Dot re-zero after removal and re-installation

I have a  M41 with a Weaver #62 rail. I am planning to also use the M41 irons as my EIC pistol. My dot is Vortex Crossfire. How close to re-zero might the Vortex be after removal and re-installation?

It should be "close" as long as you torque the screws down the same and put it on the same place on the rail each time.

You will need to verify the zero....a few clicks is quite possible....each time you remount the optic.  Only way to avoid that is to have two barrels. One dedicated to the optic, the other for irons....it all depends on how much hassle you can put up with.  bob

Can you leave the base on? I don't think I'd be able to see the sights on mine over a Weaver rail.

If you have to pull that too, there's another layer of potential error to deal with. It depends how well it fits the barrel, how straight and square the holes are, etc.

I can pull my 'home made' rail off my 45 slide, replace it, and call it 'zeroed' within my wobble zone. But it's not a precision rifle, so a couple minutes is nothing in my case.

You might want to try a different scope. Most of those scopes that have the mount cast in the base don't repeat zero well when remounted. You would be better-off using the Ultradot style tube with Weaver Rings. No I'm not suggesting use Ultrsdot but rather the tube style that uses rings. Of the few different scopes I purchased as I'm always looking for a better one I have quite a few with the Crossfire type mount. Actually they are not Weaver but will fit a Weaver base but are not exactly correct. Yes I have used the other style but rather than put them on a Weaver base I make the base to fit the scope. On the other hand if you intend to shoot EIC match and Bullseye, If Bullseye is shot first, scope removed then shoot EIC you can re-zero later at your range since it will be in the ballpark and only need small adjustment.

Froneck's idea of removing at the range is good, but a bit of time and hassle involved.

It's a 41. Swap the barrel out ;-)

Yes, Bullseye 2700 .22 match  is prior to the EIC .22 match so I can just remove the Dot and reinstall at a later date and check the new zero. TX Outdoor Champ at Dallas Pistol Club 4/30-5/2
 
The 62 rail is low enough to still use the irons.

The mount on the Crossfire is not cast into the Dot sight. It is screwed (4) into the sight base. The first time I mounted the Dot on the Weaver 62 rail I did have to completely back out "clamp" to get the screw rod to drop into the rail slot then tighten the "clamp" 

I will get my irons sighted in and then reinstall Dot and re-zero this week. Another 2700 next Sunday.

I forgot the Vortex scopes have screw on base. I have a NIB SPARC 2
never used it, not sure why I purchased it and it's still in the box. I looked at the attachment that is still not screwed to the scope. Another still sitting in the box is a Leupold Freedom along with a couple Primary Arms red dots.
 Problem with the mount it's the same as all the others, its actually made to fit a wider mount than the Weaver but will fit the Weaver mount but not as well as Weaver rings. I had Weaver mounting on a few Riles, zero would return when re-mounted, might have needed little tweaking but it wasn't bad at 100 yards.

Froneck wrote:Problem with the mount it's the same as all the others, its actually made to fit a wider mount than the Weaver but will fit the Weaver mount but not as well as Weaver rings. I had Weaver mounting on a few Riles, zero would return when re-mounted, might have needed little tweaking but it wasn't bad at 100 yards.

From what I encountered, the Weaver 62 is wider that the Vortex is designed to fit "normally" Hence having to completely back out the "clamp" screw and hold on to the parts in place as the rod drops into the rail slot then screw the rod into the "clamp". I have only done the install once so far. Will take off Dot, sight in the irons and then reinstall the Dot again tomorrow or Wednesday and see if I was correct.

Using my bore sighting equipment, I record where my dot is on the graph when sighted in properly.  If I have to take the dot for some reason or another, I refer to my record to get it back to the proper setting.  Most of the time it is dead on, but occasionally I need to adjust a click or two.
Phil

+1 Just get a Clark barrel for the optic and swap them out.  At $325 or so, its pretty cheap and gives the shooter one less thing to worry about later. 

CR

CR10X wrote:+1 Just get a Clark barrel for the optic and swap them out.  At $325 or so, its pretty cheap and gives the shooter one less thing to worry about later. 

CR

I have a Clark STC barrel (no iron sights though) and it cant really be used even with a dot. Having mucho failure to fully eject issues right now even with passing plunk test bullet lots (have changed extractor) . If I oil up the cartridge, it works, but I get a lot of oil splatter on the dot optic.

Might look into mounting a rail that covers the bullet port area and mount the dot on that. Then I can invest in a 5 gallon pail of Hoppes gun oil.. LOL

I also have a Clark barrel for my 41, it was seriously tight so I ever so gently used a 22 reamer to get it to the point where it would extract consistently. The oil on the first round trick would work initially but at round 4 or 5 it would fail to extract the spent round correctly. Now it runs like butter, still picky on ammo though CCI seems to be about the only choice based on what I had on hand to test.

PMcfall wrote:Using my bore sighting equipment, I record where my dot is on the graph when sighted in properly.  If I have to take the dot for some reason or another, I refer to my record to get it back to the proper setting.  Most of the time it is dead on, but occasionally I need to adjust a click or two.
Phil

This is what I do with all my red dots, as well as with rifle scopes. I keep a notebook for each gun so the info is easy to find. Works great.

xman wrote:

Froneck wrote:Problem with the mount it's the same as all the others, its actually made to fit a wider mount than the Weaver but will fit the Weaver mount but not as well as Weaver rings. I had Weaver mounting on a few Riles, zero would return when re-mounted, might have needed little tweaking but it wasn't bad at 100 yards.

From what I encountered, the Weaver 62 is wider that the Vortex is designed to fit "normally" Hence having to completely back out the "clamp" screw and hold on to the parts in place as the rod drops into the rail slot then screw the rod into the "clamp". I have only done the install once so far. Will take off Dot, sight in the irons and then reinstall the Dot again tomorrow or Wednesday and see if I was correct.

Yes I was correct. The Weaver 62 is wider than the Vortex Crossfire mount. The "clamp" screw must be totally backed out to get the rail slot rod to drop in or out of the slot. It was easy to hold onto the clamp and keep it in position to get the rod aligned and tightened.

Took maybe 15 seconds total to remove and get the rod aligned and tightened to store the Dot after the last rapid and get ready for EIC

No most of the mounts especially from China are wider than the Weaver/Picatinny base (.838"). Most will measure .890" or somewhere near that. One style that Vortex uses has the metal clamp that fits loose so that when clamping on the base the upper side of the mount has an angle (45°) it will cant the scope a small amount so that on the other side is does not fit into the 90° (45° + 45°) Therefore the base never fits the mount correctly as Weaver ring will! Most that after mounting daylight can be seen in the angle between the base and the mount opposite the clamp! On my Vortex Sparc2 mount the lower angle is removed from the mount and is only on the clamp, on others the lower angle is there so when I make a Base to fit as it should I make it what ever the mount dimensions are around .890". In order to remove the scope I must completely remove the screw and slide the scope off the end! Now the base fits as it will with a Weaver ring, does not cant and will repeat when taken off.

Froneck wrote:No most of the mounts especially from China are wider than the Weaver/Picatinny base (.838"). Most will measure .890" or somewhere near that. One style that Vortex uses has the metal clamp that fits loose so that when clamping on the base the upper side of the mount has an angle (45°) it will cant the scope a small amount so that on the other side is does not fit into the 90° (45° + 45°) Therefore the base never fits the mount correctly as Weaver ring will! Most that after mounting daylight can be seen in the angle between the base and the mount opposite the clamp! On my Vortex Sparc2 mount the lower angle is removed from the mount and is only on the clamp, on others the lower angle is there so when I make a Base to fit as it should I make it what ever the mount dimensions are around .890". In order to remove the scope I must completely remove the screw and slide the scope off the end! Now the base fits as it will with a Weaver ring, does not cant and will repeat when taken off.

The result of my re-mounting the Vortex on the USA made Weaver 62 rail on my M41(I still have the packaging) was by impact at 10 o'clock from zero at 50 yards about 6 clicks up and left.

I might take out the caliper just out of curiosity at a later date. to measure the rail width. I did look closely from all angles in the sunlight at the range and saw no canting, angling, odd spaces or tipping of the base. All looks true and straight.

I can live with that change of zero and when at the range for my weekly practice and then re-zero after re-installation.

The variation in rail widths could be the reason a number of makers dont make their rings to Picatinny spec. They leave out the upper angle surface, effectively turning the entire thing into a large dovetail. Likely never an issue, but the top face of the rail isn't a controlled surface. I think with a little care I could bandsaw that and meet Mil Spec. And their rings would choke on it.

Picatinny and Weaver are the same in cross sectional width. Only major difference is slot size and spacing. To get best fit for those that are usually made in China is to make a base to fit like I do. If my memory is correct the Ultardot micro is wrong too! The non clamp side is made just like a Weaver ring. The V has a small flat on the top but the other side don't have that flat causing the scope to cant! The small amount of cant I don't think will cause aiming problems but the fit in the V is not correct! I'm thinking a Band saw might make things worse, a milling machine will do a better job!