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Thread: How can I improve this load?

  1. #1

    How can I improve this load?

    I've been re-loading for 2 years and had good success with both 22-250 and 6-5x55. Achieving ammo which out performs the factory stuff I started with. I now only use re-loads. However I have recently bought a .308 Heym with 23" barrel and a shot count of 40 rounds.
    Using some once fired federal cases full length sized and trimmed, cci #200 primers, and speer 150 gn SPBT (2022) bullets.
    I started with
    45gn Varget and worked upto 47gn (stated max load) with a COL of 2.700"
    Results were 3 shot groups as follows.
    45gn= 2 5/8"
    45.5gn= 1 7/8"
    46= 2 3/16
    46.5= 3/4
    47= 1 13/16"
    So from this I took the 46.5 gn load and played with the COL begining with 2.650 upto 2.800 in 0.05 increments.
    Groups were.
    2.650=15/16"
    2.700=1"
    2.750=1 1/2
    2.800= 1 3/4.
    Admitidely this was prone of my rucksack at 100 yds and wold have been better of a nice bench. I do have access to a range but only when my mate can attend, so I just wanted to crack on.
    I should also say this rifle is un-moderated and I am just getting to grips with the extra recoil compared with the 6.5.
    1" group is all I need for hunting so not looking for clover leaf etc but can shoot 1" fairly consistently with the 6.5. My question. Is there anything else that could be done to improve this initial loading?
    Would a flat base bullet nearer the lands make much difference?
    Any idea's would be welcomed.
    Thanks.

  2. #2
    3/4" is perfectly acceptable, if you can replicate that consistenly then I'd stick with that one.
    Anecdotally, I'd be suprised to see such a swing in groups due to a half grain of Varget (46 to 46.5) as it's quite a slow powder.

    I take it you're chamfer/deburring the brass before loading it?

    Boat tails are forgiving in this respect, flat base aren't and if you're chamfering isn't sufficient you'll have some issues when seating i.e. little slivers of copper visible at the seated case neck.

    My preference is to play with length first and then powder. Reason is primarily that I've found my rifles to be quite charge tolerant once the length is right. Also, shortening a load near max will bump pressure quite quickly, conversely, lenghtening a low charge will drop it quickly.

    Good work, enjoy!

  3. #3
    Can't comment on the 308 aspect and relative lengths, but if the groups get bigger as you lengthen the OAL what happens if you shorten them from 2.65"

  4. #4
    Thanks Milligan. Yep all cases chamfered after length cut. I'm yet to fire more than one group of the same load/spec so difficult to say if consistent. Couple of the best targets had 2 touching and one straggler to make the group. Where as the other loads were all evenly spaced leading me to develop the former. I have never thought about doing things the other way round with COL first. I'll make a few of the best two up and see if repeatable. On another note why is it that this .308 which weighs the same as my 6.5 firing a bullet only 10gn heavier gives noticable more kick? Is one 308 likely to give more kick than another of the same weight?

  5. #5
    Not tried yet brewsher. Looks like the down ward trend may be better but at current COL charge is compressed. So since I've never had to compress powder before didn't want to go to far.

  6. #6
    Quote Originally Posted by woodmaster View Post
    ..
    Results were 3 shot groups as follows.
    45gn= 2 5/8"
    45.5gn= 1 7/8"
    46= 2 3/16
    46.5= 3/4
    47= 1 13/16".
    I would explore the powder weights a bit further before doing anything else. I would load up as before and try 46.1, 46.3 46.5 and 46.7. Then review the results. I would also try one other powder (N140 perhaps?) and see how that fairs. I would only tweak the seating once I felt happy I was in a good place for powder weight.

    I would also highlight the following article that a more scientifically minded Forum member has brought to my attention - Group Size Analysis

    If you agree with the logic in this article, then you should apply a correction factor of 1.158 to your group sizes. Have fun. JCS
    Last edited by jcampbellsmith; 19-02-2013 at 20:47.

  7. #7
    If your after better accuracy then i would say that the bullet/powder combination isnt the best. Either try a different bullet or different powder.

  8. #8
    Quote Originally Posted by jcampbellsmith View Post
    I would explore the powder weights a bit further before doing anything else. I would load up as before and try 46.1, 46.3 46.5 and 46.7. Then review the results. I would also try one other powder (N140 perhaps?) and see how that fairs. I would only tweak the seating once I felt happy I was in a good place for powder
    Plus 1 for the above.

    Everyone seems to have there own system for developing a new load, I would normaly shoot a powder ladder first and then mess about with seating depth, before finaly going back to fine tune the powder weight again.
    I was speaking to an acquaintance recently who uses a slightly different method to get his initial powder weight. He has access to an accurate chronograph, instead of shooting a powder ladder at paper at 300m or more meters, with the inherant variations that can creep in, he shoots his ladder through the chronograph. What he looks for is a group of weights that give the same or similar velocity for example

    45.5 2760 fps
    45.7 2785 fps
    45.9 2815 fps
    46.1 2825 fps
    46.3 2830 fps
    46.5 2836 fps
    46.7 2857 fps
    46.9 2886 fps


    This table is hypothetical and for demonstration purposes only, but you can see that the velocities between 45.9 and 46.5 are fairly similar. His assertion is that this represents an accuracy node and by taking the middle powder weight and playing around with seating depth he manages to get good accuracy without having access to a range in excess of a 100m.

    I haven't got a chronograph, but its now on the top of my wish list
    Dcg

  9. #9
    The simplest thing to do would be to try a different bullet.

    The Speer spbt is a good bullet and accurate in my 06 but for some reason hornady interlock and barnes TSX are much better. Conversely I have never been able to get the same grouping from Nosler partitions or Accubonds.

    For the bullets the rifle seems to like just about any appropriate powder willl yield a good load, for the ones it doesn't like i have tried several powders without significant improvement.

    Try a flat base bullet if speer is the brand you can get most easily or shop a little further afield.

    Of course different rifles may be more sensitive to powders than bullets but in my experience the experimenting to find the right bullet makes the whole thing easier and cheaper.

  10. #10
    Good advice here. I'll try a few of them out and see how I go. TBH I'm happy with a 1" group for hunting deer as I've never shot one more than 160 yds away. So only likely to be about 2" off target. At that range I'd be going for a nice safe HL shot if off sticks so likely to be my lack of marksmanship rather than ballistics that produce poor results. If in a good high seat I'd be happy for Head/neck shots. I do wonder if really it's just more practise with this rifle that is needed, however I do find I not that keen on putting too much lead down range before my shoulder says it's had enough. I'll try tinkering a bit more and just test half a dozen at a time to reduce fatigue problems.

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