Necking up

howlnmad · May 20, 2010, 10:48 AM

Just a simple question. Anyone see any problems with necking up a 264 Win Mag to a 7mm Rem Mag?

howlnmad

briandg · May 20, 2010, 10:49 AM

not really, but how do you plan to expand it?

I just realized, have you checked the case dimensions so that you know that it can safely be done? IIRC, they were both based on the .338, but that doesn't mean that the shoulders and other landmarks will match.

**Unclenick** · May 20, 2010, 11:24 AM

It looks like a pretty good fit. The only fly in the ointment that I see is that a maximum neck wall thickness for the .264 looks to be about .0170", while the maximum neck wall thickness for the 7 mm is 0.0155". Expanding 0.0170" up from 0.2640" to 0.2840" ID will reduce its neck thickness not quite enough, to 0.0159". So, while it is unlikely your .264 brass will be exactly at maximum neck wall thickness, it is still possible you will need to outside turn half a half a thousandth off the finished case.

Otherwise the shoulder angle and root position and body and head sizes are all the same. You should be good to go.

howlnmad · May 20, 2010, 12:16 PM

Thanks guys. I thought it would work buy just wanted others opinions.
briandg,for the initial pass I planned on using a Lee FL sizer with the expander turned down just a bit. I think the long taper on these will help.
unclenick, I guess I better polish up on my neck turning. It's been awhile.

howlnmad

**Unclenick** · May 20, 2010, 01:09 PM

You may need to, but you may not? It occurred to me after posting that, if you would do a chamber cast or even just check the OD of a fired case neck, you might well find your 7 mm chamber has extra neck room, anyway? Benchrest shooters go to a lot of trouble to minimize the extra room around the neck to improve accuracy, often getting special chambers with smaller neck portions than normal just so they can turn their case necks down and still have only a thousandth of an inch clearance or so. So, if your chamber neck is big enough, take advantage of the tighter fit.

howlnmad · May 20, 2010, 04:18 PM

Unclenick,
Thanks again, I hadn't thought of that and probably never would have.

howlnmad

tkofoid · May 20, 2010, 04:50 PM

In terms of neck thickness: Fire a round or two, then, without resizing try to to push a bullet into the neck of the fired cases. If it goes freely,,,you are good to go. If it is really tight, it needs neck turning. Remember in turning; a little dab will do ya!

**Unclenick** · May 21, 2010, 04:04 PM

Hmm. Sounds like a test sequence where you risk a high pressure event, then check to see if the case was the right size? It's pretty typical for the very edge of the case mouth to be slightly curlled in and not reflect the chamber diameter. That happens because pressure has equalized around the edge of the mouth as gas started to bleed out past it and around the bullet before it expanded that last little bit.

You'd need to cut the curl off or use a universal expander die to open it slightly, then see if the bullet slips in the rest of the neck to learn how tightly the neck holds the bullet? But the fact your gun survived is the first clue that the case neck wasn't jammed into the chamber overly tightly. Just do a diameter measurement on the neck of the loaded round and again afterward to see if it expands enough? SAAMI specs on some cartridges allow for as little as half a thousandth between maximum brass and minimum chamber, so it doesn't take much.

May 20, 2010, 10:48 AM	#1
howlnmad Senior Member Join Date: April 29, 2009 Location: Harriman Tn Posts: 424	Necking up Just a simple question. Anyone see any problems with necking up a 264 Win Mag to a 7mm Rem Mag? howlnmad

May 20, 2010, 11:24 AM	#3
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	It looks like a pretty good fit. The only fly in the ointment that I see is that a maximum neck wall thickness for the .264 looks to be about .0170", while the maximum neck wall thickness for the 7 mm is 0.0155". Expanding 0.0170" up from 0.2640" to 0.2840" ID will reduce its neck thickness not quite enough, to 0.0159". So, while it is unlikely your .264 brass will be exactly at maximum neck wall thickness, it is still possible you will need to outside turn half a half a thousandth off the finished case. Otherwise the shoulder angle and root position and body and head sizes are all the same. You should be good to go. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

May 20, 2010, 01:09 PM	#5
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	You may need to, but you may not? It occurred to me after posting that, if you would do a chamber cast or even just check the OD of a fired case neck, you might well find your 7 mm chamber has extra neck room, anyway? Benchrest shooters go to a lot of trouble to minimize the extra room around the neck to improve accuracy, often getting special chambers with smaller neck portions than normal just so they can turn their case necks down and still have only a thousandth of an inch clearance or so. So, if your chamber neck is big enough, take advantage of the tighter fit. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

May 21, 2010, 04:04 PM	#8
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	Hmm. Sounds like a test sequence where you risk a high pressure event, then check to see if the case was the right size? It's pretty typical for the very edge of the case mouth to be slightly curlled in and not reflect the chamber diameter. That happens because pressure has equalized around the edge of the mouth as gas started to bleed out past it and around the bullet before it expanded that last little bit. You'd need to cut the curl off or use a universal expander die to open it slightly, then see if the bullet slips in the rest of the neck to learn how tightly the neck holds the bullet? But the fact your gun survived is the first clue that the case neck wasn't jammed into the chamber overly tightly. Just do a diameter measurement on the neck of the loaded round and again afterward to see if it expands enough? SAAMI specs on some cartridges allow for as little as half a thousandth between maximum brass and minimum chamber, so it doesn't take much. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

May 20, 2010, 10:49 AM	#2
briandg Senior Member Join Date: May 4, 2010 Posts: 5,468	not really, but how do you plan to expand it? I just realized, have you checked the case dimensions so that you know that it can safely be done? IIRC, they were both based on the .338, but that doesn't mean that the shoulders and other landmarks will match.

May 20, 2010, 12:16 PM	#4
howlnmad Senior Member Join Date: April 29, 2009 Location: Harriman Tn Posts: 424	Thanks guys. I thought it would work buy just wanted others opinions. briandg,for the initial pass I planned on using a Lee FL sizer with the expander turned down just a bit. I think the long taper on these will help. unclenick, I guess I better polish up on my neck turning. It's been awhile. howlnmad

May 20, 2010, 04:18 PM	#6
howlnmad Senior Member Join Date: April 29, 2009 Location: Harriman Tn Posts: 424	Unclenick, Thanks again, I hadn't thought of that and probably never would have. howlnmad

May 20, 2010, 04:50 PM	#7
tkofoid Senior Member Join Date: October 10, 2008 Location: N. D. Posts: 149	In terms of neck thickness: Fire a round or two, then, without resizing try to to push a bullet into the neck of the fired cases. If it goes freely,,,you are good to go. If it is really tight, it needs neck turning. Remember in turning; a little dab will do ya!