9mm mathematics puzzle

[AnselHazen]

I am working on a load for 147 gr 9mm.

X-Treme RN bullet measures .667 I seated a group to 1.13
I switched to Hornady 147 gr XTP which measures .656
A 10 xxxxxx (thousandths) shorter bullet.

I did not adjust my seating die, expecting the shorter bullet to seat longer and need to be brought down to the 1.13 I wanted to seat to. First one seated at 1.06.

I assume I have been fooled by differing bullet profile, had the xtp been a RN it would have seated longer at the outset?

 

[rcmodel]

Ten thousandths.

Yes, bullet profile effects seating depth tremendously.

Especially when going from RN to FP or HP.

rc

 

[OilyPablo]

11 thousandths. .011".

Indeed shape and where/how the seating die contacts is everything. Dial in for shape. I like dies (RCBS?) that come with 2-3 seating heads to better match more bullets.

 

[X-Ring]

The length of the bullet alone will not change the OAL. Only the depth the bullet is in the case. The profile can change where the bullet contacts the seating stem and that could either increase or decrease the OAL.

 

[AnselHazen]

Thousandths yes, thank you.

Sigh, so even with bullet seating their ain't no such thing as a free lunch.

 

[Duvel]

Thousandths yes, thank you.

Sigh, so even with bullet seating their ain't no such thing as a free lunch.

No.

If every bullet profile was the same, and you always wanted the same COL, the seater would be a set-and-forget.

Alas, hand loaders strive for diversity, so such is not life

 

[FROGO207]

The closest thing to a free lunch is sacrificing a bullet for use in a dummy round ( no primer) to use to set up the die at a later date for that particular bullet. I use a sharpie to ID what bullet and weight on the brass. Saves lots of die setup time over the years.

 

[Captaingyro]

With so many of us being bullet agnostics...we'll buy different bullets in the same caliber depending on what's on sale...I just keep two or three seating dies for each caliber. I number them, and then keep notes on what bullet and COL they're adjusted for.

Seating dies just aren't that expensive, especially if you buy used, and I find it very handy to just swap dies when I start with different bullets.