338 lapua pressure? HELP PLEASE

Discussion in 'Reloading' started by MTDOGGER, Jun 9, 2011.

  1. MTDOGGER

    MTDOGGER <strong>SPONSOR</strong>

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    I just got a 338 lapua with the tac 338 action, 28 inch rock barrel and ive been working up loads for it and every load i try i get a ejector mark. I cant figure it out. Im using fed 215 and started out with 87 gr of retumbo and went up to 93 with the same ejector mark. primers are not flat, and no hard bolt lift either. ive also tried h1000 and started with 87 gr and went to 90 and got the same mark. I just bought another 100 brass thinking maybe the lapua brass that i had was soft but got the same result. Im shooting the 300gr SMK and seated them from 20 thousanths off to just touching the lans. I dont no what the heck is the problem. Has anyone else had this issue with the stiller action or could it be something else. Any help would be appreciated and thanks in advance
     
  2. J E Custom

    J E Custom Well-Known Member

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    When seating close to or touching the lands pressure will go dramatically.

    Check a fired case and see if a bullet will go in the neck,(It should have 2 or 3 thousandths
    clearance. If not, The necks need to be trimed.(They are longer than the neck chamber)

    I would recomend backing off a minimum of 20 0r 30 thousandths and working up to max loads
    slowly.

    I dont think it is Head space but it should be checked.

    Let us know what you find.

    J E CUSTOM
     

  3. MTDOGGER

    MTDOGGER <strong>SPONSOR</strong>

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    I just tried that and the bullet did go into the fired case. I called the guy that built the rifle and he told me that stiller actions do that and it's nothing to worry about, in fact thats how he counts how many times he's fired the brass. now im not a no it all when it comes to reloading but its always been my assumption when i see ejector marks then theirs pressure and it isint right. This is driving me crazy its a new gun that i waited for to be built and bought the best equipment i could afford and now ive already got this @$^#$^$ problem.
     
  4. rscott5028

    rscott5028 Well-Known Member

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    Might the chamber be too slick and/or the cases too clean and/or some lube left on them or in the chamber?
     
  5. JOSE A. MARINE

    JOSE A. MARINE Well-Known Member

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    is the ejector too long?

    i once had this issue with a savage in 6.5-284....

    Joe from mexico.
     
  6. Bart B

    Bart B Well-Known Member

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    Tests done years ago at the H.P. White Laboratory and the NRA showed peak pressure increased only about 3 to 5 percent when bullet jump to the lands went from 20 thousandths or so down to zero. Same thing was observed by folks using Oehler's strain gage pressure system. That means it goes from 50,000 CUP (or 58,000 PSI) up to a max of 52,500 CUP (60,900 PSI). That's not a dramatic pressure increase. My own crude tests measuring pressure ring diameters show about the same difference. And no brass extruded back into bolt face holes.

    Most cartridge brass starts to extrude back into the bolt face cutouts at around 65,000 CUP (80,600 PSI). It only happens when pressure inside the case gets above those numbers.

    I've asked several powder companies about brass starting to extrude back into bolt face ejector cutouts and they all say the same thing. The load's too high in peak pressure for safety. One's gone way past the normal and SAAMI limits for safety. The brass case is the weakest link in containing pressure and is the best indicator of pressure signs in the unsafe range.

    Too much bullet extraction force to get the bullet out of the case typicaly causes much higher pressure increases than zero bullet jump to the lands. I'd measure how much force it takes to pull a seated bullet from a reloaded case. If it's more than 40 to 50 pounds, I'd be suspect of that being the reason for brass extruding into bolt face holes. I've seen this happen with sizing dies make fired case mouths too small for the bullet diameter.
     
  7. Edd

    Edd Well-Known Member

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    I'd be interested in seeing some data showing that the tension from a .015" inch ring of brass gripping the bullet can dramatically raise the pressure.
     
  8. aroshtr

    aroshtr Well-Known Member

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    Im no expert either, but one step I have tried in the past is to try factory ammo and see if it replicates the problem with reloaded ammo. It would be my opinion that, if a factory round gives the same ejector mark, then you may not have a problem. If I had to pick a source of the problem, I would think that the chamber could be too polished causing the brass to be forced back into the bolt face too hard.

    Hope this helps

    Joel
     
  9. rscott5028

    rscott5028 Well-Known Member

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    I tend to agree except that if factory ammo does the same thing, you may still have a problem. Rather it's just not necessarily the ammo's fault.
     
  10. J E Custom

    J E Custom Well-Known Member

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    After all of the comments I would check out the ejector. It sounds like it is to long or the retaining
    slot is not long enough to let it move out of the way when the case comes backward.

    In order to head space a cartrige correctly you "must" remove the ejector first to prevent false
    readings with the head space gauge.

    If this is not done you could end up with excessive head space and high impact velocities with the
    case head striking the bolt face.

    I would have trouble believing that this is normal. The ejector hole is drilled deep enough to allow
    the ejector to recede just below the bolt face but not far enough to allow it to much travel creating
    a crater for the brass to flow into.

    When re facing the bolt face you must check the plunger length to make sure it will retract enough.

    So if you are getting a ejector mark that is bright(The case is shaved while extracting) there is
    pressure from some problem because the brass should not extrude into the ejector hole with normal
    pressures.

    If there is a dimple in the case head then there is a good chance that the head space is to much or
    the ejector is not set up correctly as long as pressure is not excessive. and shooting factory ammo
    tells me that pressure is not the problem as long as everything else is correct.

    Don't give up looking, because something is just not right. and just because it is a custom action
    does not automatically rule out any possibility that there is not something wrong with it.

    It is hard to trouble shoot a problem without actually looking at it (Kind of like when your wife
    tells you the car is making a funny noise).

    I hope some of this gives you some ideas.

    J E CUSTOM
     
  11. Bart B

    Bart B Well-Known Member

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    Reload some ammo two different ways using a full length sizing die with an expander ball. Pay particular attention to the force needed to seat bullets in each method.

    Load two rounds the way you normally do.

    Load two more rounds the same way, but don't use an expander ball on the decapping stem. If you have to use one, use one a couple calibers smaller so it won't expand the sized down case neck. You might want to use an Easy Out turned clockwise to debur the case mouth so bullets will seat without too much trouble.

    Shoot both rounds of each type noting pressure signs on each. Chronograph them to see the difference.
     
  12. Edd

    Edd Well-Known Member

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    I said I would be interested in seeing some data. I'm not interested in an R&D project. I already have more projects than I have time.
     
  13. Bart B

    Bart B Well-Known Member

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    Here's some facts; you may consider it data. Or heresay. Doesn't matter to me.

    I suggested to two people years ago they should lap the necks out of their .308 Win. full length sizing dies to a few thousandths less than a loaded round neck diameter so expander balls were not needed. They instead just removed the decapping pin, full length sized some cases then loaded them normally. Both noted bullets seated harder. When fired, case head brass had extruded back into ejector holes in the bolt face. Their normal reloads didn't. Pressure was noticably higher.

    I and others who seated Lake City match ammo bullets a couple thousandths deeper to crack the asphultum seal to get more uniform release force noted they needed another minute or two up on the sights for zeroing at 600 yards. While the cracked rounds had less elevation spread from more uniform muzzle velocity and therefore were more accurate, it was low enough below normal ammo zeros to make a difference. Pressure ring diameters from new case to fired dimensions was greater by a few ten thousandths with regular ammo; rounds with their bullets reseated just enough to break the seal had less pressure.

    Someone mentioned that few thousandths extra jump made up the difference. So we pulled some "seal cracked" round's bullets back out a bit then reseated them to standard length. They shot the same as those seated a few thousandths deeper.

    While not laboratory-grade testing and measurement, the difference was noticable to folks holding the highest NRA classifications for competition.