Is my load slow?

[Outlaw45]

I have a Rem700 VLS, factory 26" barrel with about 1000 rounds through it. I'm loading win brass, 175 smk, win large primers, with Reloader 15. I get the best accuracy with 43.0, about .5 - .75 inch @ 100 yards.

Last year this same load was about 2610 fps. A couple months ago my velocty was 2570. Today my velocity is 2520 fps. What could cause the difference? I can only assume it was summer time last year with about the same conditions.

The brass I'm using has been loaded about 10 times. Today I loaded once fired brass and it showed no difference, velocity is the same.

After getting the 2570 velocity I noticed my brass needed trimming. I trimmed it to the trim-to-length of 2.005. Then I noticed the velocity of 2520. Could the difference in case length cause velocity difference?

 

[RobG]

Re: Is my load slow?

Slower lot of powder? Temp extremes could possibly have an effect.

 

[5R Milspec]

Re: Is my load slow?

different lot of powder I would say

 

[Outlaw45]

Re: Is my load slow?

Then I'll have to burn through all of this lot.

 

[buffybuster]

Re: Is my load slow?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Outlaw45</div><div class="ubbcode-body">Then I'll have to burn through all of this lot. </div></div>

Bump up 0.5gr

 

[Greg Langelius *]

Re: Is my load slow?

This is a valuable lesson.

When changing component lots, it pays to confirm the existing load before you go ahead and make up lots of it.

Make up ten or so of the load, and bracket it with ten more each using charge increments of about + and - .2 to .5gr; how much an increment depends on the overall charge weight.

Call it a tweak, call it a refinement; it's good to be sure you're getting the best performance from your load. Things <span style="font-style: italic">do</span> change, and being complacent about proven loads can nudge you right out of the X ring.

10 reloading cycles can be overmuch for some situations; there are a lot of variables that impact brass useability.

When I buy brass, I buy enough so I can hold half aside. When loads start getting freaky like what's happening here; I commit a few of the fresh cases and see what it gets me.

If it makes for a significant improvement, I know it's time to go with the newer brass. The older stuff can be relegated to hunting loads, Zombie loads, or maybe annealed.

Greg

 

[josephberry]

Re: Is my load slow?

what kind of chronograph? check your distance between the sensors.

 

[josephberry]

Re: Is my load slow?

BEFORE you start adding powder.

 

[Outlaw45]

Re: Is my load slow?

Using the Pro Chrono. I usually set it about 6 feet in front of the muzzle.

I tried some once fired brass. Velocity was the same.