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Thread: Two groups - any suggestions?

  1. #1

    Two groups - any suggestions?

    I thought I had my rifle zeroed with a new load using partitions. It is a 308Win and I had it zeroed 2 inches high at 100 as per tradition. I did the zeroing a while back and knew what adjustments I would need so made the changes and checked it with two rounds off a bipod that went on top of each other. Yesterday I shot it at 100 and the first shot went about 3 inches high while the 2nd went almost dead on the bull. Stuff happens. Another two shots and same pattern so I had two groups forming on the target one 3 inches high and one right at the point of aim. This wasn't in the plan. checked mod was tight etc. but all OK.

    I then took out my Hornady Spire Point load and it was giving me only one group on the target. So, I set the rifle back to the HSP zero and we did some plinking out to 350ish yards and all was OK.

    Has anyone any suggestions as to what is going wrong with the partitions? I'm pretty sure it isn't a rifle/scope problem as the other load shot OK. I've no idea of velocity but it is a max load however it was giving me good groups in the past and after zeroing put two check shots on top of each other. Of course it could have been me and I can't eliminate that but seems odd that I was shooting the other load OK to 350 yards while the partitions wouldn't group at 100.

    All thoughts and suggestions gratefully received.

  2. #2
    I have similar things quite often and after lots of fretting about X, Y and Z, actually came to the conclusion the other day that its me and the way i was holding the rifle. Just the other day, i sprayed 6 rounds in a 3'' circle, changed my seating position and put another 5 (after barrel cooling) into an inch circle.

    Im not saying this is whats going on with you, but its never occurred to me before that position and how you hold a rifle can make so much difference.

  3. #3
    Quote Originally Posted by caorach View Post
    I thought I had my rifle zeroed with a new load using partitions. It is a 308Win and I had it zeroed 2 inches high at 100 as per tradition. I did the zeroing a while back and knew what adjustments I would need so made the changes and checked it with two rounds off a bipod that went on top of each other. Yesterday I shot it at 100 and the first shot went about 3 inches high while the 2nd went almost dead on the bull. Stuff happens. Another two shots and same pattern so I had two groups forming on the target one 3 inches high and one right at the point of aim. This wasn't in the plan. checked mod was tight etc. but all OK.

    I then took out my Hornady Spire Point load and it was giving me only one group on the target. So, I set the rifle back to the HSP zero and we did some plinking out to 350ish yards and all was OK.

    Has anyone any suggestions as to what is going wrong with the partitions? I'm pretty sure it isn't a rifle/scope problem as the other load shot OK. I've no idea of velocity but it is a max load however it was giving me good groups in the past and after zeroing put two check shots on top of each other. Of course it could have been me and I can't eliminate that but seems odd that I was shooting the other load OK to 350 yards while the partitions wouldn't group at 100.

    All thoughts and suggestions gratefully received.
    Are you saying it was alternating at 1" high and 2" low (given that you zeroed 2" high originally)?..1" high could be just cold-bore or man-error, but 2" low is worrying..now if 1 went high, 2 when low, 3 went high, and 4 went low, I would almost be inclined to have a 3rd and 4th series to see if it was a true pattern.

    Did you fire two rounds, then walk to the target and let the barrel cool? could be then that both the 1st and 3rd shot acted like cold-bore shots, and the 2nd and 4th didn't...still the variation is huge. could be the partitions are just not right for your rifle..what grain and load are you using?

  4. #4
    Thanks for the replies - I'm certainly not ruling out the fact that it might be me causing the problem and hope to do more testing perhaps this coming weekend. Hopefully that will eliminate me though i was shooting the hornadys OK on the same day.

    PKL - the load is 49 grains of RL15 and a 150 grain partition in Lapua cases. This is a book max load but is exactly the same load as i use under my hornady spire points. There are no pressure signs and I have some cases loaded with the spire points that have at least 10 and maybe 15 of these loads through them so it isn't hard on cases either. Your thoughts on the cold bore thing also crossed my mind but the spire points were fired in a similar way and didn't do the two group thing. As you say might just be that the partitions are not for me but the interesting thing is that when I first adjusted the scope for the partitions I then fired 2 test shots and they were on top of each other at about 2 inches high.

  5. #5
    Coarach

    My initial thought is that you haven't actually got a working load for the partitions. A picture of the target would help. The fact you say the load is 49 grains makes me wonder. I was working with a load on Saturday and am homing on 46.8 grains +- 0.1 grain. I don't have any loads for my 243 or 260 that are a whole number of grains. What I am searching for in a load is point where the load is weight insensitive and this window may be only 0.3 or 0.4 grains wide.

    Some more detail on case prep and seating depths would also be helpful.

    Good luck. JCS

  6. #6
    ..the 'fun' part of testing loads is having the thought of Nosler Partition acquisition costs go through your mind setting up 10 different 5 shot loads, and then repeating say 2-3 of those with 2-3 different seating depths, knowing only one will work it takes a strong man not to cry

  7. #7
    Quote Originally Posted by PKL View Post
    ..the 'fun' part of testing loads is ... repeating say 2-3 of those with 2-3 different seating depths, knowing only one will work it takes a strong man not to cry
    I have (slightly) moved on from this because what happens if the first tried seating depth works? You've 2 / 3 / 5 (more!!) sets of rounds that will all need pulling?

    Best solution I have found (not mine, I pinched it) is to load (say) 50 rounds at max COL (measured to ogive) then take press / dies / B&D workmate to the range and keep squeezing in at 5 thou intervals until you get good grouping. After that - STOP - and squeeze remaining rounds to that COL.

    The last 1/4" at 100 yards just ain't worth it for live shooting?

    Enjoy.
    Last edited by Eyefor; 22-03-2011 at 11:33.

  8. #8
    Quote Originally Posted by Eyefor View Post
    I have (slightly) moved on from this because what happens if the first tried seating depth works? You've 2 / 3 / 5 (more!!) sets of rounds that will all need pulling?

    Best solution I have found (not mine, I pinched it) is to load (say) 50 rounds at max COL (measured to ogive) then take press / dies / B&D workmate to the range and keep squeezing in at 5 thou intervals until you get good grouping. After that - STOP - and squeeze remaining rounds to that COL.

    The last 1/4" at 100 yards just ain't worth it for live shooting?

    Enjoy.
    I think I recognise that method Eyefor but I take a hand press instead of the full on press and workmate, much more compact.

  9. #9
    Quote Originally Posted by pierred View Post
    I think I recognise that method Eyefor but I take a hand press instead of the full on press and workmate, much more compact.
    Good idea. Hadn't thought of that Pierre. Which one would you recommend ('cos I know you will have trialed the lot )

    Also, you selling that .222 yet.....

    Brgds

    Iain
    Handle every stressful situation like a dog. If you can't eat it, hump it or learn from it then piss on it and walk away.

    "HOSPITALITY" - the art of making guests feel at home (when you wish they were).



  10. #10
    Quote Originally Posted by Eyefor View Post
    The last 1/4" at 100 yards just ain't worth it for live shooting?
    I agree with this but it was the 3 inches at 100 yards that I was worried about :-)

    Being serious though it is often necessary with sika, certainly the sika I stalk, to take a longer shot if you are to get any shot at all so while a one inch group is more than good enough for rock and roll two seperate groups 3 inches apart isn't.

    I think you might be right JCS. I thought the load was good to go as I had shot maybe 6 groups of 3 shots each with this load and had adjusted my OAL to 2.760. To be honest my Blaser shoots almost all loads into an inch, including factory stuff, but I can't get anywhere near the lands while loading from the mag. My absolute max COL with the partitions is 2.905 so I'm a good 0.145 off the lands, I can't load longer than 2.810 for the mag and keep myself to 2.800 just to have a margin for error. I tried a few different lengths and settled on 2.760 but to be honest they were all as near the same as made no difference in the real world.

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