getting wrapped around the axle in the other minutia is most often lost because the rifle/ammunition isn't capable of making any difference.

This is true of so many cartridges, not just the .223/ 5.56mm.

Robert