Can cleaning change my zero this much? Update, sort of fixed.

[jasonb]

I was off today and went to the range to help my buddy sight in his rifle. I was content, because my LMT is a shooting machine and shot great last time I used it.

Well, before we left, I put a few rounds down range and couldn't hit the empty spray paint cans at 100yds. I wasn't even on paper at 100. I switched from proven handloads of 24gr of AA2230 and 24gr of benchmark over a 55gr Hornady to some 55gr Hornady TAP practice. The practice ammo shot true.

I set up a target at 50yds and it was shooting about 12in high with my reloads. I eventually worked it out at 100 that it was shooting about 18in high, with the correct windage.

A week ago I shot a 500 round class with the same rifle and a mixture of Wolf, Barnaul, and TAP Practice. No trouble, but we shot 25yds and in.

I cleaned the rifle this morning because it was a mess from the class still, and didn't do anything different than my normal routine. could that have affected only the elevation?

Did cleaning my rifle change my zero? This is tha strangest range experience I've ever had. Do AIMPOINT's spontaniously adjust themselves? The weather was about 70 and lightly raining. Unfortunately, it'll be a week befire I can go back out.

[Heavy Metal]

Make sure your barrel nut hasn't come loose.

[Blankwaffe]

Kind of a tough call...but if the handloads were off and your Hornady Tap practice ammo was shootin true,I'd say your handloads are suspect.
By chance was the handloaded ammo out in direct sunlight,i.e. hot etc..?
As far as a clean bore,the only time I see accuracy affected slightly is on a completely clean bore,as in no copper or fouling remaining.And then its only slight and my zero is restored after a few foulers.

[jasonb]

Kind of a tough call...but if the handloads were off and your Hornady Tap practice ammo was shootin true,I'd say your handloads are suspect.
By chance was the handloaded ammo out in direct sunlight,i.e. hot etc..?
As far as a clean bore,the only time I see accuracy affected slightly is on a completely clean bore,as in no copper or fouling remaining.And then its only slight and my zero is restored after a few foulers.

It was solid clouds, the ammo was in a 30cal can in cardboards. The primers didn't show signs of overpressure like flattened or cratered, or popped. I decoppered it with Butches. Weirdest thing.

Heavy Metal

How lose will your barrel nut get before it pinches the gas tube?

[Heavy Metal]

Take the upper off the lower.

Put one hand on the FSB and the other around the upper. Twist in opposite directions and see if it moves.

[rat31465]

A clean bore will shoot differently than a dirty bore...as for being 12" off...well that does seem excessive. Even when I shot Benchrest we always shot a fouler or two to settle the POI down.

[spamsammich]

What kind of mount are you using for your aimpoint? Check it against your irons. I had a problem with ADM mounts which the manufacturer resolved for me.

[R.Miksits]

Because its only elevation and not speratic i dont suspect the mount, cant help but to check though.

What kind of aimpoint? what mount?

Were these handloads from the same lot as the ones run during the class? same powder same projectile same brass?

What round was the rifle sighted in for? if the TAP was spot on and your handloads were off, well you get the point.

how many rounds have been shot through the barrel?

Keyholing anything like that happening?

any chance the handloads got wet, hot, loaded with the wrong powder?

we need more information to narrow it down.

[spamsammich]

My ADM mount would rock forward and backwards on a dowel pin despite being torqued to and a little above speck. This would cause my zero to shift EXACTLY like OP is describing. That's why I suspect the mount. My elevation was the only thing that would shift, windage stayed constant.

[Blankwaffe]

My ADM mount would rock forward and backwards on a dowel pin despite being torqued to and a little above speck. This would cause my zero to shift EXACTLY like OP is describing. That's why I suspect the mount. My elevation was the only thing that would shift, windage stayed constant.

spamsammich,
Are talking about the base pin on the ring?

[Robb Jensen]

I agree it sounds like the Aimpoint is lose on the mount or the mount is lose on the gun.

[spamsammich]

spamsammich,
Are talking about the base pin on the ring?

exactly. There was too much clearance between the base and ring. ADM hooked me up with what looked like an entirely new mount!

[jasonb]

I have been working alot, so today I had a chance to run to the range before work. I brought the same ammo as before. First I confirmed that it was still too high. It was too high with my 69gr SMKs and the 55gr stuff.

Then I checked my Irons. They were right on.

I cranked the elevation down and fired some more and was rewarded with these two groupes at 100yds. There are 5 on the left and then I adjusted the windage right and fired 5 more. I fired 60 rounds total this morning. I think the verticle stringing was me, not bad for bulk packed 55gr FMJ's.

http://i132.photobucket.com/albums/q22/jbabal/002-1.jpg

THe setup is a 16in LMT with a VLTOR CASV and an Aimpoint M2 with a 4moa dot in a LaRue mount. I checked the CASV, and one screw was tight, one went another 1/4 turn at most. I still have no idea what the culprit was. Todays weather weather was almost identical to the other day, right down to the rain.