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Rifle Scopes USO & CST...EREK Ops

BattleAxe

Chief
Full Member
Minuteman
  • Mar 3, 2010
    1,225
    50
    Earth
    This question is for the folks at USO and Mike at CST. I found something interesting today that I've never seen mention of.

    For brevity sake I'm going to refer to a USO SN3 TPAL 3.2 x 17x simply as the "17, and the exact same scope in 5 x 25x magnification as the "25", both with EREK.

    Background:

    I've had a USO SN3 3.2 x17x for 6 months now. It's been used primarily on my SASS but has acted as a sub for my Barrett while awaiting my 25 build. I've used both the USO and CST method of EREK adjustment, and both have worked as advertised on both rifles althouh the CST version is simpler.

    I received my 25 a week ago (for the Barrett) and hit the range to dial it in. I carried with me the EREK procedures that came with my 17 thinking they'd be the same. I started with the CST version, obtained zero, but ended up with only 13 mils elevation from zero after EREK adjustment. However I expected the same 22+ mils I achieved with the 17. Thinking I was screwing something up I used the USO procedures from the 17 and got the same result...only 13 mils up from zero.

    I started to think at this point that maybe the 2nd base I ordered (identical Aadmounts) was NOT the 20moa down version so I headed back to the shop for further evaluation. For the helluvit I dug out the EREK procedures that came with the 25 and to my surprise they were very different.

    Using a Leupold bore culminator I rezeroed the scope with the USO 25 procedures and magically it now appears that I have a proper zero with 22 mils up elevation so I think I'm going to make another trip to the range today to verify.

    My question is this...I assumed that the procedures would be the same regardless of model but neither the 17x USO or CST procedure will work on the 25 but the USO 25 procedures appear (at least on a culminator) to work properly.

    Am I going freakin nuts here?

    These are 1st steps the 17x procedures from USO that work just fine on a 17x but not on a 25x...

    1. Hold knob and back out EREK CCW until it stops
    2. Turn knob CCW until it stops
    3. Hold knob and turn EREK CW until reticle moves
    4. Turn knob CW until you reach your zero

    These are the procedures that came with the 25x...

    1. Hold knob and back out EREK CCW until it stops
    2. Turn knob CW until it stops. This will be your zero stop.

    Clearly something is different here. Can someone please educate me? Why 2 different procedures for <span style="font-style: italic">apparently </span>the same optic?
     
    Re: USO & CST...EREK Ops

    Sure enough the new procedure supplied with the 25x obtains zero with 20+ mils elevation left. Definately strange.
     
    Re: USO & CST...EREK Ops

    BattleAxe,

    Can you supply a little more info on your scopes? Mainly, what is the tube diameter for each model?

    Also, when following the CST video as well as our own video, do you have free clicks after your scope has reached its maximum elevation travel? Meaning, does the knob continue to turn CCW after the reticle stops moving?
     
    Re: USO & CST...EREK Ops

    1.
    SN3 TPAL 3.2 x 17x
    EREK 1/10 mil
    US #1 1/10 mil
    Left side parallax
    30mm tube, 44mm objective
    Lo-Pro rapid focus
    Mil Scale Gap

    2.
    SN3 TPAL 5 x 25x
    EREK 1/10 mil
    US #1 1/10 mil
    Left side parralax
    30mm tube 58mm obj
    Lo-Pro rapid focus
    Mil Scale gap

    Same except for objective and magnification.

    Just tried what you asked with a boresighter...yes the reticle stops moving before I run out of knob travel
     
    Re: USO & CST...EREK Ops

    Just tried the same drill with the 17x on my SASS and there's only 4 or so clicks left after the reticle stops moving.

    With the 25x there's a whole lot of rotation left after the reticle stops.