6BRA second go

Discussion in '6BR, 6BR Improved & Wildcats' started by comagutsa, Sep 11, 2018.

  1. comagutsa

    comagutsa

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    OK after last barrel that I couldn't get working I decided to get a new one (Krieger 1:8 28" HV .237.. 272 no turn 104fb)
    I ran in barrel with 107gr serrias mk that I had laying around and it showed promise
    Once it had 120 rounds on it I got my 103gr copperheads (similar to vapor trails I hear) and tested some cc BR4s and 450s with 30.5gr of 2206H/H4895 with Cooperheads jammed.0.010 and 450s had better ES and SD with a flatter group. So I decided to stay with 450s
    I then did a quick seating depth test and likes 0.005 jump and jam
    Barrel had 160 rounds on it before I started test below
    I then loaded up from 29.7gr to 30.7gr of 2206H/H4895 and 0.005 jam with 0.002 neck tension and tested at 200m. Wind wasn't perfect but shot over flags and wind was coming from behind at approx 10km/h (approx 6mph I think) with gusts flicking
    IMG_20180911_132611.jpg
    I have noticed the 103gr copperheads are a lot faster than 105gr hybrids and 107gr mk that's for sure
    Now 29.9gr was the standout but 0.1gr is a bloody small node... Normal? Or just me

    Anyone else see anything or what I should try next.. Numbers on 30.3gr and 30.4gr look good
    Looking at loading up at 29.9gr and doing a better seating depth test from 0.015 jam to 0.020 jump in 0.003 increments with 5 shot groups
    This gun does 98% of its shooting at 500m/547y.
    Cheers
    Pethy
     
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  2. comagutsa

    comagutsa

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    Copperhead (left) vs 107gr serrias mk
    IMG_20180911_151640.jpg
    IMG_20180911_151651.jpg
     
  3. mikeeg02

    mikeeg02 Michael Glantz Silver $$ Contributor

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    I could be wrong on how I do things, but if it was up to me, I would do the seating depth test on 29.9 and see how well that group holds including trying the same to see that its repeatable. I would likely try a 5 shot group on the repeat.

    If you want to try the faster velocity group, based on the group shapes I would try a seating depth test on 30.4. Looking at the targets to the left and right of 30.4 shows the trends, and 30.4 only shows slight vertical that may come out in seating, it may make it more of a round group. I suspect .003-.005 more in from there would tighten that one up. I look forward to your results. Hopefully that helps.

    Edit: Also, I think it would be wise to note ambient temperature if you haven't. I had a similar 4895 load that worked through maybe 60-80 degrees. But at the open it printed with a lot of vertical. But is was also 90+ and super humid on both days. I think I needed to take a tenth out.
     
    Last edited: Sep 11, 2018
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  4. comagutsa

    comagutsa

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    Thanks Mike
    Will let ya know
    Cheers
    Pethy
     
  5. SPJ

    SPJ Silver $$ Contributor

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    Any chance that 29.9 was just a lucky shot?
     
  6. comagutsa

    comagutsa

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    find out tomorrow haha
     
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  7. SPJ

    SPJ Silver $$ Contributor

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    Just a novice thought here but perhaps a Berger style seating test from-0- to .120 would be in order at the lower charges 29.7 or 29.8 as none of these seem to grouping well for 200m
    you may find that .040 or .060 jump brings them together.
    Jim
     
  8. Nature Boy

    Nature Boy

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    If you used the Erik Cortina method your node would be between 29.7 - 29.9. Those group centers seem to have the least amount of vertical deviation in comparison to adjacent groups.
     
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  9. Curious

    Curious

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    If your first barrel didnt shoot too well, have you re-barreleld the same gun again so the only change is the new barrel?
     
  10. comagutsa

    comagutsa

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    Yeah mate I got a new barrel for it . I also shoot a 6BRX so I just swap barrels between them.. 6BRX barrel in its shoots great put old 6BRA in it was crap and not consistent .. New 6BRA and its already more consistent and easier to clean (old barrel from 1st shot was a pain to clean)

    Well the wind gods are not kind to me today.. Started out with bugger all but picked up as I shot. Coming at me from 1 to 2 o'clock
    IMG_20180912_104958.jpg
    But looks around 005 jam is a goer. 002 the wind picked up more but I just wanted to finish
    I will try fine tuning powder again (29.7 to 29.9gr and 30.3 to 30.5gr) with 003 neck tension this time with 005 jam and see what happens . Then try primers
    Jump seating test nothing stood out
    Oh that 1 on 005 test that went left, my gun shot funny that round (didn't act normal at all) and bolt was tight as to open even tho speed what in middle of other shots.. Found this weird make on case so I will toss it out, also like a burn mark round that area
    IMG_20180912_120254.jpg
     
  11. Ccrider

    Ccrider Silver $$ Contributor

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    What caused the shoulder to blow like that?
     
  12. Rushty

    Rushty Gold $$ Contributor

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    Looks unusual, to me anyway.. How many firings on it?
     
  13. comagutsa

    comagutsa

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    No idea why.. I think about 6 or 7 firings on that brass
     
  14. SPJ

    SPJ Silver $$ Contributor

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    That is a bit unusual, at least you found seating depth to work with.
    Bummer about that wind.
     
  15. Rushty

    Rushty Gold $$ Contributor

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    Hopefully you haven’t gas axed your chamber!!!
     
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  16. comagutsa

    comagutsa

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    Haha you would like if I have
     
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  17. mikeeg02

    mikeeg02 Michael Glantz Silver $$ Contributor

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    I have a case with a similar mark, though down in the body. It shoots within my groups at 1k. Sometimes down in the 5s. Though yours being at a junction area like that, I would have some concern.

    Edit: Im not sure if you can account for the other one out of the group condition wise at .005 jam, but it looks like that should work.
     
    Last edited: Sep 12, 2018
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  18. Nature Boy

    Nature Boy

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    Is it a hole or just an imperfection in the brass?
     
  19. mikeeg02

    mikeeg02 Michael Glantz Silver $$ Contributor

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    Mine, which looks oddly similar to his, is an imperfection in the brass I would say. Mine is definitely not leaking. Ill get a picture tonight.
     
  20. AlloyTargets

    AlloyTargets Site $$ Sponsor

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    I would try +.022, +.020 & + .018" if I were you. Throwing out the cold bore shot +.020" looks great. The happy spot for mine with the 103VT is +.018". +.020" is pretty good. +.016" is garbage. I shoot for .018" + a smidge to stay away from the bad news at .016".

    I still cannot wrap my head around why such a small difference in seating depth makes such a huge difference on target, but it does.

    My touch length is determined by the stripped bolt method that Alex posted the video of & my Hornady comparator.
     
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