Jamison 408 Chey Tac brass updates....

Discussion in 'General Discussion' started by Fiftydriver, Dec 4, 2007.

  1. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    TO all,

    I have been working with Jamison International to make me brass for my 338 Allen Magnum. As you know this is based on the 408 Chey Tac case. I am investing in tooling to get preformed, correct headspaced brass for my 338 Allen Magnum and 375 Allen Magnum.

    First however we had to figure out the problems that Jamison was having with their 408 CT cases.

    The first lot of brass I tested nearly a year ago was their original design. it had many problems:

    -Necks way to thick
    -Solid case head to thin
    -Rim thickness to large
    -Primer pocket to large
    -Necks and shoulders had poor annealing

    These cases would loose the primer pockets on the first high pressure firing, literally loose the primer pockets.

    Jamison then changed the alloy they used in their cases but that was about the only change they made as they figured the harder alloy would solve the blown primer situation. They marked these cases with a double star on the case head to tell them from the original lot.

    Unfortuantely, this did little to help the problems that the original cases had and Jamison really took a hit on this poor quality brass.

    As a result, everyone went with TTI cases and soon, the TTI supply ran dry and there is no sign of getting that brass back. To bad because it was great brass.

    Back to Jamison. With all the bad press, Jamison decided they better get their game together so they colaberated with many top minds in the industry to get the cases up to a high standard to compete and offer what we demand in a quality case.

    While I was working with them on testing some prototype solid 338 projectiles, they also asked me to test some of their new cases and offer any input I could to make their brass better.

    My comments to them were:

    -Thin the necks to no more then 13 thou in thickness
    -Increase the thickness of the solid case head, even if case capacity was decreased.
    -Thin the rim thickness to no more then 62 thou.
    -Anneal the neck and shoulder softer.
    -Tighten the primer pockets so they were no larger then 0.2070" in diameter.

    Early this week I received a batch of new cases that they wanted me to test. There were some dramatic improvements but still a couple disappointments, still, they are getting much closer.

    For comparision, the previous lot of 408 CT brass that they sent me for testing lost the primer pockets with a load of 145.0 gr H-50BMG under the 300 gr SMK. Primers literally fell out of the case when they were ejected.

    This time was a bit different. On the first high pressure firing, the primers held. When seating a new primer, the pockets were noticably loosened but still held the primers. On the second and third firing, the primer pockets continued to loosen but still hold primers sufficently to prevent any gas leakage.

    On the fouth firing, the primer fit was looser then I like but the 4th firing was still safe so we went from loosing a primer on the first firing to cases that while the primers loosened , they allowed at least 4 firings at top end pressures.

    I then dropped the load to 142.0 gr H-50BMG, velocity dropped from 3345 fps to 3268 fps. Again, the primer pockets behaved nearly the same, only difference was that one more firing could be had before I felt primer fit was to loose to reuse. This is a bit redused load but still a solid 300 fps more velocity then the next largest 338 magnum in this length barrel(32").

    After seeing this I wanted to compare the new jamison cases to my idea of the gold standard in 408 cases, the TTI hulls.

    Interestingly enough, the Jamison cases and the TTI cases averaged with in 0.1 grain of each other in case capacity. The Jamison cases are nearly 15 grains lighter in weight which tells us the internal dimensions are the same as the TTI but the alloy used is much lighter then the TTI alloy.

    I do not think this is the reason for the loosening primers however.

    The neck thickness issues have been corrected as well with these test cases. All ran from 0.0131" to 0.0135". Compare that to around 0.016" for the old cases. This is still thicker then the TTI cases but only by around 1/2 to 3/4 thou.

    The neck annealing is also much better. On the old Jamison cases, I had to anneal the cases after the second neck down step or I would get crushed necks. With the new cases, they sized down to 338 caliber easily with no annealing. They should be annealed after forming however.

    The solid head thickness has also been increased dramatically. It is now nearly identical to the TTI cases or nearly 40 thou thicker then the old head was. The rim thickness are also right on as none were thicker then 0.060" which functioned perfectly through all my 408 class receivers. The old cases did not allow proper extractor function because of their thicknesses.

    I also noticed that while the alloy in the new Jamison cases is lighter, it also seems to be harder. The reason I say this is because the 145.0 gr load in the TTI cases resulted in slight but noticable ejector marks on the case head.

    The new Jamison cases showed no sign of an extractor mark in any way telling me the case head is hard enough to resist setting back into the ejector hole in the bolt face.

    All bonuses.

    So why do the primer pockets loosen up??

    Of all the things I recommended to Jamison, they did every one except one, tighten the primer pockets. They are still running between 0.2082" to 0.2085" in diameter. I fully believe if the primer pockets would be tightened up to 0.2070" which is slightly tighter then the TTI cases, there would be no problem at all with primer pockets opening.

    The reason I believe this is because the primer pockets loosen up the most in the intital high pressure loading. Then the primers continue to loosen but only slightly.

    In the TTI cases, with this same load, the primer pockets will gradually loosen as the case is fired more and more. Its much more noticable from firing to firing with the TTI cases. Not so with the new Jamison cases, they loosen dramatically on the first firing and then level out after that.

    What this tells me is simply the oversize primer pocket expands a certain amount on the first firing, they stabilizes after that. If the pockets were 1 thou tighter, that intital expansion would be much more limited and case life would dramatically improve.

    I have passed on my findings and opinions to Jamison so we will see if they continue to modify the cases. Until they get the cases where I want, I will be holding my 2000 case order from them but as soon as they get it right, I will place that order and then once those cases are proven up to the challange, I will instantly place another order for 2500 338 AM cases and 2500 375 AM cases.

    I plan on keeping cases in stock at all a times for customers once they get the cases where they need to be as far as quality goes.

    They are working very hard to do this, at least they are putting in great effort to correct the problems they have had with their original design. That tells me they want to send out a quality product. It has taken some time and may still take a bit more time but I fully understand that they want to get it right this time before sending cases out to customers.

    Have to appreciate that.

    More to come.

    Kirby Allen(50)
     
  2. Wild_Bill

    Wild_Bill Well-Known Member

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    Keep us posted

    Thanks Kirby it sounds like some companies actualy listen to the consumers and they dont just say if you want them you get them as they come.

    Keep us posted if you have Allen Mag cases that will help with decisions on making an allen mag or a base Chey Tac case to some.

    Cheers Bill
    Australia
     

  3. Buffalobob

    Buffalobob Writers Guild

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    Low lead content of the alloy to make the brass most likely.
     
  4. joecool

    joecool Well-Known Member

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    Kirby

    Will the neck thickness make any difference in my camber compared to the two star brass I’m using now? Also the rim thickness is the problem I told you I was having ejecting some rounds.

    I notice you are running 145gr of 50-BMG is that for a speed of 3345? I’m using 142gr for 3380 last time I checked after the barrel brake in before the barrel brake in that same load was 3325 does that make any since.

    Anyway once they get it figured out I’ll be getting some brass from you

    Larry
     
  5. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    The neck thickness will be a thou or thou and a half smaller in diameter then the brass you are using now. Will make no real difference, only talking about .5 to .75 thou clearance on both sides of the bullet.

    In fact, your cases may be a bit to tight, if that is the case, you will probably see some pressure drops with the new brass which may allow you to load to where you are with less pressure.

    That is very common to see the velocity shift like you have before and after break in. Before break in, the barrel is somewhat rough, if you want to call a finely polished Lilja barrel rough!!!

    As it breaks in, the bore diameter will increase slightly and the rifling land edges will round slightly, all reducing friction and pressure will drop.

    In a conventional chambering, this may not be as evident, when your putting 142 to 145 grains of powder under a 300 gr bullet, it shows up more obviously. That is sure why you are seeing it.

    ALso, as the throat wears it gets larger in diameter. This allows a bit more blowby around the bullet so some of the powders energy is lost ahead of the bullet. This is why older barrels tend to loose velocity compared to when they were new.

    Make any sense????

    Kirby Allen(50)
     
  6. stephen newberry

    stephen newberry Member

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    408 Jamison new batch

    I've got this guy Johnnysg@optonline.net telling me for 10 months now that he was shipping it to me. Last week he e-mailed saying he has new brass.Is the brass any good???? I'm a man of my word this guy is not.


    Thanks Stephen
     
  7. Boss Hoss

    Boss Hoss Well-Known Member

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    I would like to try one of these rifles but not until the brass situation is completely solved with the users verifing that this has indeed happened.
     
  8. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Stephen,

    I would have to say, I would bet the brass he has is not quailty as they are just now starting to run the lot of brass with all the corrections except the properly speced primer pocket.

    As such, they will survive high pressure loadings but the primer pocket will loosen up quickly. STill, that lot of brass has just been made, I suspect he does not have them because those are the test cases I was set to work with and offer a review back to Jamison.

    Kirby Allen(50)
     
  9. Roll-Yur-Own

    Roll-Yur-Own Well-Known Member

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    Kirby, I have that same Brass that you do. It was hand delivered to me by the CFO of Jamison who happens to live 20 minutes from me.

    In fact, I'm sending some off to Shawn Carlock this week so he can test some in rifles he is building.

    As you know Jamison put brass out several months ago that is isn't fit for the trash heap. The primer pockets looked twisted like a pretzle. That is why they retooled the plant to make better brass.

    Fortunaltely, Jamison has done a lot to make better brass. Unfortunatley, we have been waiting a long time to get it.

    I'm also sending some of my solid 350 grain bullets to some guys for testing on the 375 CT. If you want to test some on your 375 AM, shoot me a PM.
     
  10. stephen newberry

    stephen newberry Member

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    408 brass

    I paided this guy $500.00 by pay-pal back in Feb. 07 I have asked many times that I want my $$$ back. I get the same repley that the brass will be here any day.What can I do????


    Thanks Stephen
     
  11. Roll-Yur-Own

    Roll-Yur-Own Well-Known Member

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    Stephen, I relayed the same info to you as was given to me by Jamison. It's not like everyone around had brass except me. If you wanted your money back I would have gladly sent it.

    I apologise for the delay, but every who needed this brass knows that Jamison has issues with quality and it took some time to get to this point.

    I have many satified customers on this forum who have done business with me. I feel bad that you are not one of them.

    Per your request, I sent you 20 pieces of Brass to try. If you like them I will send the rest. If not I will promptly refund your money. Regardless, I will also send you some of my 375 bullets as a gesture of goodwill.

    Hope you and I can make amends.
     
  12. Boss Hoss

    Boss Hoss Well-Known Member

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    You know the problems with the brass have just about killed my desire to build one of these and I have even discussed it with my Smith but from what I keep reading there are some real problems with getting brass!
     
  13. Black Diamond 408

    Black Diamond 408 Well-Known Member

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    Kirby, and the rest of the "Fire Breathing Dragon" shooters

    I have talked with Marc Jamison about the 408 brass, i gave him the measurements from two other brass makers primer pockets. The best brass ever made was from Horneber in germany. Those pockets were .207 vs .208 or larger from jamison. Marc said he uses the mil spec standard on pockets, .208. He was adament about this. I tried to explain the difference between a 308 case and a 408 case primer pocket but he didnt seem to care at all what i had to say, he wanted my opinon on the brass he sent for me to test, then when i gave him my results,,,,he didnt want to hear it. Everything i told him is what you came up with. I ran some pretty hefty loads through my German brass and no failure.

    I'm sure now that Chey-Tac has brought in the Winchester consultants the brass problem will get fixed. When the added machines get tooled up there will be plenty of brass for the sportsman consumer. Right now all brass is going to Chey-Tac for military contracts.
     
  14. lazylabs

    lazylabs Well-Known Member

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    I can't believe brass is this difficult.... I would think you take a sample of lapua brass, have the composition "proximated" and then form it. It seems the forming part is the easiest. Why has lapua always been so good and the big big US plants so far behind? If it's quanity related then why wouldn't Jamison be able to be follow lapua? It seems many one man shops can master bullet making but not even one small company can duplicate lapua's work? I sent lapua an email asking about 300 RUM brass and they said there wasn't enough interest...... so everyone please email them and ask for another 1,000,000 cases!!!!