Question about Olympic AR

[Rootin Tootin 19]

I have a 2005 Olympic Arms AR and want to know if it can shoot higher pressure Nato rounds or am I limited to 223? If not can the upper be changed to shoot Nato Rounds.

[Michigan Slim 9,852]

Is the barrel labeled .223 or 5.56?

[Michigan Slim 9,852]

It's all about the chamber and throat dimensions. 5.56 can raise pressures in a .223 chamber but the other way around is ok. I trim and load all my brass to .223 spec to run in anything.

[Rootin Tootin 19]

Markings state Multi,   M.F.R on the lower.  I'm assuming it will shoot both 223, and 5.56.  I have only shot 223 in  it to date but now with the new gun climate I'm looking for options if 223 get harder to find.......

[Michigan Slim 9,852]

It's all about the barrel chamber. What the lower says is irrelevant. Multi on the barrel?

[Rootin Tootin 19]

OK.........

[Kansas City Munny 28]

Barrel will be marked with chamber spec. (5.56 or .223) and twist rate. That will be the determining factor.

[Michigan Slim 9,852]

[Not Dead Ed 95]

you need to read the barrel, not the lower.   If stamped 223 then it is only good for 223 rounds.  
if stamped 5.56 or Wylde, it’s good for 223 & 5.56.   
to answer how to change it, you would need to rebarrel the gun to either a wylde or a 5.56 barrel.  
there are a few more tools armorers wrench, barrel nut wrench, punches, delta ring tool if you have a clamshell hand guard, and a big torque wrench, plus some blocks to hold the upper that you need to do it right.  

 

[Capt. James H. Callahan 2,591]

One of mine is an Olympic. IIRC they were also a govt. contractor for M16s, so if they made the barrel I would think it would be OK. I've never shot military thru mine. As mentioned the barrel stamping would probably be the safest bet. From what I've heard (for what it's worth) the only difference in barrels is the 5.56 has a longer throat.

JHC

[Horace Patootie, SASS #35798 73]

9 minutes ago, Not Dead Ed said:

you need to read the barrel, not the lower.   If stamped 223 then it is only good for 223 rounds.  
if stamped 5.56 or Wylde, it’s good for 223 & 5.56.   
to answer how to change it, you would need to rebarrel the gun to either a wylde or a 5.56 barrel.  
there are a few more tools armorers wrench, barrel nut wrench, punches, delta ring tool if you have a clamshell hand guard, and a big torque wrench, plus some blocks to hold the upper that you need to do it right.  

 

+1

My Olympic is an early 45 ACP gun, but I have 5.56 and 300 BO uppers also.

Edited February 15 by Horace Patootie, SASS #35798

[Michigan Slim 9,852]

4 minutes ago, Capt. James H. Callahan said:

One of mine is an Olympic. IIRC they were also a govt. contractor for M16s, so if they made the barrel I would think it would be OK. I've never shot military thru mine. As mentioned the barrel stamping would probably be the safest bet. From what I've heard (for what it's worth) the only difference in barrels is the 5.56 has a longer throat.

JHC

Correct. And that longer neck is what raises pressure when it jams home in the chamber.

[Capt. James H. Callahan 2,591]

I just checked my barrel. It's marked SS (stainless steel?) over 5.56. No twist rate. Bought mine back in the early-mid 90s

JHC

Edited February 15 by Capt. James H. Callahan

[Hardpan Curmudgeon SASS #8967 6,195]

If it it is a .223 just have it reamed to 5.56 or .223 Wylde.  

 

Or, buy/rent a reamer and do it yourself.

[Subdeacon Joe 28,414]

34 minutes ago, Capt. James H. Callahan said:

I just checked my barrel. It's marked SS (stainless steel?) over 5.56. No twist rate. Bought mine back in the early-mid 90s

JHC

 

If it is marked 5.56 you are good with either .223 or NATO 5.56.  

 

The "Multi" on the lower means you can swap out the upper for uppers in order calibers.   You may need different magazines and/or bolt carriers for the other calibers. 

[Texas John Ringo, SASS #10138 67]

2 hours ago, Michigan Slim said:

Correct. And that longer neck is what raises pressure when it jams home in the chamber.

There is no outside dimensional difference between a .223 rem and a 5.56 nato. The main differences are that 5.56x45 mm NATO operates at a higher chamber pressure (about 60,000 p.s.i. versus 55,000 p.s.i. on the . 223 Rem.) and the 5.56's chamber is slightly larger (throat is longer .125" longer) than that of the .223 Rem Also, the throat or leade is longer in the 5.56x45 mm chamber.223 Rem

Edited February 15 by Texas John Ringo, SASS #10138

[Michigan Slim 9,852]

1 hour ago, Texas John Ringo, SASS #10138 said:

There is no outside dimensional difference between a .223 rem and a 5.56 nato. The main differences are that 5.56x45 mm NATO operates at a higher chamber pressure (about 60,000 p.s.i. versus 55,000 p.s.i. on the . 223 Rem.) and the 5.56's chamber is slightly larger (throat is longer .125" longer) than that of the .223 Rem Also, the throat or leade is longer in the 5.56x45 mm chamber.223 Rem

Correct! Not the neck.

[Pat Riot, SASS #13748 28,561]

12 hours ago, Rootin Tootin said:

I have a 2005 Olympic Arms AR and want to know if it can shoot higher pressure Nato rounds or am I limited to 223? If not can the upper be changed to shoot Nato Rounds.

Read this, look on page 5:

http://danielpeart.net/pdf/Olympic Arms AR-15 Manual 2010.pdf
 

 

[Grass Range 117]

I have an Olympic AR. Would not shoot point of aim so I had to shim the scope. Talked to a rep at Olympic who was coming to my are to see a relative. I asked him to stop and look at my rifle . He would not. Case closed.

[Buckshot Bob 2,435]

18 minutes ago, Grass Range said:

I have an Olympic AR. Would not shoot point of aim so I had to shim the scope. Talked to a rep at Olympic who was coming to my are to see a relative. I asked him to stop and look at my rifle . He would not. Case closed.

Don’t feel bad . I used to work at a Colt warranty station and when colt first started making the Hbar rifles they had a batch where the bbls were so misaligned with the upper that the customers could not get the guns to sight in for windage the rear sights ran out of travel. 
The colt factory approved fix was to put the bbl in a arbor press and bend it until the sights aligned. 
every company has their issues, and they all usually look for the cheapest way to rectify the problem 

[Sixgun Sheridan 4,565]

6 hours ago, Buckshot Bob said:

The colt factory approved fix was to put the bbl in a arbor press and bend it until the sights aligned.

 I hope you were careful not to bend it too far, lest the bullet come back around and hit the shooter from behind!

[Buckshot Bob 2,435]

3 minutes ago, Sixgun Sheridan said:

 I hope you were careful not to bend it too far, lest the bullet come back around and hit the shooter from behind!

No looney tunes bbls . But I do remember seeing some pics of a German WW2 gun that was intended to shoot around corners that had a pretty severe bend in it . I think it was a sub gun 

[Horace Patootie, SASS #35798 73]

52 minutes ago, Buckshot Bob said:

No looney tunes bbls . But I do remember seeing some pics of a German WW2 gun that was intended to shoot around corners that had a pretty severe bend in it . I think it was a sub gun 

Stg44 with Krummlauf?  It had a sight on it for just that. https://en.wikipedia.org/wiki/Krummlauf

Edited February 16 by Horace Patootie, SASS #35798