308 overpressure

Discussion in 'Big Stuff--7mm, 30 Cal, .338+' started by Tim-o-thy, May 9, 2019.

  1. Trevor60

    Trevor60

    Joined:
    May 24, 2010
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    Good Afternoon

    There are a number of variables which will affect pressure and velocities.
    --To be safe you should always follow reloading manual numbers

    Here is a variable

    https://bergerbullets.com/wp-content/uploads/2013/03/COAL.pdf
    Pg 148
    Effects of Seating Depth / COAL on Pressure and Velocity The primary effect of loading a cartridge long is that it leaves more internal volume inside the cartridge. This extra internal volume has a well-known effect; for a given powder charge, there will be less pressure and less velocity produced because of the extra empty space. Another way to look at this is you have to use more powder to achieve the same pressure and velocity when the bullet is seated out long. In fact, the extra powder you can add to a cartridge with the bullet seated long will allow you to achieve greater velocity at the same pressure than a cartridge with a bullet seated short.

    Thanks
    Trevor
     
  2. Don_Parsons

    Don_Parsons

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    I find the nodes before I magospeed.

    178 ELD-X & M @ 43.5 Varget from a 32" barrel with 10 1/4 twist...

    My other 308 likes 42.9 gr Varget with same 178 grain'ers.

    Velocity means nothing to me if I don't get good groups.

    The ELD series of bullets still get frontal expansion as low as 1300 ft-per seconds,,, I don't like to see lower than 1600 to be on the safe side...

    Good luck as you find the magic load
     
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  3. Zero333

    Zero333 Silver $$ Contributor

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    2,600 fps from 18"bbl with 178's is right up there.

    The other issue is new brass relieves some of the initial pressure by having to fireform. I've had this issue with 308win Large primer Lapua brass.

    I suggest full length sizing with about 0.003" shoulder bump and taking it easy for the first few firings.

    You should have a solid load around 43 - 43.5 gr of Varget. Nevermind the ES/SD unless you're shooting beyond 600 yards.
     
  4. esromvre1

    esromvre1

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    Ran into the same problem. For me it was case lingth
     
  5. moorepower

    moorepower

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    Try measuring case capacity between Lapua and LC, and I think you will find your answer.
     
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  6. kevinbritvec

    kevinbritvec Silver $$ Contributor

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    Your too hot. 2600 fps from a 18" with 178's is probably 2.0 whole grains over maximum.
     
  7. Kurz

    Kurz

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    Hodgdon's reloading website specifies 45.0 grains of Varget for the two bullets which are both shorter than the 178 ELD you chose. So by using the same OAL of 2.800" and that 45.0 grain charge of Varget you boosted the pressure to over SAAMI spec.

    We routinely shoot the 175 class bullets to 1,000 yards with excellent accuracy in 18" barrels and long before the trans-sonic kicks in. See GAP Gladious, shot by Frank Galli:



    I think the biggest drawback is the use of Varget. I tried it years ago on the recommendations of a couple of top 1,000 yard shooters. Dirty, carbon creating powder, useless for my needs, your mileage may vary. :(

    I happen to enjoy shooting the .308 Win. out to 1,000 yards but I threw out the Varget and tested quite a few other powders. Top producer for lighter bullets was IMR8208XBR followed by Re-15 and with a lesser powder charge, AR-Comp. Now I'm sure there is a Doubting Thomas or two present so do a search on Accurate Shooter for "Varget Carbon Build up":

    https://www.google.com/search?client=firefox-b-1-d&q=varget+carbon+build+up

    http://forum.accurateshooter.com/threads/carbon-from-varget.3869197/

    The alternative when using Varget is clean religiously every 15-20 shots as recommended by our fellow members.:(

    Enjoy the process!:D
     
  8. David101

    David101

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    8208 would normally be considered a bit fast for a 175 grn in a 308 but because you are using really short barrels it would be a good choice. if you really dont like the Varget you could skip down to the 2209 but in that short barrel I dont think it would all burn. You only real other alternative is AR2206H that is used by the majority of 308 target shooters.
     
  9. Kurz

    Kurz

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    The 'really short barrels' has nothing to do with the choice of IMR-8208 BRX since it is a choice I use in 30" and 32" barrels as well. This all stems from some testing two us did when challenged to shoot .308 Win to 1,000, 1,100 and 1,200 yards by some friendly competitors. On our bellies and front bipod only. The search for a powder and bullet combination took a few days but we ended up selecting 8208 and the 175 Berger VLD which showed a terrific shot-to-shot consistency over the course of 60 rounds. :D

    H-4895 (AR2206 H) was tested but did not show the consistency we were looking for, at least not with the lot we were using that day. :(

    I completely support shooters who choose to use Varget and get the results they need or want. I find there are too many other powders to use.;):)
     
  10. Clark

    Clark

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    Nov 1, 2005
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    308 H335 168 gr test.jpg

    A test I did in 2003 on overloading 308.
    It seems 7 grains over Hodgdon max published is where a change in brass starts.
    10 grains over max published is where primer falls out.

    I have done this test with a lot of different cartridges.
    a) This is about what I would expect from a Mauser case head large Boxer primer pocket.
    b) Belted magnums go a little higher is pressure before brass yield.
    c) 223 case heads go higher still.
    d) I cannot reach the limit of 6mmBR case heads, the best primer CCI 450 [small magnum rifle primer with thickest cup] will pierce.
    e) I cannot reach the limit in rimmed cases, unless Norma makes the brass.

    --------------------------------------


    Hodgdon max book load:
    308 WINCHESTER, CASE: WINCHESTER, BBL: 24", PR: FEDERAL 210M, 168 GR. SIE HPBT COL: 2.800" H335, 42.0 gr., 2631 fps, 49,300 CUP

    My test:
    Pacific .308 Win reamer, VZ24 trued action, A&B fluted stainless 24" F54 barrel, H335, CCI200 primer, 2.9" OAL, Speer 168 gr. HPBT Gold Match, brass: Win308Win:

    0) 42 gr. QL= 2565 fps & 46 kpsi, 0% overload, did not load 42 gr.
    1) 43 gr. QL= 2618 fps & 49 kpsi, 2% overload, ok
    2) 44 gr. QL= 2670 fps & 52 kpsi, 5% overload, cratered primer this and higher
    3) 45 gr. QL= 2722 fps & 56 kpsi, 7% overload
    4) 46 gr. QL= 2774 fps & 60 kpsi, 10% overload
    5) 47 gr. QL= 2825 fps & 64 kpsi, 12% overload
    6) 48 gr. QL= 2875 fps & 68 kpsi, 14% overload, mark on brass from bolt face extractor this and higher,
    7) 49 gr. QL= 2925 fps & 73 kpsi, 17% overload
    8) 50 gr. QL= 2974 fps & 78 kpsi, 19% overload, extractor cut on brass expands .0020"
    9) 51 gr. QL= 3024 fps & 84 kpsi, 21% overload, extractor cut on brass expands .0020"
    10) 52 gr. QL= 3073 fps & 90 kpsi, 24% overload, extractor cut on brass expands .0110", primer fell out,
     
  11. DennisH

    DennisH Life Time NRA member Gold $$ Contributor

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    43.9 grains of Varget is max for me pushing 180 grain Berger Jag's. I normally load them @ 43.5 grains.

    I am using Lapua Brass, CCI primers.

    I am or was getting around 2,780 fps, 10 twist 30" long SS Barrel.

    FYI, Dennis

    PS: Your 50 grain plus loads scare me, JMO
     
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  12. Don_Parsons

    Don_Parsons

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    Nov 27, 2017
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    Ok, I run some tests on my 2018 factory Remington SPS 24" Sporter barrel.

    Lapua brass Palma
    Varget powder
    CCI BR-2 primer
    COAL 2.810
    150 Hornady Interlock FB

    41.3 on up to 45gr of Varget,,, the best 4 & 500 meter water line showed up at 42.2 gr's...
    The happy node...

    Next week we're doing a old school Remmy semi auto to find the node in it as well...

    Winchester Brass
    Varget powder
    CCI LR primer
    COAL 2.780
    Nosler Partions 150gr

    41.3 on up to pressure signs,,, we might see it in the 42 to 44gr category depending on how tight the bore is using Varget powder...

    Yes,,, this is a lower change then in the book and on the Hodgdon site at 46.5 and 47 grains,,, no need for us to blow out the primers or flash burn the head of the brass since we're after accurate loads...

    I like the idea of dropping at least 1 grain off max """book""" charge for my F Class rig,,, and at least 2 ish grains on my hunting rifles give or take...

    I like the old school pressure check,,, using 1 peace of brass I like to be able to shoot it at least 2 to 3 times neck sizing only,,, on the 3rd or 4th reload of this single brass needs a shoulder bump-back of 2 to 3 thou...

    If the bolt handle is super snug closing on the 2nd neck sizing only,,, I know I need to lower the charge...

    Like the old guy said,,, if this 1 peace of brass is damaged in the 5th reload,,,, that's the end of longevity of the other brass as well,,, do I want to get 14 to 20 reloads on the brass,,, or finish it off before the date of expire...

    To each their own...

    PS: The above load data I shared is only for the rifle(s) we're testing and should not reflect on other rifles that are out there...

    The book and world wide web recommends minimum charge for safety reasons,,, find what works and enjoy the good times...
     

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