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Thread: Question on pairing a dawson .170 x .125 front with a stock rear.

  1. #1
    Member
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    Mar 2011
    Location
    Fairfield County, CT

    Question on pairing a dawson .170 x .125 front with a stock rear.

    I just received my Dawson front .170 x .125 sight, but haven't gotten my matching rear sight yet.

    Dawson says this front is supposed to match to a .285 rear, but if I'm reading some posts here, people are matching this front with a 10-8 rear which is supposed to be .270 - and that rear is supposed to be the same height as stock sights.

    So... are different companies measuring differently, or am I missing something?

    Does the math work with a .170 x .125 Dawson front with a stock rear (while I await my Dawson rear)?

  2. #2
    Site Supporter
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    Jan 2012
    Location
    Upper Michigan
    What gun?

  3. #3
    Site Supporter
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    Feb 2011
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    NH
    Up1911 got there first.
    Last edited by EricP; 09-08-2014 at 04:56 PM. Reason: too slow

  4. #4
    Member
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    Feb 2012
    Location
    Walker,La.
    Sounds like a Glock and using the .170 H front with a OEM rear will result in your POI approximately 1" low at 25 yards with a G17.

  5. #5
    Member
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    Mar 2011
    Location
    Fairfield County, CT
    HK45c.

    I've been trying to get the specs of the stock rear and haven't been able to find them.

  6. #6
    Just measure the stock front sight vs the DP front sight.

    Measure the sight radius, and then do the math (the formula is on the DP website).

    That will give you an idea how things will change compared to stock.

  7. #7
    Member JMS's Avatar
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    Feb 2011
    Location
    Fredericksburg, VA
    ^^^Ding.

    Sight radius in inches x vertical POI deviation in inches / Range to target in inches.

    Wait for your rear to arrive, and install it. Leave the stock front on the gun.

    Measure your sight radius.

    Shoot for group. Note how far under or over your desired POI the groups fall.

    Use the formula. Add the result to stock front sight height if printing high. Subtract result from front sight height if printing low. That'll confirm whether or not your Dawson front is the height you need/want to go with your Dawson rear.

    If not, the fact that it's uninstalled means you should be able to exchange it for the height you require with a minimum of fuss.

    EX: I have a CZ that's shooting 4" over the blade @ 25yd. If I want it POA/POI, 4" is my input. If I wanted it to print 1" over the blade, I'd use 3" as my input to the formula. Range input is 900".

    So -- for my CZ, it'd be:

    5.625" x 4" / 900" = .025" more front sight height required, for me.
    Last edited by JMS; 09-10-2014 at 07:06 PM. Reason: math good, but tipin no gud...

  8. #8
    Member
    Join Date
    Mar 2011
    Location
    Fairfield County, CT
    Quote Originally Posted by JMS View Post
    ^^^Ding.

    Sight radius in inches x vertical POI deviation in inches / Range to target in inches.

    Wait for your rear to arrive, and install it. Leave the stock front on the gun.

    Measure your sight radius.

    Shoot for group. Note how far under or over your desired POI the groups fall.

    Use the formula. Add the result to stock front sight height if printing high. Subtract result from front sight height if printing low. That'll confirm whether or not your Dawson front is the height you need/want to go with your Dawson rear.

    If not, the fact that it's uninstalled means you should be able to exchange it for the height you require with a minimum of fuss.

    EX: I have a CZ that's shooting 4" over the blade @ 25yd. If I want it POA/POI, 4" is my input. If I wanted it to print 1" over the blade, I'd use 3" as my input to the formula. Range input is 900".

    So -- for my CZ, it'd be:

    5.625" x 4" / 900" = .025" more front sight height required, for me.
    They actually made and shipped the matching rear within 36 hours of ordering.

  9. #9
    Chasing the Horizon RJ's Avatar
    Join Date
    Jan 2014
    Right, so probably stupid slash dumb slash noob question but: I have a M&P 9FS. The stock front sight is 0.160" high.

    So I assume if I swap in for a DP FO 0.160T front sight, the POI for my pistol would not move in elevation? (assuming no change to stock rear sights)

  10. #10
    Member JMS's Avatar
    Join Date
    Feb 2011
    Location
    Fredericksburg, VA
    If you shoot to the top of the blade, no mathematical or mechanical difference.

    However, if you shoot to a dot on the front sight, and that FO isn't in exactly the same spot as the front you replace, you may see a POI shift. Not all manufacturers put their painted dots, trit vials, or FOs in the the same spots, so just be mindful of the potential differences.

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