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Left Sig
06-15-09, 21:43
I'm not exactly new to the AR platform - I bought my first one over two years and have developed a lot of technical knowledge about the platform since then. I can do a lot of armorer type work, and I've sent more than a few rounds down range. However, I've never had any formal training on rifle shooting or AR-specific training.

Yesterday I tried to sight in my new Aimpoint M3 and 3x magnifier on my Stag 3L carbine. Previously, I was using a Leupold Mark 4 PR 1.5-5x scope in a LaRue SPR mount. The last time I shot with the Leupold on 5x power (actual power is more like 4.5x) I was able to hold 25-30 rounds into a 2" circle at 50 yards, with another 10 rounds or so within a 4" circle. Not the best, but then again I'm not the best shot either, nor do I claim to be. It's good enough to tell me that the carbine is probably more capable than I am.

So I started zeroing the Aimpoint and seemed to be doing OK. I got to the point where I figured I was close to zero. I was holding 3-5 shots within 1"-2" on a sight in target and reaching the point where I thought it was time to stop messing with the adjustments and change targets.

After changing targets, I was way right - maybe 3" or so, and pretty consistent. Any efforts to adjust the Aimpoint from this point on seemed to result in random changes. Overshooting or undershooting the expected adjustment. I checked the Aimpoint for any shifting in the mount and it seemed solid. The ring bolts had all been previously torqued to 30 in-lb and blue loctited, and seemed OK. I tightened the LaRue QD lever a little and made sure it was solid. I had to leave the range so I called it a day after a total of 80 rounds and figured I'd try again later.

Here's the stuff I know:

- The carbine seems to be capable of holding at least 2" at 50 yards in my hands, and likely 1" or so inherently, which is about normal for an M4 profile chrome lined barrel (2 MOA).
- The Aimpoint and 3x are not fakes, I got them from a very reputable vendor.
- The LaRue mounts came direct from LaRue, so they are genuine. They are adjusted correctly to starting clamping at 45 degrees from closed and are firm to close, firmer to open. The ring is solidly clamped to the Aimpoint.
- I was using a GG&G/Bobro Gen 1 bipod and sandbags for the back.
- Ammo was Federal Lake City XM193F 55 grain.

Here's the stuff I don't know:

- Is my shooting technique any good? Along with me at the range was a cousin-in-law who served 4 years in the Marine Corps. He advised me to make sure I have the stock in the pocket of my shoulder and hold very firmly. I suspect I have bad follow through and I'm allowing the recoil of the carbine to "throw" the shot. I guess I'm too used to shooting a scoped CZ452 .22 LR with no recoil that holds less than an inch easily at 50 yards.

- Is shooting with a 3x magnifier and an Aimpoint while wearing eyeglasses somehow distorting the dot or making it appear in the "wrong" place? The glasses haven't seemed to cause any problems with regular scopes.

- I don't think an Aimpoint with a 3x magnifier is that much worse than a Leupold SPR reticle at 4.5x. I was doing OK with the Aimpoint at first until things started to go weird. Could it have been due to a hot barrel? I wasn't shooting that fast, less than 100 rounds in an hour. But it was pretty hot to the touch at some points. Maybe it's just fouling. Last time the barrel was completely cleaned was maybe 200 rounds ago.

I'm staring to think I just got fatigued and lost what little technique I have, then started chasing my tail. But if anyone has any ideas, let me know.

spamsammich
06-15-09, 22:02
I always zero my irons first, then leave them up and put the red dot on the tip of my front sight post when viewed through the sights. From there I shoot with the red dot and see where it prints. I've never had it differ more than a couple clicks from point of aim with co-witnessed irons. The one time I did have trouble was my ADM mount was rocking back and forth despite being torqued to spec. ADM sent me a new one and it has been fine since.

Also, at 50 yards, I do everything point of aim = point of impact. If the range goes out to 200M I will re-confirm poa=poi at 200M

CarlosDJackal
06-15-09, 23:20
If you started using your 3x magnifier, did you remember to adjust it so that the dot is centered (thus reducing the amount of paralax)? Yes, the Aimpoint magnifier does have just such an adjustment.

Where you shooting off the bench and if so, did you change your cheek weld and/or eye relief? Could the barrel have been resting against something when you shot after you change targets?

Did you change ammo? Did you have someone else shoot the rifle to see if it was not shooter error? Is the Aimpoint mounted on the receiver or the handguard? Good luck!!

Left Sig
06-15-09, 23:28
I didn't adjust the 3x, but the dot looks centered already. I was shooting off the bench with a bipod in the front and sandbags in the rear. Bipod attached to a free-floated Daniel Defense Omega Rail. Nothing touching the barrel, and ammo was the same the whole time. Aimpoint on receiver. No change in cheekweld or eye relief that I am aware of.