.308 case to 7mm 08 case?

[Siiri]

Hello,
Can you take a full length sizing die for a 7mm 08 and put a .308 case into it to make that .308 case into a 7mm 08 case?
If not, how do you size down cases?

Thanks!
Siiri

 

[swede7]

you sure can, just lube it and run it through and you're good to go

 

[Preacher]

That is exactly how you would make a 7/08 out of a 308 case...the only difference is the neck size...
Lube it up, be careful of putting to much on the shoulder and have right at it.....
Depending on the brass you may need to turn the necks for a perfect fit....

 

[Varminator]

This pops up all the time. Originally, there was a 7mm-308 with a short neck and several iterations of neck thickness. Fast forward to 1980 when the round was standardized. Having owned and shot both .243 and 708 I decided to try the .243 brass as opposed to necking down the .308 and ending up with a short fat neck that requires turning even in a factory barrel however starting with lapua brass I quickly found that the necked up .243 brass was the ticket. I have some if you want to verify the headstamp. Generally if you neck down .308 brass and just shoot it you will encounter high pressure because the neck wall is too thick and can not expand enough to allow the bullet to freely escape. A note on this high pressure, it is high enough to ruin some guns and is at best extremely dangerous in most. If you have a Remington bolt or a clone you may get away with it for awhile but accuracy and brass life will will be all over the map. I have a BLR in 708 and a XP-100 and several (take off) barrels I have not tried for my bolt guns, I do know that in these two guns that I have extensive experience with there is no way I can simply neck down .308s and load and shoot. Be safe.
Mark

 

[Siiri]

This pops up all the time. Originally, there was a 7mm-308 with a short neck and several iterations of neck thickness. Fast forward to 1980 when the round was standardized. Having owned and shot both .243 and 708 I decided to try the .243 brass as opposed to necking down the .308 and ending up with a short fat neck that requires turning even in a factory barrel however starting with lapua brass I quickly found that the necked up .243 brass was the ticket. I have some if you want to verify the headstamp. Generally if you neck down .308 brass and just shoot it you will encounter high pressure because the neck wall is too thick and can not expand enough to allow the bullet to freely escape. A note on this high pressure, it is high enough to ruin some guns and is at best extremely dangerous in most. If you have a Remington bolt or a clone you may get away with it for awhile but accuracy and brass life will will be all over the map. I have a BLR in 708 and a XP-100 and several (take off) barrels I have not tried for my bolt guns, I do know that in these two guns that I have extensive experience with there is no way I can simply neck down .308s and load and shoot. Be safe.
Mark

I have a Savage Edge XP 7mm 08 and some .308 cases just laying around. Would this be safe to neck down? How could I safely neck them down?

 

[RonAKA]

I have a Savage Edge XP 7mm 08 and some .308 cases just laying around. Would this be safe to neck down? How could I safely neck them down?

My calculations show the maximum your brass thickness could grow is 0.001". Even Lapua brass has changed that much in the blue box to old cardboard box lots. I would suggest the growth is insignificant in a factory chambered sporting gun like the Edge. I do it all the time with 7mm RM brass, in necking down to .264. Just put some case lube on the outside, graphite on the inside, and run it through a full length sizing die.

The only downside is that the brass headstamp becomes incorrect. Be aware of that in how you mark and handle it.

 

[DCRYDER]

I did this with Lapua brass a couple of years ago. Gun was a Remington model 7 7mm-08 with factory barrel and chamber. Seems like loaded rounds measured around .316 and just had around 0.0005 clearance and shot like crap. Had to turn necks to get .003 clearance. Be careful because if there is not enough clearance it can be dangerous. I would fire a 7mm-08 cartridge in your gun then measure neck diameter of that case, then make sure necked down 308 case loaded is around .002" smaller.

 

[Siiri]

What does turn necks mean? I'm new at this and still getting to know all of the terminology.

 

[Dgd6mm]

DCRYDER, how did it shoot after you turned the Necks? Siiri, Grafs & Sons have an asortment of 7-08 brass. They have Privi for 34.99 @ 100. I don't know how good the brass is ,but the price is not bad. You take a neck turning tool with the proper size mandral and thin the wall thickness of the neck for better concentricity and fit for a tight neck chamber. If you start searching around on this site and ask questions you will get a wealth of information. Always remember safety first.

 

[RonAKA]

What does turn necks mean? I'm new at this and still getting to know all of the terminology.

Have a read of this article. It is basically machining down the outside diameter of the neck.

http://www.6mmbr.com/neckturningbasics.html

It is not a lot of fun, and I would suggest you don't want to get into this just to save some old brass. The current trend is to avoid neck turning. You would be better off to just buy some new 7mm-08 brass. I still don't think you will have a problem using the 308 brass just full length resized. The easy way is just to resize and load a few. Color the neck outside diameter with a black permanent marker, and chamber them. If they chamber well and you don't have any significant scoring marks on the neck OD indicating it is too large, then you are good to go.

 

[jonbearman]

If you use commercial brass you are closer to factory spec ,however I would measure the neck thickness anyways to make sure it is to spec.Do not use military brass as it is thicker in the body and the head and web.This could cause catostrofic failure.Midway has them on sale on and off and there are segveral sites where you can purchase once fired 7-08 case's cheap.Also advertise in our classified ad's for someone to give some up.

 

[DCRYDER]

dgd6mm, model 7 was a ss/syn with a weaver v16 scope, shooting sierra 140 prohunters. before turning i had bad fliers shooting around 2" groups at 100 for 3 shots. same load after turning most groups were around 1". traded it off and got a Remmy LVSF 7-08, used the same brass and 120gr TSX's and it shot in the .5's and .6's. Both guns fired brass necks measure .316 figuring in springback i guess chamber was .317 or a little less. unturned loaded round of lapua brass was .316 so i turned them to .312. Factory winchester loaded is .310.

 

[Dgd6mm]

Thanks DCRYDER for the info.

 

[bozo699]

Siiri,
I do this quite often,though I am use to checking everything before shooting as I have many wildcats and use the same brass for several projects lots of guy's do this and get away with it.(I DONT SUGUEST THIS FOR YOU) and the reason why is your just getting started and there are many varibles when you start changing things. Sooner or later you will probably get more involved and will learn all about this type of loading and will no doubt be teaching us new tricks you have learned But for now Siiri I suguest you stick with 7mm-08 brass as others have said,its cheap and safe. I am afraid you may be out with friends shooting and one of them may have a .308, well you can see how easy it could be to get confused and things could go very wrong.
Wayne.