Strange high speed from Obermeyer barrel

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by James Jones, Apr 24, 2006.

  1. James Jones

    James Jones Well-Known Member

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    I did some load development for a new 300Win mag I have , it s Sako L691 action barreled with a 25" 1-11 twist Obermeyer barrel. I worked up a load for the 190gr Breger VLD's and ended up with 81grs of H-1000 with a velocity of 3206fps avarage !!! the bullets were seated into the lands .005" and the brass is once fired neck sized Lapua lit by a CCI-BR2 primer.
    Their are no pressure signs on the case at all the primmers took seemingly the same pressure to pop out as any other load and the I even miced the case just above the belt and it showed only .002" expansion over the unfired cases.
    I checked the velocity against two other rifles that have a known velocity and they are the same as when I worked them up. This is a compressed load and the bullets are seated into the lands which to me would think that the pressure would be higher faster.

    I know that some barrels are a little faster than others and that the 5R barrels are a little faster than conventional barrles but damn this seems a little over what it should be , I was hoping for 3000fps.
    This is the only Obermeyer barrel I have ever delt with and to say the least I'm amazed with the speed and the accuracy which the groups for this load are just under 1" at 300yds.

    Anybody have any ideas on what could be causing this.
     
  2. sambo3006

    sambo3006 Well-Known Member

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    Do these bullets have a long bearing surface? That could contribute to high pressures along with seating into the rifling. If you are getting that high of vlocity, your pressures almost assuredly have to be high as well. Hogdon lists 81 gr of H1000 as max with 180 gr and 79 gr as max for 200 gr. so you are a grain or so above the book max for a 190 gr loaded to SAAMI length. Of course, every bullet will produce different pressures based on shape, but if I had to guess, I would say again that your pressures are probably too high. I would think that 3000 to maybe 3100 fps would be achievable with your bullet in that cartridge at safe pressures.
    I'm sure you will get some more input from others who have more knowledge than me, but hope this helps.
     

  3. James Jones

    James Jones Well-Known Member

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    Sambo3006 , thats exactly what I was thinking the Berger VLD's don't have to long of a bearing surface less then a SMK , the jackets are thiner and I'm pretty sure that the lead is softer.
    I would surely assume that I'm way over pressure with this velocity but I'm not getting any signs out of it at all.

    I don't know it has me baffeled , I'm gonna back off a full grain as the accuracy and ES was about the same just a little slower, but still alot faster than expected
     
  4. Jimm

    Jimm Writers Guild

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    Dang JD,

    The lottery falls in your lap and you are ........complaining /ubbthreads/images/graemlins/laugh.gif

    Take it like it comes , oh yeah , say your thanks when it goes your way ! /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/laugh.gif

    Jim B.
     
  5. Meister

    Meister Well-Known Member

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    5R strikes again... Gotta love those Obermeyer sticks!
     
  6. Carbonman

    Carbonman Active Member

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    Boots Obermeyer barrel's have as small as a .299 bore and .3075 groove. The tight bores really squirt them out.
     
  7. James Jones

    James Jones Well-Known Member

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    I know that a tighter bore can help with the velocity but man that seems a little high

    DOn't get me wrong , I'm not complaining about the extra speed , it just has me concerned , the physics say that the pressure has to be higher, but thier are no signs of it

    I'm gonna back down the load and test several other bullets soon so see if the slugs could be the issue
     
  8. jwp475

    jwp475 Well-Known Member

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    An action that has been trued and the lugs lapped with custum chambered barrel can shoot a higher pressure load without showing conventional pressure signs.
     
  9. James Jones

    James Jones Well-Known Member

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    I have seen where a realy tight chamber will not show typical pressure signs until its dangerously high. But even in a factory gun I don't think that these loads would be so high that it would cause major pressure problems , and like I stated even the listed book loads were way faster than listed in the book. I know that the case volume varies from one to another but I seriously doubt that the Lapua cases are that much thicker that it would cause perssure so high as to warrent velocities this high especialy at book listed powder charges.

    Typicaly I would think that the best indicator of pressure would be the case expansion followed by shinney spots on the case head and primer cratering. I also know that when one experiances velocities higher than what the load books list that your typicaly over the SAMMI spec on pressure which is another quick way that alot of guys guage pressure by.
    All of these reasons are why I'm concerned about these velocities. My final test is going to be case life , I'm gonna take one case and fire it by itself and measure the case streching and when the primmer pocket gets loose. I'll be running this test this afternoon. guaging fromother Lapua cased rounds I have loaded for (308,30-06,243) I'm ecpecting to get at least 8 shots before the primmers start to get loose and typicaly 3-4 shots before they need trimming when neck sized.
     
  10. abinok

    abinok Writers Guild

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    This isn't THAT big a deal.
    Most barrels will drive the 190SMK to 3050 without complaints, add another 75fps for the softer jacket and reduced bearing surface of the berger VLD gets you to 3125... and weve all seen 75fps differance from barrel to barrel, especially barrels known for high velocities!
    Your guns shoots good bullets at high velocity, with good accuracy!
    Do a little victory dance, give your barrel man, and gunsmith a call of praise, and go kill something! /ubbthreads/images/graemlins/smile.gif
     
  11. Meister

    Meister Well-Known Member

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    Here! Here! I'm with Abinok.
     
  12. James Jones

    James Jones Well-Known Member

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    well fellas , I got 11 reload before the primers got loose not falling uout but loose and had to trim every 5 firings.
    I even went up in powder charge by two grains in another piece of brass and started to get some shiney spots on the case head. this was a very compressed load and accuracy had fallen off so I'm gonna stick with the 81gr load.
    I may try some R-22 with some 200gr accubonds.

    Sorry for sounding like a worry wart , just that these velocities seemed awfully high to me without pressure problems and I know that when pressure get high in custom guns it does it in a hurry.
    well thanks to all , now I just gotta see if I can get hole of a couple more of Boot's barrels.
     
  13. jwp475

    jwp475 Well-Known Member

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    Better to be safe than sorry and you were! Now all you have to do is enjoy /ubbthreads/images/graemlins/smile.gif /ubbthreads/images/graemlins/smile.gif /ubbthreads/images/graemlins/smile.gif
     
  14. RMulhern

    RMulhern Well-Known Member

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    What's causing the HS?? Yeah...I got an ID!!

    Because 'Boots' Obermeyer is the best barrel maker that has ever krapped betwixt a pair of boot heels! I've won a chitload of matches shooting his barrels in NRA HP and all were 5R barrels!! You're fortunate to have one of his tubes!!