Necking down 408 cheytac to .338
- Thread starter dj300ack
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trebark
Well-Known Member
PM 'Kevin Cram' of www.montourcountyrifles.com He shoots a 338-408.
Joel Russo
Well-Known Member
If you are starting with the .408 case, simply go to .375, then to .338.
RDM416
Well-Known Member
Kirby Allen (Fiftydriver) has a wildcat called the 338 Allen Mag that is a 338-408. He has formed brass available with a 338 AM headstamp. I don't remember what the price he quoted me was, but it seemed reasonable. He is currently building a 338 AM for me. I am just going to buy 100 rounds of his formed brass and be done with that part.
djtjr
Well-Known Member
Get the Jamison 375ct brass then neck down from there in one but preferably 2 or even 3 equally spaced steps
Make sure the reamer the rifle is being chambered with is setup to use neck thickness from the 408 brass formed to 338 and not 375. If your reducing the neck .070 and want to use three steps it will be about .025 per step with spring back it will get you close. Do you plan to anneal at each step or neck turn/ream at all? I would anneal at least the last step before you final size to load.
My reamer Is ground with a .365 neck. I should have to turn a little off the necks. I will be necking the 408 brass down. I was going to neck brass down and turn necks and then anneal. I have a junk barrel I'm going to chamber for forming brass. I 'm planning on creating a false shoulder on the neck to have crush fit in the blow out barrel, and use cream of wheat to form with. I turn my necks on my lathe. I turn out a mandrel the dia. of bullet and then press brass up on the mandrel with a fixture, I made for the tail stock. I've found that if I anneal before I turn necks. Some of the brass will slip on mandrel while turning necks. If I anneal after neck turning I have no slipping issues.
Joel Russo
Well-Known Member
Before I started using the brass we had custom made for this caliber, I prepped thousands of pieces of the .408 Jamison stuff...
Don't make it anymore difficult than it has to be.
Like I said before, go from .408 to .375, then to .338. Use your .338 mandrel, then neck turn. With the Jamison brass and a .365 nk, you will need to turn the brass to about .012" neck thickness. I had thousands of pieces of Lot 210 from Jamison and .012" worked fine with my .365 nk.
Anneal after neck turning. Forget the cream of wheat routine, not a good Idea..
Just fire form while doing load development.
Don't make it anymore difficult than it has to be.
Like I said before, go from .408 to .375, then to .338. Use your .338 mandrel, then neck turn. With the Jamison brass and a .365 nk, you will need to turn the brass to about .012" neck thickness. I had thousands of pieces of Lot 210 from Jamison and .012" worked fine with my .365 nk.
Anneal after neck turning. Forget the cream of wheat routine, not a good Idea..
Just fire form while doing load development.
Joel Russo
Well-Known Member
If you run into any snags, get a hold of me and I'll help you out.
NZ Longranger
Well-Known Member
Whether there's a need to fire form depends on your version of the 338/408. If its just simply a necked down 375 or 408 with the same or similar shoulder angle in the same position, then your first shot with a projectile is your fire forming. If you're running a much sharper shoulder pushed forward from the original position as Kirby does in his 338AM and we do in the 338 Lunatic, then it certainly is worth fireforming, or just buy Kirby's brass as someone else suggested. Joel, I'm not sure about your shoulder angle and position?
We fireform by using any fast burning powder surplus to requirements with half a 4x2 cleaning patch pushed down on top to hold the powder in position. With the current powder we're using up, Viht N320, we use 45gns. We have a fireforming barrel chambered up in all our calibers, so we can run them through without worrying about cooking a good barrel. We have pressure testing equipment hooked up to our fireforming barrels to work out our fireforming loads. The other fillers you hear talked about for this project can produce very erratic and potentially dangerous results. You can get huge pressure spikes with fireforming loads of fast burning powder if you're not paying attention. If you get any of the conventional pressure signs such as any brass flow at all - back off! You are way too hot with any of the 408 brass, especially the older TTI stuff no longer available. Even the Jamieson stuff shows no pressure signs till well over 70,000psi.
We have found the half patch jammed on top of the powder to be consistent and safe.
And you're quite right about when you should neck turn. Ideally after you've finished all your necking down and the brass is work hardened. Annealed and soft brass doesn't turn as well and is inclined to gall on the mandrel. The exception to this is some wildcats that need fireforming to position the neck correctly before you can turn them. Some will split shoulders on fireforming if not annealed first, so we anneal, fireform, then turn. The fireforming work hardens the brass sufficiently to allow good neckturning.
That's our take on it anyway for what its worth!
Greg
We fireform by using any fast burning powder surplus to requirements with half a 4x2 cleaning patch pushed down on top to hold the powder in position. With the current powder we're using up, Viht N320, we use 45gns. We have a fireforming barrel chambered up in all our calibers, so we can run them through without worrying about cooking a good barrel. We have pressure testing equipment hooked up to our fireforming barrels to work out our fireforming loads. The other fillers you hear talked about for this project can produce very erratic and potentially dangerous results. You can get huge pressure spikes with fireforming loads of fast burning powder if you're not paying attention. If you get any of the conventional pressure signs such as any brass flow at all - back off! You are way too hot with any of the 408 brass, especially the older TTI stuff no longer available. Even the Jamieson stuff shows no pressure signs till well over 70,000psi.
We have found the half patch jammed on top of the powder to be consistent and safe.
And you're quite right about when you should neck turn. Ideally after you've finished all your necking down and the brass is work hardened. Annealed and soft brass doesn't turn as well and is inclined to gall on the mandrel. The exception to this is some wildcats that need fireforming to position the neck correctly before you can turn them. Some will split shoulders on fireforming if not annealed first, so we anneal, fireform, then turn. The fireforming work hardens the brass sufficiently to allow good neckturning.
That's our take on it anyway for what its worth!
Greg
Joel Russo
Well-Known Member
The case I'm using for the .338-.408 is an improved version, both shoulder angle and body taper.
Before we ordered cases that were made to our specifications, I was fire forming brass.
There are many different opinions about fireforming brass. What I speak of is what I have proven to work for me. I shoot mostly wildcat cartridges in all different calibers. it is not uncommon for me to show up at a 1,000 yard or mile match and fireform brass while competing. I have found that brass is no longer "competitive" after three to four firings, and the most "competitive" in the first two. Just my .02, and your mileage may vary...
Before we ordered cases that were made to our specifications, I was fire forming brass.
There are many different opinions about fireforming brass. What I speak of is what I have proven to work for me. I shoot mostly wildcat cartridges in all different calibers. it is not uncommon for me to show up at a 1,000 yard or mile match and fireform brass while competing. I have found that brass is no longer "competitive" after three to four firings, and the most "competitive" in the first two. Just my .02, and your mileage may vary...
