Extreme spread in velocity

[fps plus]

This may help a few guys out in figuring why they may have a large extreme spread in velocity

Story starts out as I built a 6-284
Gun was extremely accurate. However when I shot over the chronograph my extreme spread was just over 100 fps . I weighed brass , powder bullets. Checked primers , was none of those .

I had formed brass from standard 284. I decided to anneal the necks. Problem solved , extreme spread was 15 fps after annealing

[Smokinyotes]

Interesting. Must be that the annealing gave consistent neck tension.

[tchardy1972]

Did you outside neck turn?

[BigRedJeep]

Thank you for sharing your observation and remedy!


Sent from my photon beam particle emitter

[fps plus]

Cases were trimmed and neck turned
I attribute it to neck tension

Brass work hardened when been sized

[tchardy1972]

Cases were trimmed and neck turned
I attribute it to neck tension

Brass work hardened when been sized

Brass is also work hard end during the neck turning process.

[DaleJ]

This may help a few guys out in figuring why they may have a large extreme spread in velocity

Story starts out as I built a 6-284
Gun was extremely accurate. However when I shot over the chronograph my extreme spread was just over 100 fps . I weighed brass , powder bullets. Checked primers , was none of those .

I had formed brass from standard 284. I decided to anneal the necks. Problem solved , extreme spread was 15 fps after annealing

Had best results loading for accuracy. Too many variables with chronographs. Trigger time and playing in the wind at 300-500 yards will reveal consistent loads. When you fine tune accuracy the velocity extreme spread tightens up.

[gunner1911]

I've heard stories from a guy who claimed to be shooting 5/8 groups at 500 yards (don't really buy it but whatever) claimed that when you resize your brass, downsize the expander ball down so it doesn't touch the casing on the down stroke. Creates extra neck tension so you get a better powder burn. Makes sense to me at least. Haven't tried it but I'd consider it for my target rifle when it's done.

[tchardy1972]

I've heard stories from a guy who claimed to be shooting 5/8 groups at 500 yards (don't really buy it but whatever) claimed that when you resize your brass, downsize the expander ball down so it doesn't touch the casing on the down stroke. Creates extra neck tension so you get a better powder burn. Makes sense to me at least. Haven't tried it but I'd consider it for my target rifle when it's done.

Higher neck tension generally creates more runout. To each their own.

[jmedical]

Two simple ways either anneal or run a expander mandrel through if you dont use bushing dies to maintain uniform tension.

[gunner1911]

Higher neck tension generally creates more runout. To each their own.

He measured runoff and used a tool to correct it. He said the best way to get groups like that is to have everything as consistent as possible. He claimed to do a few things differently from normal procedure but I don't see any harm in trying it once... Start with less powder than normal and just see the velocity differences... Experiment I think yes!!!!

[Dean2]

This may help a few guys out in figuring why they may have a large extreme spread in velocity

Story starts out as I built a 6-284
Gun was extremely accurate. However when I shot over the chronograph my extreme spread was just over 100 fps . I weighed brass , powder bullets. Checked primers , was none of those .

I had formed brass from standard 284. I decided to anneal the necks. Problem solved , extreme spread was 15 fps after annealing

Consistent neck tension is often overlooked when searching for a consistent load. Thanks for sharing.

Not all loads with 15 FPS variation shoot great groups at 1000 yards but the best 1000 yard loads do definitely have low SDs. A load with a SD of 100 fps WILL make a horizontal and wind drift distance over 600 yards so I see nothing wrong with using a chronograph to tune an already accurate load to have the lowest SD possible.

[gitrdun]

Things don't always work out as one might expect. Case in point with a 7-08 that I had taken care to reload to precision standards. Annealed, case weighing, match primers, neck sized, accurate seating depth, concentricity, all that jazz. Yet using Aliant powder, the SD was horrible, BUT the grouping was stellar. Go figure eh?

[gitrdun]

He measured runoff and used a tool to correct it. He said the best way to get groups like that is to have everything as consistent as possible. He claimed to do a few things differently from normal procedure but I don't see any harm in trying it once... Start with less powder than normal and just see the velocity differences... Experiment I think yes!!!!

I'm of the opinion that one must achieve concentricity during the sizing process. Trying to fix it afterwards when a bullet is seated with whatever tooling is akin to a band-aid solution or putting lipstick on a pig as some might say.

[Ivo]

I find tuning with accuracy and a chronograph being equally important and really one in the same. You may have an accurate load at 200m with bad SD which means at 1000m it's no longer accurate. So really, over a variety of distances, you need both to be effective.

If I get a load during load development that shoots okay but has really good SDs, I'll pursue it further leaving the primer and charge weight the same and start playing with seating depth to tweak the accuracy.

Forgot to mention: there are some that believe that the majority of runout issues are caused by expander balls. I'm not sure if I agree but I haven't used an expander ball for years and I have no issues.