Rifle Scopes  Using the MST-100

long-shot

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I've received some PM's regarding zeroing and shooting the MST-100. I can sympathize. It's easily the hardest optic to setup I've ever used. I thought I would try to compile the information like in the "M40a1 Build Guide" in the Rifles section.

Most of us can identify this optic, but very few of us have used it. It holds a special place in some of our hearts because of its history and I have enjoyed shooting it in matches, and range sessions that last few years.

Zeroing:

This just plain sucks!

The way I do it is bore sight the rifle to get close at 100 yards. I know the Marine Corp does it differently, but they are also using standard ammunition. I'll cover this later. I use a large target (aprox 3'x3') to ensure I can get on target.

Loosen the small set screws like most optics. Send 1 or 2 rounds down range. Hopefully, you're on target. This is where things get tricky. With most other optics you would measure the difference between POA and POI (with ruler or reticle) adjust the knobs, zero the rifle, verify results, and be done with it.



With the MST-100 you physically have to move the reticle using the center larger allen wrench. I would "HIGHLY" recommend a vice or a strong rest for this part. With the reticle centered on the bullet holes you just shot move the allen wrenches to shift the reticle until it's on the POA. It takes me several attempts to get this right, and you will move the reticle in the wrong direction at least twice!



Once you're happy with the results tighten the small set screw. This is important for the BDC. I once shot an entire match without doing this, and couldn't figure out why I was hitting dirt beyond 300 yards.

Shooting:

I am a dial for elevation, hold for windage guy. I have a pet .308 load and had no intention of loading 2 different .308's. I needed to know the BDC drops, and this wasn't the easiest information to find. Once I knew what the BDC was set for, and by using the fine adjustment knob I could use my data with my load with very accurate results. The BDC is as follows:

100 - 0
200 - 2 MOA
300 - 5 MOA
400 - 8 MOA
500 - 12 MOA
600 - 16 MOA
700 - 20.5 MOA
800 - 25 MOA
900 - 31 MOA
1000 - 37.5 MOA





When adjusting for say 550 yards my drop chart tells me I need 12.7 MOA. I would place the large BDC on 500 (12 MOA), and move the fine adjust up 1 click (.5 MOA) giving me a total of 12.5 MOA. I have tested this method out to 800 yards in matches with more than satisfactory results (for me at least!). Using this method you can use your information. I determine my drops using density altitude and knowing the MST-100 drop values allows this.

Adjusting Parallax:

This is the anti-technology scope for most of us. I shoot a USO T-PAL normally so this thing is a bit different. Most people I speak to recommend the parallax be set at or around 300 yards. This will leave your 100 yard sight picture blurry as hell. This concerned me greatly at first. I started shooting it, and my groups opened up but nowhere near as much as I expected. I can easily shoot my M40a1 under 1" with a blurry target, terrible eye relief, and 10x magnification. This scope will never win a 100 yard bench match, but it won't disappoint you either when you get used to it.

You will need the spanner wrench to loosen the front of the scope. By screwing in or out you can set the parallax wherever you want it. When you tighten the lock ring back though the parallax will shift slightly.



Hope this Helps.
 

JBW3

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Re: Using the MST-100

To add to this;

After adjusting the parallax, re-confirm your zero. Sometimes the zero will change slightly when you move the objective.

This is implied but not defined. The center zeroing screws in the knobs are as follows, elevation-clockwise is down(bullet impact lower), windage-clockwise is left(bullet impact left).

Good bit of info above, this should really help some of the users.
John III
 

chad3

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Re: Using the MST-100

Thanks, builder put mine close, but good info for once I get out and true zero.
 

One-Eyed Jack

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Re: Using the MST-100

JBW#3, would you please confirm the BDC values in long-shot's post? Over the years I've collected two sets of BDCs for the MST-100 and that's one of them. The second set of BDCs has, for example, 39.5 MOA at 1kyd. I dunno which set is correct.
 

JBW3

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Re: Using the MST-100

The BDC above is correct, that is what I have as well. I can't find the BDC for the MST-150, must have put it somewhere so I wouldn't loose it!

John III
 

One-Eyed Jack

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Re: Using the MST-100

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: long-shot</div><div class="ubbcode-body">You will need the spanner wrench to loosen the front of the scope. By screwing in or out you can set the parallax wherever you want it. When you tighten the lock ring back though the parallax will shift slightly.
</div></div>
It's important to know that <span style="font-weight: bold">changing the parallax-free distance from 100 yards to 1000 yards is about 1/4 turn of the objective ring</span> - change it in small increments and check the parallax-free distance after each change.

I found the easiest method is to find an object at the distance you want to be parallax free (I'm using 300 yards, determined with a LRF). While looking at the object, turn the objective ring in small increments while moving your head side to side or up and down and observe the parallax shift. At some point the image of the object will stop shifting and you've made the adjustment. Then tighten the locking ring with the USO tool and recheck the parallax.
 

MtGoat

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Re: Using the MST-100

For zeroing the scope a set of allen wrenches with the long handles seem to help. I jumped back and forth trying to get the round perfectly centered until I about wore out the barrel. Finally figured out with the longer handled wrench I could adjust in much finer increments (no clicks here). It will be a cold day in **ll before I remove the optics on this gun


Pat
 

BasraBoy

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Re: Using the MST-100

Great thread...just about to head out and shoot with my GAP/MST combo for the first....think this could have saved me a lot of time, or at the very least pointed out some of the pitfalls and fixes.

Thanks guys!
 

merlinnnn

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Re: Using the MST-100

Ditto... MST-100 inbound FedEx today.. to mount on GAP M40A1 on smear stock... hope get it zeroed this weekend if the weather cooperates... doesn't look promising though..

Great thread, really helps us new to this great optic!!

Thank you,

merlinn
 

JBW3

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Re: Using the MST-100

BTW- the little "dent" in the objective tube is supposed to be there! I don't know how many calls we get on that. It is a keyway for the objective cell.
John III
 

long-shot

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Re: Using the MST-100

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MtGoat</div><div class="ubbcode-body">For zeroing the scope a set of allen wrenches with the long handles seem to help. I jumped back and forth trying to get the round perfectly centered until I about wore out the barrel. Finally figured out with the longer handled wrench I could adjust in much finer increments (no clicks here). It will be a cold day in **ll before I remove the optics on this gun


Pat </div></div>

Excellent point. There's nothing more awkward than looking through the scope, holding it steady, and moving the allen wrench.
 

kft101

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Re: Using the MST-100

Thanks for all the helpful info on the Unertl 10X and MST-100.

Getting myself one very soon, so this is great knowledge to have.
 

ChrisF

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Re: Using the MST-100


I have 2x MST-100s , and after I adjusted the parallex from the factory setting , its not usable , dosn't matter which way you turn the objective , will not focus at all .

The other one I have not played with the objective at all , and its still OK to use .

Its certainly not a very user friendly scope in terms of para & zeroing .


Later Chris
 

BasraBoy

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Re: Using the MST-100

Thanks Chris - that's not really what I wanted to hear
but I appreciate your help.

Surely it has to be retrievable, it's just mechanical....and it does cover it in the manual. Just hope I'm missing something simple?

I'll PM John III, see if he has any ideas.
 

mdmp5

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    Re: Using the MST-100

    Sounds like way too big of a pain in the ass.
     

    long-shot

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    Re: Using the MST-100

    My inbox is empty now. Sorry about that. I have always been able to focus my parallax, but sometimes rotating the focus doesn't adjust until you tighten the lock ring and it then "pops" in to place. It took me awhile to focus it properly for me. I was also new to the optic at the time so I really didn't know what I was doing. It doesn't take much to focus from 25 yards to infinity so small adjustments are best, and if you have a buddy who can rotate while you're behind the rifle it can really help. My biggest gripe about the optic really has to do with the M40a1 and not the optic. The length of pull on the stock with no real adjustment in the mount leaves me about 1/2" too far back. It's pretty easy to overcome, but just something to be aware of.
     

    JBW3

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    Re: Using the MST-100

    Just because I had this question asked a few minutes ago;

    When you want to adjsut the parallax to a closer yardage, unscrew the lock ring with your spanner wrench, then unscrew the outer adjustment ring a few revs. Then use your fingernails to grab the outer lock ring, pull it towards you, as if you are trying to pull it out of the scope. This will slide the objective out, then use the adjsutment ring to fine tune it.

    God I hope that all made sense.
    John III
     

    Anchor Zero Six

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    Re: Using the MST-100

    While I find this to be very interesting, it solidified the fact that I will never own one LOL. My ST-10 is much less complicated. I know its more about sentiment than function but wow I never realized they were this complicated.
     

    BasraBoy

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    Re: Using the MST-100

    Thanks for the encouragment long-shot...I've only had the scope /rifle a week so I'm not giving up on it just yet!


    With the tips both JBWIII and yourself have given...should get it back on track soon....if I don't, it won't be because of lack of help or effort.

    Mind you.....was looking enviously at a S&B PMII 4-16x42 at the range on Sunday


    Cheers

     

    MtGoat

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    Re: Using the MST-100

    The scope is a pain in the a$$ to get set-up and to use. If you have original base and rings you will NEVER want to remove the scope after dinking with it forever. With that said after you are done dinking they are great scopes


    Pat
     

    Sawyer

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    Re: Using the MST-100

    Ok... I have the allen wrenches... but what spanner wrench do I need? Sorry for the dumb question...
     

    BasraBoy

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    Re: Using the MST-100

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sawyer</div><div class="ubbcode-body">Ok... I have the allen wrenches... but what spanner wrench do I need? Sorry for the dumb question...</div></div>

    The wrench for the objective should come with the scope.....looks like this:

     

    BasraBoy

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    Re: Using the MST-100

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MtGoat</div><div class="ubbcode-body">The scope is a pain in the a$$ to get set-up and to use. If you have original base and rings you will NEVER want to remove the scope after dinking with it forever. With that said after you are done dinking they are great scopes


    Pat</div></div>

    Pat, once it's done, I'm locking it off, hiding the objective wrench in a deep, dark hole and forgetting it exists!
     

    Pinmaster

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    Re: Using the MST-100

    Since it may be a PITA to use maybe somebody will sell me theirs for my M40a1 build (LOL).
     

    Sawyer

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    Re: Using the MST-100

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BasraBoy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sawyer</div><div class="ubbcode-body">Ok... I have the allen wrenches... but what spanner wrench do I need? Sorry for the dumb question...</div></div>

    The wrench for the objective should come with the scope.....looks like this:

    </div></div>

    Hmmm... I do not remember seeing that. I will have to go home tomight and recheck the package. Thank you for the photo and info!

    Sawyer
     

    littlebarney

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    Re: Using the MST-100

    #1 rule of the MST-100.never ever screw with the parallax.in the Marines it would take all day or longer to get it adjusted just right.

    as far as zeroing a MST-100,its fairly simple.it should be done in a few minutes with under 10 rounds..at 300yds.

    when its finally zeroed and parallax free tighten everything down like the hinges of hell.

    make sure your o rings are nice and tight and lubed.if not and its raining and the scope gets soaked you will know why real quick.

    also if your going to shoot the scope/rifle in freezing weather leave it outside for a few hours so the scopes nice and cold before shooting it.otherwise it will fog up.in the Marines we just left the rifles outside in the cold,we never had them inside in 0degree weather



     

    littlebarney

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    Re: Using the MST-100

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: long-shot</div><div class="ubbcode-body"> The length of pull on the stock with no real adjustment in the mount leaves me about 1/2" too far back. It's pretty easy to overcome, but just something to be aware of. </div></div>

    the early M40A1 smear stocks are a 1/2" or so shorter in the LOP than the later M40A1 woodland stocks that the marines used.
    maybe change your stocks out.
     

    WRM

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    Re: Using the MST-100

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: littlebarney</div><div class="ubbcode-body">#1 rule of the MST-100.never ever screw with the parallax.in the Marines it would take all day or longer to get it adjusted just right.

    as far as zeroing a MST-100,its fairly simple.it should be done in a few minutes with under 10 rounds..at 300yds.

    when its finally zeroed and parallax free tighten everything down like the hinges of hell.

    make sure your o rings are nice and tight and lubed.if not and its raining and the scope gets soaked you will know why real quick.

    also if your going to shoot the scope/rifle in freezing weather leave it outside for a few hours so the scopes nice and cold before shooting it.otherwise it will fog up.in the Marines we just left the rifles outside in the cold,we never had them inside in 0degree weather

    </div></div>

    Perfect - I agree 100%. You don't reset the parallax for each shot - you make sure your eye is centered in the scope for each shot! I set/zeroed at 300 w/175MKs, and haven't touched it since. There are are a couple hints I'd like to offer.

    Parallax - if not set at 300, where is it set - 100, 200, 600? If at 100, then screw the AO IN a turn (as noted in JBW3's post above), snug the lock ring, and check it again. Repeat until you're there. Screwing the AO IN when you want parallax OUT seemed counter-intuitive to me, but that is what I found....

    Zero (at 300 yards) - set knob at 300, fire a group to determine POI. Hold rifle in steady rest w/crosshair on original POA, and use center allen screw(s) to move crosshair to POI. Verify zero. Lock it down. Done.

    And you only need to set it once!

    Cheers,

    Bill
     

    merlinnnn

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    Re: Using the MST-100

    Got to shoot the M40A1 (GAP) with the MST-100 for the first time this weekend... hands down my favorite set up.. The MST was different than I am accustomed to setting up, but very logical. Very pleased with the outcome of this project. The rifle shoots, and the scope rocks:)

    merlinn
     

    merlinnnn

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    Re: Using the MST-100

    Will do, I drilled out a broken front swivel stud, awaiting a tap to install a new swivel. It's in an early smear stock, have a issue MRT dated sling to finish it off.. a few days.

    merlinn
     

    chip8541

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    Re: Using the MST-100

    Thought id add my two cents in here especially for Chris F.

    Your 2 scopes are still good, here is the problem: Set your focus at 100. Move back to 300 to adjust parallax. unscrew lock ring till you have an 1/8th or so of an inch gap. Take your fingernails and pull the lock ring towards the muzzle to reset to baseline. Get behind the rifle. have someone slowly turn the fine tune clockwise if they were looking at the objective. Communicate with each other until parallax is fixed. If parallax appeared good but you have turned too much past that point and it started to get worse again, take your fingernails, reset and start again. Repeat until you are there. Once there keep your eye through the scope as your helper tightens the lock ring on the fine tune. Said helper shold be holding the fine tune rock steady, possibly backing off ever so much to where the tightening of the lock ring will only nudge the fine tune into its original position of adjustment.

    As this is happening you are checking to make sure that no problems in parralax shift has occured during tightening.

    Go back to the 100. Refocus. Go back to the 300 and check to see if parallax is still good. Adjust again if necessary. Go to 100 check focus and if good its ready to zero.

    When zeroing keep set screws semi tight while firing. fire your 2 or 3 rds, loosen set screws and turn the adjusting screws to adjust impact. the direction of travel of the set screw will dictate change in impact. (i.e. on the elevation turret if you are turning clockwise the screw is screwing down or into the scope pushing impact down. Counter clockwise you are screwing out or up and away from scope pushing impact up.) Very little movement of the adjustment screws goes a long way. Once adjusted semi tighten set screws, and shoot your 3 and repeat till zeroed. Once zeroed tighten the set screws real good. It helps to hold the allen in the adjusting screw and hold tight while adjusting the set screws to avoid movement of your zero. Shoot a confirmation. Should take 10 no more than 20. More than 20 you get made fun of.

    We most of the time had one chance to get the parallax and focus done right due to range schedules to complete training. As a result I had some guns that werent adjusted quite right in that department before. But as was said that is mitigated in sour fundamentals and consistency of all aspects of marksmanship through follow through. Since you have the time take the time to get it as dead nuts. Set it and forget it. Hope this helps

    P.S. Before you zero, loosen set screws and screw the adjustment back and forth a little to make sure there are no hangups in the mechanism and return to original setting. Semi tighten set screws and get to zeroing. Especially helpful if scope hasnt been adjusted in a long while, new or old.
     

    chip8541

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    Re: Using the MST-100

    Chris F once you have gone past that point of no return on parallax you have to reset. You cant turn the fine tune back, it will do nothing. No amount of focus will fix it if you dont go back and reset to adjust again and get it right. Hope your fingernails are strong, it can be painful.
     

    Pinmaster

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    Re: Using the MST-100

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BasraBoy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sawyer</div><div class="ubbcode-body">Ok... I have the allen wrenches... but what spanner wrench do I need? Sorry for the dumb question...</div></div>

    The wrench for the objective should come with the scope.....looks like this:...


    pic

    </div></div>



    The MST-100 that I received did not have the wrench in the box either...I wonder if I can order one from USO???
     

    Sawyer

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    Re: Using the MST-100

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Pinmaster</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BasraBoy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sawyer</div><div class="ubbcode-body">Ok... I have the allen wrenches... but what spanner wrench do I need? Sorry for the dumb question...</div></div>

    The wrench for the objective should come with the scope.....looks like this:...


    pic

    </div></div>


    The MST-100 that I received did not have the wrench in the box either...I wonder if I can order one from USO??? </div></div>

    Give Becky a call:

    Becky
    (714) 582-1956
    becky@usoptics.com

    I would bet if it was left out they will send you one... but They will sell you one for sure.
     

    Pinmaster

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    Re: Using the MST-100

    <span style="font-weight: bold">Flase alarm</span>...the guy that I bought the scope from found it and is going to mail it to me.

    Thanks for USO's info though.
     

    BasraBoy

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    Re: Using the MST-100

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: chip8541</div><div class="ubbcode-body">Chris F once you have gone past that point of no return on parallax you have to reset. You cant turn the fine tune back, it will do nothing. No amount of focus will fix it if you dont go back and reset to adjust again and get it right. Hope your fingernails are strong, it can be painful. </div></div>

    chip - you're dead on....I managed to get mine back in. long-shot and John III were a great help with advice and instructions.

    I was being a pussy seeing as how it was a new scope/rifle. Once I realised I wasn't going to break it, it came together fine.

    Yes, zeroing the scope first time is a bit of a performance but once in....seems to work fine.

    Hope to post pics of first groups with the rifle in a week or so.
     

    ChrisF

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    Re: Using the MST-100


    Thanks guys for the info , I have very short nails at the moment , but will give it a go later , and hopefully , I can sort it myself .


    Cheers Chris

    One of my scopes will be going on a Bastard M40A1 ( I cannot bear to make it on a Rem700 , so will be a better clone action ) , and the other on a Parker Hale M87 ( C3A1 ) clone .
     

    hrt4me

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    Re: Using the MST-100

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: chip8541</div><div class="ubbcode-body">Set your focus at 100. Move back to 300 to adjust parallax. Unscrew lock ring till you have an 1/8" or so gap. Take your fingernails and pull the lock ring towards the muzzle to reset to baseline. Get behind the rifle. Have someone slowly turn the fine tune clockwise if they were looking at the objective. Communicate with each other until parallax is fixed. If parallax appeared good but you have turned too much past that point and it started to get worse again, take your fingernails, reset and start again. Repeat until you are there. Once there keep your eye through the scope as your helper tightens the lock ring on the fine tune. Said helper should be holding the fine tune rock steady, possibly backing off ever so much to where the tightening of the lock ring will only nudge the fine tune into its original position of adjustment.

    As this is happening you are checking to make sure that no problems in parralax shift has occured during tightening.

    Go back to the 100. Refocus. Go back to the 300 and check to see if parallax is still good. Adjust again if necessary. Go to 100, check focus and if good, then it's ready to zero.

    When zeroing keep set screws semi tight while firing. Fire your 2 or 3 rds, loosen set screws and turn the adjusting screws to adjust impact. The direction of travel of the set screw will dictate change in impact (i.e. on the elevation turret if you are turning clockwise, the screw is screwing down or into the scope, thus pushing impact down. Counterclockwise you are screwing out or up and away from scope, thus pushing impact up). Very little movement of the adjustment screws goes a long way. Once adjusted, semi tighten the set screws and shoot your 3 and repeat till zeroed. Once zeroed, tighten the set screws really good. It helps to hold the allen in the adjusting screw and hold tight while adjusting the set screws to avoid movement of your zero. Shoot a confirmation. Should take 10, no more than 20 rounds.

    We most of the time had one chance to get the parallax and focus done right due to range schedules to complete training. As a result I had some guns that weren't adjusted quite right in that department before. But as was said that is mitigated in sour fundamentals and consistency in all aspects of marksmanship through follow through. Since you have the time, take the time to get it as dead nuts. Set it and forget it. Hope this helps!

    P.S. Before you zero, loosen set screws and screw the adjustment back and forth a little to make sure there are no hang-ups in the mechanism, and return to original setting. Semi tighten set screws and get to zeroing. Especially helpful if scope hasn't been adjusted in a long while, new or old. </div></div>

    Thnaks for the good info!
     

    D_TROS

    Flag-Sword-Cross
    PX Member
    Minuteman
    Aug 19, 2010
    2,081
    1,489
    North Denver, CO
    Re: Using the MST-100

    Anybody know the adjustments of the windage knob? [similiar to how the elevation is: 1 (100yds)=0, 2 (200yds)=2moa, 3 (300yds)=5moa, 4 (400 yds)=8moa, etc,] what does the number correlate to in moa of the windage knob??

    Just want to know how to correlate the info to my rifles dope similiar to how you did in your explanation for elevation.

    Also, are they supposed to be the adjustment for a 10 mph wind at each of the ranges?

    thanks for the informative thread,
    DT
     

    D_TROS

    Flag-Sword-Cross
    PX Member
    Minuteman
    Aug 19, 2010
    2,081
    1,489
    North Denver, CO
    Re: Using the MST-100

    And the fine fine tune knob under the elevation turret is also in 1/2 moa increments?

    Thanks, I thought I read this somewhere but I cant seem to find it.

    Regards,
    DT