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Thread: why the massive improvement in velocity?

  1. #1

    why the massive improvement in velocity?

    Been running 55 gn ballistic tips over 35gn H4895 in my 22-250, getting 3700 fps, quite respectable and excellent accuracy. I just tried some ammo I made for my old R93 22-250 which was giving 3600 fps in that rifle(41gn H380, same col) and I got 3850 fps from the custom Tooley. fantastic improvement on velocity well over book speeds, can I put this down to the tight neck? Barrel is only 24.5.

  2. #2
    Different rifling config. maybe just a different barrel no two are the same.

  3. #3
    Gary, I don't know why, but I have seen it and it seems to relate to certain bullets and powders in certain barrels.

    My 260 has a LW match barrel, 1450 weight, Saami min spec chamber and a really short throat. I spec'd it to shoot 120gr BT's. Bullet is in the lands at about 2.5mm short of magazine OAL. When cleaning the barrel bore, it seems very smooth.

    It won't shoot for s**t with H4831. With Varget I get very good accuracy, but velocity is not so good, 100 - 150FPS short of the book.

    However, change the powder to Benchmark, or Reloder 17, it is a different beast.

    With Benchmark and the 120gr BT's, it is hitting book max velocity (2900FPS) at about 1.5gr short of book max. It is badly over pressure at book max powder loads, flattened primers, extractor marks etc. Reloader 17 gives almost identical results with an extra 1.5gr's of powder.

    Load a 100gr BT over Benchmark or Reloder 17, it turns into a pure animal. In excess 3300FPS, again with 1.5gr short of book max loads, again this is max load in this rifle. As you approach max powder charge, pressure goes mad. That is kicking the tripe out of a 25/06 with an '08 case. I am actually backing this load off, as I think it is too fast for deer. Confirming trajectory, I found a 2cm high zero at 100m gave a 2cm low POI at 200m. That is seriously flat shooting.

    I should say all this is with a 20" barrel. I had 2" knocked of the barrel a few months ago for the net loss of about 40fps per load.

    My conclusion is that this is as a result of a good quality barrel, combined with a tight chamber, short throat and fast for cartridge powders.
    Last edited by Claret_Dabbler; 30-06-2010 at 16:15. Reason: Spelling and Grammar
    Brian.

    Just because you are paranoid, doesn't mean they aren't out to get you......

  4. #4
    forgot to add, the same load in a 26" vssf2 made 3700 fps - theory says longer the barrell means more beans!

  5. #5
    Well! If there was ever an argument for working up loads from scratch for a new rifle (or batch of components, for that matter) you made it with this post, Gary. The only way you got extra speed was from extra pressure; if you got that losing an inch and a half of barrel, then you can add that to the equation. It's all physics. More speed requires more push. I wouldn't be so giddy. Something is wrong someplace. Since H-4895 usually tops out around 3700 fps with max loads @ 62K pressure, your extra speed should be a cause for concern. Don't put your eye out, Amigo.~Muir

  6. #6


    Gary -

    Next time you shoot it can you do so somewhere far away...... like Sussex? I have no wish to become a cinder in a scorched hole that once was West Berkshire

    Thank you.
    Last edited by KevinF; 02-07-2010 at 13:14.
    KevinF -

  7. #7
    bought a tub of H380 today, watch out, i rekon i can beat the 4k mark by the weekend

  8. #8
    i still dont get it...

    h4895 gives me 3700
    h380 gives me 3850

    why does h4895 behave as expected yet h380 give massive "over velocity" with NO pressure signs??

    can anyone explain?

    ps. with regard to trying the h380 loads in my new gun, a bloke who has dsc1, dsc2 and is an AW told me that it would be ok!

  9. #9
    Quote Originally Posted by Offroad Gary View Post
    i still dont get it...

    h4895 gives me 3700
    h380 gives me 3850

    why does h4895 behave as expected yet h380 give massive "over velocity" with NO pressure signs??

    can anyone explain?

    ps. with regard to trying the h380 loads in my new gun, a bloke who has dsc1, dsc2 and is an AW told me that it would be ok!
    There's just a chance that a "massive over velocity" reading is a pressure sign in itself.
    I really hope you were taking the Mick with your last line.
    You can't say muntjac without saying, Mmmmmm.

  10. #10
    Quote Originally Posted by Harry mac View Post
    I really hope you were taking the Mick with your last line.
    would I?

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