Velocity dropped on once fired brass.

[Mtstalker]

I tested 10 rounds of the original 70.5gr load and 10 rounds at 71grs. The 71 grain load put me back at 2825 FPS with a es of 12Fps over 5 rounds, and it was shooting 3 shots in .5". So that made me happy. This is a factory rifle so I am perfectly content with this. Thanks for the input. Temp today was the same as yesterday with same pressure and humidity.

 

[Richard Coody]

that is why i don't even start load development until i have fireformed brass

 

[308BAR]

While some are focusing on the cartridge and internal ballistic. What chronograph are you using and was it setup the same way ? Most chronograph including labradar have a 1% error so like some mention before is well withing the error of the chrony.

 

[Mtstalker]

I was shooting over a Caldwell and using a magneto speed. All numbers were taken from the magneto speed. I don't shoot group's with it attached.

 

[Mtstalker]

that is why i don't even start load development until i have fireformed brass

I find it a waste to not do anything productive while on the first firing. Might as well get some data and find some starting points.

 

[fguffey]

The load was rem brass that was prepped with cci 250's and 70.5grs of IMR 4350 with a hornady interlock .010" off the lands. Virgin brass velocity was 2820 FPS with a sd of 11. Once fired was 2790FPS with a sd of 8.

Time.

F. Guffey

 

[L W P]

I find it a waste to not do anything productive while on the first firing. Might as well get some data and find some starting points.

Yep, I agree 100%. It's always nice to have any data available on your loads for a particular rifle and components. I always try my best least expensive load combo for firing virgin brass on practice targets. Then improve from there.

 

[INTJ]

While some are focusing on the cartridge and internal ballistic. What chronograph are you using and was it setup the same way ? Most chronograph including labradar have a 1% error so like some mention before is well withing the error of the chrony.

The Labrador website says it has a .1% error. Has anyone verified that?

 

[fguffey]

I find it a waste to not do anything productive while on the first firing. Might as well get some data and find some starting points.

Yes but that would require discipline as in measuring before and again after.

F. Guffey

 

[Medic505]

some how you are allowed to be a "know it all"

I agree! Greg is pretty much a know it all, and a very respected one at that. He goes above and beyond to help anybody with a problem. I've seen it many times. He's helped me out a time or two, and I've been very grateful for that.

You on the other hand..... well, I'm just going to leave it at that.

 

[Delfuego]

I would have assumed a fair amount of energy was expended to push your brass out and now the load should actually be warmer even though you gained case capacity. I've had cases, 6XC comes to mind where I always end up pulling powder on once fired brass.

This is interesting and I think I just experience it with my new 7 SAUM brass. I was convince beforehand that I would loose pressure/velocity after fireforming and the case expanding to the chamber. I resized the brass only 1-2 thousands and reloaded the same charge. I had great accuracy, but very heavy bolt lift. I got worried and called a buddy, he advised dropping the charge .5-1.0 grains. I did both. The .5 still shot great but had slightly heavy bolt lift and matched the velocity of the original charge. The 1.0 grain less did not exhibit heavy but had poor accuracy. I am a little befuddled as to how to proceed now.

 

[Milo 2.0]

This is interesting and I think I just experience it with my new 7 SAUM brass. I was convince beforehand that I would loose pressure/velocity after fireforming and the case expanding to the chamber. I resized the brass only 1-2 thousands and reloaded the same charge. I had great accuracy, but very heavy bolt lift. I got worried and called a buddy, he advised dropping the charge .5-1.0 grains. I did both. The .5 still shot great but had slightly heavy bolt lift and matched the velocity of the original charge. The 1.0 grain less did not exhibit heavy but had poor accuracy. I am a little befuddled as to how to proceed now.

I think some of it is hammering the brass too hard first firing and brass absorbs too much. My first 6 comp match was a nightmare, I ended up hammering my brass too hard, gained way more capacity but my fireforming load proved too hot after formed. I had to step down from a dtac to a 105 hybrid to make it work and was happy, lol