New AR review and questions (S&W)

[msr]

Picked up a new M&P 15 last week and have a quick review and a few questions. Fit and finish are excellent. No loose parts, no overlapping parts, and the finish looks very durable. I removed the carry handle and attached an ARMS 40 flip up rear sight and an ARMS mounted Aimpoint. One trip to the range to sight in both. 40 rounds to sight in the Aimpoint first then 40 rounds to set the iron sights at a farther distance. One malfunction at the 25th round. While shooting at 20 yards for the Aimpoint it failed to completely eject the spent case then tried to feed the next round in past it resulting in both the case and the new round jammed in the feed ramp/chamber. It took a bit of force to remove them and both are damaged a good bit. No other malfunctions. Two additional notes before my questions; both sights were removed from a Colt and functioned perfectly. The ARMS mount for the Aimpoint while locked in place does slide back and forth a fraction of an inch. I have not noticed point of aim shift but have not fired nearly enough rounds to feel comfortable about it. Second, the ARMS flip up rear sight has had to be moved four clicks from the end of adjustment to the far right to zero at 100 yards. I don’t like that it is so close to ‘no adjustment room left’ but there is some room! First question; I have heard that some new feed ramps are sharp and benefit from polishing. If the malfunction occurs again should I look into polishing the feed ramps or will they self polish from use? Second, should I be concerned about the rear sight being almost all the way to the right?

[tikkafan]

The malfunction sounds like an ejection problem to me. You may want to look into getting a crane O-ring.

When you run out of room to adjust windage it's usually a canted front sight.

Also an optics mount that slides around is not cool. You must get that replaced.

[Robb Jensen]

ARMS stuff is known pretty well for not being 'just right', your windage problem with the rear is probably an error in the ARMS 40 sight itself. The Aimpoint ARMS mount fits some receivers pretty tightly but other pretty loosely, which is why many use Larue mounts.

[msr]

As for the ARMS rear sight I am leaning towards the front being canted as it was pretty much centered on the Colt.

[Austin_Nichols]

The malfunction sounds like an ejection problem to me. You may want to look into getting a crane O-ring.

When you run out of room to adjust windage it's usually a canted front sight.

Also an optics mount that slides around is not cool. You must get that replaced.

I agree with tikkafan; this is a failure to extract. You need more rounds down range. Keep a log during your break-in. The O-ring is always good medicine as is the proper spring and insert.

[msr]

Another 100 rounds today with no issues. I am keeing track of everything. Thanks for the input.

[tikkafan]

Knowing S&W, if you have problems they will fix it.

[Heavy Metal]

Extraction problem.

Bet is came with a standard spring with the blue insert.