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Thread: fps and preasure

  1. #1

    fps and preasure

    is fps a good indicator of preasure ? i have a .204 and after much surfing for info it seems i'm getting very low speed for max powder load.yes i only have a 20" barrel but i'm getting 3200 with the 39 sbk and 25.2 grains of ri10x .most seem to get a sweet spot at between 3600 -3800 fps .i took it up to 25.5 grn but loads started to open but did not chrono test.would you keep going (in small increments)watching for preasure knowing your getting well above max if it was you ?

  2. #2
    No. Stop. When your velocity starts falling off with the incremental increase in powder, you are just jumping pressure at a faster rate. The groups are opening up because of larger deviations in MV shot to shot. Back off.

  3. #3
    velocity was not falling off and the group opened up same as it would between sweet spots.

  4. #4
    I don't load .204 but I looked it up and my Sierra data shows 24.2 gr RL-10 as MAX with 3,790 FPS from a 26 inch barrel at 57,900 PSI, 94.2% case fill.

    Alliant lists max load for the 39 gr Sierra BK as 25.1 gr of RL-10X at 3,700 FPS
    A friend ran it on Quickload - calculates that as 69,000 PSI with a COAL of 2.400 inches.

    Big discrepancy,....so ...Err on the side of safety.
    Last edited by Southern; 31-03-2014 at 21:39.

  5. #5
    Quote Originally Posted by triggersqueezer View Post
    is fps a good indicator of preasure ? i have a .204 and after much surfing for info it seems i'm getting very low speed for max powder load.yes i only have a 20" barrel but i'm getting 3200 with the 39 sbk and 25.2 grains of ri10x .most seem to get a sweet spot at between 3600 -3800 fps .i took it up to 25.5 grn but loads started to open but did not chrono test.would you keep going (in small increments)watching for preasure knowing your getting well above max if it was you ?
    Let me offer the text book answer: No. Pressure and velocity are not related.~Muir

  6. #6
    Quote Originally Posted by triggersqueezer View Post
    i took it up to 25.5 grn but loads started to open but did not chrono test.
    Quote Originally Posted by Southern View Post
    No. Stop. When your velocity starts falling off with the incremental increase in powder, you are just jumping pressure at a faster rate. The groups are opening up because of larger deviations in MV shot to shot. Back off.
    Quote Originally Posted by triggersqueezer View Post
    velocity was not falling off and the group opened up same as it would between sweet spots.
    How do you know?

  7. #7
    Quote Originally Posted by JabaliHunter View Post
    How do you know?
    groups were hitting higher at 100 by a very small amout but not chronod so an asumption.

  8. #8
    thanks guys for your input .one thing i have learnt about rl powders the fps differs batch to batch a lot.i know some guys are using 26 plus on the 204 forum .

  9. #9
    I reload for the 204 but don't chrono my loads yet...

    Sierra manual says max load for the 39gr sbk is 25.1 gr of rl10x. I find my tikka shoots them at pretty much max load, I have backed off to 25gr and find it groups as a ragged hole at 100yrds and then 1" at 300yrds.

    i would say go back to basics and focus on a load that shoots accurately rather than speed, I found the advice of using ocw route was very helpful and within a couple of tests found my perfect match.

    Rl10x seems to be a very good powder for the 204, I have tried cfe223 but nowhere near as good results.

  10. #10
    yeh the best accuracy was at 24.6 but slow and i seem to allways have this were my sweet spot is slow.thought i might be missing something.

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