Switching to Lapua brass. How much should I reduce my charge?

[nikonNUT]

Hi guys,
So I am guessing that my Google-Fu sucks but I didn't find anything concrete. I'm switching to Lapua brass from my current maker (Peterson blems) and wanted to ask how far I should back off my charge. The current sweet spot is 95.2gr of Reloder 33 under a 300gr SMK but should I back up 10% and start over?Is a a grain or two (or 3) lower sufficient to start the process? Or is it a wash? Dumb I know and while I am shooting for safety I was curious. Thank you in advance and if the word idiot crosses your mind don't hesitate to let me know. It's how I learn!

-Chris

 

[DTF370]

To my knowledge, 95 grains of rl33 is mild correct? If your nowhere near max, I personally wouldn’t worry too much about it. I would probably shoot a group with my current load and make small adjustments as needed. Do you have a chronograph? That’s just me, there’s a lot of experience here and I’m sure others will soon chime in.

 

[nikonNUT]

To my knowledge, 95 grains of rl33 is mild correct? If your nowhere near max, I personally wouldn’t worry too much about it. I would probably shoot a group with my current load and make small adjustments as needed. Do you have a chronograph? That’s just me, there’s a lot of experience here and I’m sure others will soon chime in.

I do have a chrono and will put it to work for sure. As for max, per Sierra 96.1gr is their max while Alliant says 97.5gr (compressed) for the same bullet so 2.5% under the Alliant max and .625% under the Sierra Max.

 

[1moaoff]

If you dont back it off enough during testing you may miss a node.

 

[clcustom1911]

Hi guys,
So I am guessing that my Google-Fu sucks but I didn't find anything concrete. I'm switching to Lapua brass from my current maker (Peterson blems) and wanted to ask how far I should back off my charge. The current sweet spot is 95.2gr of Reloder 33 under a 300gr SMK but should I back up 10% and start over?Is a a grain or two (or 3) lower sufficient to start the process? Or is it a wash? Dumb I know and while I am shooting for safety I was curious. Thank you in advance and if the word idiot crosses your mind don't hesitate to let me know. It's how I learn!

-Chris

Get your cases to the same dimensions by sizing and trimming to the same length..

Weigh 10 pieces of your Peterson brass. Weigh 10 of your Lapua.

If Lapua is 10gr heavier. Reduce by 1 grain.

If Lapua is 10gr lighter, keep same charge as Peterson, maybe increase by up to 0.5gr.

Containers with the same external dimensions, composed of the same material, but are heavier, have what?

Less internal volume.

*edit. BOTH cases need to be the same size primer pocket!!

 

[nikonNUT]

Get your cases to the same dimensions by sizing and trimming to the same length..

Weigh 10 pieces of your Peterson brass. Weigh 10 of your Lapua.

If Lapua is 10gr heavier. Reduce by 1 grain.

If Lapua is 10gr lighter, keep same charge as Peterson, maybe increase by up to 0.5gr.

Containers with the same external dimensions, composed of the same material, but are heavier, have what?

Less internal volume.

*edit. BOTH cases need to be the same size primer pocket!!

Did the math and looks like about a 4.6gr difference between the Lapua and the Peterson. I'll back off accordingly and see what's what! Thank you!

 

[clcustom1911]

If lapua is heavier, back off half grain. If my running hypothesis is correct, it should be money.