Is it just me?

[diderr]

I was doing OCW testing for my 190 load, and noticed something odd. Every charge weight would put two bullets on top of each other (in the .1's, smallest was .07") but the third consistently would be about .25" outside of the two shot cluster somewhere. That was with 5 charge weights. Is it just me getting "excited" seeing the small group and shanking the last one?
The only thing I can think it would be other than just me would be my bedding. My smith bedded it in Devcon 10110 for me, but he went about 2 1/2" out from the front of the lug for the barrel support. (supports entire length of the chamber)
Thanks.

 

[oldfatguy]

While tiny little groups are wonderful, OCW is about the location of the averaged POI of the different charge weights in relation to the POA. Your loads need to be shot round-robin to reduce ambient influences on your results.

OFG

 

[groundhogbuster]

While tiny little groups are wonderful, OCW is about the location of the averaged POI of the different charge weights in relation to the POA. Your loads need to be shot round-robin to reduce ambient influences on your results.

OFG

+1 What he said. Never shoot the same charge for 5 shot groups in a row. Ex. If you have 43/43.3/43.5gr, shoot 1 43gr 1/43.3 etc, just shoot same target of course with same charge.

 

[scudzuki]

The OP did not indicate that the rounds were not shot round robin.
While group sizes are not relevant to an OCW test, if they were shot at 100 yards, it's pretty impressive that all of the charges resulted in groups as described (under 1/2" if my math is correct).

Joe

 

[diderr]

I didn't shoot round robin. I went from 42 to 43.2 in .3 increments and shot 3 in each charge. Just the way i've always load developed. I just find it odd that the third shot is consistently off. I'm going to load 20 of the charge weight that shot the .07" two shot cluster and chrony and see what it does at 400 yards.

 

[scudzuki]

Not shooting round robin may or may not change the results of the test, depending on how much your barrel is affected by heat and fouling. It makes the test a little more difficult but given the potential benefits, it's worth the added hassle.

As for the tendency you observed where the first 2 shots touched and the third opened up the group, I suspect it was a fluke and you will not see that again, just like how an inaccurate rifle will every once in a while shoot a tight group if you shoot enough groups.

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