Neck sizing causing runout

pearson1662 · December 31, 2004, 10:37 PM

I bought some .260 Remington brass, loaded it up, fireformed it, measured runout was .002" or less. I neck sized them and they measured .004" or more.

Is my brand new Redding Competition bushing style neck siziing die at fault or am I doing something wrong/ set up incorrect etc? Thanks, Jay

Nnobby45 · January 1, 2005, 12:00 AM

Four thous. run out is pretty good. I used to worry about it, but numerous trips to the range could detect no difference between 2-4 thous, and 4-6 or even more. Kind of disheartening considering all the time I spent figuring it out, and trying to segregate my cases. Maybe a good chamber is more precise than a good die. Using the same die, I've had runnout improve upon sizing and have had it get worse. Go figure.

HSMITH · January 1, 2005, 11:02 AM

Loosen the locknut on your die, then run a case in it to size it, leave the ram all the way up and tighten the lock nut. This should help concentricity, it basically lets the case pull the die into better alignment with the shell holder. You can also mark cases up, measure the runout, and determine which way it is out, then rotate your shell holder to get some of the runout out too. With good dies, a good press and a good shell holder these two steps will get most of the runout taken care of.

trk · January 1, 2005, 02:02 PM

Jay -

Interesting observation in having measured the runout at this stage.

I've found that commmercially reloaded ammo is junk compared to even casually reloaded handloads, namely .004 and worse to .002 or so.

For matches I used to sort .308's to .001 to .0015, .0015 to .002 etc.

If you're measuring runout of the neck, do you mean ID or OD compared to the OD at two points of support on the case?

At some point I assume also that you're going to outside neck trim to control coaxiality of the ID and OD, hence coaxiality of the bullet's axis to the bore.

I usually position my support points just above the base (last point of contact with the chamber) and just below the shoulder. Then I'll neck size only - and then only 1/2 way down the neck to ensure the larger diameter (unsized) of the neck centers the neck in the chamber.

FWIW

Tim K

trk · January 1, 2005, 02:05 PM

HSMITH -

Good technique. Even if the problem is elsewhere you will KNOW what the process is doing.

pearson1662 · January 1, 2005, 02:36 PM

Quote:

If you're measuring runout of the neck, do you mean ID or OD compared to the OD at two points of support on the case?

I'm using an RCBS CaseMaster Gauging tool to measure OD runout halfway down the case neck. How do you measure ID runout?
`

Quote:

At some point I assume also that you're going to outside neck trim to control coaxiality of the ID and OD, hence coaxiality of the bullet's axis to the bore.

I like the idea of increasing the control of "coaxiality" of the ID and OD, but no, I hadn't intended to. I am not familiar with the term "outside neck trim". Is this similar to using a mandrel to turn the outside necks to uniform thickness? If so, does this statement imply that without it, measuring runout is of no value?

Would varying neck wall thickness increase runout after neck sizing?

Quote:

I usually position my support points just above the base (last point of contact with the chamber) and just below the shoulder.

This is how I have my gauge set up as well.

I am not an expert and all other disclaimers apply.

pearson1662 · January 1, 2005, 02:59 PM

HSMITH

Thanks, I'll give that a try. Jay

trk · January 2, 2005, 06:10 PM

Outside neck turning (as opposed to inside neck turning - which only thins the walls) uses, as you say, a mandrel inside and a cutter on the outside to make the neck wall uniform. If you don't, you're using what ever you've got and adding the offset or angular displacement (caused by neck wall irregularities) to the error of alignment of the bullet to the axis of the bore.

You might compare the runout of the neck compared to the runout of the bullet. Since, assuming the chamber is coaxial with the bore, the alignment of the bullet to the outside of the case will be analogous to the alignment of the bullet's axis to the axis of the bore.

Nnobby45 · January 3, 2005, 12:02 AM

Don't forget that the purpose of neck turning is to even the neck so that both sides are the same thickness. Cutter should be adjusted so the the thin side isn't cut---only the thick side. Cutting the inside of the neck is REAMING. Since it cuts the inside diameter equally all the way around, it does nothing to change the difference in wall thickness from one side of the neck to the other. Reaming is not a substitute for neck turning. It has a different purpose not related to concentricity.

December 31, 2004, 10:37 PM	#1
pearson1662 Member Join Date: June 4, 2004 Posts: 52	Neck sizing causing runout I bought some .260 Remington brass, loaded it up, fireformed it, measured runout was .002" or less. I neck sized them and they measured .004" or more. Is my brand new Redding Competition bushing style neck siziing die at fault or am I doing something wrong/ set up incorrect etc? Thanks, Jay

January 1, 2005, 12:00 AM	#2
Nnobby45 Senior Member Join Date: November 20, 2004 Posts: 3,150	Four thous. run out is pretty good. I used to worry about it, but numerous trips to the range could detect no difference between 2-4 thous, and 4-6 or even more. Kind of disheartening considering all the time I spent figuring it out, and trying to segregate my cases. Maybe a good chamber is more precise than a good die. Using the same die, I've had runnout improve upon sizing and have had it get worse. Go figure.

January 1, 2005, 11:02 AM	#3
HSMITH Senior Member Join Date: June 21, 2002 Posts: 2,019	Loosen the locknut on your die, then run a case in it to size it, leave the ram all the way up and tighten the lock nut. This should help concentricity, it basically lets the case pull the die into better alignment with the shell holder. You can also mark cases up, measure the runout, and determine which way it is out, then rotate your shell holder to get some of the runout out too. With good dies, a good press and a good shell holder these two steps will get most of the runout taken care of.

January 1, 2005, 02:02 PM	#4
trk Junior Member Join Date: January 1, 2005 Location: Pulaski, VA Posts: 3	Jay - Interesting observation in having measured the runout at this stage. I've found that commmercially reloaded ammo is junk compared to even casually reloaded handloads, namely .004 and worse to .002 or so. For matches I used to sort .308's to .001 to .0015, .0015 to .002 etc. If you're measuring runout of the neck, do you mean ID or OD compared to the OD at two points of support on the case? At some point I assume also that you're going to outside neck trim to control coaxiality of the ID and OD, hence coaxiality of the bullet's axis to the bore. I usually position my support points just above the base (last point of contact with the chamber) and just below the shoulder. Then I'll neck size only - and then only 1/2 way down the neck to ensure the larger diameter (unsized) of the neck centers the neck in the chamber. FWIW Tim K

January 1, 2005, 02:05 PM	#5
trk Junior Member Join Date: January 1, 2005 Location: Pulaski, VA Posts: 3	HSMITH - Good technique. Even if the problem is elsewhere you will KNOW what the process is doing.

January 1, 2005, 02:59 PM	#7
pearson1662 Member Join Date: June 4, 2004 Posts: 52	HSMITH Thanks, I'll give that a try. Jay

January 2, 2005, 06:10 PM	#8
trk Junior Member Join Date: January 1, 2005 Location: Pulaski, VA Posts: 3	Outside neck turning (as opposed to inside neck turning - which only thins the walls) uses, as you say, a mandrel inside and a cutter on the outside to make the neck wall uniform. If you don't, you're using what ever you've got and adding the offset or angular displacement (caused by neck wall irregularities) to the error of alignment of the bullet to the axis of the bore. You might compare the runout of the neck compared to the runout of the bullet. Since, assuming the chamber is coaxial with the bore, the alignment of the bullet to the outside of the case will be analogous to the alignment of the bullet's axis to the axis of the bore.

January 3, 2005, 12:02 AM	#9
Nnobby45 Senior Member Join Date: November 20, 2004 Posts: 3,150	Don't forget that the purpose of neck turning is to even the neck so that both sides are the same thickness. Cutter should be adjusted so the the thin side isn't cut---only the thick side. Cutting the inside of the neck is REAMING. Since it cuts the inside diameter equally all the way around, it does nothing to change the difference in wall thickness from one side of the neck to the other. Reaming is not a substitute for neck turning. It has a different purpose not related to concentricity.