steve2267
09-05-06, 20:54
Summary:
Sunday I fired the first 120 rounds through a new 16" M4gery A3 carbine. The first few mags ran fine. Then I began getting failures to extract / eject. Either the spent shell was stovepiped, half sticking out of the ejection port, or it was still inside the receiver, more often than not wedged against the top of the receiver by the next round that had been stripped from the magazine and was trying to get fed up into the chamber -- it appeared to be a double feed, but one shell was spent (the top one) and the other shell was yet to be fired.
Details:
Brand new M4gery homebuilt:
lower: Rock River Arms lower with a RRA lower parts kit that I had installed
upper: brand new Stag Arms 16" AR15 A3 (flattop) complete upper (i.e. came fully assembled from Stag Arms)
ammunition: Winchester Q3131
magazines: used 20rd magazines purchased from someone on AR15.com
Note: before you start blaming the magazines, which I will admit could possibly be the problem, or contributing to the problem, please understand that these same magazines ran without nary a problem on a 20" Bushmaster A3 that I own. Also, my shooting buddy, Low Drag, fired my carbine and experienced a failure to extract/eject using one of his brand new 30rd magazines (that came with his new Bushmaster).
Initially no failures to extract/eject were noted. But as more rounds were fired, the problem occurred more frequently. By the last 20 rounds (rounds 100-120), the carbine had almost been reduced to a single shot.
The carbine had not been cleaned prior to firing. My bad. I will clean it thoroughly and lube it per TM 9-1005-249-10, which came with the Stag Arms upper.
The chamber appears to be smooth, well, smooth to my fingers anyway. The bore, chamber, and firing pin are chromed. The carrier key appears to be well staked -- it appears that the hex-head screws had been wapped with a chisel. A 1/8" hex key was too small for the hex-head, but a 9/64" hex key would not go in (due to metal deformation of the chiseling, perhaps?) I could not wiggle the carrier key by hand, as much as I tried, so it does not appear to be loose as best I can tell.
Removal of the bolt carrier and field stripping of the bolt revealed a lot of brass buildup underneath the extractor claw/groove. I cleaned this out with a Spyderco today. The extractor felt smooth to the touch, and close examination by eye; no burrs were found. However, there was NO o-ring around the extractor spring.
The vendor has initially blamed either ammunition (Winchester Q3131 -- although he did not know it at the time) or poor magazines, claiming the upper had been test fired at the factory (concluding apparently, that, the upper cannot be at fault).
Corrective actions I will be taking:
1) procure brand new magazines (any recommendations? I'm thinking D&H from 44mag.com or possibly the AR-Stoner mags w/ Magpul followers available at MidwayUSA)
2) procuring an o-ring for the extractor spring assembly here: http://www.adcofirearms.com/itemdetails.cfm?inventorynumber=2689
3) cleaning and lubricating the firearm
Any other suggestions? Why the extraction problems? Fitting a cartridge into the bolt face (with the bolt removed) seemed to indicate the extractor had a very good grip / fit onto the cartridge.
Thx for any help, insights, and/or recommendations.
Sunday I fired the first 120 rounds through a new 16" M4gery A3 carbine. The first few mags ran fine. Then I began getting failures to extract / eject. Either the spent shell was stovepiped, half sticking out of the ejection port, or it was still inside the receiver, more often than not wedged against the top of the receiver by the next round that had been stripped from the magazine and was trying to get fed up into the chamber -- it appeared to be a double feed, but one shell was spent (the top one) and the other shell was yet to be fired.
Details:
Brand new M4gery homebuilt:
lower: Rock River Arms lower with a RRA lower parts kit that I had installed
upper: brand new Stag Arms 16" AR15 A3 (flattop) complete upper (i.e. came fully assembled from Stag Arms)
ammunition: Winchester Q3131
magazines: used 20rd magazines purchased from someone on AR15.com
Note: before you start blaming the magazines, which I will admit could possibly be the problem, or contributing to the problem, please understand that these same magazines ran without nary a problem on a 20" Bushmaster A3 that I own. Also, my shooting buddy, Low Drag, fired my carbine and experienced a failure to extract/eject using one of his brand new 30rd magazines (that came with his new Bushmaster).
Initially no failures to extract/eject were noted. But as more rounds were fired, the problem occurred more frequently. By the last 20 rounds (rounds 100-120), the carbine had almost been reduced to a single shot.
The carbine had not been cleaned prior to firing. My bad. I will clean it thoroughly and lube it per TM 9-1005-249-10, which came with the Stag Arms upper.
The chamber appears to be smooth, well, smooth to my fingers anyway. The bore, chamber, and firing pin are chromed. The carrier key appears to be well staked -- it appears that the hex-head screws had been wapped with a chisel. A 1/8" hex key was too small for the hex-head, but a 9/64" hex key would not go in (due to metal deformation of the chiseling, perhaps?) I could not wiggle the carrier key by hand, as much as I tried, so it does not appear to be loose as best I can tell.
Removal of the bolt carrier and field stripping of the bolt revealed a lot of brass buildup underneath the extractor claw/groove. I cleaned this out with a Spyderco today. The extractor felt smooth to the touch, and close examination by eye; no burrs were found. However, there was NO o-ring around the extractor spring.
The vendor has initially blamed either ammunition (Winchester Q3131 -- although he did not know it at the time) or poor magazines, claiming the upper had been test fired at the factory (concluding apparently, that, the upper cannot be at fault).
Corrective actions I will be taking:
1) procure brand new magazines (any recommendations? I'm thinking D&H from 44mag.com or possibly the AR-Stoner mags w/ Magpul followers available at MidwayUSA)
2) procuring an o-ring for the extractor spring assembly here: http://www.adcofirearms.com/itemdetails.cfm?inventorynumber=2689
3) cleaning and lubricating the firearm
Any other suggestions? Why the extraction problems? Fitting a cartridge into the bolt face (with the bolt removed) seemed to indicate the extractor had a very good grip / fit onto the cartridge.
Thx for any help, insights, and/or recommendations.