Problems with 308 velocity

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  • camobob

    Active Member
    Feb 18, 2013
    482
    I'm a long time pistol reloader but have stayed away from rifle until recently.
    My velocities are varying by up to 90fps, I'm not sure where to start.
    I'm loading 308 with new Starline brass, Remington 9-1/2 primers, 45g RE15 and 150g Hornady SST pills. The new brass is consistent within 1g and when I weigh the final loads they have the same consistency.
    The chrono is a Labradar - it measured some PPU military ball I had laying around at 14FPS ES so it seems tight. I checked the PPU and my loads several times with the same results.
    I was hoping to be under 40fps....any thoughts on how to tighten up these speeds?
     

    deerhtr

    Active Member
    Nov 22, 2011
    231
    eastern shore
    I wonder if neck tension could be the case. in other words maybe the smallest bullest is loaded in the biggest hole. and vice versus. would that cause enough of a difference to see fps changes.
     

    steves1911

    Ultimate Member
    Dec 2, 2011
    3,026
    On a hill in Wv
    Did you full length size the brass before loading it? Did you weigh every charge or were they thrown from a powder measure? Do you have any other primers you could try?
     

    camobob

    Active Member
    Feb 18, 2013
    482
    Thanks for the questions.
    Charges were measured on my digital Chargemaster 1500. Each charge read exactly 45g. All brass was FL sized. I didn't feel anything unusual when seating the bullets. I agree that 45g is below max. QL predicted 2642fps at the muzzle and I measured 2550 10ft from the muzzle so I believe the predicted pressure of 52700psi. QL puts 47g at 60kpsi so I'm not that far below SAAMI. Is it normal that a light charge would cause a variance?
     

    camobob

    Active Member
    Feb 18, 2013
    482
    Usually when I see this in I change the primers first. How accurate is your scale your throwing charges with? And are you FL sizing or you using a bushing

    This was my first thought as well. The only other primers I have available are magnums. Unless someone wants to swap, primer options are non-existant.
     

    steves1911

    Ultimate Member
    Dec 2, 2011
    3,026
    On a hill in Wv
    The magnum primers can be used in a pinch. If your willing to meet me in westminster I can swap you 100 large rifle for 100 magnums so you can see if thats your problem.
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,673
    Never used reloaded 15. My experience with several rifle powders is that lower charge weights are typically less consistent for velocity. Doesn’t mean you need to juice it to max, but the bit of rifle reloading I’ve done so far my most accurate and consistent nodes are typically within about 1-1.5gr of max up to max.

    Example, CFE223 in 223 cases (I am going of memory of what the charges were).

    23gr 90fps ES
    24gr 110fps ES
    24.5gr 60fps ES
    25gr 48fps ES

    I think max is 25.7gr or something like that. Haven’t tried closer to max yet. SDs were quite a bit tighter of course, but things tightened up a lot as I crept closer to max.
     

    Speed3

    Ultimate Member
    Aug 19, 2011
    7,816
    MD
    What rifle and barrel out of curiosity, so we can level set on normal fps(20" are slow in general).

    There are usually 2 accuracy nodes, one high and one low....you just might be under the low node. Too much empty capacity can cause inconsistent burning of the powder and throws wild ES figures. Likely your issue.

    Since you have a lab radar, tune your load off that! You're running 45gr and max is 49gr?

    Start at 45gr and go up .1gr at a time if nervous. Record speeds for each shot and look for .3gr spreads that run about the same fps(those are your nodes). Once you nailed charge weight, play with seating depth in .003 increments. For seating depths, start .020 off the lands. You are looking for the same point of impact over a .006-.009".

    I'll see if I can dig up a chart on my phone which might help articulate what I'm trying to say

    Found a pic
     

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    camobob

    Active Member
    Feb 18, 2013
    482
    I appreciate all the advice.
    'll put together some 45.5g and 46g loads and hopefully check them out tomorrow.
    Wish me luck!
     

    camobob

    Active Member
    Feb 18, 2013
    482
    I've seen Eric Cortana discuss this relating to seating depth but it makes sense that velocity would work the same way. Ordinarily I'd be willing to test in 0.1g increments but with components being hard to find can I make it work in say 0.2 or 0.3g steps?


    What rifle and barrel out of curiosity, so we can level set on normal fps(20" are slow in general).

    There are usually 2 accuracy nodes, one high and one low....you just might be under the low node. Too much empty capacity can cause inconsistent burning of the powder and throws wild ES figures. Likely your issue.

    Since you have a lab radar, tune your load off that! You're running 45gr and max is 49gr?

    Start at 45gr and go up .1gr at a time if nervous. Record speeds for each shot and look for .3gr spreads that run about the same fps(those are your nodes). Once you nailed charge weight, play with seating depth in .003 increments. For seating depths, start .020 off the lands. You are looking for the same point of impact over a .006-.009".

    I'll see if I can dig up a chart on my phone which might help articulate what I'm trying to say
     

    Speed3

    Ultimate Member
    Aug 19, 2011
    7,816
    MD
    I've seen Eric Cortana discuss this relating to seating depth but it makes sense that velocity would work the same way. Ordinarily I'd be willing to test in 0.1g increments but with components being hard to find can I make it work in say 0.2 or 0.3g steps?

    Yes your fine using 1% increments or .4gr in your case
     

    Trigger Time

    Amazed
    MDS Supporter
    Feb 23, 2013
    1,231
    I've seen Eric Cortana discuss this relating to seating depth but it makes sense that velocity would work the same way. Ordinarily I'd be willing to test in 0.1g increments but with components being hard to find can I make it work in say 0.2 or 0.3g steps?

    You use .01g increments from staring loads of 45gn ?
     

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