Lee neck sizing die for same caliber but different cartridge

[tmd16556]

I generally like Lee dies and have no problems with them, but I did finally find the one that they just got wrong: the 7.5 MAS sizing die. I’m pretty sure it’s just a 300 Savage or 308 die with slight modifications by the amount it oversizes brass.

I only have one rifle in the cartridge (MAS 36), so neck sizing is a good idea anyway. My thought was that I could use a collet neck sizing die from another cartridge. The Hornady manual case drawings show the same neck outer size for 308, 30-06, and 300 Savage. I assume if I set the height right it should work. I’m using 0.308 bullets anyway so neck tension should be fine. The base fit in my 30-06 neck sizer so it should be possible. I did realize as I was writing this that the length of the 30-06 die may be a problem with a 9 mm length difference, but a 308 should be easy to get too.

Are There any problems I’m missing here? In the longer run I’ll probably end up getting the RCBS sizing die, but it may take a while before my stash of new PPU brass needs that much sizing for a low-volume shooter of a rifle.

 

[AJC1]

Maybe a mosen die would be a better fit ????

 

[FROGO207]

I would opine that you already spent good money with Lee. I would call them and talk to sombody about your problem. It is possible you ended up with a mismarked or miscut sizing die and they will make you happy with your purchase. I had a friend that had a 243 die that was actually cut to be a 22-250. He sent it back and they sent the correct die.

 

[FLIGHT762]

What do you mean by "oversizing the brass"? Do you mean it is shoving the case shoulder too far back.

An easy thing to do is to take a comparator measurement off of the shoulder of the fired cases and adjust your F/L sizing die to only size the case shoulder back to minus .002" from the fired cases. By doing that, your brass will last a long time. Just as long as neck only sizing.

Do you own or use a comparator?

 

[tmd16556]

I’ve looked up the Lee die issue. It’s a known issue (that I didn’t know when buying them). The body is too small and cases feel close to stuck. I suspect they work for fireformed converted brass but not the real thing. 7.5 MAS has an unusual head size but really normal neck size.

I do think the Mosin factory crimp die is the same for both, so I might play with that too.

 

[rdnktrkr]

I would contact Lee and see what they say about your concerns, What about other die manufactures? Do they also have a known problem oversizing brass? Are there any gunsmiths that have a reamer for that caliber that can "finish" ream your die? I've had good luck with my Lee dies for milsurp cartridges.

 

[FLIGHT762]

Before buying another die, try backing off the F/L die a 1/2 turn or more from the shell holder where the die will size enough of the neck to hold a bullet, but not size the case body all the way down. you could likely back off quite a bit. That may work for you.

 

[AJC1]

I would contact Lee and see what they say about your concerns, What about other die manufactures? Do they also have a known problem oversizing brass? Are there any gunsmiths that have a reamer for that caliber that can "finish" ream your die? I've had good luck with my Lee dies for milsurp cartridges.

I don't think a reamer would survive a factory die that has already been threw heat treat. For the cost of a reamer you could get a custom die....

 

[SingleActionAndrew]

As someone who has a set of these dies but hasn't used them yet, very curious and appreciating your question. I have a good deal of new manufacture PPU brass too

 

[Show Me]

Going with the title, the collet neck sizing dies are operated by a specific distance from bottom of die to top of shellholder. This one lm holding is .308 and you can't use it for 30 06 or a 7.62x39.
That is if I'm picking up what's being layed down.
The original problem is with the full length sizer sizing the brass too much? Have we measured the diameter of the fired brass and compared to measurements in a reloading manual .
I have a popular brand .308 barrel with a large chamber that caused excessive die handle pressure to resize. Measurements proved the problem. Swapped barrels to end that.
I'm just flapping my jaws at the lack of better clues. Love a mystery

 

[plumberroy]

I have a 30 caliber universal die set Saeco made them neck sizes punches out the primer and a bullet seating die

 

[tmd16556]

I did remember I have a plan C option. I forgot about the ancient Belding and Mull neck sizers I have. They are older than the 7.5 MAS cartridge design but would work and don’t depend on cartridge length.
I‘ll check with Lee on the die. It’s not urgent, so it’ll go on the roundtoit list.

 

[BJung]

I tried resizing a 7.7 Arisaka case neck using a Mosin Nagant die. It didn't work because the should was different.

 

[csjavi]

Going with the title, the collet neck sizing dies are operated by a specific distance from bottom of die to top of shellholder. This one lm holding is .308 and you can't use it for 30 06 or a 7.62x39.

Yes, Lee neck sizing dies require a certain length to work. However, you can shorten a longer neck sizing die to the correct length pretty easily. You just have to make sure your cut is square. You may also need to cut the mandrel/decapping rod. A separate decapper is then required. You can also use washers or something similar to make a shorter neck sizing die the correct length. The washers will sit on the shell holder enveloping the base of the case. That will be a bit of a slower process.

 

[Random 8]

7.5x54 MAS has some peculiarities. The chambers tend to be cut generously. The brass I have seen is very thick in the neck and base. These translate into difficult sizing.

There is difficulty in using a different caliber collet die for your 7.5 MAS as the Lee dies are length specific, and also need a cartridge of correct base diameter. 7.5 Swiss WILL work for 7.5 MAS. 6.5Swedish WILL work for 6.5 Jap. I know these 2 from personal experience.

I would simply back off your FL die up to 2 full turns. You only need to size half of the neck and this should barely graze the shoulders and body.