Resizing brass, 308 to 260

I want to resize some 308 brass down to 260. I am under the understanding that all I have to do is run the 308 through my 260 sizing die and make sure that its trimmed to length. Is this correct? Or do I have to turn the outside of the necks? Im am not really sure what that entails because I have never turned the necks before.

I tried this once for my son's 260 and on the first loading I had no problems at all. They functioned great. However on the second loading my primer pockets were extremely loose. I have been leery of trying it again. I also tired this by turning 7mm Mag into 264 and the 7mm would lock up my bolt. I ended up just buying the right kind of brass..... (smart huh?) But I have 700 pieces of 308 match brass that I would like to try on again....

Thanks all

Ryan

Yes all you have to do is run it through the fl sizing die and yes you will need to turn the outside of the necks. If you have never turned necks before and you have to buy a neck turner I might suggest just buying some 260 brass as the neck turners can be quite expensive. $65-$70 bucks. On the other hand there are lots of calibers that can be made out of 308 and a neck turner can be a good investment.

Ok I have seen them on line but I have no idea how they work..... wow that makes me sound bad.... anyway because I didnt turn the necks on my sons I caused pressure problems by not having enough room on the OUTSIDE of the neck to expand and that loosened the primer pockets.... am I on the right track here?

Yes when you neck down brass the neck area gets thicker and then in turn holds the bullet tighter in the neck causing pressure spikes. Your loads will be very inconsistent until the necks are trimmed up.

one more question.... is the same true if you neck up in size..... like say from 243? Just trying to wrap my head around this.... do the inside of the necks need to be trimmed too?

No necking up from 243 should be fine.

factory chambers are as a rule sloppy enough that neck turning isnt necessary even when necking down cases.
even custom chambers can be cut so that neck turning isnt necessary. commonly referred to as a (no turn neck chamber).
turning is a pita that should be avoided unless your a serious competetor. a gunsmith could tell you what your neck dimensions are
by making a chamber cast. other than that im not sure there is another way of telling what the true dimensions are.
turning necks for the sake of turning necks can be counter productive and actually ruin brass as far as using it in standard dies.
trust me on that. loose primer pockets are as a rule caused by pressure. it would be unusual that it would occur after just 1 firing
unless it was an excessive ammount. id be double checking the load to make sure that wasent an issue. pressure can also show up
more in some brands of brass than with others. the pressure is there but some brass can handle it better. you usually get what you pay for.

I have always had to turn necks factory chamber or not. Only about .002 thou at most and the rifle shot like crap until I turned them. An easy way to check if you need to turn is to smoke the neck and chamber a round. With no powder or primer of course. If the necks thick it should leave shiney marks on the neck.

If you neck 308 down to 260 you may need to reduce your load some. By necking down you have reduced the space inside the case and the load for 260 brass is now to hot for the necked down brass. The flip side is not as bad but when necking up 243 brass you may also have to adjust your load. Other than just cleaning up the neck a little when shooting a factory chamber you shouldn't have to turn even necked down brass. Now making brass out of something totally different like 260 out of 30-06 brass where the wall of the '06 is now the neck of the 260 will require neck turning. It is also a real PITA

Stomp, I am hoping you meant .002.

Yes I did.

The only 308 brass that I use and have necked down has been lake city match stuff I know that stuff is thicker than your average Winchester or Remington stuff and may explain why I have to turn my necks.

I preffered the 243 size up method until I got the real stuff.

Im lost. So when I tried last time to neck down 308 to 260 I did it just like I stated in my first post. The load that I made was no where near max as I was loading for my 13 year old son. I dont recall the exact load as a scapped it because I had so many problems. The brass was once fired Hornady brass. I didnt notice any pressure signs nor was the bolt hard to open. like I stated before the primer pockets would hardly hold the new primers. I didnt try to resize anymore as I was able to get my hands on 260 brass. I havent had any problems since.

Now Im asking because I got a 260AI barrel and tons of 308 match brass.... I guess I dont understand the whole process... Im sorry of this is a dumb question.... I dont shoot bench but I do like to make accurate and most importantly safe ammo. This is also my first time ever having to fire form brass....

Ryan

Now we have more info. The hornady brass may have been a little soft which would be why the primer pockets loosened up or the primers you used a hair smaller than what the original ones were. The LC match brass should work fine as that is what i use in my 260. It would seem that stomp has a tight neck or is just cleaning up his necks. The closer you can get to a 3-4 thousandths total clearance the less you will work your brass and the longer it will last. For hunting you would want a little more clearance so you don't have feed problems. A good way to find out if you have enough clearance is take a loaded round and measure the OD on the neck and do the same with a fired round before sizing. Ideally there should be 3-4 thousandths difference. If you have a larger difference that is fine. A good example would be my Grendel. It has .009 clearance or .0045 on any side of the neck on loaded rounds. I have made brass for it from 7.62x39 brass without turning the necks. It all depends on YOUR chamber.

I used 243 Lapua brass to form into 260, until Lapua started making 260. Now I can't find any of that, so back to the 243 brass. Go figure.

I have a box of Lapua on order so when it gets here I will be using that. I ended up necking up Federal 243 brass. I didnt have any problems getting it to resize and it looks great so far. I have about 20 loaded up and ready to go out and fireform them into AIs. Its just been to darn cold for me to get out. It was -24 day before yesterday, Im not shooting it that....