load variations

[Buck268]

Was wondering if anyone had seen these types of increase/decrease in the STW charges all seated at the same depth and barrel cooled between shots?

Barnes 145 LRX

80 gr 3 shot average 3,459
80.3 gr average -2 fps
80.6 gr average -14 fps
80.9 gr average +29 fps
81.3 gr average +18 fps

 

[kyron]

to me that looks like your muzzle velocity standard deviation is exceeding the change in muzzle velocity from the small change in the load.

 

[dok7mm]

What chronograph were you using and how do weigh powder charge? And how many firings on brass? It could be any of those 3 or several other inconsistencies. More info will make it easier to solicit answers to your problem.

 

[Buck268]

I'm using a LabRadar
Charge is weighed on mechanical RCBS scales
Brass had 4 firings on them

 

[dok7mm]

Sounds like brass is work hardening and neck tension is not consistent from case to case, therefore different velocities. Needs annealing, most likely, if you're good with other variables.

 

[Buck268]

Sounds like brass is work hardening and neck tension is not consistent from case to case, therefore different velocities. Needs annealing, most likely, if you're good with other variables.

Thanks, I'll switch over to new brass while I'm getting the annealing down, I'm also using Reading Comp Dies with neck bushing.

 

[dok7mm]

Sounds like you're doing a lot of things right, but variances in neck tension can sometimes ruin things for all of us. You might have success changing neck bushing size to control amount of tension, but I have had much better luck with a good annealing schedule. Good luck to you.

 

[Buck268]

Thanks for all the feedback, just started dabbling in annealing so got some learning to do.

 

[eshorebwhntr]

A good annealing machine can be pricey for sure. There are also a lot of differing opinions out there on how much, how often, and how important it is to do.

The only times I do it are when I'm reloading for myself or friends and I'm using a hard variety of brass like Winchester, Federal, or Remington. Nosler or Norma I usually don't worry with it. I've also never done it to improve accuracy. I've actually never seen it effect accuracy in all the reloading I've done. Not saying it doesn't matter. I've just never seen it. I've annealed to prevent the brass from cracking at the shoulder/body junction, neck/shoulder junction. I've also annealed to aid in the fireforming process...my thinking being softer brass will form better to the chamber and also reduce the chance for cracking.

Also to be noted I don't own an expensive annealing machine. I use the handheld drill with a socket and torch method and I've had good luck.

I do use tempilaq. This helps in making sure you're doing things correctly. When you heat your brass necks/shoulders inevitably some heat will flow to the case head where you don't want to soften things. Basically heat the necks until they reach the annealing state (assumed to be around 650-700 for most brass) and then remove from the heat. Some think you need to place it in water. You can do that, but it's not necessary. Air cooling is fine. Paint 4-5 necks and place them in the flame while spinning them. Count how long it took you to get the temilaq to activate and change. Usually 4-6 seconds depending on the variables. Then repeat that process for the rest of your lot.

Uniformity and consistency is what you're going for.

I don't know if he's still around or offering the service but there use to be a guy on SnipersHide (before it switched hands back and forth) that for like $0.20-$0.30 a piece would wet stainless tumble clean your brass and anneal it. I'll have to see if I can find any info on that for you if you're interested.

 

[Buck268]

Thanks for the info, I was thinking of using the past to start that way I could get a good feel for flame and timing.

 

[Lefty7mmstw]

might I ask why you are bothering with such small charge changes in a cartridge of this size; I usually use a two grain hop between charges and drop to a grain when I'm close to the top. You also need uniform brass to see any difference, but your charge hop is more akin to a 22 or 6 br than a magnum rifle.

 

[Buck268]

I feel that I'm close to the top of my charge range and was just playing around to see if I could see any differences in accuracy. My goal was to try and hit 3,500 with the 145's and keep my clover leaf. I'm so close I can taste it, that why I'm working on small details.
In the factory set up we always kept the 0.50 jump as Barnes recommended, with my custom I just found that 0.10 jump is working great. I know I'm limiting myself a little because 1st and foremost, this is a hunting rifle and for all my adult life Barnes is my favorite pill. I shot Barnes in my Black powder, Slug gun and rifles and has performed flawlessly from Elk, Bear and Deer.

My next test within the next few weeks is to shoot at 300 yards to check my group there.

 

[doverpack12]

I feel that I'm close to the top of my charge range and was just playing around to see if I could see any differences in accuracy. My goal was to try and hit 3,500 with the 145's and keep my clover leaf. I'm so close I can taste it, that why I'm working on small details.
In the factory set up we always kept the 0.50 jump as Barnes recommended, with my custom I just found that 0.10 jump is working great. I know I'm limiting myself a little because 1st and foremost, this is a hunting rifle and for all my adult life Barnes is my favorite pill. I shot Barnes in my Black powder, Slug gun and rifles and has performed flawlessly from Elk, Bear and Deer.

My next test within the next few weeks is to shoot at 300 yards to check my group there.

What powder buck? I have a few 145s I plan to try out later this spring.

 

[Buck268]

I'm using 80.6 gr of IMR 7828