sighting in issues

[mcbain4344]

I purchased an XCR-L chambered in 5.56. I lubricated the rifle and set it to gas setting 4 as per instructions. I zeroed the rifle at the 25(meters) firing point. When I started shooting at the 100m firing point the rifle was not hitting paper. I then went back to 25m point and proved the rifle was on target. I progressively shot my way back from the 25m point to the 100m point in 10 meter increments. The grouping progressively travelled high and to the right until it was off paper at 100m. I have not altered the rifle in anyway. The grouping travels approximately 9 inches between 25m and 100m. I am taking off the barrel and re-seating it. I will use the 200 inch/pounds of torque. But I don't see how this will work as there did'nt seem to be any debree in the barrel socket for misalignment.

Please help, thanks
-Mike.

[mcbain4344]

*UPDATE*
After taking the barrel off I re-tightened it to 200 inch/pounds. I took it to the range. I sighted the rifle in at 25m. I then went to the 100 meter firing point. The rifle is shooting 4 inches high but is now centered on the paper. Correct me if I wrong, but if a rifle is sighted in for 25m it should shoot an inch high at 100m. (I am basing this off my Ar15). The XCR sights are higher from the barrel then the ar15s. Does it naturally shoot 4 inches higher between the 25m and 100m?

Thanks Mike.

[Bravo]

Depends - what are the height of your sights?
The 25 meter zero on an AR doesn't work for me with the XCR - I use a 300 yard zero instead.
But yes, the difference in bore-to-sightline height makes a big difference. I don't remember exactly how much, but I know it was some.

[mcbain4344]

Thank you for the reply. I am using an ACOG TA31 m4. I guess if that accounts for 4 inches at a 100 the problem is solved. I am going to try a lower optic just to be sure.

[Bravo]

I'm surprised at 4", but my ACOG sits pretty high. Far too high for me to want to use on my XCR - glad it works for you!
I wouldn't worry about it to tell you the truth.
Here's what I'd do in your shoes:
Sight it in at 200, then shoot it at 25, 50, 100, 200, 300, and 400.
Then sight it in at 300, and shoot at the same ranges. And for kicks, since your optics are high, I'd do it at 400 as well.
The idea is that at some range, dependent on the height of the optic to the line of the bore, you'll get rounds hitting in a small area at a wide range of distances.
Mine, with the optic lower than a standard AR, groups really well from 25 yards on out to 300 - about the size of a softball for all distances combined. I've got to hold a little high for 400.
With your optics that high, you MIGHT get the same effect out to 400, I don't know. It's worth a try to see though!
FWIW, if you run those ranges with a 25m zero on an M4, you get like a 15" range (chin to center of chest) going from 25 yards to 300 - the 400 round shot goes in the gut.
With a 300 yard zero on an M4, you get like a softball sized group in the center of the chest from 25 yards to 300, with 400 being about in the gut. Zero distance really does make a big difference.
Sorry I'm not as much help as I'd like to be......

[Ghost-6]

Bravo's advice and expertise are absolutely correct, I'd like to add a few points in support.

1. Which barrel do you have and what rate of twist? M16s and M4s have a 1/7 twist. You likely have a 1/9 twist barrel which imparts a different spin, resulting in different stabilization and a unique pattern at different ranges than an AR.

2. ACOGs (and Aimpoints, Elcan's, HAMRs, and a few others) have sights set-up for an AR with either a 14.5" or 20" barrel and a direct-impingment gas system. The XCR has a long-rod piston which, when combined with the bolt, weighs something like 15 to 17 ounces. All that reciprocating mass slingshotting around in there alters the muzzle velocity (and barrel harmonics, recoil pulse, thermal expansion rate, etc) in a way that is closer to an AK or FAL than a AR, so rules-of-thumb based on AR sighting-in distances, dimensions, and group-dispersion ratios might not fit.

3. Bravo's suggestion about finding a sight-in distance "best case" for YOUR rifle is a great way to wring the best accuracy out of your setup. If it doesn't work, write back and we'll all help.

[BuddyChryst]

I'll toss my uneducated two cents in.

I've zeroed for 100 yards. From there, I adjust my hold-over for different ranges. I use an EOTech. At close range, my point of aim isn't the center dot. It's the bottom of the circle. So I don't worry as much about the exact inches, but the hold over on my sights.

[Benjamin Kurata]

Ah, the infamous 25 yard / meter "battle zero"...brought to you by the same branch of the military that saddled us with the M16 and all of its variants, and the finest sidearm - cum - trolling anchor, the Beretta M9.

A couple of years ago I was assigned to the "back" range at Lackland Annex (formerly Medina). When I drove by the front 600 meter rifle ranges (all meticulously groomed; they could have been from a golf club), there was a group (squadron?) of young airmen going through basic dis-assembly and reassembly on their M4s.

When I drove by at noon on the way to lunch, they were firing sighting in shots at the famous 25 meter sighting in target (the bulls eye with the grid).

At afternoon break they were still shooting at 25 meters, but had switched to the "hump" target. (It looks like a black normal distribution curve with scoring rings in the center.)

At the end of the day, they were still shooting at 25 yards, just at a smaller version of the "hump" target.

My curiosity got the better of me. I pulled my car into a parking space by the range, put on my ear and eye pro, got out and assumed a respectful distance from the firing line. When they ceased fire for the day and started policing up the brass, I found the Training Officer and introduced myself. I confirmed with him that these were newbie airmen, and this was the first day of their live fire training with the M4. I then asked him at what stage of the small arms training would the airmen fire at longer distances, and I got the "you moron" look and flat hat retrieved a new target and patiently explained to me that the reduced size targets represent what the sight picture would look like at 100, 200, and 300 yards. I then (wait for it...wait for it...) got the standard gospel that an M4 battle zeroed at 25 yards is no more than plus or minus X inches all the way out to 600 yards.

I pleasantly thanked the TO for his time, shook his hand, and then got back into my car.

Here's the bottom line. I have no scientific data, just a few years of watching riflemen (and women) zero their rifles at 25 yards and then wonder Whiskey Tango Foxtrot! at 100 yards and beyond. I have never seen an M4 with a 14.1 inch barrel shooting 62 grain green tips hit squat at 100 yards when zeroed at 25 yards. They all shoot well over the target. (I use predominantly IPSC / IDPA or FBI Q silhouettes.)

The 25 yard battlefield zero is for those who intend to engage the threat at 25 yards or closer. It is useless at distances greater than 25 yards, unless you find the second zeroing point (the "far" zero) well downrange, at about 500 - 600 yards.

Personally, 25 yards is comfortable handgun range. I carry a rifle to engage at longer distances.

Choose a zero that makes sense for your situation and then fire your rifle at 100 yard increments to see where the projectiles go "farther out". Learn range estimation and "Kentucky windage". (Hold over / under.)

Or, wait till the threat is 25 yards away or closer and hope that they didn't zero their rifle at a longer distance...

[mcbain4344]

thanks for the help everyone. I have not been able to message for quite a while. I was away at camp for a month. The problem is solved. It would seem that the height of the sights from the bore accounts for this precieved problem. I have had little experience with rifles outside of the ar15 design which is close to the barrel.