Help with Mystery

[texas270]

Fortunate to own a 6.5 PRC that shoots sub .2 MOA when I do my part. Has been great for over a year, then I decided to upgrade the scope, which had originally been mounted by the custom gun maker. after over 100 rounds and 3 different scopes, I can;t figure out what is wrong. First shot is always 1 to 3 MOA from where the subsequent shots are, and in somewhat rabdom direction. the next shots are OK (about half MOA) but not as good as it used to be. I think everything is tight, certainly all the screws are tight. Have purchased new Leupold rings and now using a swarovski scope which has always been excellent on another rifle.

last time out shot my other nice rifle and put two shots in the same hole, so think I am doing my part.

any ideas as to what could be going on? thanks in advance!

 

[antelopedundee]

Go back to the scope the gunmaker put on and see if the inconsistency persists. If it doesn't you probably have defective scopes. Also check/recheck the base mounting screws just in case.

 

[The Oregonian]

That sounds like a gun issue and not a scope issue to me but as mentioned above, try it with the old scope to see where the problem is.

 

[Weaver93]

All you did was remove scope ring caps and replace scope?

 

[1mechanic]

Do you have a bore scope, check for carbon ring.

 

[The Oregonian]

If you use factory ammo it could be changing lots, same for reloading components. Could this be the case?

Also as mentioned, a carbon ring could be the problem. How many rounds do you have on the gun, and how often do you clean it for a standard cleaning, and when is the last time you removed a carbon ring?

 

[Bucklowery]

Put the old scope back on and try again for sure

Thanks

Buck

 

[texas270]

All you did was remove scope ring caps and replace scope?

yes, 3 times with different rings. through the process, pretty sure I discovered that the rail is not perfectly aligned with the barrell (had always had trouble with horizontal adjustments at longer ranges), but that would cause this?

Maybe the seating of the action/barrel on the stock???

 

[texas270]

Put the old scope back on and try again for sure

Thanks

Buck

thanks. hadn't thought of that. will try just to be sure.

 

[texas270]

If you use factory ammo it could be changing lots, same for reloading components. Could this be the case?

Also as mentioned, a carbon ring could be the problem. How many rounds do you have on the gun, and how often do you clean it for a standard cleaning, and when is the last time you removed a carbon ring?

shooting same batch of good hand loads. during the process of shooting the 100+ rounds cleaned the barrel several times.

don't even know what a "carbon ring is".. would love to learn that is it......?

 

[The Oregonian]

shooting same batch of good hand loads. during the process of shooting the 100+ rounds cleaned the barrel several times.

don't even know what a "carbon ring is".. would love to learn that is it......?

There have been tons of threads….enter the below phrase into Google and it should bring up all the relevant results.

carbon ring site:www.longrangehunting.com

If you have a bore scope I would check for one, and if you don't own one I would borrow or buy one. A chrono helps also bc it should cause higher pressure and velocity. But no replacing a bore scope.

 

[Roughrice]

Without knowing which scope bases you are using … I'd suggest you replace the windage type of Leupold base and ring set if that is what you are using.

I've had trouble like you have with those windage mounts more than once.

I'd try Talley's, Leupold dual dovetail or picatinny rail with good rings

 

[texas270]

There have been tons of threads….enter the below phrase into Google and it should bring up all the relevant results.

carbon ring site:www.longrangehunting.com

If you have a bore scope I would check for one, and if you don't own one I would borrow or buy one. A chrono helps also bc it should cause higher pressure and velocity. But no replacing a bore scope.

thank you. this sounds like it might be my issue. i do bump the shoulder only about .002" so could be a problem

 

[The Oregonian]

thank you. this sounds like it might be my issue. i do bump the shoulder only about .002" so could be a problem

I only bump the shoulder back about .002 as well. But I definitely have had carbon rings. I went about 100 rounds without cleaning at a shooting school with a 28N and I was getting sharper recoil and less drop than expected. I stopped shooting and researched when I got home.

I bought one of those piece of crap travel 4 piece cleaning rods and only use the final piece. It put that in a cordless drill and put an oversized nylon brush, one caliber larger, in the end and wrap a patch around that. I use iosso and use that for maybe 10-20 seconds at a time, stop and clean it out to see progress, and go a few more times if needed.

If your experience is like mine, you may see a noticeable drop in velocity from your most recent shots. Depends on how much carbon was baked on.

I have a 6.5 PRC and have cleaned the neck like that once so far in about 150 shots. It isn't as overbore as a 28N but it is a hot enough cartridge that it 100+ shots could easily cause a carbon ring.