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A little help with drops on 338 rum

 
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  #1  
Old 04-04-2012, 11:35 PM
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A little help with drops on 338 rum

OK, I am trying to learn to stretch my ranges out and I am stuck at 700 yards with a question. I just started using 300 gr bergers and they seem to be doing great. I went to the range today and made up a new drop chart from vortex site. My chono showed 2858, my elevation is 4200, temp today was 80. I dialed the scope dead on at 100 and then dialed 53 clicks for my 700 yard shot. Two shots, both hit high. One shot about 10 inches above POA and the other about 15 inches above. I was also several inches left. I moved one click right and down two clicks. My next three shots hit about 8 inches below POA. I came up one click and fired two more and I was still about 7 inches low. I dialed up one more click, same as where I started and was 6 inches below POA. The groups kept getting better the more I shot. The barrel was super clean when I started with 4 shots at 100, so the first two shots at 700 were no. 5 and 6. The barrel was warm, but not hot. I am thinking of shooting again in the morning without cleaning the barrel and see where the shots place. Am I missing anything?

I also dialed back 11 clicks according to my drop chart and center punched a gong at 600 yards on my last shot. I want to keep stretching the range, but I need to find out why my POA is changing. Any thoughts?
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Remington model 700 300 RUM LH 26" rem ss/blued receiver lam stock 215 Berger @3025/180 NAB @3300
Remington model 700 338 RUM LH 27" Broughton 5C 225NAB@3300 /300gr Berger@2830
Savage LH 22-250
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  #2  
Old 04-05-2012, 12:14 AM
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Re: A little help with drops on 338 rum

Check your rings and BASE. 10" high, 15" high left then a couple clicks dropped 8" low......... sounds like a loose base. double check your zero first thing. Something in the mechanics is moving to create that much inconsistency. When I had similar problems it kept leading back to the scope base. Now I bond those suckers to the action.
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Old 04-05-2012, 08:08 AM
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Re: A little help with drops on 338 rum

your barrel is deffinatley a "dirty girl". My .338 RUM starts to get good after 8 shots, but really shines around 10 down the tube.

Like D.I.D has already said, check the mounts.

one other thing is that your scope could have poor tracking... Have you done a box test? I think ive heard you say that its a Sightron, so I doubt that its the problem, but every once in awhile one slips through.
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Old 04-05-2012, 09:04 AM
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I agree with D.ID and angus. I would check the scope installation, starting with the rings. Does the base mate to the receiver well? Did you lap the rings? Are all the screws properly torqued?

I think you should check your groups at 100 yds. Start with a clean barrel. Fire two sighters. Then fire three groups of five shots each for score. Do successive groups get smaller?

Also, your scope has 1/2 moa clicks? What model is it?

Have fun.
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  #5  
Old 04-05-2012, 08:00 PM
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Re: A little help with drops on 338 rum

The scope is a Sightron SIII 8-32 x56, the rings are burris extra high dual dovetail with inserts. The repeatability of the scope is good. It tracks back to the same place every time. It seems that maybe I have been guilty of cleaning too often, usually after around 10 shots. It seems that the accuracy is getting better after 8 + rounds and then the POI is settling down. I wanted to go out and test this theory today, but the wind was more than I wanted to test this theory. My theory is that the barrel starts grouping tighter with more shots down the tube. The barrel is a broughton 5C and it cleans very easily. I want to test POI compared to the last shots I took yesterday to see if a cold shot with a dirty bore will duplicate where the rounds were hitting at the end of my session yesterday. At the end of my shooting session yesterday, I was grouping under 4 inches and when I made adjustments to the scope, the bullet was moving like it should. More testing and I will report back.
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Remington model 700 300 RUM LH 26" rem ss/blued receiver lam stock 215 Berger @3025/180 NAB @3300
Remington model 700 338 RUM LH 27" Broughton 5C 225NAB@3300 /300gr Berger@2830
Savage LH 22-250
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  #6  
Old 04-06-2012, 09:56 AM
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Re: A little help with drops on 338 rum

I went to the range this morning before work and popped off two shots @ 700, my target from the other day was still intact. I had about a 5 mph wind from the west, so I held at the west edge of my 8x11 target. First shot from a cold bore, 2 inches high from point of aim. Next shot, 12 inches high, 6 inches west from point of aim. Not much time, so I took one shot at 100 yards to check zero elevation perfect, 2 inches west from point of aim. When I shot at 700, I dialed 54 clicks up. My first two shots the other day were dialed 53 clicks up and they were about 4 inches higher than my shots today. The other day temps were about 75+, this morning was about 40 with a cold front coming in.

So the big question is now why did my point of impact change lower the other day as the barrel warmed up? I haven't cleaned the barrel and I am up to about 18 rounds since cleaning. I am wondering if lack of clearance in my barrel channel could be a problem. When I free floated this new B&C alaskan stock, I can barely get a piece of paper in between the barrel and the stock. Should I remove some more material? I will try the recommendation of several 5 shot groups at 100 to see what my loads are doing. I haven't adjusted powder charges or oal at all since these shot so good first time out. My oal is max for my magazine and powder charge is 91 gr H-1000 velocity showed 2850+- with SD of under 20
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Remington model 700 300 RUM LH 26" rem ss/blued receiver lam stock 215 Berger @3025/180 NAB @3300
Remington model 700 338 RUM LH 27" Broughton 5C 225NAB@3300 /300gr Berger@2830
Savage LH 22-250
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  #7  
Old 04-06-2012, 10:13 AM
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Re: A little help with drops on 338 rum

I would deffinatley remove a bit more material. My rule of thumb is thick computer paper folded twice (four thick). are you shooting from a bench or bi-pod? do you load your bi-pod for the shot (can cause flex on the fore-end)?

Have you chorographed your load? You can shoot good groups at 100 yards but if you have big extreme spread, or even small ES itll show at 700.

I might be saying what you already know, but gotta sort through the variables.
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