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wierd velocities, Load or chrono problem?

 
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Old 05-16-2010, 07:48 PM
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Join Date: Apr 2010
Posts: 20
wierd velocities, Load or chrono problem?

hello all!
i started load development for my wife 260 rem model 7 this morning.
i use remington once fired brass
cci br 2 primers
nosler 120 gr. ballistic tips
and h4350 powder
coal is 2.780"
i tried the newberry method for the first time. as far as grouping goes
i'm satified, for a first attempt.
here's the target.

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group number three has a flier, probably my error, i just don't know.
so here's the chrono i got on those
group 1 is 44.8 grains vel. was 2744,2789,2005???
group 2 is 45.2 grains vel. was 2803,1969,1766
group 3 is 45.6 grains vel. was 2772,2002,2650
group 4 is 46.0 grains vel. was 1999,2063,2715
group 5 is 46.4 grains vel. was 2054,2867,2825.
i also shot 3, 3 shot group with my 308 and factory loads, and all were around 2700 fps.
so what do you long time reloaders think?
i never experienced something like this with this chrono so far.
after the first few odd readings i relocated the setup somewhere else
to make sure the sun angle wasn't playing tricks on the chrono.( prochrono pal)
all the loads were carefully weighted on a beam scale.
scale was zeroed before and checked after loading session.
all the shot felt the same (recoil and muzzle blast).
should i use magnum primers with this powder?
is it possible that it's the load?
would i get groups like that at 100 yard with some bullets going 800 fps slower?
i'm a bit lost right now.
thank's for your help.
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Old 05-16-2010, 11:06 PM
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Join Date: Apr 2009
Location: Carrollton, Ohio
Posts: 578
Re: wierd velocities, Load or chrono problem?

When I was load testing for my 357 I was getting false readings from what I thought might have been powder skewing the readings.

I moved the chronograph back 15 feet instead of the 10 I usually set it at. When I set it back the 5 feet the readings registered in the norm.

Just a thought.
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  #3  
Old 05-16-2010, 11:51 PM
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Join Date: Mar 2006
Posts: 848
Re: wierd velocities, Load or chrono problem?

Group #3 could be what Dan calls a "scatter group" Usually the OCWis about 1-2% above that load, which would be in the 46-46.5 range. Looks like things are coming together at 46.4gr. so I would work around that charge.
I would try another round robin starting at 46.2,46.4,46,6,46.8 if the upper charges are within safe pressure ranges.

If you think you caused it, then load that charge of 45.6 up again and shoot it to make sure. If it groups tight and in the same relative position it could very well be your OCW

I think it is most likely the chrono problem since you are carefully weighing the charges.

Last edited by RockZ; 05-17-2010 at 12:03 AM.
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