pressure reduction from real shallow bullet seating

[bajabill]

Loading my 35 whelen and to hit the lands with the bullet, I am barely seating the bullet into the case.  Maybe .1" of case engagement. 

Is there a way to estimate the reduction in pressure from doing this, relative to a more average bullet seating depth.  I would probably be seating .25" deeper as a normal loading.  But with a .358 dia x .25" cylinder, this is a  lot of additional starting volume.

I am loading to levels between starting and max, but am wondering if I am getting too low of pressures because of this.   I have to hit the land with the bullet on these first loadings with fresh brass.

[butterman]

You could use heavy for caliber bullets that normally seat deep in case to help hold the bullet better
 With a load out of a manual , they usually have 5-6 grains to work up a load , I would pick one and maybe start one grain up from the start load , sounds like you are  " fireforming brass "   is that it ?

[quickdtoo]

Bill, I had to do this with some new 35 Whelen brass, the shoulder was too short right out of the box, they had way too much headspace,  I loaded 250gr bullets long and crimped so when I closed the action, it jammed the bullet hard into the lands so it wouldn't move forward when the firng pin hit the primer, used start loads to fire form and push the shoulder forward to where it should be. This was in my RMEF Ultra, it was only about 5 or 6 rounds from the box, the rest were fine, they've been reloaded twice now with no problems.

Tim

[MnMike]

Interesting question. I would like to add a couple of questions.
There are one and maybe two pressure changers in your post:
1. Long seating lowers pressure (fact).
2. Seating to the lands raises pressure?

When I fire form, I use reduced loads because of 2.
Is that right?
Does a firm crimp also increase pressure?

mike

[sgtt]

.1 of an inch isn't much.  I don't think the reduction in pressure from seating long is signifigant but, the spike in pressure from loading long can be.  That said.  I usually do start my loads at the lands and work back.  I ALWAYS use the lowest starting load that I think may produce the results I want.   When I fireform I usually use lead bullets or scrape jacketed bullets and modest amount of Unique.  5-7 grains seems to be sufficient.  I prefer to seat these to the lands.  However if they don't reach.........so be it.

[beemanbeme]

If you are fire forming, you don't need to be that precise.  You aren't shooting for accuracy.  I would want more bullet in the neck myself.  just to keep from dumping a case full of powder into the action.  The actual fact remains, that you don't even need a bullet to fire form.  Load a 75% max load into the case, put a little gob of toilet paper on top of the powder and let drive.