Thanks for those who helped and believed and no thanks to those who called me a liar.

I will no longer be posting because I don't like being called a liar or that I'm giving a BS story.

You'd probably better send it to me for extensive testing.

Quoted: I have a Colt Lightweight Sporter with a 11.5 inch barrel with a permanent 4.5 flash Suppressor. It is only marked 5.56 on the barrel with no Colt Markings.

That sounds like Olympic Arms.  Whats worse - is it probably has a .223 chamber if it is Olyarms.

(I have confirmed this is the only part that does not seem to be stock on this Model  Colt 6530) I called the company that originally sold the weapon and they said that it was "Probably" a Match Barrel with a 1/9 twist and to shoot .223 Remington 55 grain UMC ball ammo out of it  ... Since it was sold around 1991 the company said they could not be for sure on the barrel type. I looked through some paper work that came with it  on an invoice it was written H-bar Sporter. Questions ------------------------------------------------------------------------- -Is there any way to determine the twist  or does any one have any ideas on what this barrel might be?

I am guessing Oly - they sold a lot in that config and marking style.  To determine twist - you just need to see how many inches is a full revolution.  You can so this with a cleaning rod and mark it, and measure as you push it thru.

-Is this an H-bar?

Technically, an "Hbar" just means heavy profile barrel, which was common to the 20 rifle (.750 in front, heavy under the guards) and 16" carbine (.750 in front, heavy under the guards)

From the pic - we can see it is .750 up front - but dont know whats under the guards.  I would bet it is either heavy, or .750 at the smallest.

-Is 223 Remington 55 grain UMC ball ammo the way to go?

Not necessarily - but if it is a .223 SAAMI chamber - you MIGHT have pressure issues shooting 5.56 mil pressure ammo.  Just have to try it.

-Can I use Military grade/ surplus in this? If so any suggestions

See above.

-I have been reading about the effective range and FPS which is great reduced from barrels under 14.5 inches. Is there an specific ammo I should use since I technically only have a 11.5 inch barrel(+4.5 inch make it Legal..) ..

Those threads are for maximum terminal ballistics.  You can shoot anything it will stabilize.  For that barrel IF it is a 1:7 (doubtful) then 75 ot 77gr is the way to go, for maximum terminal ballistics.  If it is a 1:9, that short - I would stick with the 68gr loadings.

For plinking/fun, shot whatever it is reliable with and shoots ok.

Would like plinking rounds as well  rounds that are effective to at least 100-150 yds..... or is this asking too much from my barrel size?

11" barrels are hard pressed to have good fragmentation capabilities out to 150yds.... but that would be the least of my concerns.  If you plan to keep it, just shoot it.  

Buy several different types of ammo, 55 grain, 62 grn and whatever else (69/77 grain) you can find FMJ or TAP.

Take it to the range, and start shooting 100/200/300 yard targets.  If you have problems with the heavier rounds keyholing, don't use them anymore.  If it is accurate, then you probably have a 1/9 or 1/7 twist barrel...which is my (public education) guess as to what you have.


`edit, I didn't even think about it being an Oly barrel..  I do remember reading that Oly does SAAMI chambers, and marks their barrels 5.56.  One more reason not to buy one.

How can I tell if I have a saami barrel?

You can fire a couple test rounds, and make sure to inspect the spent casings.  Flat or blown out primers are the first indication of over pressure.
Hopefully someone with more experience knowledge will pipe in here.

Thanks for those who helped and believed and no thanks to those who called me a liar.

I will no longer be posting because I don't like being called a liar or that I'm giving a BS story.

Anything that is .223 labeled should do fine in a SAAMI chamber.  Only Mil pressure 5.56 labeled ammo might be problematic.

Federal AE should be fine.

Thanks for those who helped and believed and no thanks to those who called me a liar.

I will no longer be posting because I don't like being called a liar or that I'm giving a BS story.
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Quoted: Will this same ammo work well in a 5.56 barrel? thanks for sll the help

You can use 223 in a 5.56 but can't use 5.56 in a 223.  A 5.56 has too much pressure for a 223 chambered rifle.  

Thanks for those who helped and believed and no thanks to those who called me a liar.

I will no longer be posting because I don't like being called a liar or that I'm giving a BS story.

Since no-one has brought this up yet - it would be wise - as a new AR15 shooter - for you to spend some time at the ammo oracle:

www.ammo-oracle.com/

Thanks for those who helped and believed and no thanks to those who called me a liar.

I will no longer be posting because I don't like being called a liar or that I'm giving a BS story.

I have a Oly upper just like the one pictured. The barrel has 5.56 SS marked on it. I have fired thousands of rounds of  mil surplus through it mostly stuff from Southern ammo also SA and MAL and I have never had a problem with it.