Colt AR short stroking with .223

[Swannytheswan]

I am having a problem with a Colt AR short stroking with american eagle 55gr .223 If I use 5.56 it runs just fine. But with .223 it is having FTF problems and won't lock open on the last round. It is fairly new will the buffer spring break in and it be fine or should I start messing with it. I already checked the gas rings and cleaned well gas key seems tight. 

[ellensburgpo]

I will send you a pm.

[demontang]

Dirty gas tube or under power load hard to say without it in my hand I have had a colt and rockriver do this.

[HuntandFish]

I have a colt that does this as well. I have found it is a load problem with cheap ammo, if I run 60 gr. that has a little more energy it cycles perfect and have never had a jamb (and is more accurate), if I go to 55 gr. I get a jamb almost every clip unless it is high quality stuff ( or black hills for some reason). But my AR is a Colt "Match Target" that has a little tighter tolerances, but boy is it accurate

Good Luck!
H&F

[mrolen]

If you have a aftermarket gas block i would check alignment with the gas port if it is just slightly off they wont cycle with some rounds.

[Swannytheswan]

it has the stock gas block and it was with american eagle 55gr ammo...i would really like for it to run with what ever I can get my hands on

[FALFire]

Oil the bolt carrier, use Mobil 1 motor oil.

[Bone_Collector]

My buddy had the same problem with his AR but it was not a colt. He took it home and cleaned and oiled and it worked fine after that. So like the other guys have said clean it and oil it!

B_C

[demontang]

Its not a matter of tight talerance as much as it is the gas pressure from the lite bullet not running the gun. The length of the gas tube has play in this justblike if there is anything wrong with the gas block alignment or a partly blocked hole.

[Three_Oh_Eight]

If its truly a gas-pressure issue do to lightweight bullets, I'd be pretty disappointed myself.  55gr ammo is as common as it gets for 223.  I'd want the rifle to digest any common 5.56x45 or 223 I could get my hands on.

You may check the recoil buffer and spring.  Maybe your MFG puts a stiffer spring or more weight in the buffer?  This may be possible if your gas system is clean and your bolt carrier runs smoothly and is well lubricated.

[Fl0und3rz]

If everything is in spec, properly assembled, and properly lubed, I would expect it to handle at least the mil-spec level loads reliably.  Otherwise, small discrepancies can add up (tolerance stacking). And while things like lubing the bolt/carrier might rectify the immediate issue, it might not be the sole problem or the primary problem that is causing the problem. 

I have a BM predator that appears to have gas block/tube leakage that I need to correct (the issue described by prior owner was short-stroking with cheap 55 grain).  In any event, check out the link below to try and approach the problem from an informed perspective.

http://www.ar15barrels.com/prod/operation.shtml

[Swannytheswan]

well I haven't read that link yet but I will I just bought a lighter buffer (it had a H buffer 3.8oz in it and I bought a carbine buffer 3oz) with the lighter buffer it ran through 20rds of 55gr AE .223 without a hiccup but didn't hold the bolt open on the last rd. Before the lighter buffer I tried 62gr .223 and I still got FTF after almost every rd I thought I was missing something cleaning it because at first it ran 5.56 just fine but not .223 but then I had my brother in law (who just got back from Basic and AIT) clean it and he did show me one spot I had missed but even after he clean the whole thing good it was still malfunctioning. that is when I decided to get the carbine buffer. i don't know how to tell which spring I have or need or if it is the wrong one or not IDK.

[JLS]

How many magazines do you have?  Is it doing this with the same mag?  Can you try with another one? 

[Swannytheswan]

3 mags 2 steel 1 pmag does it with all three...well at least it was... I only shot 20rds with the new buffer didn't have time for much else and that was with the pmag

[JLS]

Check your gas key again, clean it well, and lube the BCG well.  What kind of oil are you using?  Remoil is too light to use in an AR and will give you headaches.

Have you taken the handguard off and inspected the gas tube?