308 projectile seating depth

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • 308 projectile seating depth

    I am loading 308 150 grn Hornady SST projectiles into once fired Hornady SST super performance cases in the Omark.
    Using a know load of 45.5 grn of 2208 with Nosler Ballistic tips, and others. I find the Hornady factory ammo shoots higher and best of several lots of factory loads all 150 grn.
    Question is if I seat out to close to the lands [ all measured using a comparator ] with SST projectiles I am 15.06 mm or around 5/32 inch longer load than factory loads

    Will I get much difference in pressure than factory or even loose some velocity.
    I have other measurements / loads from federal cases with the 45.5 load and Nosler bt`s [150 grn] and they shoot fine, as a guide but its not a fair comparrison with different cases and possibly different powder free space.

    All will be shot at 800 yds.
    Got some thoughts to share reloaders ?
    [center]
    Don’t poke the snake, walk around it and come back later with a double-barrelled shotgun and blow its [email protected]#!ing head off!.

    Australia in future, the outcome is the same, a bloody dictatorship run on the whims of a very few ego-centric pathological elitists.

  • #2
    Factors that may come into play:

    Jacket composition

    Bearing surface length

    The angle and length of the "lead"

    Case neck tension

    Crimp

    Lastly, the pressure curve and powder burn rate.

    There are probably more factors, but I assume everything else such as case and primer are no change, and relative humidity was the same or negligible when loading.

    Some points to think about....

    Comment


    • NoFerals
      NoFerals commented
      Editing a comment
      Originally posted by Oddball" post=27590
      Factors that may come into play:

      Jacket composition
      same brand same projectile weight I imagine no changes

      Bearing surface length.
      Slightly less than the factory load 15.06 less at the case mouth

      The angle and length of the "lead"
      ?Unsure what you are calling "lead "

      Case neck tension
      would be different than factory but which way and how much ??? unsure , Cases are all prepped and full length sized as normally done.

      Crimp
      No crimp just the standard seating die finish off in the press.


      Lastly, the pressure curve and powder burn rate.
      I figure Hornady is using its latest and greatest powder 2280 ? --- where I will be using 2208

      There are probably more factors, but I assume everything else such as case and primer are no change, and relative humidity was the same or negligible when loading.

      Some points to think about....

  • #3
    I find with my 308 loading 178g Amax and 168g Nosler BT, 168g Sierra HPBT and 165g Sierra Gamekings with ADI 2208, that 20 - 30 thou of the lands works the best with all the projectiles. The closer to the lands that the projectile is seated the more pressure signs I encounter when developing my loads. All the 308s I have ever loaded for like some jump. I think the only way you will work out what's best is trial and error. I find that generally speaking factory ammo is loaded up to the hill with a lot of jump to accommodate an array of rifles.

    Comment


    • jasmay
      jasmay commented
      Editing a comment
      Originally posted by Macca" post=27647
      I find with my 308 loading 178g Amax and 168g Nosler BT, 168g Sierra HPBT and 165g Sierra Gamekings with ADI 2208, that 20 - 30 thou of the lands works the best with all the projectiles. The closer to the lands that the projectile is seated the more pressure signs I encounter when developing my loads. All the 308s I have ever loaded for like some jump. I think the only way you will work out what's best is trial and error. I find that generally speaking factory ammo is loaded up to the hill with a lot of jump to accommodate an array of rifles.
      All the projectiles you mentioned a tangent ogive designs, they tend to be very forgiving and a best suited for mag fed rifles due to there nature, they can handle large jumps, you will probably find if you have a stable load, changing seating depth small amounts i.e. .010" either way has little effect, and you will also quite easily find a suitable hunting load simply by loading to max magazine length and tuning powder.

      May I ask why you load such a spread of projectiles that are in such a close weight class?

  • #4
    All Good thanks shooters.
    I am as close as I can figure about 30 thou off the lands.
    I have a dummy load with a projectile reversed for a guide and the only problem with it is I need to put it in a small lathe to take the raius off the base.
    Then measure it in the comparator and I have the true length.
    Was mainly concerned just how much pressure diff Gain or loss would happen compared to the factory load which is quite a bit further off the lands.
    Tomorrow and with not a lot of wind fingers X`d will tell the story.
    Thanks
    [center]
    Don’t poke the snake, walk around it and come back later with a double-barrelled shotgun and blow its [email protected]#!ing head off!.

    Australia in future, the outcome is the same, a bloody dictatorship run on the whims of a very few ego-centric pathological elitists.

    Comment


    • #5
      Okay I was not going to say anything but what is "the lands" it seems to be a very important part of your reloading equasion. I am unversed and have not seem this phrase in the books about reloading I am reading. Thank you for humoring a noob.
      "He got the whole nine yards" - as it happens World War II (1939–1945) aircraft machine gun belts (US 50 cal) were nine yards long.

      Comment


      • Pitty
        Pitty commented
        Editing a comment
        Its the start of the rifling in the chamber!

    • #6
      Lands, the raised section of rifling.

      Grooves, the shallow section of rifling.

      Throat, the area between chamber and lands.

      Lead, the angle of the start of the lands , which influences throat length and cartridge OAL. Can be gradual or sharp, to almost non existant.

      Chamber, the area where the loaded cartridge case sits.

      Comment


      • Laflamme
        Laflamme commented
        Editing a comment
        Originally posted by Oddball" post=27741
        Lands, the raised section of rifling.

        Grooves, the shallow section of rifling.

        Throat, the area between chamber and lands.

        Lead, the angle of the start of the lands , which influences throat length and cartridge OAL. Can be gradual or sharp, to almost non existant.

        Chamber, the area where the loaded cartridge case sits.
        once I read that with my gun in my hand I got it just fine. ill file that for future use. thank you.

    • #7
      Take me to your leader is not the same.

      Leade : from google.
      http://www.hps-tr.com/guidance/barrel_runningIn.asp

      Make of it what you will.
      [center]
      Don’t poke the snake, walk around it and come back later with a double-barrelled shotgun and blow its [email protected]#!ing head off!.

      Australia in future, the outcome is the same, a bloody dictatorship run on the whims of a very few ego-centric pathological elitists.

      Comment


      • Guest's Avatar
        Guest commented
        Editing a comment
        Originally posted by NoFerals" post=27888
        Take me to your leader is not the same.

        Leade : from google.
        http://www.hps-tr.com/guidance/barrel_runningIn.asp

        Make of it what you will.
        Leade, ok I missed the lesson on its spelling.....

        from the link NF supplied:

        "Just ahead of the throat is the leade, a tapered area where the throat diameter reduces down to the groove diameter and onwards to the bore diameter. When the rifle is fired, the bullet impacts the leade and is squeezed down in diameter and into the shape of the grooves."

        The leade can be shallow to sharp, which will effect pressure and engagement of the lands.

        If you follow this link, this article, (including pictures, and diagrams), gives an excellent explanation of leade, and leade angles etc, I cannot explain it better than this, highly recomended reading:

        http://riflemansjournal.blogspot.com.au/2010/09/basics-leade-angle.html

        Thanks,

        Oddball

    • #8
      Ok tested my loads of 45.5 of 2208 in the original once fired and full re sized Hornady shells at 800 yds against the factory loads of the same brand and projy.
      For all intents and purposes they equaled other shooters on that range and bettered some.
      2 0clock fish tail wind and miracle { no typo it was a miracle to hit the dam target}was running right , boiling or whatever
      I conclude that in an unknown barrel life rifle its not to bad.
      Not BR but its not a 7 mm Either so happy enough.
      I know there are personal tweaks for me and the rifle but Its ok.
      It seems that 308 is not all that fussy about Jump to the lands but ogive shape has a lot to do with it and how fast you drive it matters.
      No sighns of pressure I could go to 45.7 and back of the lands a bit but in trying to duplicate Hornadys SST load it still prints 3 minutes lower at 800 yds.
      Coincidentally or not the same results applies with federal cased loads of the same configuration but using Nosler 150 grn projys and only neck sized.
      But those cases were a mix from two rifles so its a bit iffy there.
      I will prevail.
      Thanks re loaders
      [center]
      Don’t poke the snake, walk around it and come back later with a double-barrelled shotgun and blow its [email protected]#!ing head off!.

      Australia in future, the outcome is the same, a bloody dictatorship run on the whims of a very few ego-centric pathological elitists.

      Comment


      • Guest's Avatar
        Guest commented
        Editing a comment
        That's still a pretty light load there NF.
        I know it is early days for you with loading but just as an example (don't try this just yet) I'm running 46.4gr behind a 168gr pill & early load development with 175grainers at 44.5 (both 220 Should be able to push the latter up around 45.5 I think.

        I found that the 155gr pills preferred 2206h in mine. (about 1/2 gr down from max by memory)

        The biggest thing with loading for LR shooting will be getting consistant neck tensions & minimal runout.
        The neck tensions can be solved by Turning & Annealing (one or both) but runout is a combination of these two plus your equipment & methods.

        Mick.

    • #9
      Always ready to learn I am vaguely remembering ADI had a feral load out some time back from memory it was 172 grn or close to that.
      Seems I might need to go to 170 or near that AMax to get the profile and a 170 is grn to get the weight for those longer ranges.
      Miragfe and wind was playing hell withte best blokes and though few they are GOOD so keeping close to them is Happy for me.
      Buggers have years of experience on ranges where as most of my shooting is bush and running "get me out of here" snap shooting at anything that runs most times, or that puase and look around second shoot now or its gone .

      Damit I need a few grand to buy a HB 7 mm -- now that would be nice - - and has about as much chance as a snow ball in hell of happening
      [center]
      Don’t poke the snake, walk around it and come back later with a double-barrelled shotgun and blow its [email protected]#!ing head off!.

      Australia in future, the outcome is the same, a bloody dictatorship run on the whims of a very few ego-centric pathological elitists.

      Comment


      • Guest's Avatar
        Guest commented
        Editing a comment
        Originally posted by NoFerals" post=27972

        Seems I might need to go to 170 or near that AMax to get the profile and a 170 is grn to get the weight for those longer ranges.
        155gr SMK's will make 1000yds no worries. (BC 0.47)
        Your Omark's are more than likely 1:13 twist barrels aren't they?
        Will suit the 150 - 155's nicely.
        Might struggle to stabilise 170's

        My 155gr SMK load is doing 2900 at the muzzle & according to Sierra Infinity is still doing 1300 at 1000yds, backed up with field results where they performed very well for me. No sign of destabilisation & landed right where expected, my 1:10 twist might be helping out there if they are going transonic because they are slightly overstabilised by the 1:10

        Don't be afraid to seat them very shallow if your trying to minimise jump. Mine are only bearing in the case neck by about 3mm. (gives me 0.010" jump)



        The main issue with seating this shallow is maintaining minimal runout, only good for single feed (but that won't bother you) but might require some careful case prep & good dies to get them seating straight.

        A comparison between the 155gr SMK, a 168gr Amax & a 175gr SMK.
        Ivé found that the 155's like minimal jump (.010" in my rifle) but the other two like .030" the former is likely due to the shorter bearing area, not sure about your Hornady pills but would assume 150gr SST's to have a relatively short bearing area too.



        Similar to Jas,
        I start all my load development at .010" jump, work up a load & then increase the jump to see if it improves (0.005" in my .222)
        Being a hunting rifle I don't want to be jamming & I use the same method for these target loads too.
        Bushing dies let you control/adjust neck tension which can help adjust ignition pressures too (that's how I got that Amax load so high)

        Mick.

    • #10
      Happy enough now with some fire formed cases to work with the next trick will be to seat them once turn 180 degrees and repress to get them straight [ if they are not straight ] , its a Lee breach lock press so they might be off line a bit.
      May be even try shimming the die at the top with a few thou to take out that interrupted thread slop.
      There are also a few human errors and sighting errors to clen up as well.
      Cant do much about the wind though dammit, that`s just skill and more skill over a very long learning period and the best still get wound out chasing it
      [center]
      Don’t poke the snake, walk around it and come back later with a double-barrelled shotgun and blow its [email protected]#!ing head off!.

      Australia in future, the outcome is the same, a bloody dictatorship run on the whims of a very few ego-centric pathological elitists.

      Comment


      • Guest's Avatar
        Guest commented
        Editing a comment
        Originally posted by NoFerals" post=28146

        May be even try shimming the die at the top with a few thou to take out that interrupted thread slop.
        :
        Try not locking them down tight. Let them centre them selves with a little float.

        Wind................tell me about it.
        Shot F Class yesterday in a howling 30+km wind.........was getting Biblical at times, only 300yds but was still very interesting.
        Shot a 55.3 with those 155gr Sierra's in my 1st set but the 175's didn't prove as good in the second. (still working on that load)
        Seems there is no substitute for speed at shorter ranges in the wind!
        While 55.3 is not spectacular, it is doing OK for me, my gear & those conditions.

        Mick.

    • #11
      @OddBall . Can you define your interpretation of insane ?,
      [center]
      Don’t poke the snake, walk around it and come back later with a double-barrelled shotgun and blow its [email protected]#!ing head off!.

      Australia in future, the outcome is the same, a bloody dictatorship run on the whims of a very few ego-centric pathological elitists.

      Comment


      • Guest's Avatar
        Guest commented
        Editing a comment
        Originally posted by NoFerals" post=28977
        @OddBall . Can you define your interpretation of insane ?,
        Insane=large amount of effort and resources for an over the top, to some, but functional device, that others secretly envy....
    Working...
    X