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Thread: 243 and new load development

  1. #1

    243 and new load development

    Gents, thoughts please. Made up some test loads for the 243 with 100gn Hornady BTSP starting at 38.5 and going up to 42gn (max load) test shot last night. The lower loads were appalling 4" for three rounds at best. Only when I got to 41gn did I start getting down 1 and bit inches. Got dark before I tried the max load. Even the 41gn was still shooting 3" lower than factory RWS 100gn which has a box velocity of 3000fps. The Heym shoots RWS very well and three rounds touching is the norm.

    My thinking is that with the lower loads they were not giving anything like the velocity to get good consistent spin on the bullet, nor enough pressure to get a good clean burn. Once it's getting up to 3000 fps there is enough rotational spin to keep 100 gn bullets stabilised.


    Real question is even at the high loads will there be enough spin to keep the bullet stable down range, or does spin slow down as velocity falls off down range.


    I'm looking at the 100gn bullet as its the legal minimum in Scotland for the bigger deer and I want one load to do everything. I want something that's good for 200yds, but most shots at 100 or so.


    My default is the RWS ammo, but at 35 a box of 20 it's getting expensive. I suppose I could go 85 gn for roe/foxes and keep 100gn RWS for hinds.

  2. #2
    3000fps mv is quite quick for a 100 grain bullet in a .243. Have you got access to a chronograph ? It would be helpful to chrono the factory rounds then compare the home-loads. You will need a muzzle velocity of 2,850 fps to achieve the 1,750 foot pounds muzzle energy with a 100 grain bullet.
    When I used 100 grain Sierra Gamekings in my .243 I needed to achieve 2,768 fps mv to get 1,700 ft lbs (England and Wales). However 42 grains of Viht N160 produced 2,868 fps mv (1,826 ft. lbs m.e.) So a similar load to that should do the 1,750 ft.lbs for Scotland.
    I did not experience any problems with accuracy if the mv was over 2,700 fps. Rifle was a Sako 75. So hopefully, once you establish the real mv over the chrono, you should be set fair. Best wishes.

  3. #3
    what powder and who's max loads?

    i found huge variation between VV, Hornady and Lee data!
    their max may not be yours

    my spreadsheet data has Lee Max data for 100gr over N160 at 43.5gr whilst VV was 39gr!! according to VV data they got 2850fps from that.....not convinced!


  4. #4
    P,

    you may wish to try a flat based bullet instead. you may also wish to experiment with powders, I'm sure Ed can sell you a few film canisters to try out,,and some bullets too for that matter! personally, the 160 with 100g partitions is sweet in my 1:10 twist .243 to well over 200yds..on that note, do you know the twist of your barrel?

    regards

    ​Peter

  5. #5
    Quote Originally Posted by Heym SR20 View Post
    Gents, thoughts please. Made up some test loads for the 243 with 100gn Hornady BTSP starting at 38.5 and going up to 42gn (max load) test shot last night. The lower loads were appalling 4" for three rounds at best. Only when I got to 41gn did I start getting down 1 and bit inches. Got dark before I tried the max load. Even the 41gn was still shooting 3" lower than factory RWS 100gn which has a box velocity of 3000fps. The Heym shoots RWS very well and three rounds touching is the norm.

    My thinking is that with the lower loads they were not giving anything like the velocity to get good consistent spin on the bullet, nor enough pressure to get a good clean burn. Once it's getting up to 3000 fps there is enough rotational spin to keep 100 gn bullets stabilised.


    Real question is even at the high loads will there be enough spin to keep the bullet stable down range, or does spin slow down as velocity falls off down range.


    I'm looking at the 100gn bullet as its the legal minimum in Scotland for the bigger deer and I want one load to do everything. I want something that's good for 200yds, but most shots at 100 or so.


    My default is the RWS ammo, but at 35 a box of 20 it's getting expensive. I suppose I could go 85 gn for roe/foxes and keep 100gn RWS for hinds.
    A trawl through the archives confirms that I used the Hornady 100gr a lot in my Heym SR20N, but with Norma 204, Nobel 0, and IMR 4350 powders. The best overall length was 68.0mm ('cannellure 1mm clear of the neck' I wrote) and the best results usually near Max. @ 2980 fps.

    Sierra 100gr Prohunters were more accurate than the Hornady.

    The barrel is 60cm/23.6" so it's no problem to get factory nominal ballistics in the Heym. I may be wrong on this, but the rate of rotation on exit is set by the rifling twist & barrel length, which is a fast 1 in 10" in the .243..... so I'm sure it'll be fine at extended stalking ranges.

    ATB.
    If I'm going to be accused of it then it's just as well I did it.

  6. #6
    Thanks for the comments. In terms of powder I am using IMR 4350, with IMR load data.

  7. #7
    Just a thought, but what depth are you seating the bullet at. If you're seating further out than your load data, then you wo'nt be developing the pressure or velocity you're looking for with that load. As you're obviously aware 100g .243 bullets can be notoriously difficult to stabilise in some rifles, especially if you're not getting the velocity.
    dcg

  8. #8
    Quote Originally Posted by Heym SR20 View Post
    Thanks for the comments. In terms of powder I am using IMR 4350, with IMR load data.
    I use 37gns of H4350 with my 100gn .243 loads. 20 thou off the lans - 1/4" groups when I do my bit.

    I looked at imr4350 as a replacement but apparently it doesn't quite burn the same despite common opinion that it does.

  9. #9
    My tikka T3 loves 80 grain hornady spitzers behind 35.5 grains of Viht N140. Gets me out of +500 yards all day. What's the twist rate of your barrel? Mine is 1 in 10 but dislikes anything above 95grains, however Lapua 90g Scenars are also really good with about 33g N140

    i can pm you some of my load data if needed.

    ​j

  10. #10
    Quote Originally Posted by bewsher500 View Post
    what powder and who's max loads?

    i found huge variation between VV, Hornady and Lee data!
    their max may not be yours

    my spreadsheet data has Lee Max data for 100gr over N160 at 43.5gr whilst VV was 39gr!! according to VV data they got 2850fps from that.....not convinced!

    Hmmm did VV use your barrel?

    The problem is that people never consider that the testing done by powder makers would be in a barrel made to their specifications and a pressure gun. These often give hugely different results to a normal production barrel.

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