Forming 7mm-08; better to neck up or down?

[longrangehunter]

I'm giving up on looking for 7mm-08 Winchester brass. A while back someone gave me some Lapua 308 brass to neck down so I could size them down to 7mm-08. I'd prefer to size down and have a thicker neck for a tighter chamber fit :?: :?: and not have the neck wall moving brass only to one side of the neck sizing up 260 Rem. brass.

Which is better? Would using 260 Rem. brass be better then the shorter 308 case? Or the other way around?

I plan on buying Lapua brass for this once I make up my mind?

 

[Rem Jim]

Your neck outside diameter is always going to be the same to fit in the chamber and you should inside ream any of the the brass with the proper diameter cutter ! JMO RJ

 

[longrangehunter]

Your neck outside diameter is always going to be the same to fit in the chamber and you should inside ream any of the the brass with the proper diameter cutter ! JMO RJ

I assumed that when you seat a bullet, it will measure a few thousands of an inch larger in dia. due to the thicker neck from sizing the brass down? That is unless I ream the inside of the neck?

 

[longrangehunter]

Oh, the price difference leans towards the 308 Win. brass by a lot; $75.00 vs. $110.00 for 260 Rem. Lapua brass. And since I'm rather frugal with my $$$, I'd say the price makes better sense? But I'd still like to hear from anyone with a opinion.

 

[Wincheringen]

Size down and outside trim.

 

[kraky]

I shoot alot of 30 Cal and have a neck turner all set up for that. I turn 308 necks and then downsize...works great.

 

[Jimbeaux82]

If I am only going up one bullet size, I prefer to neck up. I frequently neck up 243 brass to 260 without any problem, since I have a ton of 243 brass and find it at the range often. However, 260 brass is not as common so might be more difficult to find enough to expand up to 7-08.

 

[rick smith]

I have up/down sized a lot of necks. Normally turning or reaming is not necessary in a factory chamber. I would size one down, seat a bullet and try it in the chamber. Probably have room to spare. If you happen to have a piece of brass fired in that chamber and not sized, measure the OD of the neck. It will not be the chamber neck diameter due to springback but it can give you an idea. Or do a chamber cast.Rick.

 

[JD338]

I agree with Rick.
With 243 brass, I would go 6.5 mm first than 7 mm.
Imperial case lube is your friend.

JD338

 

[kraky]

I don't know that I've ever experienced the do called "doghnut" at the base of the neck. But isn't the theory that when you neck up the shoulder comes up into the neck and eventually makes the brass at the base of the neck slightly thicker?

 

[longrangehunter]

I agree with Rick.
With 243 brass, I would go 6.5 mm first than 7 mm.
Imperial case lube is your friend.

JD338

Like I said before, the cost of 308 Winchester lapua brass is 46.66% cheaper then 260 Remington or 243 Winchester lapua brass, it just seems to make more sense to neck down then up due to the hugh cost savings. That and I already have 20 pieces someone gave me.

I read you can run the brass first through a seater die, which is slightly oversized and then through the F/L die. But in this case I have a Redding Match Bushing die set that uses the Competition bullet seater. I may have the right bushings to do it in steps, but I'm pretty sure not enough to do it in small increments.

 

[rick smith]

My experience with donuts came when using factory 6.5x284 brass in a custom chambered rifle. I had formed 284 brass into 6.5x284 without a problem and did not have donuts. But had them with the factory brass. Removed them with a reamer.Rick.

 

[longrangehunter]

I ran the 20 pieces of 308 brass up into the F/L Bushing die without any resistance at all, but the down stroke was really hard on most of the pieces even with graphite and a carbide sizing button. Not sure what that was all about but it was rather harsh being pulled from the expander ball. All in all they looked good, just a tad on the short side 2.015"-2.010".

 

[Wincheringen]

You can outside trim first to make it a little easier.

 

[nvbroncrider]

SPS has 7-08 brass

 

[Horsethief]

I haven't necked up much, but it seems to be easy on the necks if you lubricate them and go in small increase possible. Taking GI 30-06 up to .366 for a 9.3mm Mauser was easy. Use a .323 cal / 8mm expander ball, then a .358 and finally the full-length 9.3x62mm Mauser die. About 1mm of brass needed to be trimmed to make the right case length.

Taking a .243 Win case to .284 by going to a .257 neck, then a .277 and finally the .28 cal you need in the full-length die.

 

[longrangehunter]

I've lately be necking down Lapua 308 Winchester brass to form 7mm-08 remington, and now seem to have a tight neck situation due to the extra brass increasing the thickness of the neck.

The 7mm-08 Federal and Winchester brass I've used in the past of a loaded round tends to measure around .3110", but the neck sized down Lapua brass of a loaded round measures .3150"-.3155". Which according to SAAMI is at the case neck dimensions of the case (.3150"), the chamber dimension is .3170" at the neck shoulder juncture and .3160" at the end of the chamber. Which in this case is rather tight for neck expansion to release the bullet upon firing. These loads have also not produced the same bug holes as the previous loads with the other brass leaving me to think I'll need to turn down the necks. I also think for a tactical comp gun that could give me a head ache in a match or am I incorrect in my thought process?

Which reminds me why I went with a .300 neck on the 6.5/300 WSM in the first place? Honestly at the time I was swamped with building my house and then to find the gun's chamber cut too long, and having to ship it back, then not doing anything with it until two years later I spaced out why I came up with that number in the first place? I had read the WSM's don't seem to shoot all that well with tight neck chambers.

But now I realize why? Necking down a 300 WSM to 6.5 mm and not wanting to turn the neck left me with using that number. Although somewhere along the interim I traded the Norma brass to a friend for work since I thought why not neck down a 270 WSM brass instead since it was such a pain in the ass using the 300 WSM brass. Either way I was kinda dumb founded by why my numbers weren't coming together until now? I was using a number from a dummy round made from 300 WSM I made up before I ever built the gun. If my 6.5/300 WSM runs so well with a sloppy neck and so did this gun, a Wby. Vanguard with a Heart barrel, something is wrong with the "tight neck theory" in my opinion.

So I ordered a .308 pilot for my neck turner so I suppose I'll see if turning the necks before sizing them helps with running them over the expander ball. Or should I turn them after sizing down? I've ask this question to even the owner of K&M and he still wasn't sure which was better? To me it seems if the brass has moved after neck sizing down that is when it should be removed?

 

[kraky]

I've been using 308 brass and downsizing. Win brass is ideal cause it normally has thin .013" necks. If its brass with thicker necks I turn it before downsizing.
I pulled the expander stem from my rcbs FL die and use it sort of like a body die.
After reforming I lube case mouths w/imperial sizing wax and plunge them onto the eliptical expander of my hornady neck die. Pushing the expander down through the case mouth does not pull the case neck off center.
Doing it this way results in a Max of. 002" run out on the reformed case before loading.
I'm going to continue sizing this way after fireforming as run out comes to near zero this way.....

 

[Oldtrader3]

I prefer going up. I buy .308 match brass for my .338 Federal and use an elliptical carbide forming plug to stretch the brass .030 inches to .337 for seating. I also have found that the process works better if I stretch the brass, let it sit overnight and resize it again the next day with the forming plug. The second pass corrects some small amount of case neck spring-back overnight.

 

[FOTIS]

Always up so you do not have to neck turn. I am a lazy bastid!