Seating depth question

[Alex Wheeler]

I agree, with Jim, Donovan, and Erik. Heres a question, do any of you ever find your seating depth before your powder charge, and does the prefered seating depth change with powder charge? ;D

Yes…… they all inter react with each other. After you work with one round long enough you have a pretty good idea what it should be. but change the reamer and you just might as well throw all that away. The reamer dictates the load not the barrel……. I have proved it as recently as this year, couldn't get the new reamer to shoot real small just average .1, so ran the old reamer in and it opened the free bore and diameter up and it went right in the zeros…….. amazing…….. jim

Jim,
Heres one for ya. The gun that set the record this year has a .2435" freebore. The bullets measure .2435"/.2439". When I strip the bolt to check the throat I can feel the shank of the bullet dragging in the throat. It is very tight. It shot! The pressure ring will not even drop into the throat. After the next match that barrel is coming off so I can accurately measure the freebore diameter.

 

[johara1]

Alex, that is what i had last year, it works better not squeezing them you want them to start easier …….. LOL…….. jim

 

[Keith Glasscock]

I agree, with Jim, Donovan, and Erik. Heres a question, do any of you ever find your seating depth before your powder charge, and does the prefered seating depth change with powder charge? ;D

To answer the question - yes. I did that experiment. I ran my Dasher at both jump and into the lands. The powder charge and tune velocity changed dramatically. I settled on one because it was consistent. As Jim would say 1's @ 300 yards. If I were to change bullets, I'd have to give it another go.

Even small changes in seating depth change the center of the powder charge node. That is why many shooters go back and test for the center of the charge node after finding the seating depth.

 

[mikecr]

Being into the lands(ITL), if that's actually where your load shoots best, isn't free either. This relationship is more sensitive to throat changes.
Anything off the lands is immune to throat changes from what I've seen. But then the sensitivity goes to tension variances.

Some cartridges need peak pressure, most need best seating.

 

[Alex Wheeler]

Being into the lands(ITL), if that's actually where your load shoots best, isn't free either. This relationship is more sensitive to throat changes.
Anything off the lands is immune to throat changes from what I've seen. But then the sensitivity goes to tension variances.

Some cartridges need peak pressure, most need best seating.

My best barrel likes to jump .010" I have to chase it to keep in tune. I have another good barrel that started at .010 off and never needed a change....

 

[Alex Wheeler]

I agree, with Jim, Donovan, and Erik. Heres a question, do any of you ever find your seating depth before your powder charge, and does the prefered seating depth change with powder charge? ;D

To answer the question - yes. I did that experiment. I ran my Dasher at both jump and into the lands. The powder charge and tune velocity changed dramatically. I settled on one because it was consistent. As Jim would say 1's @ 300 yards. If I were to change bullets, I'd have to give it another go.

Even small changes in seating depth change the center of the powder charge node. That is why many shooters go back and test for the center of the charge node after finding the seating depth.

My intent was to see if others had tried seating depth tests at different powder charges in and out of the node and if your best seating depth was the same at different powder charges.

 

[cocopuff]

good luck with it...I go for powder charge first..I like to run a low MV...

 

[mikecr]

if your best seating depth was the same at different powder charges.

Best seating is independent of powder. That's why I can test for seating while fireforming cases -with any load chosen.
Powder however, is affected a bit by seating.
So if you go powder 1st then change seating, you're chasing your tail in a sense, unless real lucky or accepting of less than the best load.
The exception to this(there always is) is underbore extreme pressure cartridges which are jammed or otherwise relying on high starting pressures to get there. This condition is dominant over most other things, and I see it as a golden work-around. Good for 6PPC/30br/etc, not viable for LR cartridges.

 

[Alex Wheeler]

if your best seating depth was the same at different powder charges.

Best seating is independent of powder. That's why I can test for seating while fireforming cases -with any load chosen.
Powder however, is affected a bit by seating.
So if you go powder 1st then change seating, you're chasing your tail in a sense, unless real lucky or accepting of less than the best load.
The exception to this(there always is) is underbore extreme pressure cartridges which are jammed or otherwise relying on high starting pressures to get there. This condition is dominant over most other things, and I see it as a golden work-around. Good for 6PPC/30br/etc, not viable for LR cartridges.

Mike, that mirrors my tests. I found while testing random charges the best seating depth was always the same. Thanks for the reply!

 

[savagedasher]

if your best seating depth was the same at different powder charges.

Best seating is independent of powder. That's why I can test for seating while fireforming cases -with any load chosen.
Powder however, is affected a bit by seating.
So if you go powder 1st then change seating, you're chasing your tail in a sense, unless real lucky or accepting of less than the best load.
The exception to this(there always is) is underbore extreme pressure cartridges which are jammed or otherwise relying on high starting pressures to get there. This condition is dominant over most other things, and I see it as a golden work-around. Good for 6PPC/30br/etc, not viable for LR cartridges.

+1 From me. The answer is high starting pressure from around jam. I have no number how far back it is off of jam it takes to relive the High start pressure. I know when I start around .020 off I adjust my powder charges . Neck tension isn't as critical also when jumping . Larry