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Thread: Incremental load test anomalies

  1. #16
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    I do ladder, seating and any other tests in the hope that everything will go as expected,incremental and predictable results so that maybe some conclusions can be drawn.often there will be.some random variable that I can't explain ,well outside of what was expected.Replaced my old chrony with labradar and now at least trust my velocities,so there is one less question mark.
    Had one of those rare days recently,walked away believing I had.finally cracked it with a 308 load,had some acceptable results in the past but this was more consistent than anything before.
    Almost afraid to go back to the range in case I blow it.
    Micky Duck and Jhon like this.

  2. #17
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    Quote Originally Posted by Rated M for Magnum View Post
    Sometimes brass can be the culprit, weight sorting can help as often the heavier cases can have a lower internal capacity creating higher pressure.
    It's been found that differences in the average mass the mass of the case often comes down to the extraction groove cut on a rimless case which has no effect whatsoever, you'd need to be measuring H20 capacity on each case to be sure, and...

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    Quote Originally Posted by Waimauku View Post
    finally cracked it with a 308 load,had some acceptable results in the past but this was more consistent than anything before.
    Almost afraid to go back to the range in case I blow it.
    If a .308 does not shoot a 175 SMK seated to 2.8" COAL with 40 odd grains of Varget or similar, it's time to sell the rifle
    Micky Duck likes this.

  3. #18
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    Quote Originally Posted by shooternz View Post
    It is the neck of the case there is only so much gas can flow through the neck of the case when the maximum flow rate is exceeded there is a bottle neck and the gas flow
    can't flow fast enough and starts to swirl slowing down the gas and drops the velocity, I did some tests years ago and found as the powder charge went up the velocity
    started to go backwards as much as 10fps for 0.5 grain increase .
    Thats very interesting, thks!
    I know a lot but it seems less every day...

  4. #19
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    Quote Originally Posted by Jhon View Post
    Thats very interesting, thks!
    Greetings @Jhon, @shooternz,
    I had read about velocity decreasing with increasing powder charge before but it is nice to hear from someone who has actually tested it. From what I remember pressure still increased with the charge so you seem to to have found your load @Jhon. Generally I load up to a max velocity rather than a max charge so for me my 35P chronograph is essential. I use a 4 foot screen spacing which improves accuracy and the proof channel (a separate reading using a second stop screen) alerts me to the very occaisional dud reading. This system is very useful for loading for older cartridges where load data is varied to say the least. No need to go doawn any rabbit holes for this one. As far as the longer range stuff you need to verify your longer range POI by actually shooting at that range. Preferably zero at 200 metres as well.
    Regards Grandpamac.
    Jhon and RugerM77 like this.

  5. #20
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    Quote Originally Posted by dannyb View Post
    I started typing up a post with all this and other variables but didn't want to bamboozle the O.P there are so many many things....every time i think i have my system down to a point I'm happy with my process something else crops up
    My latest battle is trimming and getting consistent and even chamfering
    Yes in hindsight I could've left the first paragraph out

    What I was getting at is there is a list of culprits so long it's not even funny and trying to nail it down can you make you tear your hair out. Especially when there is a chroni involved ay @micky_Duck ?

    My method I pressure test with a ladder, load some to shoot groups at the high end of pressure, pick the load with the best grouping (fluke) load up some more and validate at range. Plenty good for shooting animals at 300.

    As for trimming and chamfering, I keep having to decide if I'd rather jump off a bridge or trim and chamfer brass.
    Micky Duck, Jhon and dannyb like this.

  6. #21
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    Quote Originally Posted by caberslash View Post
    It's been found that differences in the average mass the mass of the case often comes down to the extraction groove cut on a rimless case which has no effect whatsoever, you'd need to be measuring H20 capacity on each case to be sure, and...

    Attachment 198713



    If a .308 does not shoot a 175 SMK seated to 2.8" COAL with 40 odd grains of Varget or similar, it's time to sell the rifle
    Couldn't agree more

 

 

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