Increased Pressure
- Thread starter Netloss
- Start date
Ridge_Runner
Handloader
- Sep 29, 2006
- 1,463
- 885
depends on bullet jump, my 6.5 gibbs gains 120 fps with .030 jump over .010.
not necessarily...powder combustion (rate/completion of burn) have effects along with seating
I have been doing an comprehensive bullet and powder test the last two years on three .243's (roughly 14 bullets and 12 powders) and have been charting them in a spreadsheet. Increased powder not always faster, and seating deeper same...just have to do those ladder tests and see what you get.
My 90 grain Swift Scirocco test with Staball 6.5 yielded highest muzzle velocity for a fixed charge of 43.3 grain charge at .030" jump and was slower by 95 feet per second seated another .040" deeper (total jump 0.070").
Cheers
Last edited:
Firebird24
Beginner
- Sep 3, 2024
- 155
- 566
Does accuracy increase?
some bullets...yes...some definitely not, just have to do those tests to find out
Basically there is no fixed correlation to linear increase in velocity or accuracy; so many variables at play
The previous charge I mentioned was one of the top two for accuracy nodes but the WORST SD numbers...and where I had the best SD numbers and slightly slower velocities...accuracy was awful/atrocious, like embarrasing. So much going on after the primer sparks you just have to get into your rifle and see what performs.
RiverRider
Handloader
- Dec 9, 2008
- 1,487
- 163
In handgun cartridges, seating deeper means higher pressures and that's pretty much a hard and fast axiom. I think this is so in part because of the relatively small volume of handgun cartridges. The smaller the cartridge, the more significant seating depth becomes in terms of pressure increases.
In rifle cartridges it is also true, but there are TWO factors operating, the other being proximity of the bullet to the leade in the chamber throat. That dimension has a much more pronounced effect on pressure because it can have a very significant effect on ignition from the onset and cause notably higher peak pressures. In my own experience chronographing loads, you start seeing significant velocity increases indicating higher pressures when the bullet is seated with the ogive within about 0.010" of the leade and pressure will climb as the distance to the lands decreases. Conversely, any increases presumably brought about by seating deeper seem to get lost in the noise of random variation and appear to be pretty insignificant (and I would attribute that to the relatively large volume of bottleneck cartridges)---but I never did play with seating EXTREMELY deep in the case since there never seemed to be any reason to do so. And now that I ponder that, I am somewhat curious.
In rifle cartridges it is also true, but there are TWO factors operating, the other being proximity of the bullet to the leade in the chamber throat. That dimension has a much more pronounced effect on pressure because it can have a very significant effect on ignition from the onset and cause notably higher peak pressures. In my own experience chronographing loads, you start seeing significant velocity increases indicating higher pressures when the bullet is seated with the ogive within about 0.010" of the leade and pressure will climb as the distance to the lands decreases. Conversely, any increases presumably brought about by seating deeper seem to get lost in the noise of random variation and appear to be pretty insignificant (and I would attribute that to the relatively large volume of bottleneck cartridges)---but I never did play with seating EXTREMELY deep in the case since there never seemed to be any reason to do so. And now that I ponder that, I am somewhat curious.
RiverRider
Handloader
- Dec 9, 2008
- 1,487
- 163
If you have velocity data, I'm sure we'd all like to know what you're seeing in terms of velocity/seating depth.
