Problem finding a load. HELP!!

[JARHEAD1371]

I thought I had found my magic load for my 7 SAUM using 180 Bergers and H-1000. I shot 3 rounds that measured .54" @ 300 yds with only 7 fps spread. I loaded 15 more exactly the same as the 3 and shot them a week later when the weather cooperated. I shot all 15, with a few minutes between each, in the same conditions as the 1st 3. This time the spread was 46 fps and only half of them were within the original 7 fps zone. The barrel was not heating up and the velocity varied up and down as I shot. The group measured about 1" L-R and about 2 1/4" vertical. This is the second time the same situation has happened. I am detailed in my brass prep and reloading but not sure if I am doing something wrong.

Does anyone have any ideas?

My barrel is 28" with a 1-8.5 twist, which is plenty for the 180's. I weigh each charge with a RCBS Range Master 750 Digital Scale and check the zero after each charge. I let it warm up for at least 10 minutes before each use. I use power measure to get close and a trickler and put in one grain of powder at a time until the # I need just turns on the scale. I'm using CCI BR-2 primers and hand seat them. I use a Beta Master Chrony and it is set up at the same distance each time.

I have eliminated as many variables that I know of. Am I missing something? Thanks in advance for any advise.

[BUNDUKI]

Just wondering if you experience a difference in pressure required to seat your bullets.
If so check that you have uniform neck wall thickness
Make sure the inside of the necks are nice and clean
You might also want to consider annealing if you have already reloaded the cases a few times.
After doing this the ext ream spreads on my 300winmag shrunk considerably
Hope this helps.

[Autorotate]

How many firings were on the brass that shot on the original magic load 3 shot group? Even if you anneal, if you have some virgin brass you can try the magic load with to verify your annealing process.

You didn't state it, but are all components from the same lot? Specifically your powder?

The above two would be my first bets.

Do you have access to a concentricity tool? In my limited experience, this will have a direct effect on the potential precision of any ammunition, although your group shape suggests either velocity/pressure variation, or the shooter. Since your user name suggests association with the USMC...we all know that isn't likely

Go try some virgin brass!

[JARHEAD1371]

Originally Posted by BUNDUKI

Just wondering if you experience a difference in pressure required to seat your bullets.
If so check that you have uniform neck wall thickness
Make sure the inside of the necks are nice and clean
You might also want to consider annealing if you have already reloaded the cases a few times.
After doing this the ext ream spreads on my 300winmag shrunk considerably
Hope this helps.

Looks like I missed mentioning a few details before. I did turn all of the necks when they were new. I will pay special attention to the inside of the necks from now on. The last 15 shots made all of my brass need to be sized and everything so I did anneal the necks. The brass has been loaded 4 times. Sorry that I didn't mention that earlier. Thank you very much for the info.

[JARHEAD1371]

Originally Posted by Autorotate

How many firings were on the brass that shot on the original magic load 3 shot group? Even if you anneal, if you have some virgin brass you can try the magic load with to verify your annealing process.

You didn't state it, but are all components from the same lot? Specifically your powder?

The above two would be my first bets.

Do you have access to a concentricity tool? In my limited experience, this will have a direct effect on the potential precision of any ammunition, although your group shape suggests either velocity/pressure variation, or the shooter. Since your user name suggests association with the USMC...we all know that isn't likely

Go try some virgin brass!

The brass was on it's 4th firing and I just annealed all of them. I'm looking at buying 100 Norma brass and necking then down to see if the Rem brass I have is worn out. I'll give that a try, thank you for the info.

Ironically I have trained some grunt Marines that couldn't hit anything with any weapon. Thankfully they were very few. Shooting is one of the few things I normally do well.

[Autorotate]

Originally Posted by JARHEAD1371

........ and I just annealed all of them.

I read this and thought of a recent experience I had. I noticed different pressure during bullet seating with my batch of cases, but drove on.....I had similar results, but group variation was smaller, but ESs much like yours.

Relooked my annealing procedure....and then reannealed cases using a slightly longer duration and ESs settled back down. I've surmised annealing is yet another variable that I can introduce errors into my LR shooting process:(