Inconsistent Velocity

[geraldhawaii]

Hello to all you reloaders. I need some advice. I have a 7mm Rem Mag in Tikka T3 Lite Stainless steel barrel. I have been reloading for this rifle for at least 10 years with a Nosler Partition 160 grain bullet, with Federal 215 Primers, and 63 grains of H4831sc. Used all manual specs, 3.29 overall length. Consistently shoots at 5/8 inch groups. Used regular redding dies.

Well wanted to see if I could shrink the grouping. Went to new Winchester brass. Went to 3.31 Overall length (overall length measured with Hornady gauge was 3.32). Powder charge stayed at 63 grains, with federal 215 primer. Purchased and used the Redding Master Hunter Die set. Also annealed and full resized the brass. Group spread to 1.25 inches. The velocity was totally inconsistent. 2621fps, 2672fps, 2716fps, 2724fps, 2732fps, 2737fps, 2744fps; (Caldwell Chrono was utilized for velocity) over 100fps difference between the fastest and slowest velocity. Powder charge was done on a RCBS charge master, and confirmed by RCBS M500 mechanical scale. Upon close inspection of the necks, of the fired and unfired brass (suspected the inconsistent velocity was due to neck tension issues) noticed light striations going vertically on the case neck. This must've happened during the resizing. Would this affect velocity. Any suggestions would be welcomed, as this has never happened to me.

Aloha,

 

[Bob Wright]

The new Winchester brass is getting fire formed to your chamber. That's the new variable you have.
Annealing the new Winchester brass may have caused those marks on the neck. I would just polish those with steel wool.
Make sure your dies are cleaned and use a good resizing lube.
Shoot the rest of your new brass, then, start back with some more load development.
That 2700 fps velocity is way slow. That bullet should be doing 2900 or more. Just start with a new ladder test and see where pressure signs show and call that your max charge.
Then work in the velocity nodes.

 

[Mikecr]

Went to new Winchester brass.
Went to 3.31 Overall length.
Purchased and used the Redding Master Hunter Die set.
Also annealed and full resized the brass. Caldwell Chrono,

Lotta changes

 

[RegionRat]

Agree there are too many simultaneous changes that may have taken you out of tune.

So now the question would be, if you go backward and re-create your original recipe will that performance repeat?

 

[birddog 68]

Lotta changes

Agree there are too many simultaneous changes

One change at a time is the best way to go.

 

[Tiny Tim]

What velocity were you getting with the old load? Why did you change your seating depth? Too many variables changed. Brass volume could explain some velocity differences and seating depth may change accuracy. Just some things to consider.

 

[Phil Rizzo]

I like to play as much as anybody, but for a hunting bullet in a hunting gun, you had a very good accuracy result with the original load!

 

[Window]

Hello to all you reloaders. I need some advice. I have a 7mm Rem Mag in Tikka T3 Lite Stainless steel barrel. I have been reloading for this rifle for at least 10 years with a Nosler Partition 160 grain bullet, with Federal 215 Primers, and 63 grains of H4831sc. Used all manual specs, 3.29 overall length. Consistently shoots at 5/8 inch groups. Used regular redding dies.

Well wanted to see if I could shrink the grouping. Went to new Winchester brass. Went to 3.31 Overall length (overall length measured with Hornady gauge was 3.32). Powder charge stayed at 63 grains, with federal 215 primer. Purchased and used the Redding Master Hunter Die set. Also annealed and full resized the brass. Group spread to 1.25 inches. The velocity was totally inconsistent. 2621fps, 2672fps, 2716fps, 2724fps, 2732fps, 2737fps, 2744fps; (Caldwell Chrono was utilized for velocity) over 100fps difference between the fastest and slowest velocity. Powder charge was done on a RCBS charge master, and confirmed by RCBS M500 mechanical scale. Upon close inspection of the necks, of the fired and unfired brass (suspected the inconsistent velocity was due to neck tension issues) noticed light striations going vertically on the case neck. This must've happened during the resizing. Would this affect velocity. Any suggestions would be welcomed, as this has never happened to me.

Aloha,

Virgin brass can be all over the place. Fire form it and start from scratch with your load development and you'll be able find the new sweet spot. Also, check to see if there's a carbon ring (if so, take the time and effort to remove it). That can cause velocity swings from shot to shot as well.

 

[skipglo]

Any brass change can have a dramatic effect on accuracy and especially during initial fire forming! Wait for round 2 results. And to reinforce what all others have said....one change at a time!

 

[xsn10s]

My Caldwell chrono gives me 100 fps variations at times. I'm not sure it''s the chrono or the load. but the way the rifle shoots I'm guessing chrono. It's had varying changes on two rifles. The worst is on my 223. Start taking note of the lighting and try your loads out to max range distances you'll shoot at.

 

[Mike Matteson]

Winchester brass is okay, but why you didn't go to a top of the line brass. Peterson does make 7mm RM brass. Still needs to be fireformed.
I use Winchester brass of years. It weight less but at the same time they veryed in weight.
Becareful in setting your shoulder back. Only a .001 or 2 th. I went to neck sizing a long time ago, and stop the case separation in it's tracks with belted cartridges. I am headed back to bumping my shoulder back a 1th or 2 to see how that works.
I could go on and on, but will stop here.

 

[Phil Rizzo]

If you see vertical stringing at longer distance it's confirmation of "large" velocity variations.
One way to double check the chronograph.

 

[geraldhawaii]

I never played with the overall length before, and just wanted to see if it would be more accurate if I got it closer to the lands. I got the original length from the nosler manual. Like most have said, back to the drawing board. I will go and shoot the original load this weekend to see what happens, and try a few reloads with the older dies to see if the dies could be a problem. I really appreciate all of your comments and suggestions. Thank you very much!!! Aloha!!!

 

[KH_Outdoors]

Just my first thoughts but if you went to a new lot of brass but also introduced new variables in the process for your prep work then any of those variables could affect what you see on target... BUT, that big of a change is a red flag. My gut would say that the lot of brass might be different and I think I would redo load work on a freshly cleaned (clean clean and verified with a borescope) Barrel. Maybe also, since you've had the rifle for 10 years is the barrel getting shot out? Do you have data to show that it was really shooting a consistent 5/8" group? Maybe you're seeing some natural dispersion of some good groups bad groups? Idk, accuracy and consistency is a journey for every rifle. If it did it consistency before and you still have barrel life then it should do it again! Just have to isolate the tune. Good luck!