.308 cases to 7.92x33

NavyCuda

NavyCuda

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Ok so I've been trying to do a fair amount of reading on converting 308 cases to 8mm kurz.

From what I have read 308 is one of the more difficult cases to form. I have noticed in pictures that the formed 308 cases have a very noticeable radius on the case to neck taper. On original kurz brass the taper has "no" radius at all.

Is that radius part of the die, or a result of the brass naturally resisting the forming? If this is the case is there any way to combat that effect? For example I watched "how-it's-made" where they used frozen soapy water inside the trumpet tubes to prevent the brass from collapsing during bending. Would a similar procedure produce a more uniform finish?

**special thanks to google images search**
8x33.jpg

German_7.92x33mm_Kurz.jpg
 
woodchopper said:
thats a lot of trimming there. :D

I suspect that the brass is starting to get fairly thick where the new sholder is, How do they look after the fireing them??
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I have no idea, I am still researching if i will make my own cases or buy factory made new cases.

I like the idea of making something myself, but i want to do it right. The extra smoothness there really bothers me...
 
I think Woodchopper is on the right track. I could see how a thick wall would assume more of a curve than a sharp corner, as the outer surface is that much more removed from the centreline. Stress distributions always get more complicated on thick sections.
 
Doubt that the slight radius matters at all. Watch case neck diameter with the bullet seated, make sure there is not going to be an issue with the neck being too large in diameter.
I would be inclined to use .22-250 brass, might end up thinner in the neck area.
 
you will have to turn the necks for sure no matter what parent case you use. for what it is worth 300 savage would be a better parent case, trust me I know as I make 30x44 brass all the time :D
 
It should be ok with a curve instead of a sharp corner. They will get better with the first firing. I make 8mm Mauser out of 30-06 and they are a little rounded the first time through the sizing die. They look exactly like a regular 8mm Mauser brass after they are fired. I haven't noticed any difference in pressures.

Is that a .308 in the pic or is it the camera angle? They look kind of long for .308. Almost like a 30-06. (Just wondering).
 
medicstimpy said:
It should be ok with a curve instead of a sharp corner. They will get better with the first firing. I make 8mm Mauser out of 30-06 and they are a little rounded the first time through the sizing die. They look exactly like a regular 8mm Mauser brass after they are fired. I haven't noticed any difference in pressures.

Is that a .308 in the pic or is it the camera angle? They look kind of long for .308. Almost like a 30-06. (Just wondering).
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Honestly I'm not sure, took me a couple of hours of trying different google searches just to find some of the info I have...
 
fireforming will get rid of the rolled shoulder and make the angles nice and crisp. I think you may be able to use 7.62x39 comercial brass and have a lot less trimming to do. Might make a easier process for you in the long run rather then trimming major amounts of brass off those 308 brass.
 
Marstar had 8mm Kurtz brass at one time, try them. If not, I use 7mm BR. less trimming and works.. I had shot/tried to shoot some reloads using 308, it would not chamber properly. Some one else did the reloading but the problem was the brass thickness at the neck. not a problem with the 7mm BR.
 
NavyCuda said:
....I watched "how-it's-made" where they used frozen soapy water inside the trumpet tubes to prevent the brass from collapsing during bending. Would a similar procedure produce a more uniform finish?
Click to expand...

No-one noticed this?

This is surely not the first time anyone thought of something like that for forming brass, but it's the first time I have seen it. The more soap, the less firm the ice within the cartridge I imagine. Might be hard on the dies and you risk breaking the die if you're careless, or stuck cartridges - but then you just melt the ice! This might be a solution for brass forming that typically results in many lost cartridges, such as 24ga Magtech brass shotshell to 577-450 MH.
 
Andy said:
No-one noticed this?

This is surely not the first time anyone thought of something like that for forming brass, but it's the first time I have seen it. The more soap, the less firm the ice within the cartridge I imagine. Might be hard on the dies and you risk breaking the die if you're careless, or stuck cartridges - but then you just melt the ice! This might be a solution for brass forming that typically results in many lost cartridges, such as 24ga Magtech brass shotshell to 577-450 MH.
Click to expand...

So then I am not crazy to think of this as a suitable idea?

tiriaq said:
Doubt that the slight radius matters at all. Watch case neck diameter with the bullet seated, make sure there is not going to be an issue with the neck being too large in diameter.
I would be inclined to use .22-250 brass, might end up thinner in the neck area.
Click to expand...

Everything I have read states that I must reem out the neck. It is also suggested to full lenth size the case again to ensure proper shape. It seems that in preparing the cases I will have to pay close attention to what I am doing. Once the cases are good enough for service I've read that people get quite a few uses out of them.

yodave said:
you will have to turn the necks for sure no matter what parent case you use. for what it is worth 300 savage would be a better parent case, trust me I know as I make 30x44 brass all the time :D
Click to expand...

This may be true, though once fired commercial .308 cases are available to me and I already have a number of them stored up for use in my m14 or conversion to 8mm kurz. So it is likely that .308 will remain the donor.
 
Check with Hornady, they are now loading the 8mm Kurz. Might be able to get some brass or in the very least some ammo to shoot, then keep the brass.
 
Cappy said:
Check with Hornady, they are now loading the 8mm Kurz. Might be able to get some brass or in the very least some ammo to shoot, then keep the brass.
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Rumor mill: I spoke with a company in the US that said they were no longer allowed to export 7.92x33 cases or bullets. Military Calibre.
 
VERY SIMPLE to make 7.92x33 cases....
Did it for years using .308 cases....
Simply buy the RCBS case forming die set in this caliber, remember to get the inside neck reaming die and reamer, it used to be in the set.... Ohterwise your cases are too thick at the neck and will not chmaber properly in most guns....
Cases made from .308 seem to last forever.... I reloaded mine many times and they were fired FA and took a beating....
John
 
It has been suggested that .308 brass lasts a very long time, I'm not sure how long the factory made stuff lasts, but it is pretty easy to get once fired brass...

So then it would just be the time it takes for me to make the 7.92x33 cases, which I would enjoy.

I'm also thinking seriously about purchasing a setup to swag my own copper jacketed bullets, following the exact design the germans developed. I guess it is worth asking if anyone would be interested in 125 grain FMJ 7.92...
 
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