Rifle Not Grouping

[JMS906]

So my question; If a rifle isn't grouping but seems to be stringing rounds all over a vertical line - not moving up or down after every shot but more or less randomly sprayed in a 1 inch wide strip up the middle of the target spanning 6-8 inches vertically, is it most likely a scope issue or could it be a rifle issue?
Ryan

First off, if that rifle shot a 5-round group of one inch at 100 yards, I'd say your doing well. So for it to produce a vertical string one inch wide isn't surprising. The question then is, why is it producing a vertical string rather than a group?

If it is truly producing vertical strings then, ordinarily, that would be due to varying velocities. If the scope was stuffed, and the reticle moving, your shots would form a random pattern rather than a vertical string. However, that may not be the case. So, are the scope mounts secure? Test the bolts with the appropriate screwdriver/hex key. Put the rifle resting in a pair of V-blocks. (If you don't have a rifle rest, make one from some pieces of wood or even a stout cardboard box.) Hold the rifle secure and grasp the scope, try to move it - is it secure? It if moves, there is your answer. Does the front scope bell touch the barrel? If so, that is going to cause problems.

Test whether the reticle moves. Remove the rifle's bolt and then, using your V-blocks, align the bore with some object outside (the tip of your neighbours TV antenna will do). Now look through the scope and note (write down a drawing) of where the reticle is in relation to the TV antenna. PIck up the rifle and bump the butt firmly several time on the floor. Now hold the rifle in one hand and firmly belt the stock in the vicinity of the scope. Now bore sight it again. If the reticle has moved, you have your answer.

Lastly, if this rifle has iron sights, set up a target at 50 yards and see how it performs a) with the scope and b) with the iron sights. My Dragunov started shooting ridiculous 'patterns' one day (18-24 inch groups). I removed the scope and lo!, it produced two inch groups with the iron sights. Conclusion, the military POSP scope had been shaken to bits. So much for milspec kit.

I know I said lastly above, but two final points. Take the sound mod off until you've got the rifle sorted. It's only another variable, so remove it. And finally ... ask a mate to shoot it. Many times of the ranges, asking our pet benchrest shooter to shoot a rifle when someone is complaining there is something wrong with this rifle or that proves it's just "operator error".

-JMS

 

[bewsher500]

I can't see a logical reason why the mod would lead to a consistent vertical string
clipping leads to a shotgun pattern
loose mods likewise

vertical and for that matter consistent "walking" pattern of lines is almost always to do with temperatures increasing and stock to barrel interaction as it heats up

 

[User00026]

well, chances are the the moderator, like I said, creates a new peak in the standing harmonic wave that does not happen with free floated barrels (due to the pressure point. I can then say with utmost certainty that you will not get it to group with a/that moderator unless you free float the barrel and bed the action/front recoil lug. Personally, if money is no object, do that..if money 'is', then get a thread protector for a few quid and enjoy the rifle without the moderator.

 

[welshwarrior]

well, chances are the the moderator, like I said, creates a new peak in the standing harmonic wave that does not happen with free floated barrels (due to the pressure point. I can then say with utmost certainty that you will not get it to group with a/that moderator unless you free float the barrel and bed the action/front recoil lug. Personally, if money is no object, do that..if money 'is', then get a thread protector for a few quid and enjoy the rifle without the moderator.

I have got to say I agree with this a damaged moderator or poorly fitting one will give an erratic pattern. Vertical stringing often points to a harmonics issue.

Your rifle fled was made before Moderators where common kit, this is effecting the pressure on the pressure point and disrupting the barrels harmonics.

If it was me I would bed at least the front recoil lug and 1-2" of the barrel, you may as well do all the action whilst your at it. I would then free float the barrel ensuring it's free floating with the moderator fitted.

 

[Muir]

I can't see a logical reason why the mod would lead to a consistent vertical string
clipping leads to a shotgun pattern
loose mods likewise

vertical and for that matter consistent "walking" pattern of lines is almost always to do with temperatures increasing and stock to barrel interaction as it heats up

And an inconsistent hold / poor technique.~Muir

 

[purplepig]

I've got a styer .243 mountain- I've had it from new and it is unbelievably fussy it will only shoot Norma 75 grain ballistic tips and groups into 3/4 of inch with them. I've tried the same federal bullet and it sprays them up the page not deviating from the central zero, 6-8 inches. Other weight bullets I've found the group grows up to 1.5 inches. Try some more ammo you may find its as simple as that..

 

[Monkey Spanker]

The moderator was my first suggestion, but it doesn't necessarily mean that the moderator is at fault! It could be poorly fitted or it could just have altered the harmonics of the set-up. What's more likely though is that the weight of it is creating inconsistent contact/pressure somewhere which will cause the vertical errors you describe. Whilst you may not have solved the problem yet, you have probably located the source as well as clearing your scope of blame! See if you can borrow another mod of same thread and sufficient calibre and try that would be my next move.
MS

 

[macfarlane]

Had a rifle that wouldn't zero no matter what scope and mounts we put on it and me an a mate tried 6 or 7 different scopes and mounts on it ,we were baffled turned out the scopes were creeping backwards an arrester pin sorted it sometimes the silly things cause you problems.if you can't sort your scope I've a meopta 6x42 you can borrow I'll send you it you ,youse it for your stalk an then send me it back.

 

[NigelM]

My first .308 was a huge problem. Couldn't get it onto the board no matter what I did. Bloody dangerous. Someone finally suggested that I take the mod off. Noisy as you like, but grouped beautifully. Turned out that there was a burr in the mod which was causing the bullet to fly off in all sorts of directions. New mod. problem solved.