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Thread: Reverse Engineering a Factory Load

  1. #1

    Reverse Engineering a Factory Load

    Does anyone know a way to reverse engineer a factory load? Obviously it's easy enough to copy the dimensions and choose a similar bullet but I guess it's the powder that's the tricky bit!

    My .243 really likes 100gr Federal powershock...

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    but once my stock is run down I'm planning to move onto reloading for it. I have a similar issue with my .223 - it loves Sako 50gr 'Arrowhead'.

    I was wondering if there is any information out there with regards to what powders are most similar to what factory loads to assist with choosing a suitable powder. Then it would just be a question of working up the loads from minimum in the usual way.


    Or is trying to short-cut the normal process an exercise in futility?



  2. #2
    Distinguished Member tartinjock's Avatar
    Join Date
    Dec 2007
    Nairn, Inverness-shire

    My T3 Lite .243 liked Federal Powershok also, 100gr bullets.

    When I reloaded for it, I was using 36gr of H380, I was getting the same PIO as Federals, which was very convienent.

    Position and hold must be firm enough to support the firearm
    The firearm must point naturally at the target without any undue physical effort
    Sight alignment (aiming) must be correct
    The shot must be released and followed through without disturbing the position

  3. #3
    Thanks TJ, that's handy to know!

  4. #4
    Account Suspended
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    Jul 2010
    Bonnie Scotland
    Quote Originally Posted by csl View Post
    Does anyone know a way to reverse engineer a factory load?
    I have a similar issue with my .223 - it loves Sako 50gr 'Arrowhead'.

    Alex, Sako used to publish their load data on't net. I don't know if they still do.

  5. #5
    Its very easy even without a chronograph.
    Find the published MV for the load, try the side of the box, failing that the manufacturers website.
    Then use a good reloading program, I'm still using Sierra Infinity 5 and iuts good.
    Select a bullet (you can try different makes with infinity) and look up the same MV for bullet weight.
    Then load some samples and shoot them against a test group of factory from the same rifle. all being well they should group the same, same poi etc. If not then try slightly warmer or slower loads until you find the sweet spot!
    I shoot these test groups on a 4 foot board and label each group and take a digital photo with a ruler across the group. save to hard drive and hey presto go home and do the maths in the warm.
    I managed to find a 125 grain .303 load that had the same poi as my Norma 150 grain factory loads at 100 yards. Job done.

  6. #6
    With regard to the .223 Sako list the load as- 50Grn Arrowhead 21.6 grns of Vhitavouri N120. The arrowhead bullet is really a Nosler ballistic tip.

  7. #7
    Brilliant, thank you!

  8. #8
    Click image for larger version. 

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ID:	2788This is what I was on about, record the load against the group size.
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ID:	2789Gives you a comparisom to wrk against in the dry.

  9. #9
    Thanks BB, I would do that as part of a normal load development, the problem is that there must be many different permutations of loads that would give the same muzzle velocity with different ingredients, maybe the same average POI, but surely not the same grouping?

    If you have a factory load that you know works well (as in groups tightly) I am trying to avoid having to shoot loads of groups to find an equivalent. For example, now that I know the recipe for the .223 sako load I can choose an identical bullet, seat it the same as the factory load, choose the same powder, then start at book minimum (which is 21.2 for vit 120) for safety and work towards 21.6gr knowing that I *should* hit the sweet spot on or around 21.6gr.

    In theory.....

  10. #10
    But either way shooting the groups and recording them is a good thing, as you are already working up to max then you would be able to take them home and re do the calcs later if necessary!

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