new ar15 critierion barrel issue

[LongArm]

I just got a new ar15 mid length gas system 16" barrel. After shooting it I notices that my practice ammo shot find and looked good after being shot. when I shoot my duty ammo 60grain hornady the brass had a large swell near the bottom of the case. I have never noticed this in any other barrels. This one is chambered in 223 wylde. The practice ammo is federal xm193. the barrel is new the bolt is almost new. being in a hurry i dont remember if I checked the head space on the barrel when I got it. i am left handed and it seemed like i could feel gas coming out of the ejection port when the rounds were fired, which has never happened before. any ideas as to why the bottom of the brass would swell like that?

 

[LongArm]

Just checked it, its a BCM bolt and it closed on a forster "no go" guage. I would guess that caused most of the things I was seeing. I head spaced the wrong barrel and bolt combo before it was installed. this barrel got a different bolt that is almost new but was head spaced to this barrel. Either that or the barrel extension/head space if off from the factory.

 

[maggitas]

Longarm,

If the XM193 ammo is shooting fine I would guess that the Brass in the Hornady 60 Grain ammo may be defective. To be on the safe side I would have the gun checked out by a competent gunsmith. If you have measurement tools I would measure your Hornady ammo vs your XM193 ammo for length and also measure the Seating depth of your chamber in your barrel. It could be that the 60 gr ammo is jammed in the lands and spiking your pressure causing the bulge in the brass.

 

[jake6547]

it shouldn't close on the no go gauge

 

[LongArm]

I agree. I will get a new bolt and hope for the best. I just hope that the chamber is not out of spec. I would not think that the bulge would come from excessive head space? However it only did it with the hornady's.

 

[InkedIan]

I agree. I will get a new bolt and hope for the best. I just hope that the chamber is not out of spec. I would not think that the bulge would come from excessive head space? However it only did it with the hornady's.

Fulton will headspace your current bolt for you! I did that with both barrels i've bought from them.

 

[toyotatrdt]

are you using a wylde chamber go and no go gauge

 

[LongArm]

yes .223 nogo and wylde chamber

 

[bustin]

it shouldn't close on the no go gauge

The "go" gauge and the field gauges are SAAMI spec minimum and maximum chamber sizes. The "no-go" gauge is a suggested size when building NEW firearms. It is not a SAAMI spec. It should also not be used to check anything on a used barrel. .001 or .002 is not going to make much difference. If it's .010 over it will cause the primers to flatten early.
If the barrel is over gassed as in the gas port too large it can cycle early while high pressure gases are still in the chamber. If the case is pulled out of the chamber while pressure is high it can expand out side of the chamber and cause a bulge. Photos would help. You can check to see if that is causing the problem by spinning the gas block just enough to cover the gas port, shoot the same ammo in a once or twice and then compare the fired cartridge.


From Forster's website-
Forster offers three lengths of headspace gages per rifle caliber. In order from the shortest to longest, they are: GO, NO-GO and FIELD:

GO: Corresponds to the minimum chamber dimensions. If a rifle closes on a GO gage, the chamber will accept ammunition that is made to SAAMI’s maximum specifications. The GO gage is essential for checking a newly-reamed chamber in order to ensure a tight, accurate and safe chamber that will accept SAAMI maximum ammo. Although the GO gage is necessary for a gunsmith or armorer, it usually has fewer applications for the collector or surplus firearms purchaser.
NO-GO: Corresponds to the maximum headspace Forster recommends for gunsmiths chambering new, bolt action rifles. This is NOT a SAAMI-maximum measurement. If a rifle closes on a NO-GO gage, it may still be within SAAMI specifications or it may have excessive headspace. To determine if there is excessive headspace, the chamber should then be checked with a FIELD gage. The NO-GO gage is a valuable tool for checking a newly-reamed chamber in order to ensure a tight and accurate chamber.
FIELD: Corresponds to the longest safe headspace. If a rifle closes on a FIELD gage, its chamber is dangerously close to, or longer than, SAAMI’s specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been inspected and repaired by a competent gunsmith. FIELD gages are slightly shorter than the SAAMI maximum in order to give a small safety margin.