Broken Scope or Dirty Barrel

Mixed results at the range today. I took the M70 .300WM, M70 .375HH and my CZ .416 Rigby. The .375 shot just like always with my favorite A-Frame loads, so ready for next week's safari shoot. So then it was on to the .300WM.

I loaded up a bunch of 200gr Nosler AB's with 74 grains of RL25 which shot very well last time out in very windy conditions. Well the same load shot was just all over the place, and I mean several inches low to high, left to right and every mix thereof. Tried to shoot some 200gr North Fork softs and got the same results. Virtually no wind, just an occasional breeze. Temperature was a bit warmer today but not extremely so.

Now here's what happened the previous 2 trips out. With a clean barrel, I shot a Remington factory load at the 200 yard gong and the bullet hit it. I then shot 4 different AB loads, 3 shots each group, with RL25 in 72, 73, 74 and 74.2 grain loads. The first group was about 1.5", the second just a hair over and inch and the last two a bit under an inch. Again in very windy conditions.

Following this trip and the one before today with no cleaning, I used RL25 in the exact same weights as above but with 200gr North Fork softs. The 72gr load shot quite similar to the AB's at about 1.5" and so initially I was encourage it would follow a similar pattern and get tighter. Not even close, the groups for the 73, 74 and 74.2 just fell off a cliff, crazy bad in the 6 to 8 inch spread range.

Now normally I would clean the barrel after putting 20 down the tube, sometimes less. However between work this past week, a lot of reloading, opening day of Little League and rebuilding my pool pump I didn't get this done. So today's shoot started with 25 rounds down the barrel after the previous cleaning.

So my AH brethren, do you think it's the scope or a dirty barrel? I'm inclined to believe the groups might have opened some after 25 shots, but nowhere like it did. Also, I have checked the bases and rings and everything was tight. So I'm thinking it's the scope.

Next trip to the range will be with a different scope and of course a clean barrel. I'll also take the scope in question with me. If the other scope I change to shoots well, then I'll put the questionable scope back on and shoot. If it still shoots well then it was the barrel, if not well then it's the scope.

All's well that end well for the day. After shutting down on the .300WM I moved on to the .416 Rigby. I had not shot it at 100 yards yet and wasn't planning to. But I had a few minutes before the next cease fire and nothing to do, so what the heck. With the VX-R on 4x and those fat reticle wires, I shot a 1.5" group!

Phil

That the problem with big ranges.

I would find it hard to think it would be your scope unless you dropped the rifle.

After the big spread, i would have came back to 25yds and then 50yds and 100yds.

I always take my cleaning equipment with me and if that could be the perceived issue give it a good cleaning and go again.

Have fun. At 25yds you can remove the bolt and look down the tube and you should be able to see the bulls eye as a cross check.

Well I've had scopes go down before. In fact the one that's on the rifle is a replacement from Zeiss for one that went down with the same initial signs. Got another one on that I need to send back to Leupold that has a loose internal lens. I wouldn't think a .300 Win Mag would be that hard on scopes.

It could still be needing a cleaning. As mentioned I'm going to swap scopes and clean the rifle. I'll get it narrowed down. I don't normally shoot this many rounds before cleaning. But I would think the groups would gradually open up, not blow out the way they did.

I would go back to 25 yds and shoot to check if it was the scope. I wouldn't think 20 to 25 shots would open the grouping of the bullets that much. I usually clean after 20 shots....but I have let it go to 40 to 60 shots if I'm doing a lot of shooting and never had major problems.

I will say it to anyone the 300 Win Mag is a hard gun on everything, including scopes, shoulders, and ears.

Originally Posted by enysse

I would go back to 25 yds and shoot to check if it was the scope. I wouldn't think 20 to 25 shots would open the grouping of the bullets that much. I usually clean after 20 shots....but I have let it go to 40 to 60 shots if I'm doing a lot of shooting and never had major problems.

I will say it to anyone the 300 Win Mag is a hard gun on everything, including scopes, shoulders, and ears.

Not sure I see the benefit of going back to 25M - you are obviously on the target - just suddenly shooting patterns rather than groups. Do agree that a Win Mag can be tough on scopes, particularly a rather light rifle. I also agree that it is unlikely to be a dirty barrel. With today's powders, the only real issue is copper build-up, and I would be surprised if anything drastic occured below a hundred rounds. Therefore, the most likely cuprit is indeed the scope or mounts. You didn't mention the brand, but a hard kicking rifle can be tough on any of them. Generally, usually, most of the time the better the brand - the more likely it will hold up.

When you dismount the scope, pay real close attention to the mount screws. They often work loose due to constant shock and temp changes. Particular the set over the chamber. If not them, then do try an alternate scope and see if you get the same spreading issues. If not, then you have your culprit.

Definately, scope or dirty bore if the rifle shot well previously. I have a Browning 7mag that with a clean barrel will shot sub MOA. (1/2" - 3/4" consistently) After about 20 shots without cleaning, the accuracy deteriorates rapidly. Once cleaned, it tightens right back up. Sounds like you have the correct plan to solve your issues.

I had a gun(9.3x62) that was a tack driver when the barrel was clean.
I could make sub moa(close to 1/2 moa) 3 shot groups with it all the time.
But that was when it was clean.
It shot well till about 30 shots, then it suddenly started spraying the shots all over.
It could then be off with as much as 8" with some of the shots. It had a tendency to throw the shots up and left when the barrel got dirty.

Since I am very lazy when it comes to cleaning guns, I sold it to a friend of mine. He loves cleaning his guns, so he didn't mind.
Today it is the only rifle he is using.
He loves the gun and ask me rather often how I could sell that gun, but he is very happy that I did

My 6.5-0g with a Shilen Select Match Grade barrel, I hardly clean at all.
Maybe I clean it every 500 shot, but I have sometimes shot 1000+ shots before I have cleaned it. Even then it takes me just a few minutes to make it totally clean again
And it still shoots sub moa groups with 1000 shots without cleaning.
Totally clean it shoots 1/4 to 1/2 moa 3 shot groups with almost whatever bullet I use when I find the right load.

So it can happen that 20-30 shots can foul a barrel enough to totally destroy the accuracy, but I think it is very rare.
I have never experienced anything similar with all the other guns I have owned.

It is a good chance it is the scope that is the culprit, but it also might be the mount even if it seems to be totally fine.
I have seen mounts fail many more times than I have seen scopes fail.

When last have you removed the copper fouling?

The only reason I said try at 25 yds, is the 300 Win Mag is such a thumper in a light gun that if you are having problems down range, it's better to get it up close and personal and make sure you can hit a bulleye at 25 yds.. At 50 yards you should be able to shoot a square by adjusting the turrets. If you can't shoot a decent square, I would think the scope or mounts are the problem. You should be able to shoot pretty tight groups at 100 yds.

Let us know the end of the experiment and hurry up the guy needs the rifle next week.

Like minds are on this one.

Originally Posted by enysse

The only reason I said try at 25 yds, is the 300 Win Mag is such a thumper in a light gun that if you are having problems down range, it's better to get it up close and personal and make sure you can hit a bulleye at 25 yds.. At 50 yards you should be able to shoot a square by adjusting the turrets. If you can't shoot a decent square, I would think the scope or mounts are the problem. You should be able to shoot pretty tight groups at 100 yds.

Originally Posted by KMG Hunting Safaris

When last have you removed the copper fouling?

At the last cleaning, now rougly 35 shots ago.

Originally Posted by enysse

The only reason I said try at 25 yds, is the 300 Win Mag is such a thumper in a light gun that if you are having problems down range, it's better to get it up close and personal and make sure you can hit a bulleye at 25 yds.. At 50 yards you should be able to shoot a square by adjusting the turrets. If you can't shoot a decent square, I would think the scope or mounts are the problem. You should be able to shoot pretty tight groups at 100 yds.

This is my M70 Super Grade that according to Winchester's website weighs 8.5 pounds. The last time I shot AB's before this trip to the range, it had no worse than 1.5" in the four different 3 shot grops. The last two coming in under an inch. The rings on inspection last night were tight and so were the bases.

Originally Posted by Red Leg

Not sure I see the benefit of going back to 25M - you are obviously on the target - just suddenly shooting patterns rather than groups. Do agree that a Win Mag can be tough on scopes, particularly a rather light rifle. I also agree that it is unlikely to be a dirty barrel. With today's powders, the only real issue is copper build-up, and I would be surprised if anything drastic occured below a hundred rounds. Therefore, the most likely cuprit is indeed the scope or mounts. You didn't mention the brand, but a hard kicking rifle can be tough on any of them. Generally, usually, most of the time the better the brand - the more likely it will hold up.

When you dismount the scope, pay real close attention to the mount screws. They often work loose due to constant shock and temp changes. Particular the set over the chamber. If not them, then do try an alternate scope and see if you get the same spreading issues. If not, then you have your culprit.

All screws were tight. The scope is a Zeiss Conquest in 4.5-14. It's the second one I've had, the replacement to one that went bad on me with same initial signs. Eric might be on to something however. The scope has been on my Tikka T3 Lite for quite a few rounds. That rifle only weighs 6.5 pounds and perhaps was wearing something loose prior to being put on the new M70.

Looks like it will be Thursday at the earliest before I find out.

Originally Posted by Norwegianwoods

I had a gun(9.3x62) that was a tack driver when the barrel was clean.
I could make sub moa(close to 1/2 moa) 3 shot groups with it all the time.
But that was when it was clean.
It shot well till about 30 shots, then it suddenly started spraying the shots all over.
It could then be off with as much as 8" with some of the shots. It had a tendency to throw the shots up and left when the barrel got dirty.

Since I am very lazy when it comes to cleaning guns, I sold it to a friend of mine. He loves cleaning his guns, so he didn't mind.
Today it is the only rifle he is using.
He loves the gun and ask me rather often how I could sell that gun, but he is very happy that I did

My 6.5-0g with a Shilen Select Match Grade barrel, I hardly clean at all.
Maybe I clean it every 500 shot, but I have sometimes shot 1000+ shots before I have cleaned it. Even then it takes me just a few minutes to make it totally clean again
And it still shoots sub moa groups with 1000 shots without cleaning.
Totally clean it shoots 1/4 to 1/2 moa 3 shot groups with almost whatever bullet I use when I find the right load.

So it can happen that 20-30 shots can foul a barrel enough to totally destroy the accuracy, but I think it is very rare.
I have never experienced anything similar with all the other guns I have owned.

It is a good chance it is the scope that is the culprit, but it also might be the mount even if it seems to be totally fine.
I have seen mounts fail many more times than I have seen scopes fail.

I cannot imagine treating good rifles this way.

If it isn't because something is losse,then it probably has a rough spot in the barrel. I've heard of some guns that have a rough spot right from the factory, and it will shave off copper from every round. This will cause accuracy to go too pot after about 20 shots.

Rifle is clean as I think I can get it including removing copper. Yesterday's scope removed and a 6.5-20 that resides on my 7MM Mag deer gun is on the .300. Now why this silly job of mine has to get in the way of important things I do not know!! Waiting impatiently for Thursday.

Its always possible you had a bad day at the range, but its likely the scope has failed if as you say all the screws on bases and rings are tight. I recently had my bases come loose while shooting a Steyr M Professional that normally shoots superbly. When I got home to clean, I put my hand on the scope and felt the whole assembly wiggle! Took it all apart and found the bases were loosey goosey. Took the screws out and put LockTite on them, no more problems. Another thing to look for is cracks in the stock (if wood). I have seen good shooting guns start patterning when the web of wood in the trigger well develops a crack(s). Also have had the bedding pad behind the recoil lug crack in all directions. This is why I nearly always glass bed a wood stock unless it has lots of reinforcement already. If there is not enough clearance around the barrel in the channel you can get flyers if there is some torqueing going on and the barrel touches the stock. Free floating the barrel is usually a good way to go on most bolt guns and is one of the first things I do on a new rifle especially if it has the usual factory pressure point up forward. Sometimes they help but not usually. You have probably already done most of this but another look may yield more info.

Originally Posted by sestoppelman

Its always possible you had a bad day at the range, but its likely the scope has failed if as you say all the screws on bases and rings are tight. I recently had my bases come loose while shooting a Steyr M Professional that normally shoots superbly. When I got home to clean, I put my hand on the scope and felt the whole assembly wiggle! Took it all apart and found the bases were loosey goosey. Took the screws out and put LockTite on them, no more problems. Another thing to look for is cracks in the stock (if wood). I have seen good shooting guns start patterning when the web of wood in the trigger well develops a crack(s). Also have had the bedding pad behind the recoil lug crack in all directions. This is why I nearly always glass bed a wood stock unless it has lots of reinforcement already. If there is not enough clearance around the barrel in the channel you can get flyers if there is some torqueing going on and the barrel touches the stock. Free floating the barrel is usually a good way to go on most bolt guns and is one of the first things I do on a new rifle especially if it has the usual factory pressure point up forward. Sometimes they help but not usually. You have probably already done most of this but another look may yield more info.

Don't think it was a bad day shooting, the .375 and .416 shot as well as ever. The barrels on the new Super Grades are floated, but I don't know about the bedding. I haven't taken the gun apart yet.....dang it Ses that made me think. I've not checked the action screws. I did look the gun over pretty hard tonight as I also wondered about cracks in the stock, dang near made me cry thinking about it, but didn't see any.

Off to check the action screws....

Can also check the crown if the problems not found, good advice Ses....

My best always.