Runout on the 6mm creedmoore

Stats Shooter · March 5, 2019, 10:51 AM

I got a 6mm creedmoore not long ago and am finally getting to making some developmental loads. I bought Lapua SRP brass. The Lapua brass has a neck runout of less than 0.001" right out of the box. But a few of them had some case mouth dings. I typically use lee collet neck dies, but when I was getting my equipment, they were not being made. So I went with the redding body die like usual and an RCBS neck die with expander ball. I also got the lyman carbide expander ball stem so I would not have to lube the neck.

But!!! When I tried to correct some of the dinged necks with the RCBS die (3 cases tried), I wound up with a runout of 0.0075-0.010" on the neck!! I checked the cases before going into the die and neck thickness was within 0.001" for uniformity, trim length was nearly perfect, and the area behind the dinged case mouth had runout less than 0.0015"!

I tried the o-ring fix which I typically use on expander ball sizing dies as well as just screwing it down tight, tried both expander ball stems (lyman and RCBS), tried a few different cases and even a perfect one to see and all of them had the high neck runout.

So I pulled the expander ball completely just to see if that was the issue by itself, (I knew it wasn't but I had to check) and with the expander ball pulled, the runout was around 0.004" - 0.0045". This implies the die "chamber" is causing the issue and not the expander ball. It is just made worse with a non-concentric neck!

A family member had the same issue with his RCBS FL sizing die generating nearly 0.008" of runout on the neck of a 6.5 CM. When he switched to a Redding, runout went down to less than 0.0015" on fired brass.

Fortunately I talked to lee today and they will begin making the Lee collet neck die and selling them beginning April 1st.

Has anyone else run into similar issues? My old Rcbs dies do not have near this amount of issues...and a sample size of 2 does not warrant condemning the entire population. But both of these dies were purchased in the last year. My older ones are many years older.

zeke · March 5, 2019, 11:03 AM

Would try this, despite the naysayers it won't hurt to try. Take out the expander, and insert a new case into the shell holder. Run the brass up into the die before tightening anything. lower the brass and check the runout without removing the ding.

If this works okay, try a case set up the same way but with the expander installed loose. As in not locked down. If that works you can try locking the expander down when it is in the neck self aligned.

Other wise there are separate mouth expanding dies that may be able to just remove any small dings without disturbing the neck. Or just try a dummy round (no powder/primer) to remove the dings enough where they don't affect seating concentricity.

Yes am well aware

**Unclenick** · March 5, 2019, 12:22 PM

I remove dings with the Sinclair Expander die that holds neck turning mandrels. Pushing down, the case neck and shoulder is stronger than when pulling up.

If I had your RCBS die, I would chuck it the lathe with a 4-jaw chuck or a collet and zero the runout at the mouth and then check down its length and into the neck for concentricity. An alternative would be to make a Cerrosafe or sulfur chamber casting of it and measure the casting neck on a concentricity gauge like the RCBS Casemaster or the Sinclair, both of which support the case at two places rather than the case at one point and a bullet nose at the other.

I use carbide expanders when I use sizing die expanders at all, but use neck lube with them anyway, as the friction is reduced even further.

Stats Shooter · March 5, 2019, 02:47 PM

I got the die from Midway so I am just sending it back. If it was my only option I might possibly try Nick's method, but since I can I will just send it back.

If lee wasn't going to make a neck die for it, I would probably go to a bushing type neck die. But I like the Collet type dies for this with case sizing done in a separate step w/ a body die.

I just found it strange for it to be that far off. If I didn't lock the die down I could take another 0.001" of runout away, but it was still 3-4 thousandths without the expander ball even in the die. Put the expander ball in, even with everything loose and its back to 0.007" or more.

I have loaded literally 10's of thousands of rounds using FL rcbs sizing dies (this is a neck die) and never seen runout like that caused by the die.

FIFW i use the sinclair concentricity gauge. And while it can be a bit tricky and you have to go slow and be careful, it yields repeatable results.

**Unclenick** · March 5, 2019, 03:44 PM

That is a bit odd. And RCBS puts vent holes in so it shouldn't be pulling against a vacuum when you withdraw the case from the die.

Dufus · March 5, 2019, 04:00 PM

I have had very good results just using the plain old RCBS FL dies in just about everything that I load. But, like Stats, they are all from the 60s & 70s and my presses are just about as old. When I have need for something in a new to me caliber, I always try to buy the old dies. I reckon that if a newer caliber came into the household, that might not be possible.

I lube the case necks, and I leave the expander loose in the die. There was one die set that I had to return and that was because it was cracked internally up towards the shoulder area. A manufacturing defect I suppose.

I have custom fitted all the seaters to fit the bullets I use.

I almost always have runout 0.001" of less. Once I did have a problem, but it was easily taken care off with some tedious measurements.

Mr Guffey always uses transfers, well, I do too.

STats: it is good to hear that you located your problem and I hope the new dies are suitable and true.

March 5, 2019, 10:51 AM	#1
Stats Shooter Senior Member Join Date: August 26, 2016 Location: North Dakota Posts: 1,636	Runout on the 6mm creedmoore I got a 6mm creedmoore not long ago and am finally getting to making some developmental loads. I bought Lapua SRP brass. The Lapua brass has a neck runout of less than 0.001" right out of the box. But a few of them had some case mouth dings. I typically use lee collet neck dies, but when I was getting my equipment, they were not being made. So I went with the redding body die like usual and an RCBS neck die with expander ball. I also got the lyman carbide expander ball stem so I would not have to lube the neck. But!!! When I tried to correct some of the dinged necks with the RCBS die (3 cases tried), I wound up with a runout of 0.0075-0.010" on the neck!! I checked the cases before going into the die and neck thickness was within 0.001" for uniformity, trim length was nearly perfect, and the area behind the dinged case mouth had runout less than 0.0015"! I tried the o-ring fix which I typically use on expander ball sizing dies as well as just screwing it down tight, tried both expander ball stems (lyman and RCBS), tried a few different cases and even a perfect one to see and all of them had the high neck runout. So I pulled the expander ball completely just to see if that was the issue by itself, (I knew it wasn't but I had to check) and with the expander ball pulled, the runout was around 0.004" - 0.0045". This implies the die "chamber" is causing the issue and not the expander ball. It is just made worse with a non-concentric neck! A family member had the same issue with his RCBS FL sizing die generating nearly 0.008" of runout on the neck of a 6.5 CM. When he switched to a Redding, runout went down to less than 0.0015" on fired brass. Fortunately I talked to lee today and they will begin making the Lee collet neck die and selling them beginning April 1st. Has anyone else run into similar issues? My old Rcbs dies do not have near this amount of issues...and a sample size of 2 does not warrant condemning the entire population. But both of these dies were purchased in the last year. My older ones are many years older.

March 5, 2019, 12:22 PM	#3
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	I remove dings with the Sinclair Expander die that holds neck turning mandrels. Pushing down, the case neck and shoulder is stronger than when pulling up. If I had your RCBS die, I would chuck it the lathe with a 4-jaw chuck or a collet and zero the runout at the mouth and then check down its length and into the neck for concentricity. An alternative would be to make a Cerrosafe or sulfur chamber casting of it and measure the casting neck on a concentricity gauge like the RCBS Casemaster or the Sinclair, both of which support the case at two places rather than the case at one point and a bullet nose at the other. I use carbide expanders when I use sizing die expanders at all, but use neck lube with them anyway, as the friction is reduced even further. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

March 5, 2019, 03:44 PM	#5
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	That is a bit odd. And RCBS puts vent holes in so it shouldn't be pulling against a vacuum when you withdraw the case from the die. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

March 5, 2019, 11:03 AM	#2
zeke Senior Member Join Date: November 17, 1999 Location: NW Wi Posts: 1,671	Would try this, despite the naysayers it won't hurt to try. Take out the expander, and insert a new case into the shell holder. Run the brass up into the die before tightening anything. lower the brass and check the runout without removing the ding. If this works okay, try a case set up the same way but with the expander installed loose. As in not locked down. If that works you can try locking the expander down when it is in the neck self aligned. Other wise there are separate mouth expanding dies that may be able to just remove any small dings without disturbing the neck. Or just try a dummy round (no powder/primer) to remove the dings enough where they don't affect seating concentricity. Yes am well aware

March 5, 2019, 02:47 PM	#4
Stats Shooter Senior Member Join Date: August 26, 2016 Location: North Dakota Posts: 1,636	I got the die from Midway so I am just sending it back. If it was my only option I might possibly try Nick's method, but since I can I will just send it back. If lee wasn't going to make a neck die for it, I would probably go to a bushing type neck die. But I like the Collet type dies for this with case sizing done in a separate step w/ a body die. I just found it strange for it to be that far off. If I didn't lock the die down I could take another 0.001" of runout away, but it was still 3-4 thousandths without the expander ball even in the die. Put the expander ball in, even with everything loose and its back to 0.007" or more. I have loaded literally 10's of thousands of rounds using FL rcbs sizing dies (this is a neck die) and never seen runout like that caused by the die. FIFW i use the sinclair concentricity gauge. And while it can be a bit tricky and you have to go slow and be careful, it yields repeatable results.

March 5, 2019, 04:00 PM	#6
Dufus Senior Member Join Date: December 10, 2014 Posts: 1,965	I have had very good results just using the plain old RCBS FL dies in just about everything that I load. But, like Stats, they are all from the 60s & 70s and my presses are just about as old. When I have need for something in a new to me caliber, I always try to buy the old dies. I reckon that if a newer caliber came into the household, that might not be possible. I lube the case necks, and I leave the expander loose in the die. There was one die set that I had to return and that was because it was cracked internally up towards the shoulder area. A manufacturing defect I suppose. I have custom fitted all the seaters to fit the bullets I use. I almost always have runout 0.001" of less. Once I did have a problem, but it was easily taken care off with some tedious measurements. Mr Guffey always uses transfers, well, I do too. STats: it is good to hear that you located your problem and I hope the new dies are suitable and true.