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Thread: .308 to 7mm sizing die

  1. #1

    .308 to 7mm sizing die

    Hi

    I need to resize the necks on some .308 brass down to 7mm and 6.5mm

    What are the best dies to use and where can I get the dies? I currently use a standard press

  2. #2
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    This is to make 7mm-08 and 260 Remington?

    In practice it is just a case of putting your 308 case through your standard 7mm-08 die with the neck and body adequately lubricated. Now you COULD also just put the 308 case directly through your standard 260 Remington die. Me I'd try maybe going down to 7mm and then 6.5mm.

    The only thing that I would be concerned with, and I've no experience of these calibres, is if in doing so you cause headspace issues with the now re-sized brass cases. The very last thing that you want to do is somehow set the shoulder back so that, unknown until you fire it, you have created a headspace proble.

    I'd also be very wary of EVER making both 7mm-08 and 260 Remington from 308 brass where both sizes of cartridge will bear the same identical headstamp. At best it is turning up to stalk with a 260 rifle and 7mm-08 ammunition. A worst it is an accident waiting to happen in not realising that you've got the wrong ammunition and using it through the "wrong" rifle.

    Sometimes economy measures aren't always best!
    Last edited by enfieldspares; 01-01-2013 at 23:48.

  3. #3
    mildot,

    ES is pretty close. For the 7mm-08, you can run .308 brass through a 7mm-08 seating die (with the seater plug removed). Then trim, run through the Full Length die and (if necessary, which is more than likely) neck turn to remove the probably "doughnut" formed from the .308 case shoulder now being part of the 7mm-08 neck. Using the seating die, you'll need to leave the shoulder on the first formed case a bit "proud", and let the FL die set the shoulder for headspacing. The key is using the seating die to get the shoulder moved back/down close enough, and performing the majority of the swaging of the neck down to size. Once you're close the FL die will handle any slight dressing up of the case's final dimensions. Once you have a case that chambers in your rifle with an ever-so-slight resistance as the bolt closes, take that case and use it to set up the shoulder datum on the seating die. Now you can run all you cases through the seating die for the first forming stage, and have minimal working of the case by the FL die.

    For the 6.5mm, you will have to go in steps (as ES mentioned). Pushing the shoulder back and swaging the brass down from .308 to .264 in one step is just too much (IMHO). Much easier to form to 7mm-08 and then push to 6.5mm, using the same method of seating die, then FL die). Then trim, neck turn (you will have to do this with .308 to 6.5mm formed brass), and finally anneal. You'll need to anneal, as you will have significantly work hardened the brass at this point.

    Of Note: .308 brass varies widely in thickness and hardness. So regardless of what steps you take, brand, make and lots of brass will cause for some experimenting and some lost cases (if you want 100 formed cases, you're best of starting with 150 parent cases, as some will be lost).

    Of Note: The use of a good lubricant can drastically lower the number of cases lost in the forming process. I would recommend Imperial case forming/sizing wax or STOS for forming cases. I have lost cases using Hornady One Shot and other case sizing lubes, and when switching to Imperial, the issues go away.

    I'll try and get some pics posted of basic case forming, as a few have mentioned an interest in the process (and I have a bunch of the brass in various stages sitting on my cluttered workbench right now).

    As far as segregating cases formed from .308: aside from disciplined labelling of your ammunition, the use of colored permanent makers on the case heads helps visually. Red on the 7mm ones, blue on the .260/6.5mm. It'll rub off after a while (and in the tumbler), but it's easy enough to reapply.
    Last edited by MarinePMI; 02-01-2013 at 12:57.

  4. #4
    Cheers guys some great info. i hadnt thought of using the seating die to start off with.

    I usually use a spray lube for general sizing but i do have a tub of imperial.

    Pics would certainly be usefull.

    Cheers
    M

  5. #5
    What an interesting post and very helpful and informative answers, - Never needed to do this, but if I ever do then I now know how..

  6. #6
    Quote Originally Posted by enfieldspares View Post
    This is to make 7mm-08 and 260 Remington?

    In practice it is just a case of putting your 308 case through your standard 7mm-08 die with the neck and body adequately lubricated. Now you COULD also just put the 308 case directly through your standard 260 Remington die. Me I'd try maybe going down to 7mm and then 6.5mm.

    The only thing that I would be concerned with, and I've no experience of these calibres, is if in doing so you cause headspace issues with the now re-sized brass cases. The very last thing that you want to do is somehow set the shoulder back so that, unknown until you fire it, you have created a headspace proble.

    I'd also be very wary of EVER making both 7mm-08 and 260 Remington from 308 brass where both sizes of cartridge will bear the same identical headstamp. At best it is turning up to stalk with a 260 rifle and 7mm-08 ammunition. A worst it is an accident waiting to happen in not realising that you've got the wrong ammunition and using it through the "wrong" rifle.

    Sometimes economy measures aren't always best!
    Going from .308 to .260 left me with the necks too thick so it wouldn't chamber with a seated bullet.

    Likely you'll need a reamer but of course you could just buy ready made brass - I'm also a fan of having headstamps that say what they mean.
    Having .260 with .308 headstamps on the range isn't worth the risk for me.

  7. #7
    Quote Originally Posted by mildot View Post
    Hi

    I need to resize the necks on some .308 brass down to 7mm and 6.5mm

    What are the best dies to use and where can I get the dies? I currently use a standard press
    I've got a full series of RCBS .260, 7mm-08, and .308 dies for case-forming 'reference' cases. The key is to use a series of intermediate steps to reduce excessive working (those dreadful chattering/squeaking/scraping noises when friction takes control) so use the seating die of each set to help the process. I used a .270 neck expander in the process too ... so you need the same make of dies for component switching.... before you start.

    It's very difficult to reduce a .308 'drawn' neck to .264 diameter because of the residual volume of brass in the smaller calibre. The 'doughnut' mentioned mostly forms on the inside of the neck, so internal reaming is often needed more than outside neck turning. In addition, you get a tapered neck section (a quasi-shoulder of .308 on the 7mm-08 neck, and something midway between .308 & 7mm-08 on the .260 neck ... if you manage to get this far without bulging the neck or 'cocking' it off-centre). The reformed case won't chamber easily with this.

    The original case is unsupported during reforming, so it's easy to misalign the neck. You'll also have the original 'bite-mark' or deep crease permanently ironed into the shoulder of the reformed case. The .260 Rem & 7mm-08 dies only work and reform the neck, not the original shoulder junction, so this ring will stay, and look unsightly. It may not disappear even after the reformed case is fired.

    The excess brass is a problem. Being a bit ambitious ....... using 8x57 cases I've formed 7x57 (relocating the shoulder), then continued to form .257 Roberts using a 6.5mm die for the final necking.... (several sets of dies needed here of course). With an outside neck diameter for the 6.5mm (about .296") the inside neck diameter was so tight that it took some force to get the .257 bullet in. That would have expanded the outer neck to the point where it wouldn't chamber in a .257.... if I had one to try it in. If I'd continued I could maybe have got to 5.6x57 RWS which is notorious for it's thick neck. Stag1933 knows all about this cartridge I think.

    I think .308 to 7mm-08 is feasible, but it would be best to use .243 to form .260. Both parent cases are plentiful so IMO that's the easiest route,
    If I'm going to be accused of it then it's just as well I did it.

  8. #8
    Sinistral,

    IIRC, the .243 case would leave a .260 a tad short (though it probably wouldn't matter).

    As to the thick necks, as mentioned, neck turning is needed. For the cases you formed from 8x57, down to 6.5mm, you'll definitely need an expansion die. These can be had from Sinclair (at least that's where mine came from), and hold a tapered mandrel for expanding the inside diameter of the case to nominal dimensions, so that neck turning can be done on the outside. This same tapered mandrel is what is used in their neck turning tools, but in this case you would use the "T" (tight neck) version of the neck turning mandrel to actually turn the necks (it accounts for the spring back of the brass after running the case over the "regular" mandrel in the expansion die).

    As to the crease, ironed into the shoulder, that is not always the case (no pun intended). This is often a result (in my experience) due to the annealing and thickness of the brass itself. Case in point:

    When forming 6.5 Creedmoor from anything other than Remington cases, a wrinkle occurs, as well as the base of the case becoming swollen (requiring an additional step the using a .308 small base die to bring that back into spec). Most times, cases other than Remington Brand, will buckle at the shoulder junction, as the transition from .308 to 6.5mm Creedmoor is just moving too much brass at once (neck, shoulder and shoulder angle, all being changed at once). The difference is the thickness of the cases. Remington's are known for their thin case walls, thus allowing greater case capacity (that some rave about). Annealing does not solve the problem (actually, it makes it worse). Forming down, to a drastically smaller diameter must be done in steps (as you have stated), and often requires annealing along the way in very severe forming (17 AH comes to mind). To go from .308 to 6.5mm, a cut down 7mm-08 die helps greatly. Since the 7mm-08 and .308 share the same shoulder angle, but with the 7mm-08 being farther down/back it allows just the necking down and shoulder to be moved slightly back. With a 6.5 CM seating die, the shoulder angle is then change and the neck further reduced. Once trimmed to length and neck turned to remove the excess brass, annealing and FL sizing is in order.


    I'm sure that you, Sinistral, are aware of most of this, I just merely addressed it to you as way to convey additional data points to the discussion. I did not intend to lecture you on forming (you obviously have some experience in the matter.) and apologize if it comes across that way.

  9. #9
    I was thinking and therefore have plenty of .243 for the .260 and use the .308 for teh 7mm.

    I have to neck turn my .243 brass for my night neck .243Ack Imp so thats not going to be a problem. I need to buy the inside neck reamer anyway for the .243AI just incase so i might aswell get one for the other cals too.

    As for having different stamps on the case heads isnt a problem, as i can tell the difference between my.243, .260 and 7mm bullets/neck size. Plus always keep them in different boxes and seperate from other case.

    There are some good points to look out for and to be aware of.

    Cheers guys

  10. #10
    Hhmm, so I guess forming 243 from 308 in one hit and using 'out the die' shouldn't be done then. Shame, my most accurate loads are resized 308's lol. I'm guessing that the thicker neck (.277") helps in my slack chamber (.2795" at the throat)
    im not running hot loads, in fact, 24.5gr of h4895 under a 70gr smk is pretty darned slow for a 243, but it's a handy 100yd range day load

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