Strange Velocities O.C.W.

[HSNARC]

So i was working up a load for my .260 last weekend and ran into some strange velocity numbers while doing so.

Loads were in virgin lapua .260 brass with 140 amaxes over the top of variying charges of H4350 (40.0-45.0 in .5g incriments)

Started shooting my groups round robin style and velocity started to build steadily in 25-30 fps incriments per .5g increase in powder charge, Until i think i got somewhere near 43.5g and the velocities kind of plateaud (SP?) out. From 43-45 grains i got roughly the same velocitites between 2800-2900 fps, No signs of pressure.

Its kind of feels like im running it too rich, adding too much powder to the mix and its not yeilding any more velocity.

Sound strange to you?

 

[Macmathews]

Re: Strange Velocities O.C.W.


That is known to be an overpressure indication !
But you saw none ?


Kyle

 

[HSNARC]

Re: Strange Velocities O.C.W.

No no signs of pressure that i can see.

Maybe it had something to do with it being 16 degrees and they ammo going from the warm car to freezing out in the weather for over an hour.

 

[jdgray]

Re: Strange Velocities O.C.W.

My Lee manual says 39.0-42.0 for your powder, bullet selection. I would rework your load, using the powder increments in Dan Newberry's instructions. He skips the bottom spectrum of the data, and concentrates on the mid to max range. Sounds like your too hot to me.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HSNARC</div><div class="ubbcode-body">No no signs of pressure that i can see.

Maybe it had something to do with it being 16 degrees and they ammo going from the warm car to freezing out in the weather for over an hour. </div></div>
You chose a powder that is not temp sensitive, so I would look at other causes.

 

[HSNARC]

Re: Strange Velocities O.C.W.

You're probably right on the over pressure. I looked at my chrono data and i realized that my best accuracy was at 42.5g and that was yielding velocities between 2745-2800, which is right where i need to be velocity wise.

Now another mystery i cant seem to solve is why i am getting such extreme spreads in velocity. Many of my 5 shot groups with the same powder charge had an ES as high as 80FPS.

Is it because of the virgin brass? Im using federal 210's and weighing each charge on an RCBS beam scale, so i would think my ES would be fairly consistent?

 

[Macmathews]

Re: Strange Velocities O.C.W.

What Chrony?

And normally a load with es of 80 fps isn't gonna do well past 400 yards

 

[kaseyfield]

Re: Strange Velocities O.C.W.

How far out r u shooting? Should be minumum 200 yrds.. i had 1 hole grouls at 100 that did nothing at 200.. try a different primer or seating depth.. i was getting25 for es in my lapua mag.. dropped 215 match primers instead of 215 feds and my es dropped to 6 with a 10 shot group