USMC Unertl locking in the parallax on the objective

[Frank Green]

Ok... call me a homo! Yes I'm picking on myself! I should be able to figure this out but for whatever reason it's kicking my butt!

So, I shot the M40A1 today and wanted to fine tune the zero a little more as well as set the focus etc... after shooting it at my 117-yard target I then went to the steel plate at 430 yards. If I get the chance, I might be able to shoot the rifle in a vintage sniper rifle match in early Dec. out in MT. That match is shot at 300, 385 and 500 yards. So, I want to lock in the parallax/focus on the objective. Here is where it is at... but how do I lock it in without it moving on me? You can see the gap at the very front of the ring and behind the larger diameter ring.

This was my last group for getting a final zero on it at 117 yards. Yes... I was a homo on that high round. Probably too much time playing with all the adjustments and just blew it. More I think about it I didn’t blow it. I did bring the zero down on the scope with the allen wrench and locked it in. I needed about 1.5” down and tried to move it about 1 minute… I think I got it right! Only needed one windage adjustment after my bore sight job and first sighter…never touched the windage dial after that. So the scope is tracking and holding zero!

So happy with the 117 yard zero... I moved the elevation dial to 4 and initially moved the fine tune adjustment up 1 click also but knowing the 169smk have a higher bc than the old 173gr bullets and even more than 175smk... I decided to take the 1 click off the fine adjustment. On top of all that for the most part I've been having a tail wind mostly speed wise from 6-11mph. Glad I took that fine adjustment click off.

So, for 37 rounds down the barrel... I'm digging it! Average velocity is coming in at 2687fps. No need to run it any faster.

So, thoughts on locking in the objective ring without moving the whole set up please.

 

[D̷e̷v̷i̷l̷D̷o̷c̷A̷Z̷]

Bicycle inner tube? Use it like a big rubber band?

Broccoli rubber band from the produce isle?

 

[Skunk]

If the objective lens cell is against the adjustment collar, tightening the lock ring should not change the parallax setting.

Are you saying you don’t have the spanner wrench to tighten the ring?

 

[Frank Green]

To DevilDocAZ….And put it where?

 

[Frank Green]

If the objective lens cell is against the adjustment collar, tightening the lock ring should not change the parallax setting.

Are you saying you don’t have the spanner wrench to tighten the ring?

Yes I do… but if I’m doing it right and hold the larger diameter ring… as I turn in the lock ring with the spanner tool… I’m losing the adjustment. So what am I doing wrong?

I also want to say I turned the larger ring forward to the very front edge of the locking ring and then put the spanner wrench on also to tighten it all up… still moved on me .

 

[Skunk]

Ok, you’ve accomplished your parallax adjustment in reverse.

The lens cell should be pulled forward to the larger ring. You have the larger ring turned away from the lens cell, and when you tighten the lock ring, you’re pulling the lens cell forward to the larger ring.

Clear as mud?

From where you’re at, turn the larger ring in/rearward until it contacts the lens cell (you should probably be able to feel the resistance when contact is made). Then tighten the lock ring.

 

[Redmanss]

Check this post #31 here, way better detail than I can type out at the moment.

Unertl Scope Question. Zeroing

I have received my scope back from the repair shop and would like to get my m40a1 up and running. Upon reading the Technical Manual on the rifle and related optical equipment, and without a 300-yard range at this time, what is the best way to zero the scope? Should I use the FIELD EXPEDIENT...

www.snipershide.com

 

[sirhrmechanic]

Some good shooting even with the challenges adjusting things.

Great combo!

Cheers,

Sirhr

 

[Frank Green]

Some good shooting even with the challenges adjusting things.

Great combo!

Cheers,

Sirhr

Thanks! Can’t tell you how many times I hopped on the 4whlr and ran down to the 117 yard target to check what was going on. When I had it focused at a 100 yards I could see the bullet holes no problem. Not bad for a 10x scope and as ancient as the glass is.

 

[Frank Green]

Ok, you’ve accomplished your parallax adjustment in reverse.

The lens cell should be pulled forward to the larger ring. You have the larger ring turned away from the lens cell, and when you tighten the lock ring, you’re pulling the lens cell forward to the larger ring.

Clear as mud?

From where you’re at, turn the larger ring in/rearward until it contacts the lens cell (you should probably be able to feel the resistance when contact is made). Then tighten the lock ring.

OK…. That makes sense… I’ll give it a whirl and see what happens and I’ll report back. Probably during the week after work sometime I’ll mess with it.

Even though it was frustrating… still had a nice time pulling the trigger!

 

[Skunk]

Once you get the parallax set around 300yds, targets at 100 will be a hair fuzzy. Nature of the beast.

Hard to beat one of these scopes once you’ve got it properly set up and zero’d.

 

[sirhrmechanic]

Thanks! Can’t tell you how many times I hoped on the 4whlr and ran down to the 117 yard target to check what was going on. When I had it focused at a 100 yards I could see the bullet holes no problem. Not bad for a 10x scope and as ancient as the glass is.

That glass is better than 99 percent of what is available today... the advancements, IMHO, have been made in coatings. Not in 'glass.' And by 'glass' I don't mean the melted silica... but the grinding and optics design. Sometime check out Frank Cooke's "The Optics Cookebook" which was (IMHO) written in the 1940's. It's still one of the best design references. Not a lot has changed since Frank wrote it.

The incredible leaps forward have been in coatings. And some of the mechanical designs. But, yeah, the last 30 years or so have been tiny increments. All great. But not much of it has been due to 'glass!'

Same with barrels, me-bets!

That said... it's the 'increments' that are happening here on SH. AND which are continuing to make this field an amazing place to be!

Sirhr

 

[Frank Green]

Once you get the parallax set around 300yds, targets at 100 will be a hair fuzzy. Nature of the beast.

Hard to beat one of these scopes once you’ve got it properly set up and zero’d.

Yep I understand that it’s the nature of the beast. It’ll still pound though. LOL!

 

[Frank Green]

Check this post #31 here, way better detail than I can type out at the moment.

Unertl Scope Question. Zeroing

I have received my scope back from the repair shop and would like to get my m40a1 up and running. Upon reading the Technical Manual on the rifle and related optical equipment, and without a 300-yard range at this time, what is the best way to zero the scope? Should I use the FIELD EXPEDIENT...

www.snipershide.com

I actually did a search on this before I took it out and found that post as well. I took a picture of it so it was on my phone will in my shoot house.

I thought I was following it correctly but after just reading it again… I now realize I wasn’t. Probably trying to do much at one time… zero the scope, record chronograph numbers etc…

Thanks for bringing that post back up…as it made me reread it again. Pretty sure I’ve got the objective end figured out… I hope. LOL!

 

[Redmanss]

I actually did a search on this before I took it out and found that post as well. I took a picture of it so it was on my phone will in my shoot house.

I thought I was following it correctly but after just reading it again… I now realize I wasn’t. Probably trying to do much at one time… zero the scope, record chronograph numbers etc…

Thanks for bringing that post back up…as it made me reread it again. Pretty sure I’ve got the objective end figured out… I hope. LOL!

Don’t feel bad it’s giving you a bit of grief. The focusing exercise at school, even with instructors helping out, would typically take 2-3 hours. It’s a finicky process and many times requires going back to step one, several times if inexperienced.

ETA: I always preferred to walk it in slowly. Unlock, turn it in to get it somewhat close, lock it, check it, unlock, adjust a little (1/4 turn max), lock it, check it, repeat until good.

You have to lock it down to check it, that does make a difference. Don’t have to go tight, just good and snug to set the lens in place.

 

[onetopgun]

Below is a copy of a post I made a few years back. See the link contained therein for more detail than Ive ever seen in any MST 100 Manual or DOD Publication:

These are the Come Ups for the Main Elevation Turret of the US Optics MST-100:

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

Set the Ocular first to bring the Reticle to a sharp focus against a blank background.

Adjust the objective so the scope is parallax free at 300 yards

Rough Zero the scope at 100 yards with the Main Elevation Turret set at “1”

If possible, Refine your Zero at 300 yards with the main elevation turret set at “3” with “0” on or off the vernier (Fine Tune) with whatever apparent windage is necessary.

Ping the following thread for additional detail: https://www.snipershide.com/shooting/threads/using-the-mst-100.23517/

Regards
JHC

USO MST-100 Users/Service Manual

Wondering if anyone has a copy of the manual in pdf they could send me. Thanks!

www.snipershide.com

Additional Comment: Note that the come-ups listed above are for the USO MST-100. The come-ups for the Unertl MST-100 are slightly different. I’ll do some digging and see if I can a pic of them. Stand by.

Here are the come-ups for the Unertl MST-100:

 

[ODCMP]

Frank:

I have a scanned pdf of the Operator's Manual from 2003 that I can email if you want a copy. Just send me a message with your email and I'll send it. Same to anyone else who wants a copy.

I think the messages above should have you squared away. Just remember when trying to adjust the parallax that the adjustment ring only pushes the lens assembly rearward. To move the lens assembly forward, you have to manually pull it forward using the locking ring. If you turn it rearward too far past the parallax sweet spot, then you will need to pull it forward and try again.

Here is an old thread where I tried to describe it. See post #'s 5 and 7:

M40A1 Unertl/MST-100 10x Parallax Question

I recently aquired my unicorn M40A1 from @gregv and understand there is a lot of nuance to using the Unert/MST-100 10X scopes. Being that I don't have readily available access to ranges over 300 yards, I do most of my shooting at 100-300. I know the suggested parallax setting is either 200 or...

www.snipershide.com

Once you do it right, it will be obvious.

The parallax is not a real precise adjustment. If you can tell the difference between a 350 yard and a 375 yard parallax adjustment, you have a better eye than me.

Dave

 

[Jrb572]

I think I have my 175gr SMK load set to 2625fps and it’s spot on up to 600 yards. I have not had it any further yet.

 

[Skunk]

Also, just for everyone’s understanding, turning the large ring clockwise/inward (looking from muzzle) adjusts the parallax to a further distance. Conversely, moving the objective cell out toward the muzzle achieves a nearer parallax setting.

 

[bildoe308]

Below is a copy of a post I made a few years back. See the link contained therein for more detail than Ive ever seen in any MST 100 Manual or DOD Publication:

These are the Come Ups for the Main Elevation Turret of the US Optics MST-100:

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

Set the Ocular first to bring the Reticle to a sharp focus against a blank background.

Adjust the objective so the scope is parallax free at 300 yards

Rough Zero the scope at 100 yards with the Main Elevation Turret set at “1”

If possible, Refine your Zero at 300 yards with the main elevation turret set at “3” with “0” on or off the vernier (Fine Tune) with whatever apparent windage is necessary.

Ping the following thread for additional detail: https://www.snipershide.com/shooting/threads/using-the-mst-100.23517/

Regards
JHC

USO MST-100 Users/Service Manual

Wondering if anyone has a copy of the manual in pdf they could send me. Thanks!

www.snipershide.com

Additional Comment: Note that the come-ups listed above are for the USO MST-100. The come-ups for the Unertl MST-100 are slightly different. I’ll do some digging and see if I can a pic of them. Stand by.

Here are the come-ups for the Unertl MST-100:

I made that card years ago from a manual for my Unertl 10X. I still have it in my range bag/round count book…lol.

 

[Frank Green]

Below is a copy of a post I made a few years back. See the link contained therein for more detail than Ive ever seen in any MST 100 Manual or DOD Publication:

These are the Come Ups for the Main Elevation Turret of the US Optics MST-100:

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

Set the Ocular first to bring the Reticle to a sharp focus against a blank background.

Adjust the objective so the scope is parallax free at 300 yards

Rough Zero the scope at 100 yards with the Main Elevation Turret set at “1”

If possible, Refine your Zero at 300 yards with the main elevation turret set at “3” with “0” on or off the vernier (Fine Tune) with whatever apparent windage is necessary.

Ping the following thread for additional detail: https://www.snipershide.com/shooting/threads/using-the-mst-100.23517/

Regards
JHC

USO MST-100 Users/Service Manual

Wondering if anyone has a copy of the manual in pdf they could send me. Thanks!

www.snipershide.com

Additional Comment: Note that the come-ups listed above are for the USO MST-100. The come-ups for the Unertl MST-100 are slightly different. I’ll do some digging and see if I can a pic of them. Stand by.

Here are the come-ups for the Unertl MST-100:

Yep seen your post when I was doing searching about this.

I'll keep you guys posted how it turns out for me. Next time out... no shooting... just gonna try and dial it all in.

 

[Frank Green]

Also, just for everyone’s understanding, turning the large ring clockwise/inward (looking from muzzle) adjusts the parallax to a further distance. Conversely, moving the objective cell out toward the muzzle achieves a nearer parallax setting.

I seen that in playing with it... I shot it at the 117 yard target when I dialed in the focus but again when I went to lock it down it was moving out of focus on me. Same thing at distance.

Thanks for the extra tip!

 

[Frank Green]

Frank:

I have a scanned pdf of the Operator's Manual from 2003 that I can email if you want a copy. Just send me a message with your email and I'll send it. Same to anyone else who wants a copy.

I think the messages above should have you squared away. Just remember when trying to adjust the parallax that the adjustment ring only pushes the lens assembly rearward. To move the lens assembly forward, you have to manually pull it forward using the locking ring. If you turn it rearward too far past the parallax sweet spot, then you will need to pull it forward and try again.

Here is an old thread where I tried to describe it. See post #'s 5 and 7:

M40A1 Unertl/MST-100 10x Parallax Question

I recently aquired my unicorn M40A1 from @gregv and understand there is a lot of nuance to using the Unert/MST-100 10X scopes. Being that I don't have readily available access to ranges over 300 yards, I do most of my shooting at 100-300. I know the suggested parallax setting is either 200 or...

www.snipershide.com

Once you do it right, it will be obvious.

The parallax is not a real precise adjustment. If you can tell the difference between a 350 yard and a 375 yard parallax adjustment, you have a better eye than me.

Dave

Thanks for the offer... JRB already got me a copy as well.

My eyes are not shot yet although I do use cheater/reader glasses most of the time now...LOL!

 

[Frank Green]

ETA: I always preferred to walk it in slowly. Unlock, turn it in to get it somewhat close, lock it, check it, unlock, adjust a little (1/4 turn max), lock it, check it, repeat until good.

You have to lock it down to check it, that does make a difference. Don’t have to go tight, just good and snug to set the lens in place.

^^^^^ Thanks!

 

[RTH1800]

Frank,
I did not read all the post but will say this. Once you get it figured out and accept the limitations of the scope I think you will like it.
I used mine quite a bit and found it great for actual field use. As you know, it's no target scope.
Hope you find it to your liking.

 

[Frank Green]

So for a partial update.... I couldn't get out last week... just didn't have any extra time etc.. but last night I did set the eye focus and was able to lock that in.

You loosen up the lock ring... and then move the knurled ring to bring it into focus. Which I was doing but every time I tightened up the lock ring... it took it out of focus because I wasn't holding the knurled ring in place. So the whole assy was moving on me. Probably the same thing that was happening with the objective end as well.

So this time I started over and focused it. Then I held the knurled ring in place with one hand and tightened the lock ring with the other hand. Presto... focus is locked in.

The objective end is next... after the rain stops here after the next couple of days.

Thanks to all you guys that helped!

Later, Frank

 

[ODCMP]

Good job, you'll get there!

I like to adjust the ocular focus by focusing on a white piece of paper. A white page on the computer works well too. There is just less visual clutter and interference that way.

For the parallax, the best is to have a clear view of objects at known distances. Like I said before, I prefer to initially adjust parallax away from the range. I had an office just above a freeway, so I used google earth to measure the distances to several business signs along the freeway. I had them measured at 150, 300, 400, 600 and 1000 yards. Since the signs had lettering it was easy to tell whether the image was crisp, and parallax adjusted at the selected range. I still go back to the parking lot of that office occasionally to check the parallax on a scope. In that case I take the scope off the rifle first, ha!

 

[Frank Green]

I focused the crosshairs on the white wall in the basement. Normally I do it outside looking at a clear blue sky but pretty much rained all day.

 

[tfont48]

Frank, did you ever get this sorted? I have a Unertl (w/ uso mod) that I believe is giving me similar issues, if I understood your post correctly.

Problem: The objective lens cell housing that is adjusted (slid forward and backwards by the focus ring) to set the parallax does not come into contact with my locking ring when the parallax is set. So when I go to snug my locking ring down, it pulls the assembly forward and sets the parallax at something ridiculous like 5yds or so.
Note: Yes, I have set my ocular lens to where the reticle is crisp immediately upon shouldering. I have owned two other Unertl/Mst-100 and never had this issue. So I'm at a bit of a loss.

Possible Solutions: I have thought of having a spacer machined to fill the gap between the locking ring and the objective lens cell housing, which should fix the issue as it will allow the two to "lock" together without pulling the objective lens cell housing forward. I hesitate with this though, because the scope was never mounted after being rebuilt and it practically new "old stock" so surely theres not something majorly wrong, and instead some adjustments out of wack.

 

[Skunk]

Frank, did you ever get this sorted? I have a Unertl (w/ uso mod) that I believe is giving me similar issues, if I understood your post correctly.

Problem: The objective lens cell housing that is adjusted (slid forward and backwards by the focus ring) to set the parallax does not come into contact with my locking ring when the parallax is set. So when I go to snug my locking ring down, it pulls the assembly forward and sets the parallax at something ridiculous like 5yds or so.
Note: Yes, I have set my ocular lens to where the reticle is crisp immediately upon shouldering. I have owned two other Unertl/Mst-100 and never had this issue. So I'm at a bit of a loss.

Possible Solutions: I have thought of having a spacer machined to fill the gap between the locking ring and the objective lens cell housing, which should fix the issue as it will allow the two to "lock" together without pulling the objective lens cell housing forward. I hesitate with this though, because the scope was never mounted after being rebuilt and it practically new "old stock" so surely theres not something majorly wrong, and instead some adjustments out of wack.

Both of the rings on the front of the scope are threaded and move fore/aft.

Set the parallax by turning the rear/wide collar in/out WITH THE LENS CELL PULLED AGAINST IT.

There is not a thing wrong with your scope.

 

[tfont48]

With the lense cell against the focus ring, the focus ring CANNOT push the cell far enough into the scope to achieve focus. I just tested this again. The only way to get the scope to achieve focus is to thread the locking ring further out, use the locking ring to push the cell further into the housing than the focus ring had the ability to do, and then tighten the locking ring to pull the cell slightly forward to fine tune the adjustment.

I will attempt to explain this another way. With the locking ring loosened, and the objective lens cell pulled out and positioned against the focus ring, the focus ring bottoms out before the picture becomes clear, setting the parallax at roughly 43yds (I realize I understated earlier, it had been a while since I tried this again).

The cell assembly has to travel further into the scope to achieve focus further out, say 300yds. Since the focus ring bottoms out and will not carry the cell further inward, how to I remedy this?

 

[Skunk]

With the lense cell against the focus ring, the focus ring CANNOT push the cell far enough into the scope to achieve focus. I just tested this again. The only way to get the scope to achieve focus is to thread the locking ring further out, use the locking ring to push the cell further into the housing than the focus ring had the ability to do, and then tighten the locking ring to pull the cell slightly forward to fine tune the adjustment.

I will attempt to explain this another way. With the locking ring loosened, and the objective lens cell pulled out and positioned against the focus ring, the focus ring bottoms out before the picture becomes clear, setting the parallax at roughly 43yds (I realize I understated earlier, it had been a while since I tried this again).

The cell assembly has to travel further into the scope to achieve focus further out, say 300yds. Since the focus ring bottoms out and will not carry the cell further inward, how to I remedy this?

Is the ring you’re referring to as the “focus ring” spinning freely on its threads?

You should be able to completely remove the lock ring and then thread the focus ring off the scope to inspect the threads.

 

[tfont48]

Yes, sorry. The patent doesn't discuss these threaded rings specifically so I've taken the terminology from other publications. When I am mentioning the "locking ring" i am referring to the outermost ring that requires a spanner wrench to remove. The "focus ring" I am referring to is the second threaded ring that is wider and located behind the locking ring. I have removed both and inspected threads and see nothing of concern. Threading them on and off is smooth with no rough patches. The focus ring is not free spinning, when I say it "bottoms out" I mean that the focus ring has threaded all the way on to the objective housing and come to a stop.

 

[Skunk]

When it comes to a stop, you mean the ring is making contact with the end of the scope body, correct?

Did you get the scope from CMP or somewhere else?

 

[tfont48]

Correct, the ring is making contact with the end of the scope body. I got the scope from CS Tactical who procured from the CMP.

 

[Skunk]

I’m concerned it’s been “worked on” by CMP, or CST, and incorrectly assembled.

If you’re sure the ledge on the inside of the focus ring is butting against the end of the scope body, you won’t be able to lock the lens cell any farther rearward. In that case, I suppose the objective lenses could be installed in their cell incorrectly, but I think image quality would be terrible.

Can you achieve a nice, clear, parallax free image by pushing the lens cell in the way you have been?

 

[tfont48]

Yes, if I push the cell slightly further into the objective housing, I can achieve a clear parallax free image at 300yds. I was contemplating the spacer Idea but after further review it doesn't seem feasible. Other than messing with the objective cell assembly, the only way I can see to fix it would be measuring how far the cell recesses in the objective housing when it is parallax free and taking X amount of material off of the end of objective housing, somewhere between 0.020"-0.040"

 

[Jrb572]

Send it to iron sigh before you go do that.

 

[Skunk]

It is possible the scope tube is not completely screwed into the turret….

Where on the objective bell is the dimple located? I mean the small dimple that engages the obj lens cell. It will look like a small rectangular dent.

 

[tfont48]

The dimple is right about at the 6 o’clock position, maybe a few degrees off.

The scope just came back from ironsite, for repair on this exact issue. He’s repaired two other scopes for me in the past and they were great, so I’m not trying to knock his work at all. But when I got the shipping notice I called and tried to talk to Mike but he was busy with a project. I called again today but he’s going to be out for a few weeks. So I’m investigating fixing myself.

 

[ODCMP]

Your description makes me think that something could be assembled wrong. I don't know how that would be possible though.

The best thing to do would be to compare it to another Unertl and see what is going on. Some pictures might help.

 

[Skunk]

Oh, so it has been worked on…

The objective lenses are specific in their position and orientation within the cell. Were they removed for cleaning?

Without knowing exactly what was done with the scope, we’re all just guessing.

 

[tfont48]

According to the paperwork, he did not open scope up. Checked tracking on a collimator, returned scope to mechanical zero, and set parallax.

 

[tfont48]

Update, scope functions properly now as far as I can tell. Under better lighting magnification it appears the cell was flush with the objective housing when parallax free at 300yds. Also under magnification it appear the focus ring was coming to a stop just short of contact with the objective tube itself. After cleaning the threads and applying some fresh antiseize, it now sits all the way flush to the scope. I apologize, with the antiseize/grease on all the components these tiny differences (a few thousandths of an inch) were hard to tell and I incorrectly read them. Scope now locks the objective cell firmly against the focus ring properly and presents the proper parallax free image at desired range. Thank you @Skunk for helping me work through this.

 

[Skunk]

Glad you got it figured out. Years of paint and a bit of rust can bind those fine threads up pretty easily.