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shot-out

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RifleDude View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RifleDude Quote  Post ReplyReply Direct Link To This Post Posted: April/02/2007 at 10:46
Dale, I personally think you're overanalyzing this test.  If you just use a shooting technique that eliminates as much of the human variable as possible,  measure average group size of 10 five-shot groups after every 100 rounds or so, and measure throat erosion with your gauge, this should tell you what you want to know.  I would highly recommend shooting from a bench on a good front rest and rear bag to provide the most stable platform for the rifle as possible so you are testing more of the rifle than the shooter.  After finding a good accurate load, I would thereafter not recommend introducing any new variables like different loads or modifications to the rifle, because these can mask what the barrel is really telling you.  As much as possible, let barrel erosion be the only variable in the test if determining practical barrel life is indeed the goal of the test.  There is some subjectivity involved here, as the acceptable accuracy level for this type of rifle is more stringent than a deer rifle, so I would personally base the criteria for "shot out" on when the average group size becomes 50% larger than the "reference" group size established early on in the shooting.
Ted


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dale Clifford Quote  Post ReplyReply Direct Link To This Post Posted: April/02/2007 at 11:17
50% larger sounds fine to me-- usually I employ several tricks to enchance accuracy as the erosion increases, including chasing the lands, changing bullet weights, and changing powder charge levels, (sometimes powders). In this test r22 will be used through out, and the same charge, even though pressures will decrease, and same bullet type and weight, I will try to even use the same brand if possible to eliminate manufacturing differences. Just so we are using the same calculator then a 1 in. would then become 1.5 or are we doing "mark up on cost"  1/.5=2  ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RifleDude Quote  Post ReplyReply Direct Link To This Post Posted: April/02/2007 at 11:38

Yes, I was referring to the former calculation (reference group size plus 50%) rather than the retail cost markup example.  Good point! 

 

I was just thinking from a practical standpoint due to the expected application of the rifle, 50% might be a good benchmark, as in my mind this would become the point where I would rebarrel a varmint rifle.  If this were a benchrest rifle, you could probable consider a 10% increase in average group size as being "shot out".

 

Also, since we are just evaluating barrel life here, I would think chasing the lands would also mask real barrel life, as the purpose for chasing the lands to begin with is because throat erosion began to occur to the point that accuracy suffered noticeably.  To me, chasing the lands is no different than cutting off the barrel tenon and rechambering / rethreading in that both are intended to bring the bullet closer to pristine lands.



Edited by RifleDude
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dale Clifford Quote  Post ReplyReply Direct Link To This Post Posted: April/02/2007 at 14:07
probably wasn't clear-- no I won't use any mentioned techniques
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dale Clifford Quote  Post ReplyReply Direct Link To This Post Posted: April/24/2007 at 18:35

left group 5 fouling rds. right group last four of 25 shot string, last of fireforming  begin as soon as stoney point erosion gauge set, up --- had a hard time connecting with werkbeast.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dale Clifford Quote  Post ReplyReply Direct Link To This Post Posted: April/24/2007 at 18:40

4/5 mile per sec. .224 Sako action  600 rds. first 5 shots fouling rds.

 

 

 

 

 

 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote RifleDude Quote  Post ReplyReply Direct Link To This Post Posted: April/25/2007 at 09:49

DC, I may have misunderstood your post, but were the 2 targets shown under your Sako .224 fired with the Sako and the ones in the prior post fired with the Cooper you're using for the test?  The reason I ask is the right group on the bottom set of targets looks like the same group as the fouler group on the left in the previous set of targets.  Or, maybe you are just showing one 5-shot "fouler" group from the Sako, and it was to the left of your Cooper groups?  Nevertheless, if those are .22 caliber holes, minus the fouling fliers, it looks like your rifle is grouping pretty well.

 

Nice wood on the Sako!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dale Clifford Quote  Post ReplyReply Direct Link To This Post Posted: April/25/2007 at 10:37

Yea I posted that because I wouldn't have been able to tell the difference (in hole dia) between the two if I hadn't done it personally. They are the same group and to the left of those (on the target) is the .224. I used it as a test control, because I know (exactly--well mostly) what to expect on the target. So if the other gun does so and so and so on. I wanted to test the two guns as to the first 5 shots in terms of barrel break-in.

They were shot off a pickup hood at 107 yds (laser). It looks like I need to replace the heavy duty off road shocks on my truck, the groups are usually a little tighter.

top group cooper

bottom sako-cooper



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Post Options Post Options   Thanks (0) Thanks(0)   Quote RifleDude Quote  Post ReplyReply Direct Link To This Post Posted: April/25/2007 at 10:50

Thanks for clarification, Dale.  You may have mentioned it somewhere in the thread, but do you have the 8-32X56 or 12-42X56 NF Benchrest scope on your Cooper, and which reticle are you using?

 

Nice hood shooting!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dale Clifford Quote  Post ReplyReply Direct Link To This Post Posted: April/25/2007 at 11:02
8x32 np-1rr although at 32 a bit much -- shot the groups on 20 to compare with the Sako
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