5.56 in a .223 Ruger Ranch Rifle

There is still a lot of debate, with neither camp ceding ground to the other.

I’m in the “they’re interchangeable “ camp.
I’ve fired 5.56 and 223 in my old 187 and 196 series minis, as well as my AR, with nary a hiccup.
My dad worked at Aberdeen proving grounds, blowing stuff up, then improvising repairs for a long time, and he said while there is a technical difference in final specs for the rounds, and the chambers cut for them, it didn’t make enough of a difference to bother worrying about.

The responses I have had from Ruger many times over the years is NOT consistent with the statement quoted above by American Hunter’s blog article. Ruger is pretty open about which of their models use Wylde vs. SAAMI 223 chambers, and which use 5.56, just have to call.

I’ve shot 5.56 and .223 (brass and steel) through my ranch rifle mini 14. Never had a problem. Anyone shooting to the right of me within 20 yards did though, they would get peppered with the spent casings. It’s one of the newer ones.

There is a difference in leade shape and pressure specification between .223 Rem and 5.56 NATO. It is small, but it is there. It's probably the smallest difference between individual calibers to date.
The manual probably says not to use 5.56, or would if it addressed the question. It also says not to use handloads. I do both, and will continue to. I would suggest you focus on finding ammo that's accurate enough to suit your mission, and sample both .223 Rem and 5.56 NATO along the way.

Ironicaintit said:

. . . he said while there is a technical difference in final specs for the rounds, and the chambers cut for them, it didn’t make enough of a difference to bother worrying about.

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That's a very good summary.

Should a rifle marked 5.56 be able to handle .223 ammo or should it be the other way around?

The Ruger rep I talked to when I worked in the industry told me (correctly or incorrectly, I have no way of knowing) that all of their rifles currently manufactured in either caliber are designed and built to handle, at least in terms of pressure, both rounds and they do this intentionally so that if somebody does the “wrong one” the weapon won’t fail and they (Ruger) avoid bad press.

I wouldn’t be surprised if, in this day and age with the availability of both rounds being common, that many manufacturers do this.

The newer Mini's are stamped 5.56, as are the bolt action Ranch rifles. It is a bit confusing on Ruger's part to have a Mini-14 Ranch ifle AND a bolt action Ruger American Ranch rifle. I'm in the camp that says it is safe to shoot them interchangeably. But you might run into reliability issues, and possibly some long term durability issues firing 5.56 in a 223 chambered semi. In a bolt rifle I don't see how it could ever be an issue. And to my knowledge the older MIni-14's are the only semi's ever stamped 223. All AR's and other semi's are stamped 5.56. And there has never been any issue with firing either in a 5.56 stamped rifle.

This is EXACTLY the same issue with shooting Garands with modern 30-06 ammo. It isn't dangerous, but it is likely to lead to rifle damage and unreliable functioning. 30-06 at the time the Garand was developed was as much as 400 fps slower than modern loads. A MUCH greater difference than you'll see between 223 and 5.56. Yet we don't have any distinction between the various 30-06 loads. We could very easily have at least 3 different power levels for 30-06 and even have different names for them. But we don't and everyone seems to survive.

Mine are original/first issue and they are stamped 5.65/.223. My friends and I ordered them as soon as we heard about them. I just picked up another that was in parts in an estate sale, amazingly all of the parts were there although the exterior condition was poor.

Cokeman said:

Should a rifle marked 5.56 be able to handle .223 ammo or should it be the other way around?

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All 5.56 chambers can safely shoot .223. All .223 Wylde chambers can safely shoot .223.

SOME .223 chambers may have problems handling 5.56.

my understanding of the Mini-14 and variants is the same as the American Shooter citation above. But if varmitterror says he has credible evidence to the contrary, I would listen. I have had no issues shooting a lot of 5.56 through my Ranch Rifle. But that doesn’t mean there’s not a potential problem. I would be interested in any statements by Ruger on the subject.

Varminterror said:

The responses I have had from Ruger many times over the years is NOT consistent with the statement quoted above by American Hunter’s blog article. Ruger is pretty open about which of their models use Wylde vs. SAAMI 223 chambers, and which use 5.56, just have to call.

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Do you happen to know which chamber is used on the Ruger American Ranch .223/5.56 bolt rifle?

The .223 Remington cartridge and chamber spex were set in cement by SAAMI (Sporting Arms and Ammunition Manufacturing Institute) in the 1960s.
NATO has continued to "wildcat" (develop) 5.56x45mm for longer heavier bullets and higher performance.
So confusion reigns.
I suspect that there are military rifles introduced for the original spec .223/5.56 ammo that are not compatible with current NATO ammo.
I also suspect that many commercial .223 bolt actions have a larger safety margin in terms of action strength than many military 5.56 rifles.
MY rule of thumb has been to treat 55gr FMJ or HP .223 Remington and 55gr FMJ 5.56x45mm as interchangeable.
Every thing else, check with the manufacturer. I am still learning and I don't take my word as final.

For import/export, where a military caliber firearm is more restricted than a civilian caliber "sporting purposes" firearm, there are rifles marked .223 Remington that are actually fully compatible with 5.56 NATO spec. Do check questions with the manufacturer.
Personally, I'd expect a rifle barrel marked .223 Remington to be chambered and have a rate of twist for 55gr and lighter varmint bullets, and a rifle barrel marked 5.56x45 NATO to be chambered and have a rate of twist for 62gr or heavier bullets.

Supposed to be sourced to Barnes' Cartridges of the World:
Safe for sustained use in firearms chambered to either 5.56 NATO or .223 SAAMI standards:
".223 Remington" 55gr FMJ
_ 52,000 psi in 5.56 NATO chamber
_ 52,000 psi in .223 SAAMI chamber
".223 Rem M193 aka 5.56x45mm NATO" 55gr FMJ
_ 55,000 psi in 5.56 NATO chamber
_ 55,000 psi in .223 SAAMI chamber

Where the difference in throat length or lead kicks in:
Safe for use in 5.56 NATO chambered barrels only:
"M855 US, SS109 NATO" 62gr FMJ
_ 62,366 psi in 5.56 NATO chamber
_ 70,000+ psi in .223 SAAMI chamber
According to this, shooting 62gr green tip in a true .223 SAAMI spec barrel is like touching off a proof test load every shot.

danez71 said:

Do you happen to know which chamber is used on the Ruger American Ranch .223/5.56 bolt rifle?

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If a Ruger is stamped 5.56 on the barrel, it is a 5.56 chamber. If it is stamped 223 rem on the barrel, it is a SAAMI chamber.

The owner manual that came with my Mini 14 specifically states that even though stamped .223 it is safe to use either .223 or 5.56 nato. But that is for my Ruger mini 14. It nay be different on your model so check the manual or contact ruger to be sure. When in doubt ask the manufacturer.

Cokeman said:

Should a rifle marked 5.56 be able to handle .223 ammo or should it be the other way around?

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It’s the other way around

Here is the thing. .223 and 5.56 are so dang close that if you have a .223 rifle that will explode with a 5.56 round in it, eventually you are going to get a factory .223 round that exceeds that pressure.

The best information I have, though I have not verified it is that the mini 14 is chambered in 5.56 and marked .223. This make sense as it was originally designed to replace the M14 but lost out to the Eugene Stoner rifle competing for the 5.56 US military contract. I don’t know how much you know about that jack-wad “5 round Bill” but making 5.56 “military” guns illegal so he could corner the civilian market with his “legitimate hunting purposes” .223 rifle seems like just the kind of thing he would do. I could be wrong.

Carl N. Brown said:

Supposed to be sourced to Barnes' Cartridges of the World:
Safe for sustained use in firearms chambered to either 5.56 NATO or .223 SAAMI standards:
".223 Remington" 55gr FMJ
_ 52,000 psi in 5.56 NATO chamber This is CUP pressure
_ 52,000 psi in .223 SAAMI chamber This is CUP pressure
".223 Rem M193 aka 5.56x45mm NATO" 55gr FMJ
_ 55,000 psi in 5.56 NATO chamber This is transducer pressure
_ 55,000 psi in .223 SAAMI chamber This is transducer pressure

Where the difference in throat length or lead kicks in:
Safe for use in 5.56 NATO chambered barrels only:
"M855 US, SS109 NATO" 62gr FMJ
_ 62,366 psi in 5.56 NATO chamber
_ 70,000+ psi in .223 SAAMI chamber
According to this, shooting 62gr green tip in a true .223 SAAMI spec barrel is like touching off a proof test load every shot.

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CUP, or Copper Units Pressure is generally not exactly convertible to true (transducer) pressure.

However, if you read through MIL-C-9963F, dated 15 October 1976, when the military was switching between copper crusher pressure measurement to transducer pressure measurement, they stated this in the specifications for M193, Ball (55 gr, 5.56mm):

"3.7 Chamber pressure.

"3.7.1 Measurement by copper-crush cylinder. The average chamber pressure of the sample cartridges, conditioned at 70° +/- 2 degrees F, shall not exceed 52,000 pounds per square inch (PSI). three standard deviations of chamber pressure shall not exceed 58,000 PSI.

"3.7.2 Measurement by piezoelectric transducer. The average chamber pressure of the sample cartridges, conditioned at 70° +/- 2 degrees F, shall not exceed 55,000 PSI. The average chamber pressure plus three standard deviations of chamber pressure shall not exceed 61,000 PSI."

Indicating that for 5.56mm ammunition 52,000 CUP was equivalent to 55,000 psi. Prior to 1976 the standard acceptable average chamber pressure for M193 was 52,000 CUP.

However, all that information is dated. Current SAAMI limits for .223 Remington are:

Maximum Average Pressure = 55,000 psi
Maximum Probable Lot Mean Pressure = 56,400 psi (MAP + 2 standard deviations)
Maximum Probable Sample Mean Pressure = 58,500 psi (MPLM + 3 standard deviations)

Current limits for Military M193 are:
Maximum Average Pressure = 57,000 psi
Maximum Average plus 3 standard deviations = 63,000 psi

The thing to take away from this is the military allows a much wider variation in pressure. For SAAMI ammunition, if you have an AVERAGE pressure of 55,000 psi, 95.7% of the pressures within the lot shall be under 56,400 psi. With current military ammunition, if you have an AVERAGE pressure of 55,000 psi, 95.7% of the pressure within the lot will be below 61,000 psi.

Remember, the list values thrown about by everybody are AVERAGES, some will be above and some will be below. The ones on the extreme high end are the ones you have to worry about, and mix them with a short leade or a tight forcing cone and you may have trouble . . . .

brunowbe said:

I’ve shot 5.56 and .223 (brass and steel) through my ranch rifle mini 14. Never had a problem. Anyone shooting to the right of me within 20 yards did though, they would get peppered with the spent casings. It’s one of the newer ones.

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Been interchanging both for 30 plus years in m Mini...no problems yet!

Swampghost said:

Mine are original/first issue and they are stamped 5.65/.223.

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Same here and I've have been using both iterations for decades without any hint of a problem. I think the 5.56 vs .223 debates (excepting special circumstances) has been much ado about nothing for the most part.

If I owned a Winchester Model 70 or a Remington Model 700 in .223 I might consider 5.56 vs .223 much ado about nothing for the most part.
The lack-urracy of firing 62gr or heavier in a barrel rifled to stabilize 40gr to 55gr bullets would be enough to discourage me from shooting 5.56 NATO ammo.
If I owned a Savage 340 in .223 I would stay with .223 commercial ammo.