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XCR-L Shoots 8" Low at 50 Yards

2K views 8 replies 5 participants last post by  Sean K. 
#1 ·
Hello all,
I recently bought a used XCR-L in the high 3,000 serial number range that looked brand new. This rifle is the third XCR I've owned over the past five years. The rifle has mostly Gen 2 upper features, but mostly Gen 1 lower features (it does have the integral trigger guard).

It came with a lightweight 1/9 16" barrel without any modifications.
It came with the factory MI flip sights.

The Gen 1 trigger sucks.

Last night I took the XCR and my brand new Sig MCX (Gen 1) to the range for the first time. I had added MagPul PRO flip sights to the MCX prior to the range trip.

It took about 15rds to get the Sig zero'd at 50 yards (low 2.5" inches) and another 9rds to get it zero'd at 100 yards.

I fired 90rds through the XCR and could never get it zero'd. I bottomed out the front sight post, and the rifle is still hitting 8" low at 50, and off of 8.5x11 paper at 100 yards. I've adjusted windage to be exactly where I want it.

I added blue locktite to the sights a week ago so they're rock solidly mounted.
The barrel bolt is tight.

This isn't ammo, magazine, or shooter related. I tried different loads (all of which worked perfectly in the Sig, my SCAR, my ARs, etc), and have been shooting military style guns since 1984. I try to get to the range every week, and average about 180rds of 5.56 per range trip.

Any thoughts on what could be causing this? Are there any known issues with the MI sights RA use to use? Bore-axis to front sight bottom out issue? Will the rifle need "micro" height sights?

Thanks in advance.
 
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#2 ·
MI sights have to be modified to go lower. I had a set that had the problem of shooting high....though it was YEARS ago but I don't think it was 8" off. I had to put the front sight in the mill at work and bring down the shelf the front post bottoms on. You can do the same thing in a drill press...but you'll need an end mill of the right diameter to get a flat cut. Personally, I'd just try a different front sight.
 
#4 ·
MI generally makes decent quality stuff....it's just a problem we've seen here a few times with their sights on the XCR. You don't have another set of sights you can just swap to try? If it only took you 24 rounds to sight in the MCX's Magpul Pros....I'd just swap them on it and see if that solves the issue. The problem is 8" at 50 yards assuming 1/2 MOA adjustments is 16 clicks of an A2 style front post. That's a 4 full turns....which, from memory, is kinda what I remember dealing with when I had MIs on there.

You may want to remove and reseat/retighten the bbl, JIC as well. I don't think that's the issue though.
 
#6 ·
Speculation on my part: I suspect the MI front sight assembly that came on your used XCR-L is one that is supposed to be used on an AR gas block that is lower than the picatinny top rail. In order to line up with the rear sight on the AR, the gas block front sight assembly is taller. Thus, when installed on the XCR it is way too high and you are unable to lower the front sight post enough to make up the difference in heights.

Go to https://www.midwestindustriesinc.com/product-p/mi-lffg-blk.htm and watch their video. Move your front and rear sights to touch each other and see if they line up. I suspect they will not. If correct, you'll need the shorter front sight assembly designed to be on the same rail as your rear sight.

Let us know...I am curious.
 
#7 ·
JFYI though....mine was the correct sight and it was still out of adjustment (which is why I had to mill the pocket deeper).
 
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