New to precision reloading.....powder charge?

[exd3686]

Okay, I'm new to reloading for precision shooting. I've been doing some reloading and shooting and have some concerns over my powder charging based on the difference in FPS from round to round. I'm weighing every charge using a Redding BR3 powder thrower, an RCBS 505 scale, and a Redding powder trickler. Throwing Ramshot TAC to 43 grains. I'm throwing shy of 43 grains and trickling up to 43 grains on the nose. Now I have set the scale to 0.1 grain off just to see what 0.1 grain off looks like and it is quite a noticable difference. I figure by throwing shy and trickling to 43 grains on the nose that I'm getting better than 0.1 grain accuracy. Below are the chrony results from my recent outting. I'm using CCI BR2 primers, Sierra 175 SMK, 43 grains of Ramshot TAC. I'm using virgin Winchester brass which has primer pockets uniformed, inside and outside flashhole deburred, trimmed, and inside and outside chamferring. Bullets are seated with a Forster Comp. die with a difference of +/- 0.0005. The rounds are shot out of a PAI .308 Rem. 700 with a 22" barrel. I feel that the FPS spread between shots is hurting accuracy...especially if I shoot out to 1,000 yrds. I've read that a 30 FPS difference at 1,000 yards can result in a 10 inch difference. Any recommendations?

43.0 Grains TAC
2582 FPS
2598 FPS
2595 FPS
2636 FPS
2586 FPS
2606 FPS

 

[biglakesrule]

Re: New to precision reloading.....powder charge?

Ok, I'll admit being dumb (and too lazy too google): What's a PAI?

 

[One_Man]

Re: New to precision reloading.....powder charge?

Most likely the powder. Try some Varget or IMR 4064.

 

[biglakesrule]

Re: New to precision reloading.....powder charge?

Regardless of my last comment, here's some thoughts:

<ul style="list-style-type: disc">[*] Temperature - TAC might fluctuate a lot with temp??[*] How the powder sits in the case (nicely packed is good, if there's a big air gap, you'll get variation in burn)[*] Time between shots... do you wait for a complete cool down between each or anything like that (something to keep each one consistent)?[/list]

 

[Lburt]

Re: New to precision reloading.....powder charge?

I don't know how accurate a Redding powder dump is but let's pretend that with a consistent throw you can maintain an accuracy level within 1/10th grain; go with it. Dump it right in the case and eyeball the powder level in the case. If it looks good go with it.

Ideally you want to find a powder that will fill the case to the base of the bullet without showing any signs of pressure and a rythm in your throwing motion that will fill the case. My experience with small cases; PPC and 6br shows that just throwing and eye balling gives me better SD (Standard Deviation) and ES (Extreme Spread) than weighing each charge. Don't know why but it does. I have never tried it with large 06 or bigger cases so I don't know if it applies. Good luck.

 

[Winchester 69]

Re: New to precision reloading.....powder charge?

How does once-fired brass influence variation?
How much variation is due to the chrono?
What kind of vertical are you getting at 1000 yds?

TAC is probably too fast for what you want to do.
You have to experiment with powder/primer combinations.

Loading for long range is different from loading for short-range benchrest. What doesn't influence the accuracy at short range will be amplified at long range. Your powder measuring procedure is not part of your problem.

 

[shadow4]

Re: New to precision reloading.....powder charge?

Your powder weighing technique seems pretty solid. Its pretty much what I do. The only thing that I do different is that I double check my RCBS 505 against my RCBS 1500 every 15-30 rounds to make sure it is still reading properly. 99% of the time it is reading fine.

Try moving your powder charge weight up or down. You will find that as you put more powder in the case or put less powder in the case your Extreme spread will change. Could get better, or worse. You may not be at a charge weight that your particular bullet, barrel, powder, brass prefer.......

At that velocity I would say you are on the light side of the charge weight.

Also depending on light conditions your Chrony might not be getting good readings. I've noticed that as it gets later in the evening mine starts throwing crazy numbers out. It one time told me that I was spitting out 175's from my .308win at 2870fps. This particular load averaged 2650 in normal light.

A 30FPS spread is not that bad (it could be better). I've had ammo that I've loaded with that much of an Extreme spread and it still shot MOA at 1000.