Resizing brass from 308 to 7mm-08

[USAF Ret]

Is it just as simple as putting the 308 brass into the 7mm-08 die to neck it down? Any concerns or things to look for, aside from not mixing brass up with a 308 head stamp that is 7mm-08?

[The Happy kaboomer]

Will work. Long ago I necked down 308 to 243. What you end up with is a cartridge that maybe a little shorter with a VERY THICK NECK that will have to be turned down. if the neck is not thinned the loaded round may not chamber in your rifle......Also made a lot of .280's out of 270 & 30-06 brass.

[Marco Califo]

I tried and found it was taking more effort than I liked.
I bought 500 rounds of Starline 7mm-08 brass.

[44 AMP]

It will work, but the formed case will be slightly "off" for length. Going by the case drawings in a Hornady manual, the 7mm-08 case is 0.02" longer than the .308 win, and the case body from the base of the case to the base of the neck is 0.04" longer than the .308win.

you're going to be squeezing down the .308 neck and this may add a little bit of length. Case necks might need to be turned depending on the thickness of the brass used and the tolerances of your rifle.

going by the specs the 7mm-08 sizer shouldn't touch the .308 case shoulder. I'd recommend making your first load a light plinker using it to form the converted case to your chamber.

I'd also recommend only using commercial .308 brass to form. The GI stuff is generally a bit thicker, and you don't want or need that. Internal volume ought to be close enough not to matter much, BUT there's no guarantee of that, so work up loads for the formed brass the usual way, in case there is an significant difference in the internal volume of the cases.

you might also consider some kind of marking on the case head so you can identify at a glance that the formed cases are no longer .308 Win. Sharpie magic marker works, lasts a while, but does get worn, but is easily redone at need.

[Marco Califo]

I tried using milsurp 7.62, which is thicker and has less capacity than commercial. 7.62 milsurp is almost always machine gun fired and "puffed out" in generous MG chambers. For me it was a No Go. And hello Starline, with the correct headstamp, since I load both.

[bbqncigars]

I would go with Marco on this. Starline is good brass, and I personally avoid case forming when at all possible. It's too much time and too many variables for too little reward. 25-20 forming from 32-20 being the one exception for me.

[USAF Ret]

Thanks for all the input. Got some boxes of Norma Whitetail for less than $20 a box. Smoking deal. So, once I shoot through those, I can reload the brass.

Also, just love my CVA Cascade rifles. Absolute tack drivers. Caught one on Gunbroker that I noticed the sale ended with no bids. Contacted the guy. Retired military. Got a smoking deal on it as well. I would rather have camo and cerakote, but it is a black rifle with a blued barrel. It will get a custom Krylon paint job.

Another item I did not need, but I use my wife's logic. "Honey, I did not spend $450. I saved $100."

I will keep an eye out for the Starline brass as well. Not sure I want to go through all that pain with the 308 cases unless it is a dire need.

[Marco Califo]

https://www.starlinebrass.com/7mm-08-remington
It is on back order at Starline. That means you can order it and it will generally ship within one week. They pay shipping.

[USAF Ret]

Originally Posted by Marco Califo

https://www.starlinebrass.com/7mm-08-remington
It is on back order at Starline. That means you can order it and it will generally ship within one week. They pay shipping.

Thanks Marco.

[std7mag]

You can form 308 brass to 7mm-08. Simple one pull on a f/l sizer.
As mentioned, the neck may be thick. And it may end up with a "donut" inside the base of the neck.

Another option to look for, for quality inexpensive brass is PVRI Partizen (PPU).

[USAF Ret]

Originally Posted by std7mag

You can form 308 brass to 7mm-08. Simple one pull on a f/l sizer.
As mentioned, the neck may be thick. And it may end up with a "donut" inside the base of the neck.

Another option to look for, for quality inexpensive brass is PVRI Partizen (PPU).

I am probably going to go with Starline. The 7mm-08 will probably be saved as a later project, as I am working loads on other rifles after deer and duck season are done.

[Unclenick]

In resizing 308 Win brass, if all the brass went into neck thickness and none into neck length, going from 0.308" to 0.284" will increase wall thickness by 0.00107", and diameter by twice that. Most 308 Win cases run about 0.014" wall thickness. If you have that, increasing it to 0.01507" and seating a 0.284" bullet still won't exceed the SAAMI maximum for the 7mm-08 cartridge neck. So you may not need to turn anything off. That said, some 308 Win brass can be extra thick to start, so what you actually want to do is to try a few cases and seat a bullet and measure the OD of the neck over the top of the bullet. As long as it does not exceed SAAMI's limit of 0.3150" anywhere, you don't have to do anything about turning necks unless you want to for OCD reasons or to try to increase accuracy.

[USAF Ret]

Originally Posted by Unclenick

In resizing 308 Win brass, if all the brass went into neck thickness and none into neck length, going from 0.308" to 0.284" will increase wall thickness by 0.00107", and diameter by twice that. Most 308 Win cases run about 0.014" wall thickness. If you have that, increasing it to 0.01507" and seating a 0.284" bullet still won't exceed the SAAMI maximum for the 7mm-08 cartridge neck. So you may not need to turn anything off. That said, some 308 Win brass can be extra thick to start, so what you actually want to do is to try a few cases and seat a bullet and measure the OD of the neck over the top of the bullet. As long as it does not exceed SAAMI's limit of 0.3150" anywhere, you don't have to do anything about turning necks unless you want to for OCD reasons or to try to increase accuracy.

Good info. No, I am not OCD or a precision shooter. If I get a bang, good velocity and acceptable accuracy, I am good.

[Sure Shot Mc Gee]

Should be a piece of cake resizing down to 28 cal. Try annealing brass neck & shoulder first.

[jetinteriorguy]

I’ve resized .308 down to 6.5CM just using the normal sizing die. I would do it raising the ram in increments with a well lubed neck. I never actually loaded or fired any of these, just wanted to try it to see if it could be done. If I were ever to load it I’d definitely turn the necks. At first about 10% would have a kink in the necks until I figured out to just size in increments.

[Unclenick]

Going to 6.5 CM is different in that its shorter head-to-shoulder dimension means you wind up moving part of the 308 win brass shoulder up into the neck. If you do that, you need to check to be sure that move hasn't formed an internal donut thick enough to interfere with your seated bullet. If you seat a bullet down into such a thickened place, it can fatten the neck enough to have no clearance in the chamber neck, making normal bullet release impossible and greatly raising pressure. You then need either to ream the donut out or be sure you don't seat your bullets deeply enough to get their bearing surface in contact with the thick place.

[jetinteriorguy]

Originally Posted by Unclenick

Going to 6.5 CM is different in that its shorter head-to-shoulder dimension means you wind up moving part of the 308 win brass shoulder up into the neck. If you do that, you need to check to be sure that move hasn't formed an internal donut thick enough to interfere with your seated bullet. If you seat a bullet down into such a thickened place, it can fatten the neck enough to have no clearance in the chamber neck, making normal bullet release impossible and greatly raising pressure. You then need either to ream the donut out or be sure you don't seat your bullets deeply enough to get their bearing surface in contact with the thick place.

Ah yes, thanks for reminding me UN. I really have no plans on actually loading these since I have plenty of factory brass in 6.5CM. It was merely an exercise to see if I could do it. I’m going to check on it though out of curiosity just for the learning experience.

[Pathfinder45]

It should be just a simple pass through the sizing die and maybe a trim to length, but that's all. When I first got back into 270 Winchester I had a lot of 30-'06 brass and very little 270. It was one pass through the die and good to go. I've shot hundreds of them without the slightest problem. 308 sized to 7mm is even less of a change. Having proper headstamps is well and good, but it means little or nothing to a wildcatter, and those of us who are avid reloaders shouldn't let it bother us either, especially in times of shortages. Sure would be nice to see better availability and prices on primers.....

[USAF Ret]

Originally Posted by Pathfinder45

It should be just a simple pass through the sizing die and maybe a trim to length, but that's all. When I first got back into 270 Winchester I had a lot of 30-'06 brass and very little 270. It was one pass through the die and good to go. I've shot hundreds of them without the slightest problem. 308 sized to 7mm is even less of a change. Having proper headstamps is well and good, but it means little or nothing to a wildcatter, and those of us who are avid reloaders shouldn't let it bother us either, especially in times of shortages. Sure would be nice to see better availability and prices on primers.....

Much appreciated. I have 308 brass coming out my ears. I got 100 Starline new brass from Gunbroker as well, so I should be set up. Just need to get the right bullet and make sure i don't mix loads up with my 308.

[Unclenick]

You might consider taking all your .284 bullets or all your .308 bullets (whichever you have fewer of) and marking the tips with a Sharpie or something else where your seating die doesn't rub them off, and that will give you a quick visual confirmation when you are grabbing ammo at the range or for the field or even just for loading.

[Marco Califo]

"a Sharpie or something else"
I got 5 different colors of nail polish @ $1 each, and a bottle of Acetone (nail polish thinner and remover) at WalMart. Under $10 total. I also plan to color code shellholders and dies for fast ID without reading glasses.

[Unclenick]

Good tip about the shell holders. I load most rifle ammo on Co-ax presses anymore, which have just two shell holder jaw sizes, so I don't have to look for the right shell holder for those. But I'm thinking that for my second operation presses and priming tools I might try filling the number stamp markings on the shell holders with different colors. Same for my Dillon shell plates.