Uneven depth optic cut

[Cam73]

Hey guys-

I recently purchased a used CO gun out of the classifieds on a different site. Overall it looks pretty good, but the optics cut has me a bit puzzled. Its a factory slide direct milled to accept a Vortex and the cut depth is roughly a 1/16" deeper in the front. I couldn't see it in the pictures before purchasing. In person its not exactly pleasing. I have not shot the gun yet.

 

I have limited experience with red dots on pistols, but can't think of a good reason not to mill it in parallel with the bore. The gun was shot successfully by a really good shooter. I'm pretty surprised it had any elevation left to be zeroed.

 

In short, is there a reason NOT to mill a red dot optic in parallel to the bore? Thoughts?

Thanks

[dansedgli]

Some barrels have a downward slope in lockup and need the optic to have the same. 

 

What gun is it? 

[Cam73]

It's a Shadow 2

[Yondering]

I wonder if the optic cut was milled parallel to the sight plane, rather than the slide? Look at a side view of a Shadow 2 (or most any other CZ or Tanfo variant); you'll see the rear sight is significantly taller than the front, so the sight plane is not parallel to the top surface of the slide. This is because of the barrel's slope as dansedgli mentioned. 

 

In theory, milling the optic cut parallel to the sight plane makes sense; the optic should be closer to mechanically centered when zeroed. It probably looks funny, but may have been done by someone who really thought about what they're doing. 

 

With that said, the slides I've milled (other brands, never a CZ or Tanfo) all have the sight plane approximately parallel with the top of the slide, so an angled cut was never something to consider. 

 

Could you post a picture of the cut, maybe one from the top and one from the side? I'd really like to see it if you don't mind, and the pics might show something I haven't considered in the comments above. 

Edited June 21, 2019 by Yondering

[rowdyb]

a 1-2 degree difference is very common. ones done totally parallel are the reason people have to buy shims.

[PrimaryBruce]

1 hour ago, Yondering said:

 

In theory, milling the optic cut parallel to the sight plane makes sense; the optic should be closer to mechanically centered when zeroed. It probably looks funny, but may have been done by someone who really thought about what they're doing. 

 

 

Milling the slide like that is 100% wrong and incorrect on ALL 1911's and CZ 75's. Doing it that way will lead to problems:

- can't zero optic due to running out of elevation adjustment

- ridiculous variances in hold overs/under and various distances since the optic and bore are no where near parallel to one another

 

The slide needs to be indicated and milled parallel with the actual bore angle.

Edited June 21, 2019 by PrimaryBruce

[Yondering]

3 hours ago, PrimaryBruce said:

Milling the slide like that is 100% wrong and incorrect on ALL 1911's and CZ 75's. Doing it that way will lead to problems:

- can't zero optic due to running out of elevation adjustment

- ridiculous variances in hold overs/under and various distances since the optic and bore are no where near parallel to one another

 

The slide needs to be indicated and milled parallel with the actual bore angle.

 

 

Please explain how milling the optic parallel with the sight plane results in running out of elevation adjustment. It should result in a mechanically centered optic if it's done accurately; the optic needs to point parallel to the irons to be centered, if the irons were zeroed. 

 

Or maybe you thought I said something else? If you thought I said milling parallel to the slide, please read my post that you quoted again.

Edited June 22, 2019 by Yondering

[lstange]

On 6/16/2019 at 11:32 PM, Cam73 said:

cut depth is roughly a 1/16" deeper in the front

[...]

is there a reason NOT to mill a red dot optic in parallel to the bore?

Top of the slide may not be parallel to bore axis, so it's possible that the red dot cut is parallel to bore axis.

[PrimaryBruce]

On 6/21/2019 at 4:58 PM, Yondering said:

 

 

Please explain how milling the optic parallel with the sight plane results in running out of elevation adjustment. It should result in a mechanically centered optic if it's done accurately; the optic needs to point parallel to the irons to be centered, if the irons were zeroed. 

 

Or maybe you thought I said something else? If you thought I said milling parallel to the slide, please read my post that you quoted again.

Maybe I'm confusing what you're saying.

I drew these angles to the extreme so it's clear what I'm saying.

The first terribly drawn slide basically shows what a 1911 or CZ 75 slide looks like if it's sitting on a perfectly flat surface or if someone just sits it in a vise perfectly flat. 

 

Edited June 24, 2019 by PrimaryBruce

[lstange]

I don't know the CZ numbers, but 1911 slide spec calls for the breech face to be machined at 89 degrees, 08 minutes off the horizontal datum line. So bore axis points 52 minutes down, and if you want slide base to be parallel to bore axis you need to angle the cut accordingly.

 

When shooting offhand the gun begins to move before the bullet leaves the barrel, so the angle might be different.

Edited June 24, 2019 by lstange
typo

[Yondering]

2 hours ago, PrimaryBruce said:

Maybe I'm confusing what you're saying.

 

 

Thanks for the response, but yes, definitely. How did you interpret my comments that you quoted to mean milling the slide flat in the vise? I was specifically talking about why not to mill it that way. What did you think I meant by "sight plane"? Please read my post above again. 

 

Ideally we want to the optic to point to the same spot as the sights, so milling the slide parallel to the sight plane (meaning the top edge of the sights, what we aim with) gets us there. That is why the OP's slide is milled at an angle.

Indicating to the bore gets close enough as well, although not technically what the optic cut needs to be be aligned to. 

Edited June 24, 2019 by Yondering

[BallisticianX]

If the slide is milled on an angle it was, Id guess, done with best intentions based on the sight line to bore line parallelism. ... but not necessary. Ive milled many a slide for direct mini dot mounting (Glock, M&P, SIG, 1911). I always mill the footprint parallel to the slide center line (indicated parallel to the cutters x axis), never been a problem as the sight window is close enough to the bore that the sight and bore planes aren't separated enough to where a sights adjustment will be stressed in any semi on the market. With optic mounts affixed to a frame on a 1911/2011 thats a unique circumstance. Your hoisting the sight window further away from the bore with the 1911's 1 degree pitched down muzzle (slightly more with a shorty). Now your sight plain and bore line are separated more dramatically and both intersecting planes are skewed considerably. Then consider more often than not a fulls size c-more with it taller lens height is used in that application so its even more skewed and sight adjustment range is stressed. So based on that circumstance open gun builders began incorporating the same corresponding 1 degree angle in either the mount itself or with the screw pattern to address that. That's the only hand gun application I can think of where an angle needs to be considered in an optic mount foot print.  

[Cam73]

Sorry guys, I forgot to keep up on the topic. Thanks for the replies. I've attached some pictures of the optic/optic cut. 

 

Of greater concern to me now is that this gun has killed 2 Vortex Razor red dots in the very very short time I've owned it. 1 failed after a little bit of practice and a steel match, the other died today after being sighted in and 1/2 of an IDPA match. I know the previous owner killed at lest one aswell. I've had great luck with the Venom on my TP9SFx but a quick search around here makes the Razor sound like a pretty expensive POS. Not sure what kind of recovery options I have for a direct milled slide like this. I believe the RTS2 has the same foot print but it sounds hit or miss as well. 

 

Edited July 21, 2019 by Cam73

[xdnok]

Yes a 1 degree cut is needed to keep your optic in the center of its adjustment range. Yes I made the expense mistake of cutting the slide flat and ran out of elevation adjustment on the optic. Likely the best course of action would be to cut the slide for a Cz custom plate that can be swapped out for different optics, that what I did for all my S2’s

[Cam73]

43 minutes ago, xdnok said:

Yes a 1 degree cut is needed to keep your optic in the center of its adjustment range. Yes I made the expense mistake of cutting the slide flat and ran out of elevation adjustment on the optic. Likely the best course of action would be to cut the slide for a Cz custom plate that can be swapped out for different optics, that what I did for all my S2’s

 

Although hard to tell from a picture, with your experience, does it look like there is enough available real estate to use a CZC plate system?

 

Edit-

I looked at pictures of the CZC plate system on the website, it doesn't look real hopeful to me. No meat left for the pillars the plate system uses for alignment on the slide without cutting deeper.

 

My other thought was having a custom plate made locally. Looking at an RMR cut Glock slide I have, the mounting pattern between the RMR and Razor are pretty close. It would probably require new holes to be drilled and tapped in the slide to use from attaching the plate rather than using the existing Razor holes.

Edited July 22, 2019 by Cam73

[Cam73]

Part of the way there...

http://www.egwguns.com/pistol-and-red-dot-mounts/trijicon-rmr-sight-mount-for-blank/

[titandriver]

From CZ Custom web site:

 

[titandriver]

Better pic:

 

[Cam73]

Wow, the cut on that bottom slide is deeeep! 

Edited July 22, 2019 by Cam73

[ClangClang]

I'm not a machinist, but I own about 5 (properly) milled slides, and all I can say is that slide looks completely FUBAR'ed.

[titandriver]

9 hours ago, Cam73 said:

Wow, the cut on that bottom slide is deeeep! 

I believe the top slide is how CZC mills the firing pin blocked slides, the bottom one is how they mill the slides without the firing pin block. Maybe Stuart can chip in with more info as to the why.

[Yondering]

14 hours ago, ClangClang said:

I'm not a machinist, but I own about 5 (properly) milled slides, and all I can say is that slide looks completely FUBAR'ed.

 

I am a machinist, and disagree (assuming you're talking about the OP's pistol). It does look like someone milled more angle into it than necessary, but if the optic can be zeroed, it's fine. If it can't be zeroed (POI will remain too high at max adjustment), a good machinist can fix it. I'd expect the OP will need to pay full price of a milling job, or more, to have that done though; fixing someone else's mistake is generally harder than doing it right the first time.  

[Cam73]

3 hours ago, Yondering said:

 

I am a machinist, and disagree (assuming you're talking about the OP's pistol). It does look like someone milled more angle into it than necessary, but if the optic can be zeroed, it's fine. If it can't be zeroed (POI will remain too high at max adjustment), a good machinist can fix it. I'd expect the OP will need to pay full price of a milling job, or more, to have that done though; fixing someone else's mistake is generally harder than doing it right the first time.  

 

Seeing as you are local to me, maybe I found just the guy for the job... 

 

The last 2 Razors have only required 15-20 MOA down to get zeroed at 10 yds.

 

Other options to fit the current optic cut:

The RTS2 sounds hit or miss from what I read around here.

The Sig Romeo 3 (same mounting pattern according to the multi optic red dot sight base drawing on the CZC website) but is much longer overall from what I can tell.

I feel like all 3 are made in the same place, with the same terrible battery tray design.

 

I made a pretty crude drawing on my lunch break today confirming (best I can tell) that an adapter plate to go from a Razor to an RMR (SRO) would not work. The threaded mounting holes in the plate for the RMR would occupy the same space as the heads of the fasteners that would be used to hold the plate to the slide (utilizing the existing threaded holes for the Razor.)

 

Going Razor to Venom looked good for a quick second because they both have 14 mm centers between mounting holes, but the Razor uses bigger fasteners. 

 

So I'm back to drilling and tapping new holes in the slide to hold a conversion plate down, using a multi-plate system to avoid fasteners running into each other or paying real money for a real fix.

 

[xdnok]

Yes there is plenty of room to make a cut for a CZ custom plate on the OP slide, it is a deep cut. Note how far the cut is into the CZ logo by the 9 x 19 

[Yondering]

On 7/22/2019 at 6:57 PM, Cam73 said:

 

Seeing as you are local to me, maybe I found just the guy for the job... 

 

 

Sorry man, wish I could help, but I just can't take on any new work at the moment. 

 

Bummer to hear about the optics issues. I know Vortex optics have a good reputation in some circles, but I'm really not a fan of them, for a lot of the same reasons as your experiences. Pretty much any optic can break, but I've had the best results with the Trijicon RMR for carry and the Leupold DPP for competition. 

 

A mounting plate as shown above might be your best bet if you're wanting to move away from the Razor.