Mini-14 ammo question

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jimmy

Bearcat
Joined
Oct 26, 2007
Messages
6
Okay, the Mini-14 owner's manual states that "the Mini-14 Rifle is designed to use either standardized U.S. military, or factory loaded sporting .223 (5.56mm) cartridges manufactured in accordance with U.S. industry practice."

So far, so good. But it's my understanding that 5.56mm ammo is loaded to a higher pressure than .223. So, my question: even though 5.56 is officially sanctioned in the Mini, does shooting 5.56 put a significant extra strain on the gun, so that the result is excessive wear or a greater likelihood of parts breakage?

Just wondering.
 
Joined
Nov 15, 2005
Messages
9,162
Location
Greenville, SC: USA
don't worry about it... it will be fine.

actually it's not the load of the military 5.56 that is the potential problem but that the case of the cartridge is slightly different and in a rifle truly chambered for .223 the pressure can leak and blow the bolt.... at least in theory.
 

Sig685

Single-Sixer
Joined
Oct 21, 2003
Messages
177
Location
Texas
blume357":17memzcz said:
don't worry about it... it will be fine.

actually it's not the load of the military 5.56 that is the potential problem but that the case of the cartridge is slightly different and in a rifle truly chambered for .223 the pressure can leak and blow the bolt.... at least in theory.

Actually, it's the bullet used in 5.56 NATO that is the issue. The case is the same for all intents and purposes, but the SS109-type bullet has a fairly long bearing surface and the ogive is shaped such that in SAAMI .223 Remington rifle with a short leade (freebore), the bullet can actually touch the lands in the barrel. The leade or freebore is the area where the case ends, but before the rifling begins. In a SAAMI .223 chamber, this leade is quite short, around .010 or so (from memory). This is perfect for the rgular bullets shot in .223 Remington rifles. A short leade makes for a more accurate bullet, because the jump to the rifling is minimized.

With the 5.56 NATO (M855, not M193,) the bullet sits out quite a bit, because the powder charge is heavier and the tangent ogive sits out further and thus can actually contact the rifling when the bullet is chambered in a .223 Remington chamber. A 5.56 NATO chamber has a much longer leade, about double or more of freebore. For martial weapons superb accuracy is not required.

When a bullet that is not designed to be fired when chambered into the lands is chambered and touches the lands, the pressure will rise at ignition time because the bullet has no chance to gain any momentum before it engraves into the lands. The added pressure occurs at the time of maximum pressure in the curve and that can send the total pressure above what is safe.

Add to this that 5.56 NATO is indeed loaded hotter than SAAMI .223 Remington ammo, and the fact SAAMI chambers are tighter than NATO chambers and you could run into issue shooting 5.56 NATO ammo in match .223 Remington chambers.

This is not an issue for the Mini-14 however, its chamber is loose and has a long leade, so as D&H says, shoot either.
 

Sig685

Single-Sixer
Joined
Oct 21, 2003
Messages
177
Location
Texas
An excellent question and it shows that you are thinking.

Everybody knows that a bolt gun has a stronger action than a Mini-14 or an AR-15 so it must be ok to shoot 5.56 NATO in a SAAMI .223 Remington chambered rifle. Or is it.

The .223 Remington has been around a long time and there are many bolt action rifles that were chambered for the cartridge in the 60s and 70s as varmint rifles. These rifles gave excellent accuracy because their chambers were tight and the leade was short. Every body used light weight short bullets for varminting. As time went on and the AR-15 moved up in bullet weight in the 1980s (62gr) and then got adopted wholesale for competition, with even longer bullets, the chambers grew in length and some bolt action rifles (certainly more recently) have tried to keep up.

However, I would say the vast majority of .223 chambered bolt action rifles are SAAMI .223 chambered and may be subject to the additional pressure engendered by the bullet of a 5.56 NATO cartridge being jammed in the lands. Some bolt action will not be bothered by that extra pressure, especially the newer rifles, but the older ones may well be stressed.

One thing to consider is that most bolt .223 have a barrel twist of 1:12, thus restricting the bullet weight to 55gr or less, thus not NATO caliber. Also, bolt action rifles do not consume as much ammo as semis such as the AR or the Mini, so the need for cheap surplus ammo is not as strong.

So if you have a bolt action rifle with a 1:12 twist, why would you want to shoot 5.56 NATO wth its longer 62gr steel penetrator bullet? You will probably not stabilize it and why pay with extra pressures?

But let's say that you really want to shoot 5.56 NATO in you bolt rifle with the 1:12 twist. Here is a quick test to help you make your decision. Take a 5.56 NATO bullet and with a marker, paint the ogive of the bullet black, heck paint the whole exposed bullet. Then in a safe manner, chamber the round, if you can. If it chamber without you pounding on the bolt, open the bolt and slowly eject the unfired cartridge. Now examine the bullet for any scuff marks to the paint. If you see none, the chambered round did not have the bullet in the lands. If you see scuff marks, the bullet was touching the lands are you are now aware and warned about the situation.

People have been shooting surplus ammo, including 5.56 NATO ammo in all manners of bolt guns for a long time. I have never heard of any failures with that combination, but that only means that I have nt heard about any; it does not mean it has not occured somewhere.

Personally, I specify a longer leade for my .223 rifles, but with a tighter chamber than 5.56 NATO and even .223 Remington match in the case of my match rifle. I have zero interest in varminting or using light short bullets. And I would never use surplus ammo in my rifles; there is a reason it's considered surplus.

Does that answer your question?
 

Meeteetse

Bearcat
Joined
Jan 17, 2005
Messages
60
Location
Wyoming-Texas, USA
To Sig685:
Yes it does answer my question for the most part. My bolt rifle is a new Ruger and should/may be OK for some of the 5.56 ammo that is out there. I don't shoot "surplus" or steel ammo in any of my guns, although some have gone through my Mini-14 before I knew better.

I think some of the current confusion is caused by ammo manufacturers who sell both 5.56 mm and .223 and market them as the same cartridge. In fact it is often difficult for the average shooter to know what specifications they used. I have read and re-read cartridge boxes trying to determine if it is really 5.56 or .223 with no success. I suppose the only thing to do is stick with high quality ammo, from major companies and "assume" what the box says is what it really is.

Thanks for your insight.
 
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