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Thread: Interesting (and a bit odd) load development outcomes

  1. #1

    Interesting (and a bit odd) load development outcomes

    Two new loads to develop, both using ADI AR2206H. I have a question that comes at the end of the post... first the data:

    Range conditions: about 18 deg C with a medium variable wind blowing from behind at about 05h30 to 11h30 if you imagine the target sitting at 12h00.

    Load #1 - varmint load
    Cartridge: ADI twice fired brass, CCI primer, Nosler Varmageddon 55gr (17240), OAL 2.260" (0.02" off the lands)
    Powder weights tested: 25gr, 25.5gr, 26gr AR2206H
    Rifle: Tikka T3 Supervarmint in .223, 1:12" twist

    Have owned this rifle for 4 years now and it's the most accurate I've ever had. Photos of load tests at 100m below:

    Attachment 77566Attachment 77567Attachment 77568

    Pretty happy with that. The third load (26gr) is the max load in the ADI load data book.

    Load #2

    Cartridge: Lapua brand new brass, Federal primer, Sierra Gameking 100gr SPBT (1560), OAL 2.640" (0.01" off the lands (see note below))
    Powder weights tested: 31gr, 31.5gr, 32gr, 32.5gr, 33gr AR2206H
    Rifle: Howa 1500 in .243 with 20" barrel, 1:10" twist

    *Note* The COAL measured with the Hornady tool is 2.650" which is the same as the stated length for several of the 100gr hunting bullets (e.g. Sierra), Hornady is 2.630". But the Noslers are 2.680" and won't fit this Howa chamber (e.g. Partition, which normally would be a first choice pill). This means there's not much room to seat bullets back from the lands, assuming they fir ok in the first place.

    This rifle is new. I broke in the barrel and zeroed the scope using Speer match bullets, mid range loads also using AR2206H, and was reasonably happy with the results. Photos of subsequent load tests at 100m below:

    31gr and 31.5gr
    Attachment 77569Attachment 77570

    The first shot with 31gr was with a dead cold barrel and it was way off. Like, WTF??? Assumed shooter error and continued. Subsequent shots up to the end of the 31.5gr group were spaced about 2 minutes apart and the barrel was only ever mildly warm.

    32gr, 32.5gr and 33gr
    Attachment 77574Attachment 77572Attachment 77573


    Then there's a fair gap in time to the start of the 32gr group, about 15-20 minutes, and the barrel is cold again. First shot - way off, unlikely to be shooter error this time, exactly the same stance, wind, etc as before. Then another three shots, with a 2 minute gap between shots and a mildly warm barrel, this yields reasonable grouping for 32gr which might just scrape 1 MOA at 100yds.

    Subsequent groups (32.5gr, 33gr) follow with 2 minute gaps, and a mildly warm barrel. Reasonable, but not great groups.

    So I'm a bit confused. Not had this before, usually groups with my hunting loads are pretty good, 1 to 1.5MOA, no outliers. This new .243 hunting load is only 'marginally stable' according to the Berger stability calculator, but there's no sign of keyholing and I've never had problems with this length/weight bullet in .243 before.

    The soft points on these Gamekings are pretty variable. COAL is up and down by a fair bit, some of the soft points are a bit out of shape. But, with the exception the the two 'cold barrel' shots, the groups demonstrate that my medium game sized target is shot in the vitals and likely very dead, every time.

    I need to eliminate these outlier shots. Where to start? Can it be related to the apparently short maximum COAL of 2.650"?

    Any advice would be much appreciated. Don't really want to spend a fortune of different powders, bullets etc, if the obvious is right under my nose and I just can't see it... Thanks in advance.
    Last edited by dodgyknees; 05-01-2017 at 09:50.

  2. #2
    I got the orientation of the target wrong when I took one of the photos. Turns out both 'outlier' shots are identical amount higher than the rest of the group. Not so random after all...

    Attachment 77590Attachment 77591

  3. #3
    Have you tried shooting a group letting the barrel completely cool between each shot to see if the barrel heating can be ruled out?

  4. #4
    What fill ratio does 33gr of AR2206H give you? Regards JCS



  5. #5
    I use the same bullet but I use 40gr of 2209. I have found 2209 to provide very consistent sub MOA results for bullet weights over 80gr. Give it a go, I think you will find it gives you good accuracy. Won't solve the one powder for everything though.
    Blaser K95 Stutzen - the ultimate deer stalking rifle

  6. #6
    Quote Originally Posted by jcampbellsmith View Post
    What fill ratio does 33gr of AR2206H give you? Regards JCS
    Good question and one that sent me on a voyage of new discovery.

    I worked out the load density for the 32gr AR2206H charge (the mid range of my test), using some old software I had. It returns a value of 72% using some reasonably accurate measurements for the boat tail of the Sierra 1560. This seems a bit low I guess...

    I used the ADI load data manual to derive the powder weights for my load development. They don't quote the exact bullet I was using, so I used the closest type which was the Speer 100gr boat tail spire point, a pretty close match I thought. The start / end value of powder weights are 31 / 33gr AR2206H.

    ADI quotes IMR4895 as the powder equivalent for AR2206H.

    So when I cross reference with the Sierra book, I see they quote a powder range of 31.6 to 36.2gr IMR4895 for a velocity range of 2500-2900fps. That's quite a difference.

    If I was to use the max Sierra powder weight, the load density (fill ratio? same thing?) increases to 81%.

    And looking at the question below from mchughcb, his 40gr would give a load density of 90%.

    As a comparison my ultra accurate .223 load which reliably gives me very tight groups all the way out to 300m: load density 99%.

    So now I'm wondering if I should carefully increase the load of AR2206H to the IMR4895 levels quoted by Sierra on the assumption that these two powders have very similar burn rates. They are #171 and #178 on the reloadersnest Powder Burn Rate Comparison.

    Bottom line, is the fill ratio too low, and the velocity too low?


    Quote Originally Posted by Boydy47 View Post
    Have you tried shooting a group letting the barrel completely cool between each shot to see if the barrel heating can be ruled out?
    I will next time. Because I don't exactly get the chance to 'warm up the barrel' when I'm about to shoot the one deer I really want, eh? I need to reliably know what it does when its dead cold.


    Quote Originally Posted by mchughcb View Post
    I use the same bullet but I use 40gr of 2209. I have found 2209 to provide very consistent sub MOA results for bullet weights over 80gr. Give it a go, I think you will find it gives you good accuracy. Won't solve the one powder for everything though.
    I will definitely look at that option, are you also using a .243 with a 1 in 10" twist? Don't suppose you've been able to chrono your load by any chance. It's quoted by ADI as being a little shy of 3000fps which would be good to achieve with reliable accuracy.
    Last edited by dodgyknees; 02-01-2017 at 11:00.

  7. #7
    Yes 1:10 twist.
    Blaser K95 Stutzen - the ultimate deer stalking rifle

  8. #8
    I think you may have answered your own question, usually i find if you can have the case near to full you get more accuracy, and usually fast is better than slow, try to use a powder giving near 100% at max velocity might help. good luck

  9. #9
    Picked up some ADI 2209 today which should give me up to 90% load density, so will load three weights with some new Lapua brass tomorrow and head out back to see what happens next. Thanks for the suggestions so far.

  10. #10
    Thanks to the forum members who volunteered ideas / advice, today's load development yielded a very satifying outcome. The red bullseye is 40mm diameter.


    I switched to ADI AR 2209 and started at 38gr and increased in 0.5gr increments.


    Load: 40gr ADI AR2209, C.O.A.L. 2.645", Sierra Gameking 100gr BT Spitzer. This C.O.A.L. is a soft touch on the lands, no neck crimp.





    I was pissed off to the max with shot #5, which I pulled left with poor exhale / squeeze timing.


    Here's an interesting photo of what happens if you make small changes to some of the variables:


    Load: 41gr ADI AR2209, C.O.A.L. 2.625", Sierra Gameking 100gr BT Spitzer. This C.O.A.L. is 0.020" back from the lands.

    [note: earlier I mistakenly entered 39gr for the powder weight, sorry about that]




    I was a bit over it after the 39.5 gr group, thinking it was gonna be a case of poor stabilisation. But then at 40gr, suddenly the group tightened up and job done. So there's a sweet spot for sure, and that's where I'll stick.
    Last edited by dodgyknees; 05-01-2017 at 06:10. Reason: Made a mistake with one of the powder weights

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