change in grouping

[Myerslake2005]

I have a browning A-bolt 300 win mag.  The first shot out of a cold barrel is right in the center ring at 200 yards.  After the first shot the gun will change groupings and the next three shots will be 3 inches high and to the right by 2 inches.  Any idea why this might happen?

[hilbillysmoke]

All guns differ but I have 2 abolts and they are tack drivers. I also have friends that have them and they love them. I think I would check the scope and the mounts, but first go into depth about the ammo. I have found that some abolts don't like ballistic tips, and my 300 don't like 150 grain bullets.

[Jim in Mo]

Check action screws also. One shot doesn't heat up a barrel enough for that drastic a change.

[JustaShooter]

Something like an inch to an inch and a half I could see, but the only time I've seen that much of a change in a cold, clean barrel from the 1st shot to the 2nd was when there was a bit of lube / bore preservative / cleaning solvent in the barrel.  You might try running a couple of dry patches through the barrel before the 1st shot and see what happens. 

[bluesman]

I agree, the barrel will not heat up enough with one shot to change the point of impact that much.

Check the action screws and scope mount screws.

Fire a "fouling" shot, then shoot a group.  The group size should be consistent.   

If the rifle will not settle in maybe the scope is shifting point of aim internally.  What kind of scope is mounted? The recoil of a 300 mag is considerable and it will need a good quality scope.

Please take no offense but are you flinching after the first shot?  I know that for me personally a 300 mag is more than I can shoot from a bench without flinching.

[DDelle338]

  My .338 A-Bolt does the same thing except in the opposite direction. The first shot out of a clean cold barrel is about 2" higher and 1" right of where the rest hit. Sometimes it's the first two shots. I'm convinced that it is the clean barrel that is doing this. I have shot it twice, (hitting high right) then put the gun away. Came back the next day and all the other rounds land exactly where they should. I have done it enough times to prove (at least to myself) that it's the clean barrel.
  Let me ask you this,, Has the barrel in question been Fire Lapped?

[jro45]

I don't have an A-bolt But my rifles react the same with a clean barrel. I usually have to fire 2 rounds.

[Davemuzz]

I had this very same issue with a Stevens 200 in .308 a few years ago. It drove me nutz. The first shot would be high and right....and every shot after that would be within a 1" group. I posted this on a few boards and got a bunch of advice, and tried most of it....but the darn gun would still do it.

So, the stock had not been bedded.....so I purchased some Davcon (peanut butter consistency) and bedded the stock....and the problem went away!!!

Now....I think (theorize) that the barrel was touching the stock at some point (probably at the Savage barrel nut) and when it was "dead cold" it didn't touch the stock. But when it got one bullet down it, it got just warm enough to change the barrel harmonics.  So....the bedding made it much more solid.

I hope this helps.

Dave

[AtlLaw]

Now....I think (theorize) that the barrel was touching the stock at some point (probably at the Savage barrel nut) and when it was "dead cold" it didn't touch the stock. But when it got one bullet down it, it got just warm enough to change the barrel harmonics.  So....the bedding made it much more solid.

I came to the same conclusion with 2 rifles I was working with this year.  Thanks for the verification!   

[Myerslake2005]

Thanks,  after reading some posts on the muzzleloading forum I was thinking the same thing.  Wish me luck, I'm some what mechanically deficent in the area of gun smithing

[Davemuzz]

Thanks,  after reading some posts on the muzzleloading forum I was thinking the same thing.  Wish me luck, I'm some what mechanically deficent in the area of gun smithing

Hey...it doesn't take a brain surgeon to bed an action to a stock. And that's a good thing because I did it....and I'm not a brain surgeon.

Dave

[bluebayou]

RELEASE AGENT!!!!!!!!!

Seriously, it isn't hard to do.  It made me pretty anxious the first time that I pushed my Remington into 2-ton epoxy........but just follow the directions.

Good instructions here:
http://www.battenfeldtechnologies.com/downloads/instructions/190274-MG-Bedrock-Instr-Large.pdf

[Davemuzz]

For bedding I use Davcon...the peanut butter consistency type. For a release agent I use shoe polish. A clear shoe polish so it doesn't stain anything important....like a stock.

Dave

[Dave in WV]

Auto wax will work as a release agent too.

[Davemuzz]

Auto wax will work as a release agent too.

And if you can convince your son to do it.....maybe you will get your car done at the same time! 

[bluebayou]

one day he will be old enough to rake the yard..............I dream of that day...........

[41 magnum]

PAM that you spray in pans so food won't stick is a good release agent also.

Free float the barrel then glass bed the action.

[Yankee1]

Could  be bullet seating depth changing from recoil. Try shooting a group by only loading one round at a time. If the group is good try sizing the necks tighter.
                                                                Yankee1

[RaySendero]

I have a browning A-bolt 300 win mag.  The first shot out of a cold barrel is right in the center ring at 200 yards.  After the first shot the gun will change groupings and the next three shots will be 3 inches high and to the right by 2 inches.  Any idea why this might happen?

Hey M,

I had a rifle that did just that and found a CRAZY fix that worked!

But first check the usual suspects - Like barrel to forend contact before the first shot, then again between shots, scope and mounts, etc. like some mentioned above.

Now my crazy fix - After you finish cleaning the bore, use a solvent (like Gun Scrubber) to get all the carbon based oils out of the bore then lub bore with a high viscosity silicone.  Usually you can find a spray can of silicone at an automotive parts place.