Seating depth issue

Savagehawg · December 6, 2023, 10:38 PM

Im running a RCBS Rock chucker press, im using RCBS dies and also Redding Premium dies. My problem is when i get to my seating depth and lock it down its fine for a few rounds and then i have to readjust it, happens with the RCBS dies and redding dies and on multiple calibers.

**44 AMP** · December 7, 2023, 12:25 AM

How are you measuring the seating depth??

How much variance in "depth" are you getting before you decide to readjust?

Have you checked die body, seating stem and lock nuts for movement??

rc · December 7, 2023, 02:33 AM

I have noticed that once you get everything adjusted, your next round or two will have a slightly longer length of a few thousandths but if you are not running a max length it usually doesn't matter. Also, bullet radius can vary depending on consistency of manufacturing. A seater usually pushes on the radius rather than a flat like with some revolver bullets. So the length of round nose rounds will be affected by variations in bullet radius.

**44 AMP** · December 7, 2023, 05:03 AM

If you are measuring from the case base to the bullet tip, and you are seeing variations in overall length by a few thousandths, it could be due to a few thousandths of variation in bullet length, or in diameter of the ogive where the seating stem contacts it, or both.

To check for movement of the die parts. once you have the desired adjustment set, make a witness mark, or use a torque-seal type product (or nail polish, or model paint) a drop where the stem and lock nut meet, and perhaps a second drop on the lock nut and die body contact. Choose an easily seen color. Let it dry completely, then do some more loading. If the parts move in relation to each other, the paint will crack.

Consider measuring some of your bullets for length. Small variations are normal. Check to see if the range of variation in the bullet length is consistent with the variations you are seeing with your loaded rounds. IF so, the most likely explanation is that the bullets simply are slightly different lengths and the seating stem is contacting them consistently and what you are seeing is the difference in length between where the seating stem contacts the bullet and the bullet tip.

jetinteriorguy · December 7, 2023, 05:58 AM

There are a few variables that come into play with bullet seating depth. Because of this when looking for a node sometimes the best one to use is the one that has the most tolerance for variation in seating depth, not necessarily the one with the tightest group. It just depends on how deep down this rabbit hole you’re willing to go. At least this is the way I look at it, otherwise it would drive me nuts.

mehavey · December 7, 2023, 08:47 AM

FWIW: In "snugging down" the seating stem's locknut (or the die body itself ), you actually raise the assembly stem very slightly (maybe 1-3 thou/depending...) by taking up residual thread lash-up.

Ad that to bullet/ogive manufacturing tolerances you've got to also (ahem) ... tolerate.

December 6, 2023, 10:38 PM	#1
Savagehawg Member Join Date: March 31, 2020 Posts: 45	Seating depth issue Im running a RCBS Rock chucker press, im using RCBS dies and also Redding Premium dies. My problem is when i get to my seating depth and lock it down its fine for a few rounds and then i have to readjust it, happens with the RCBS dies and redding dies and on multiple calibers.

December 7, 2023, 12:25 AM	#2
44 AMP Staff Join Date: March 11, 2006 Location: Upper US Posts: 28,867	How are you measuring the seating depth?? How much variance in "depth" are you getting before you decide to readjust? Have you checked die body, seating stem and lock nuts for movement?? __________________ All else being equal (and it almost never is) bigger bullets tend to work better.

December 7, 2023, 05:03 AM	#4
44 AMP Staff Join Date: March 11, 2006 Location: Upper US Posts: 28,867	If you are measuring from the case base to the bullet tip, and you are seeing variations in overall length by a few thousandths, it could be due to a few thousandths of variation in bullet length, or in diameter of the ogive where the seating stem contacts it, or both. To check for movement of the die parts. once you have the desired adjustment set, make a witness mark, or use a torque-seal type product (or nail polish, or model paint) a drop where the stem and lock nut meet, and perhaps a second drop on the lock nut and die body contact. Choose an easily seen color. Let it dry completely, then do some more loading. If the parts move in relation to each other, the paint will crack. Consider measuring some of your bullets for length. Small variations are normal. Check to see if the range of variation in the bullet length is consistent with the variations you are seeing with your loaded rounds. IF so, the most likely explanation is that the bullets simply are slightly different lengths and the seating stem is contacting them consistently and what you are seeing is the difference in length between where the seating stem contacts the bullet and the bullet tip. __________________ All else being equal (and it almost never is) bigger bullets tend to work better.

December 7, 2023, 02:33 AM	#3
rc Senior Member Join Date: April 28, 2001 Location: CA Posts: 1,769	I have noticed that once you get everything adjusted, your next round or two will have a slightly longer length of a few thousandths but if you are not running a max length it usually doesn't matter. Also, bullet radius can vary depending on consistency of manufacturing. A seater usually pushes on the radius rather than a flat like with some revolver bullets. So the length of round nose rounds will be affected by variations in bullet radius.

December 7, 2023, 05:58 AM	#5
jetinteriorguy Senior Member Join Date: April 28, 2013 Posts: 3,182	There are a few variables that come into play with bullet seating depth. Because of this when looking for a node sometimes the best one to use is the one that has the most tolerance for variation in seating depth, not necessarily the one with the tightest group. It just depends on how deep down this rabbit hole you’re willing to go. At least this is the way I look at it, otherwise it would drive me nuts.

December 7, 2023, 08:47 AM	#6
mehavey Senior Member Join Date: June 17, 2010 Location: Virginia Posts: 6,903	FWIW: In "snugging down" the seating stem's locknut (or the die body itself ), you actually raise the assembly stem very slightly (maybe 1-3 thou/depending...) by taking up residual thread lash-up. Ad that to bullet/ogive manufacturing tolerances you've got to also (ahem) ... tolerate.