problem necking down the .308 win

kd5nay · February 17, 2009, 04:14 PM

Hi all,
I have been reloading for a few years now but I recently purchased my first 7mm-08. I have all of the dies, bullets, etc....and a LOT of 308 win brass. Since the 7mm-08 is only a necked down 308 case I figured that I could just resize my 308 brass. I have read around on the internet and heard from many people that do just that.....however......when I tried doing this the die does not resize the neck all the way to the shoulder. Sooo...about 1/4 inch of the neck is resized perfectly but there is still about 1/8" of the neck right at the shoulder 'unsized.' i wish i had a picture but camera is broken. Anyone know how to get that last little bit?

IllinoisCoyoteHunter · February 17, 2009, 04:54 PM

is your die in all the way??

jdscholer · February 17, 2009, 05:05 PM

Look at the case dimensions in your manual and you will see the problem. The 7mm is actually longer at the shoulder on up to the OAL. It will probably fire form to your chamber, but I'd want to hear it from someone who knows; I don't. jd

FrankenMauser · February 17, 2009, 06:15 PM

I don't own a 7mm-08, nor have I ever formed cases for them.

You may need to create a false shoulder to headspace for fire-forming.

Since the .308 and -06 based cartridges use a datum point of .375" on the shoulder to headspace; one of the easiest ways to do this is to neck up to .35 caliber. (.358" plus a case wall thickness of 0.010-0.018" on each side, will give you .375" +)

Once you have expanded the neck to .35 caliber, you size back down to 7mm-08. The expanded portion should give you enough surface area to safely headspace.
Fireforming with this process needs to be done very carefully, using proven data. You may have to do some research to find a method you can trust.

Of course; it doesn't matter much, if you don't have the ability to expand to .35 caliber.

wncchester · February 17, 2009, 07:11 PM

"I don't own a 7mm-08, nor have I ever formed cases for them. -- You may need to create a false shoulder to headspace for fire-forming."

Nope. Not even close.

Shoney · February 17, 2009, 09:52 PM

The case length for 7-08 is 2.035, while the case length of the 308 is 2.015.

The 7-08 and 308 cases are identical from face of head to the shoulder, both have a 20 degree slope from shoulder to the neck.

The 7-08 has a neck length of .284, and the 308 has neck length of .301.

The only other difference in the two cases is in the diameter of the necks, and that results in a shoulder slope length that is longer in the 7-08.

What is hapening because the 308 case is shorter, the 7-08 die will only size .284 of the 308 neck.

FrankenMauser · February 18, 2009, 01:22 AM

Quote:

Nope. Not even close.

Thank you for your wonderful input and enlightenment in this thread. You have been infinitely helpful. Your counter-arguement was very convincing.

Scorch · February 18, 2009, 02:27 AM

I have had FL resizing dies in the past that would not allow you to bump the shoulder. If your die does not resize all the way to the shoulder, you could have the bottom of the die faced off at a machine shop to allow it to be screwed in a bit further.

Go Kiwi · February 18, 2009, 02:31 AM

I went this route neckingpmc .308 down to 7-08 and my loaded ammunition showed severe pressure signs. I had a stock of 7-08 brass so I decided not to take things any further.

There was no need to create false shoulders etc to chamber the ammunition and fire reliably, perhaps it was headspacing on the neck? - the only problem was the flat primers and loose pockets

I guess start light and see what happens.

F. Guffey · February 18, 2009, 11:10 AM

KD5NA, I do not have a clue, I have both, to neck down a 308 Winchester to 7/08 Remington I install the die in the press, with the shell holder installed and the ram up I screw the die down to the shell holder, (I do not follow instructions by lowering the ram and adjusting the die down an addition 1/4 turn), this gives me .000 clearance between the shell holder and die, I then size a case making sure the de-primer assembly is not hitting the web of the case before sizing is complete: small amount of logic; if the case is not being sized there will be a gap between the shell holder and bottom of the die that can be measured with a feeler gage, if what you say is true, the gap will be .0625 (1/8"), if what someone else said is true the gap will be close to .021 + or - BUT if the handle was pulled and the ram made the full stroke the only gap will be the amount the press flexed during sizing, my presses size or crush.

grinding, facing off or removing material from the top of a die and or shell holder is not necessary, a feeler gage will accomplish the same thing and maintain the integrity of the die and shell holder.

F. Guffey

F. Guffey · February 18, 2009, 11:14 AM

top of shell holder (lower deck height) or bottom of die (shorten the distance between the head of the case to shoulder dimensions)

Sorry about that,

F. Guffey

jdscholer · February 18, 2009, 11:22 AM

The 7mm-08 is a longer case than the 308. You will not want to shorten your die. If you want to use 308 cases, you will have to blow them out .020 to get them to head-space correctly in your 7mm-08 chamber. jd

F. Guffey · February 18, 2009, 01:01 PM

Basically he is neck sizing.

Case length? the two cases have the same length body from the head of the case to the shoulder, the shoulders have the same angle, the only difference is the length of the neck, the neck on the 7/08 is .032 longer than the 308 W, the longer neck makes the 7/08 R longer, as has been said, the only part of the case that is being sized is the neck, this leads me to believe the die is not adjusted correctly or the primer punch neck sizer/expander assembly is not adjusted correctly. On one of my Herters, the weight of the handle will form 308 down to 7/08.

Necking a case down can make the case longer and or the neck thicker, in this situation neither will amount to much because the length of the case will not increase .020 thousands, and the sizer ball does not touch the neck when the ram is raised, no resistance.

F. Guffey

jdscholer · February 18, 2009, 05:09 PM

Ahhhh--you're right.

My Lyman book shows head to shoulder length for the 7mm-08 at 1.5598. My eyes saw 1.598. Go figure. Disregard my faux paux.

It just doesn't seem that he should be having a problem if his sizing die is contacting the shell holder. jd

RAnb · February 18, 2009, 05:30 PM

I tried necking down 308 to 7mm-08. I reduced the height of the shell holder to get the shoulder moved back a bit, but the necks required turning to chamber without excessive force. I fireformed a few cases then shot them, but accuracy sucked. I use factory 7mm-08 because I think it is not worthwhile to form and turn cases for use in a hunting rifle if factory brass is available.

Ranb

February 17, 2009, 04:14 PM	#1
kd5nay Junior Member Join Date: August 28, 2008 Posts: 2	problem necking down the .308 win Hi all, I have been reloading for a few years now but I recently purchased my first 7mm-08. I have all of the dies, bullets, etc....and a LOT of 308 win brass. Since the 7mm-08 is only a necked down 308 case I figured that I could just resize my 308 brass. I have read around on the internet and heard from many people that do just that.....however......when I tried doing this the die does not resize the neck all the way to the shoulder. Sooo...about 1/4 inch of the neck is resized perfectly but there is still about 1/8" of the neck right at the shoulder 'unsized.' i wish i had a picture but camera is broken. Anyone know how to get that last little bit? Last edited by kd5nay; February 17, 2009 at 04:39 PM.

February 17, 2009, 04:54 PM	#2
IllinoisCoyoteHunter Senior Member Join Date: December 23, 2008 Location: Southern Illinois Posts: 1,527	is your die in all the way?? __________________ ~~IllinoisCoyoteHunter~~ ~NRA LIFE MEMBER~ ~NRA CERTIFIED INSTRUCTOR~

February 17, 2009, 05:05 PM	#3
jdscholer Senior Member Join Date: March 23, 2008 Location: Jefferson State Posts: 1,197	Look at the case dimensions in your manual and you will see the problem. The 7mm is actually longer at the shoulder on up to the OAL. It will probably fire form to your chamber, but I'd want to hear it from someone who knows; I don't. jd __________________ "We're all dummies, just in different ways." Old Okie Philosopher

February 17, 2009, 09:52 PM	#6
Shoney Senior Member Join Date: February 21, 2002 Location: Transplanted from Montana Posts: 2,311	The case length for 7-08 is 2.035, while the case length of the 308 is 2.015. The 7-08 and 308 cases are identical from face of head to the shoulder, both have a 20 degree slope from shoulder to the neck. The 7-08 has a neck length of .284, and the 308 has neck length of .301. The only other difference in the two cases is in the diameter of the necks, and that results in a shoulder slope length that is longer in the 7-08. What is hapening because the 308 case is shorter, the 7-08 die will only size .284 of the 308 neck. __________________ I pledge allegiance to the Flag - - -, and to the Republic for which it stands….Our Forefathers were brilliant for giving us a Republic, not a democracy! Do you know the difference??? and WHY?http://www.wallbuilders.com/LIBissue...les.asp?id=111

February 18, 2009, 02:27 AM	#8
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	I have had FL resizing dies in the past that would not allow you to bump the shoulder. If your die does not resize all the way to the shoulder, you could have the bottom of the die faced off at a machine shop to allow it to be screwed in a bit further. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

February 17, 2009, 06:15 PM	#4
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,424	I don't own a 7mm-08, nor have I ever formed cases for them. You may need to create a false shoulder to headspace for fire-forming. Since the .308 and -06 based cartridges use a datum point of .375" on the shoulder to headspace; one of the easiest ways to do this is to neck up to .35 caliber. (.358" plus a case wall thickness of 0.010-0.018" on each side, will give you .375" +) Once you have expanded the neck to .35 caliber, you size back down to 7mm-08. The expanded portion should give you enough surface area to safely headspace. Fireforming with this process needs to be done very carefully, using proven data. You may have to do some research to find a method you can trust. Of course; it doesn't matter much, if you don't have the ability to expand to .35 caliber.

February 17, 2009, 07:11 PM	#5
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	"I don't own a 7mm-08, nor have I ever formed cases for them. -- You may need to create a false shoulder to headspace for fire-forming." Nope. Not even close.

February 18, 2009, 02:31 AM	#9
Go Kiwi Member Join Date: October 11, 2007 Posts: 40	I went this route neckingpmc .308 down to 7-08 and my loaded ammunition showed severe pressure signs. I had a stock of 7-08 brass so I decided not to take things any further. There was no need to create false shoulders etc to chamber the ammunition and fire reliably, perhaps it was headspacing on the neck? - the only problem was the flat primers and loose pockets I guess start light and see what happens.

February 18, 2009, 11:10 AM	#10
F. Guffey Senior Member Join Date: July 18, 2008 Posts: 7,249	KD5NA, I do not have a clue, I have both, to neck down a 308 Winchester to 7/08 Remington I install the die in the press, with the shell holder installed and the ram up I screw the die down to the shell holder, (I do not follow instructions by lowering the ram and adjusting the die down an addition 1/4 turn), this gives me .000 clearance between the shell holder and die, I then size a case making sure the de-primer assembly is not hitting the web of the case before sizing is complete: small amount of logic; if the case is not being sized there will be a gap between the shell holder and bottom of the die that can be measured with a feeler gage, if what you say is true, the gap will be .0625 (1/8"), if what someone else said is true the gap will be close to .021 + or - BUT if the handle was pulled and the ram made the full stroke the only gap will be the amount the press flexed during sizing, my presses size or crush. grinding, facing off or removing material from the top of a die and or shell holder is not necessary, a feeler gage will accomplish the same thing and maintain the integrity of the die and shell holder. F. Guffey

February 18, 2009, 11:14 AM	#11
F. Guffey Senior Member Join Date: July 18, 2008 Posts: 7,249	top of shell holder (lower deck height) or bottom of die (shorten the distance between the head of the case to shoulder dimensions) Sorry about that, F. Guffey

February 18, 2009, 11:22 AM	#12
jdscholer Senior Member Join Date: March 23, 2008 Location: Jefferson State Posts: 1,197	The 7mm-08 is a longer case than the 308. You will not want to shorten your die. If you want to use 308 cases, you will have to blow them out .020 to get them to head-space correctly in your 7mm-08 chamber. jd __________________ "We're all dummies, just in different ways." Old Okie Philosopher

February 18, 2009, 01:01 PM	#13
F. Guffey Senior Member Join Date: July 18, 2008 Posts: 7,249	Basically he is neck sizing. Case length? the two cases have the same length body from the head of the case to the shoulder, the shoulders have the same angle, the only difference is the length of the neck, the neck on the 7/08 is .032 longer than the 308 W, the longer neck makes the 7/08 R longer, as has been said, the only part of the case that is being sized is the neck, this leads me to believe the die is not adjusted correctly or the primer punch neck sizer/expander assembly is not adjusted correctly. On one of my Herters, the weight of the handle will form 308 down to 7/08. Necking a case down can make the case longer and or the neck thicker, in this situation neither will amount to much because the length of the case will not increase .020 thousands, and the sizer ball does not touch the neck when the ram is raised, no resistance. F. Guffey

February 18, 2009, 05:09 PM	#14
jdscholer Senior Member Join Date: March 23, 2008 Location: Jefferson State Posts: 1,197	Ahhhh--you're right. My Lyman book shows head to shoulder length for the 7mm-08 at 1.5598. My eyes saw 1.598. Go figure. Disregard my faux paux. It just doesn't seem that he should be having a problem if his sizing die is contacting the shell holder. jd __________________ "We're all dummies, just in different ways." Old Okie Philosopher

February 18, 2009, 05:30 PM	#15
RAnb Junior member Join Date: July 20, 2008 Location: WA, USA Posts: 447	I tried necking down 308 to 7mm-08. I reduced the height of the shell holder to get the shoulder moved back a bit, but the necks required turning to chamber without excessive force. I fireformed a few cases then shot them, but accuracy sucked. I use factory 7mm-08 because I think it is not worthwhile to form and turn cases for use in a hunting rifle if factory brass is available. Ranb