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Posted: 9/11/2006 10:22:34 PM EDT
| I purchased a Colt A2 HBAR 20 inch upper about some 2 years ago. Now I have the right receiver I have been looking for to finish my build. While at the local rifle range I sat down to sight my new rifle in and to have some fun. While sighting in I noticed I had two problems. (1) The rear sight seems to be way to the right when zeroed in at 100 yards and (2) I noticed that it seemed to fire 2 - 3 rounds then it would not load another round. Short stroking I think. I thought that it might be worn gas rings so I replaced them. Its still doing the same thing. Do you think I should replace the gas tube. Any thoughts or sugestions on this problem. hinking.gif |
| The barrel is marked C MP 5.56 Nato 1/7 and the upper rec carry handle is marked CM and as far as the short stroking it mastly does it on the 2-3 round. I also tried changing ammo, but still the same result happens. The ammo I has using by the way was IMI 55gr FMJ 1998 production. I then tried a box of winchester white box 55gr FMJ , but noticed no difference. I also checked the gas rings to make sure that the gaps were not aligned. Could it be a clogged gas tube or a miss aligned gas port hole under the FSB? |
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Colt is pretty good about making sure that their uppers are correctly built and the sights aligned with the bore. Having said that, and the fact that the rear sight must to clicked way over to get a zero, the problem does sound as if someone pulled the barrel and was not correctly reinstalled (or the upper was not a colt factory built unit). With the barrel sight index out of alignment, so will be the barrel extension lugs, and the problem may be a simple as the bolt just binding on unlock. Either have the barrel pulled, or break out the leather mallet and get the barrel indexed in the upper barrel socket correctly to zero out the rifle with the rear sight dam near dead center. As for the short stroke test, load only a single round into the mag, charge, and fire that round. The bolt should lock back on the bolt catch (empty mag), and if passes this test a few times, suspect that the mags are due for either a strip and cleaning, or a rebuild if the springs have weakened. Also, take a good look at the Carrier to confirm that it's a Colt unit, and not some other unit with loose carrier keys. Note: if the rifle fails the short stroke test of the single fired round charged and fired out of the rifle, first place to check is the key allen screws to confirm that they are still tight, seconded by giving the chamber/barrel the cleaning of its life. |
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