Firearm group shifting?
Ok, I was trying to help a friend out with his rifle today, but I could not figure out what was wrong, maybe one of you folks can help me/him.
He’s got a Remington 700 with a Leupold varix2 on it. Good gun, everything was properly tightened down and such. Here’s the issue:
Started shooting to get it sighted in. Shot a few rounds to get the bore warm, then sighting shots. Did about 1.5″ groups, after a little bit we easily had it sighted in. After shooting a bit more, all on target, the group suddenly shifted up and right about an inch. It wasn’t a flyer or anything, it made the same size groups, just in the wrong place. And it did this a couple of times.
Anybody have any ideas as to how this happened? I figured a couple of possibilities. Inconsistent cheek weld or the barrel getting dirty.
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I haven’t had time to read the link yet, but one of the reasons is stress in the bbl. Lesser quality, and some high dollar gun bbls. have not been stress relived. They start to move at the very first shot. Secondly, it is a problem with Not being so precisley built. The action to bbl juncture is not as strong on some guns. Not a problem in the 700’s though. 😉
Just one more reason to fire all sighting shots from a big game hunting gun from a cold bore.
Mike
I guess it could have been sloppy trigger pull. The trigger had been worked on, but it was still not great. Maybe we’ll just have to go back out and try again, with a little more control.
Knife, I know it shouldn’t take but a few shots to get it sighted in, but I always play around with it. Get the barrel warm with a few shots, then shoot about 3 to get an idea of group size. Then start sighting in from there.
Cold bore vs warm bore is something I forget about. My blaser does not do it. I can walk out from a cold bore and shoot a sub .25 moa 5 shot group. While the blaser isn’t a good example to compare to most firearms, I do believe most guns should have very little shift in the cold bore shots. Granted, there will be some as things heat up, but aren’t to super tight tolerances so they shift, but not much.
Another thing that has always made me wonder about the “cold bore shot” is how people say just one shot will be off, then the rest will be on target. Why, if it is the metal heating up, could this be? Shouldn’t you be able to see the poi “walking” to being on target? This has always bothered me, and then I found this:
Second post, very interesting read.
http://www.snipercentral.com/forums/viewtopic.php?t=24823&highlight=cold+bore+dry+fire
I think this has a lot of merit to it. It would explain why the first shot is off, but it is quickly fixed.
Try running a dollar bill between the barrel and the stock to see if it is touch somewhere, before and after shooting a group, also recheck the stock bolts after shooting a group incase it was slightly tweaked the 1st time. Brownells offers Accra-glass and Accra-gel bedding kits, very easy to use. and yes don’t forget to coat the gun with the release agent.
This might help Lama….Got this this morning from my nephew as he
looked over one of my groups that had the same high and right POI
shift…
we are taught that consistant horizontal misplacement is simply trigger
squeeze. either u have the trigger resting in the joint, as apposed to the
meaty portion of ur finger, causing a jerking motion, or just simply
jerking the trigger. then, consistant vertical misplacement is caused by
breathing. just some army stuff
Yep, sounds like a bedding issue. Bbl probably getting warm and touching the forearm somewhere.
If this is a deer gun, it should be sighted in from a cold bbl. three shots at most. Never a warm bbl.
For what it is worth, it should never take more than four shots to sight in in any scoped rifle. One to spot on paper. One to sight in. Two additional to check the setting.
Mike
Not handloads, just off the shelf ammo. Nothing special, but it was decent.
I will let him know about the bedding thing. That makes sense, as it got hotter everything starts to shift. Don’t know if he’ll do it or not, he’s not as into this shooting thing as some of us are. 😀
as riff stated
make sure the barrel is floated well
then bed the whole acton
MAKE SURE TO GREASE/TAPE ALL METAL PARTS lol
dont ask how i know but i now have a rifle permantly bedded lol
are you using hand loads?
if so make sure they are all loaded the same
poi will change with diff loads
With a bolt gun, thats almost always caused by poor stock bedding.
Temperature change will always cause the POI to change when the bedding isnt solid. I bet if he shoots that rifle tomorrow, the POI will be different from where you left off today.
Have him check the float of the barrel in the channel. Free float it all except about 2″ in front of the recoil lug. Then go and buy a glassbed kit, and be sure to follow the instructions or you will never be able to remove the stock without a hammer and chisel.
He wont be sorry, the gun will be a lot more stable.
–edit–
If the freefloating doesnt work well (some barrels dont like it), shim under the barrel about 1″ back from the tip end of the stock. Use just enough to apply light pressure to the barrel. If groups get better, glass bed that area (just a small dab about 1″ long). Leave the rest of the barrel channel floating.
Ive had 6 different Model 700 Remingtons, and every one of them benefited from doing this.
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It will be sighted in from cold bore before hunting season opens up. I understand your point there, with hunting it’s all about that first shot.
But until then I’m just playing with it to see exactly what the shifting problem is.