Is my scope broken? How do I check it?

[Jimfern]

I have a Mosin Nagant that has a side mounted Leupold 4X scope on it. The 1st shot at 100 yards is dead on, but all the other shots are all over the target with no consistancy. I have been using Norma factory ammo. I just assumed it was the rifle, but reading other people's posts, I'm begining to wonder if my scope is broken.

My father-in-law sold me the rifle for a song already "sporterized", so I'm not too worried that I got a bad deal, I just want to get better groups.

I was thinking of trying the scope on a different rifle and/or trying a different scope on my Nagant. I would greatly appreciate anyone's ideas on how to check, esp. if you have a better idea.

 

[jbkebert]

I would start with checking your mounts and rings. Make sure everything is tight. Also uneven pressure on a barrel will cause some flyers. I would look everything over real close. Either something is putting some stress on the barrel and it is not vibrating the same with each shot. Or the scope is not torqued down and is shifting although very slightly with each shot. If all that checks out mount a diff scope on the rifle and check for consistancy. YOu don't have to sight in. Just be able to hold a decent group.

 

[rcmodel]

First check the mount screws and make sure the mount isn't moving around.

Still, if the first shot is always where it is supposed to be, but following shots are not, it is not the mount moving around, or a broken scope.

It has to be the rifle.
Barrel heating up and rubbing against the stock at some point would be my first guess.

rc

 

[Zak Smith]

If you are capable of keeping the rifle still while dry-firing (on sandbags), do that. If the reticle (crosshairs) move when the striker drops, you probably have a loose erector, lens, or some other problem.

Otherwise, put it on a known-good rifle and shoot it to see.

 

[Jimfern]

pictures of the rifle/mount

Here are some pictures. The mount is a Weaver Side 1 and it appears professionally installed. Everything is very tight on it. All bolts are tight.

http://www.flickr.com/photos/30034065@N05/3349450789/

I have a Model 70 Winchester that I'm going to try the scope on next if you guys don't see any problems based on the pictures. Thanks again for the help.

The barrel does rub up against the left side of the stock. It is definately not free floated.

 

[fineredmist]

It's not the scope it's the cut off stock. The barrel is not being supported/properly free floated and it will never shoot well. Spend a few dollars and buy a after market sporter stock.

 

[Old Guard Dog]

I've had a Mosin that would move the group as the barrel heated up, and be dead on when left to cool. But it was not "all over the place", just moved left. I had the stock military stock on it. Never tried to fix it, just sold it when I was short of cash many years ago.

 

[krs]

Make sure that the stock bolts are tight, and try a dollar bill between the barrel and the wood all the way back to the action. If your dollar won't go the barrel is making contact and being pressed on. Skinny barrels like a Mosin original can and do expand and curve/bend when they heat up and one shot is enough to make a difference.

if the stock pressure is at work for the first shot and you've zero'd the rifle to that, barrel movement could increase or decrease the wood contact and make subsequent shots fly any which-a-way in an uncontrolled bedding situation.

Sometimes bedding the barrel or using adjustable contact screws help; sometimes just a piece of leather belt under the barrel at the front of the stock helps.

You need the action secure and the barrel either free to move or prevented from moving very much. The barrel contact leather and bedding screws at the forestock are old time methods that were replaced by free floating barrels, but they can still benefit some rifles in some cases.

Doubt that it's the sighting/scope although reticle movement has been seen with most any scope. If that's a Leupold M4 it's less likely to suffer than most.

 

[Jimfern]

I will try a piece of leather in the front. There is definitely barrel to stock contact on the left side. Last night I moved the scope to my Winchester Model 70 to try it out. Frankly I will probably leave the scope on the Winchester and get a cheaper scope for the Mosin. I plan to try it out next week and will post my results when I get back from the range.

Thank you again for your help.

 

[RogersPrecision]

If you are already getting sub 4" groups at 100 yds,
I'd nit worry the sights.

 

[Jimfern]

It's more like sub 11.5" X 8" target sheets if I'm lucky. I'd be happy with sub 4" given the age/shape of the rifle.

I did take it off the stock and by putting a small washer between the stock and the front action, I was able to raise the front of the barrel so it doesn't touch the stock at all, so I'm hoping that will do the trick.

 

[351 WINCHESTER]

Just attach a bore sighter and tap on the scope. If it moves you have a loose mount or the scope is defective.