Accuracy Decline Due to Harmonics?

[Jimhoodag]

I have a .243 Savage Axis that shot 1/2 moa for five years, until I upgraded to a larger, better scope. I must have gotten a lucky barrel on this cheap gun, because two out of five shots would touch at 200 yards with a cheap Redfield 3-9x40 with a laser night light mounted on it.

Last week I used the same bases to mount an Elite Bushnell 6-24x50 on Burris Signature zee rings. I am wondering if the smaller scope and laser had the harmonics perfect on the barrel. It is now only shooting one moa. I am shooting the same reloads as before.

I moved and had to place my safe in a utility room with no heat or cool. Although I have an electric dehumidifier in the safe, I thought I saw some rust on the guns so I cleaned the bore spotless and it still can't get to sub-moa. I bought some J-B Bore paste and am going to see if that helps.

I broke in the barrel and have kept it clean except for leaving it dirty since last spring. I have run no more than 400 rounds down the pipe.

My 6.5-284 with a match, select barrel was left a little dirty too, but it took a good cleaning to get it back on.

I don't know enough about barrel harmonics to determine if the scope change caused the problem. I tightened the new scope down to specs with a Fat Wrench. I tried fresh reloads and several brands of commercial loads to no avail. Although I am not impressed with the tracking of the Bushnell, its optics are almost as good as my Nightforce.

In summary, I don't think it is a cleaning issue as I have used the best copper and carbon cleaners and many patches. I am using the same reloads. I used a cheek rest for the new, higher scope. My 6.5 is shooting 1/4 moa at 400 yards after cleaning - in other words I don't think it is the shooter. Could I have changed the harmonics by changing scopes?

Jim Hood

 

[J E Custom]

I have a .243 Savage Axis that shot 1/2 moa for five years, until I upgraded to a larger, better scope. I must have gotten a lucky barrel on this cheap gun, because two out of five shots would touch at 200 yards with a cheap Redfield 3-9x40 with a laser night light mounted on it.

Last week I used the same bases to mount an Elite Bushnell 6-24x50 on Burris Signature zee rings. I am wondering if the smaller scope and laser had the harmonics perfect on the barrel. It is now only shooting one moa. I am shooting the same reloads as before.

I moved and had to place my safe in a utility room with no heat or cool. Although I have an electric dehumidifier in the safe, I thought I saw some rust on the guns so I cleaned the bore spotless and it still can't get to sub-moa. I bought some J-B Bore paste and am going to see if that helps.

I broke in the barrel and have kept it clean except for leaving it dirty since last spring. I have run no more than 400 rounds down the pipe.

My 6.5-284 with a match, select barrel was left a little dirty too, but it took a good cleaning to get it back on.

I don't know enough about barrel harmonics to determine if the scope change caused the problem. I tightened the new scope down to specs with a Fat Wrench. I tried fresh reloads and several brands of commercial loads to no avail. Although I am not impressed with the tracking of the Bushnell, its optics are almost as good as my Nightforce.

In summary, I don't think it is a cleaning issue as I have used the best copper and carbon cleaners and many patches. I am using the same reloads. I used a cheek rest for the new, higher scope. My 6.5 is shooting 1/4 moa at 400 yards after cleaning - in other words I don't think it is the shooter. Could I have changed the harmonics by changing scopes?

Jim Hood

Anything is possible, But it should not effect the barrel harmonics because you did not add anything to the barrel. You did add weight to the rifle and it is possible that the reticle has a thicker cross hair making it more difficult to hold the same accuracy.

If you still have the other scope put it back on and try it. if it doesn't get any better you have another problem.

J E CUSTOM

 

[upacreek]

Try the Redfield again. Try another scope entirely. My bet is a *** scope or action fit change. Is it a wood stock? Climate and humidity effects wood. Just a thought.

 

[Jimhoodag]

It is the standard Axis plastic stock. I think either the barrel rusted inside or it is the stress on the action from new scope. Will try J-B Bore paste first. Then try old scope.

 

[J E Custom]

It is the standard Axis plastic stock. I think either the barrel rusted inside or it is the stress on the action from new scope. Will try J-B Bore paste first. Then try old scope.

Try a barrel break in procedure first. (Shoot and clean, shoot and clean for 5 to 10 shots) This should remove any rust and will not increase the bore diameter.

Bore Lapping abrasives should only be used as a last resort, and by someone with experience.

Just a recommendation

J E CUSTOM

 

[Jimhoodag]

I agree. The cautious approach is best. Will re-break it in first.

 

[Michael Eichele]

Improperly mounting a scope can induce stress in the action. Whether or not that changes the harmonics on a barrel or not I don't know but I know first hand that a rifle can shoot with a night and day difference between proper and improper mounting.

 

[Michael Eichele]

Bore Lapping abrasives should only be used as a last resort, and by someone with experience.

Just a recommendation

J E CUSTOM

+1. Take it easy on the JB and try and only use it near the throat. Check first for a carbon ring. The nylon brush pushed through the muzzle and pulled slowly back towards the breech works well. If there's a carbon ring, the brush will stop suddenly.

 

[tikkat3270wsm]

Try some Tubbs Final Finish. see if that helps

 

[Lefty7mmstw]

I've got three of the larger elite scopes with 2 being the 6-24 and one being the 8-32 and they are some rally good scopes for the $$. I'd look at barrel fouling and make double sure everything is hunkey dorey with stock screws, scope mounting, etc.. If all is well and you still can't get a group, then switch scopes to a known good scope.

Send the scope back if proven defective; I had a 3x9 elite 3000 go cloudy after using it on my lightweight 375 for a couple of years... they sent me a new 3x9 3200 as a replacement n.q.a..