Seating depth

[BULLET 05]

when working up loads what seating depth increments do most of you use? When you find a load that is pretty good do you adjust your seating depth by .002 or .005 or more?

 

[retired]

i use 5 and then fine tune with 2
had a .3" go into .1'S on a .002 change

 

[dmoran]

To start, myself look at .015-IN to .015-OFF in .005" increments.
For fine tuning I use 002" increments.
For keeping a load in tune to advancement, I test in .001" increments.
Conducting all at the intended distance, which I find to be critical for seating depth.
Donovan

 

[stifffingers]

i use 5 and then fine tune with 2
had a .3" go into .1'S on a .002 change

IMHO I believe you can jump over the best seating depth by using 5 Thou increments. I use .003 till two bullet holes touch, then fine tune with .002, then .001.

 

[Fotheringill]

I would suggest going the link below at this site and follow the instructions. They worked for me for both VLD and regular bullets.

http://bulletin.accurateshooter.com/2009/03/berger-tips-for-loading-vld-bullets/

 

[Bart B.]

Never did any seating depth change less than .010" for three reasons. Case headspace had a 2 to 3 thousandths spread. And there's a thousandths spread across bullet ogive diameter at rifling contact point. Rifling erodes away a thousandth inch every few dozen rounds.

Unless your resized case's headspace spread is zero, whatever more there is will be transferred to bullet jump. Nothing I know of holds case heads against the bolt face when fired if any bullet jump exists. Inline spring-loaded ejectors and firing pins push case heads away from bolt faces.

Rimless bottleneck rounds' shoulders are hard against the chamber shoulder when fired. The space between the bolt face and case head (head clearance) matches the spread in case headspace. And bullet jump distance changes with it

All assuming case shoulders don't get set back from firing pin impact. Lots of them are.

I used to think otherwise.

 

[TerryH]

When load developing for my F T/R .308 I tested from .020 to .005 off in .003 increments. Pretty amazing how much .003 makes.

 

[500Stroker]

I would suggest going the link below at this site and follow the instructions. They worked for me for both VLD and regular bullets.

http://bulletin.accurateshooter.com/2009/03/berger-tips-for-loading-vld-bullets/

^^^^^^^What he said^^^^^^^^^^

 

[glockaholic]

Another thing to consider is what is .000 jump. The test is all relative to your own method of determining .000 jump so it's not critical as long as your consistant. It does come into play when you discuss .010" jump with someone else and he uses hard jamb as .000 and you use soft touch as .000.

BTW, I use .003, sometimes .0025 since its halfway between marks on the Wilson seater.

 

[mikecr]

I fully employ Berger's recommended seating testing.

 

[4xforfun]

Another thing to consider is what is .000 jump. The test is all relative to your own method of determining .000 jump so it's not critical as long as your consistant. It does come into play when you discuss .010" jump with someone else and he uses hard jamb as .000 and you use soft touch as .000.

BTW, I use .003, sometimes .0025 since its halfway between marks on the Wilson seater.View attachment 1033748

NEVER run things at .000. With tolerance stacking you may have as much as a .004 spread in your critical lengths. That could take you from a .002 to jam to a .002 jump. 4 thousands of an inch isn't a big deal when you're way in or way out, but when you were just kissing the lands the pressure difference could be very large.

NEVER USE .000!!
Just my opinion,

Tod

 

[rhovee]

Is it just me or is finding the second seating depth farther back a little more forgiving? Granted i am not a benchrest shooter. But i found some nice seating depth nodes with a 147 ELDM at .060 off the lands. All the way to .068 off seems to shoot the same... I mean .4-.5" 3 shot groups at 100.

 

[Bart B.]

Yea, if you hire slave labor to do your reloading. Myself, I find a half thousanths and look to improve.

3 thousandths spreads of head clearance let's my reloads test 1/2 to 2/3 MOA over 15 to 20 shots at long range. Small bullet jump spread is more important to me than small head clearance spread.

How much case shoulder setback ES & SD from firing pin strike do you have?

 

[243winxb]

seating depth increments

.010" X 4 different ones. Starting with bullet shank at neck shoulder junction, if magazine and chamber allow.

 

[Bart B.]

Just thought I'd mention we can do better, as bump consistency is one of the things that matters.

I, too, agree. Lots of folks don't know how rimless bottleneck rounds fit their chambers when fired.

Some chase the rifling as throats erode away down the barrel. Others dont. Some soft-seat bullets long so they push back to zero jump when chambered so it and head clearance are zero for every shot.

 

[4xforfun]

I, too, agree. Lots of folks don't know how rimless bottleneck rounds fit their chambers when fired.

Some chase the rifling as throats erode away down the barrel. Others dont. Some soft-seat bullets long so they push back to zero jump when chambered so it and head clearance are zero for every shot.

I tried to do the whole "soft seat" thing when I was shooting IBS 1K with less than stellar results.

It really SHOULD work, especially when you run neck turned brass with sizing bushings on good brass, but ...it just didn't. Might work for some...just not me.

Tod