260 rem, odd velocities, chrono or load?

[caribouhunter]

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?
wouls 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.

 

[bullet]

Light deflection can have a lot to do with it, the angle of the light in the morning can effect how the chrony reads. Also if you are not at least 10feet away you could have the muzzle flash causing some of the difficulty.

 

[jmad_81]

Last week Remingon man lied our two chronies up and shot through both of them. His was about 130-150 FPS faster and would have been very extreme speeds. If if was showing he right numbers with your known load, I might have to throw something out there a ways, but could you have some powder that went bad?

The fact that it was riht on wih your .308 makes me think maybe its not the chrony. I could be very wrong.

 

[caribouhunter]

I`m also afraid it` the load
But the powder is brand new i unsealed the bottle to reload these.

 

[bullet]

I`m also afraid it` the load
But the powder is brand new i unsealed the bottle to reload these.

It is not the load, it was your chrony and more than likely what I mentioned. Your groups are to consistent for it to be the loads.

 

[Powerstroke]

+1 with Bullet -

Loads are consistent - The .260 isn't too bad to laod for.

Let us know how the next trip works out.

 

[SJB358]

I know I have issues getting good readings with my 22-250 if everything isn't perfect. It will read heavier, bigger bullets fine, but the smaller bullets seem to make the chrony have odd readings sometimes. Scotty

 

[DrMike]

Bullet has given you good advice. Your groups are too tight to give velocities that are so seriously variant. It is an artifact of your chronograph. As one thought, at what distance from the muzzle did you set up the chronograph? Is there a possible of muzzle flash creating this artifact?

 

[caribouhunter]

DR. Mike
i first set it up at 15 feet.
when i saw the problem i tried to set it up at 30 yard but got the same
kind of readings.
so anyway it's good to hear that it's not the load.
i will try the 45.6 grains load again to see if it shoots better than that
3 shor grouip i got. if it shoots, it should be my newberry method load i guess. because group 2,3 and 4 all went in the same area of the target.
i will also try 45.4 and 45.8

 

[DrMike]

Muzzle flash might have created such an artifact, but at that distance and with your cartridge that would be more than a remote possibility. It does seem as if there is another artifact at work here. Possibly a dirty lens on the chronograph? With that combination of powder and bullet, QL projects a maximum velocity of 2909 f/s at a maximum charge of 45 grains. Your readout does not even approach that velocity.

Despite the fact that your .308 gave the results you anticipated, the variation would make me think that it would be worthwhile to send the chronograph back to have it checked by the factory. Perhaps a phone call or Email to the company would provide some guidance for you.