How to fix front pistol sight too small for dovetail? - Page 1

Site Notices

[ARCHIVED THREAD] - How to fix front pistol sight too small for dovetail?

Posted: 7/13/2018 3:25:40 PM EDT

Today I was shooting an M&P 40 (1st generation), when the front sight fell off.

This pistol was purchased a few years back by me as a police trade-in.

I’ve put around 750 rounds through it without issue.

I’ve never touched the front sight. I recovered the sight and it is finger loose in the dovetail. I can push it wel past the center of the slide before I feel any resistance, andvthis well past where it should be for windage zero.

Any thoughts how to secure this sight in the front dovetail?

Attached File

Posted: 7/13/2018 3:37:09 PM EDT

[#1]

If you have a way to support the sight(like a vice), a good center punch to the base will move some metal and make it tighter. You can snap the blade off doing that however.

Alternatively, chuck the slide in a vice and dimple the dovetail with the punch. Finish the install with some high strength loctite.

I would probably look for a new sight and hope it fits tighter.

Posted: 7/13/2018 3:38:05 PM EDT

[#2]

Take a brass punch and hammer and peen each side of the dovetail cuts on the sight. Or take a steel punch and dimple the bottom of the sight. Don't over do do it!! It won't take much and you shouldn't be cosmetically noticable if you do it correctly. I'll post a video

Brownells - Temporarily Fixing a Loose Dove Tail Sight

https://www.youtube.com/watch?v=unhP7JMpiG0

Note in that video the dovetail itseld was deformed. A brass hammer and light peening of the dovetail cut is how I would have done that one.

Posted: 7/13/2018 3:39:01 PM EDT

[#3]

Put a shim under the site to tighten it up.

Posted: 7/13/2018 3:54:33 PM EDT

[#4]

Quote History

Quoted:
Put a shim under the site to tighten it up.

View Quote

Could Aluminum foil make a good shim material?

Posted: 7/13/2018 3:56:21 PM EDT

[#5]

Quote History

Quoted:
Take a brass punch and hammer and peen each side of the dovetail cuts on the sight. Or take a steel punch and dimple the bottom of the sight. Don't over do do it!! It won't take much and you shouldn't be cosmetically noticable if you do it correctly. I'll post a video

https://www.youtube.com/watch?v=unhP7JMpiG0
Note in that video the dovetail itseld was deformtd. A brass hammrt and light peening of the dovetail cut is how i would have done that one.

View Quote

Thanks, useful video.

Posted: 7/13/2018 4:01:10 PM EDT

[#6]

Quote History

Quoted:
If you have a way to support the sight(like a vice), a good center punch to the base will move some metal and make it tighter. You can snap the blade off doing that however.

Alternatively, chuck the slide in a vice and dimple the dovetail with the punch. Finish the install with some high strength loctite.

I would probably look for a new sight and hope it fits tighter.

View Quote

The sights on this pistol are old, fairly dim night sights. I had planned to replace them at some point, so I’ll go ahead and just do it sooner. But I wanted to try some sort of fix just so I could learn what to do

Posted: 7/13/2018 4:32:47 PM EDT

[#7]

Quote History

Quoted:

Thanks, useful video.

View Quote

You're welcome.

Posted: 7/13/2018 5:32:44 PM EDT

[#8]

A shim under the site would be the easiest and least damaging way of reinstalling it

Posted: 7/13/2018 5:57:42 PM EDT

[#9]

Quote History

Quoted:
A shim under the site would be the easiest and least damaging way of reinstalling it

View Quote

Beer cans make great shim stock.

Posted: 7/13/2018 5:59:59 PM EDT

[#10]

Quote History

Quoted:
Could Aluminum foil make a good shim material?

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
Put a shim under the site to tighten it up.

Could Aluminum foil make a good shim material?

Steel would be better.
You could cannibalize a feeler gauge set, or hit up a hobby shop (often scarce now) for some thin steel sheet.

Long ago I used a punch to create dimples but was never all that happy with the small contact area it creates.
You have to put multiples in to make the thing come out straight.

Cannibalizing a steel feeler gauge is not expensive at all and it has multiple thicknesses to pick from.
If you cut a thin edge or just the end of the feelers it is still usable for other thing also.

Posted: 7/13/2018 9:10:45 PM EDT

[#11]

This is with a homemade Two ply aluminum foil shim.

It’s definitely locked in place. I needed a brass pinch and hammer to rap the sight into place.

Maybe it holds, maybe it doesn’t. I did see some of the auto parts chains have small feeler gage sets pretty cheap, or I could see what Harbor Freight has to offer.

But even aluminum foil improved the fit dramatically.

Thanks for all the responses. This was a good learning project.

Attached File

Posted: 7/15/2018 6:07:41 AM EDT

[#12]

Unless it was one of a kind front sight I would just buy a new one and fit it, being very careful to only take off a little metal at a time while fitting it.

Posted: 7/15/2018 6:12:06 AM EDT

[#13]

Quote History

Quoted:
This is with a homemade Two ply aluminum foil shim.

It’s definitely locked in place. I needed a brass pinch and hammer to rap the sight into place.

Maybe it holds, maybe it doesn’t. I did see some of the auto parts chains have small feeler gage sets pretty cheap, or I could see what Harbor Freight has to offer.

But even aluminum foil improved the fit dramatically.

Thanks for all the responses. This was a good learning project.

https://www.AR15.Com/media/mediaFiles/314595/A9294B51-36BC-4A7B-9CD8-EB39D52258BD-606763.JPG

View Quote

Last time I was in there, they had Feeler gauges by the checkout.

Posted: 7/15/2018 3:11:57 PM EDT

[#14]

Looks good OP. When you are looking for a replacement try Dawson.

Posted: 7/16/2018 3:51:42 PM EDT

[#15]

Quote History

Quoted:
Looks good OP. When you are looking for a replacement try Dawson.

View Quote

I found this video on YouTube where Dave Dawson goes through installation of a dovetail sight. I think this is one of the best YouTube gunsmithing "how to" videos I've ever watched.

Installing Dovetail Front Sights with Dave Dawson

https://www.youtube.com/watch?v=do8sHBDfIGk

Posted: 7/16/2018 3:56:47 PM EDT

[#16]

For anyone who has used feeler gauges to cut out shim stock, I have a question. Since (to my knowledge), steel feeler gauges are simply high carbon steel, did you do anything to prevent rusting?

I'm imagining if a pistol gets carried a lot outdoors (my M&P in this thread sees a lot of time in the woods), the carbon steel shim could start to rust beneath the sight. Is it even a concern? Maybe hit it cold bluing?

I've seen brass feeler gauges, but I don't believe they are usually nearly as thin as steel gauges.

I'm also going to wander down to the manufacturing area to see what sorts of shim stock leftovers or scraps the technicians may be willing to let me have.

Posted: 7/16/2018 5:18:48 PM EDT

[#17]

Quote History

Quoted:

I found this video on YouTube where Dave Dawson goes through installation of a dovetail sight. I think this is one of the best YouTube gunsmithing "how to" videos I've ever watched.

https://www.youtube.com/watch?v=do8sHBDfIGk

View Quote

That was my how to vid. Very informative.

Posted: 7/16/2018 10:05:12 PM EDT

[#18]

Quote History

Quoted:
For anyone who has used feeler gauges to cut out shim stock, I have a question. Since (to my knowledge), steel feeler gauges are simply high carbon steel, did you do anything to prevent rusting?

I'm imagining if a pistol gets carried a lot outdoors (my M&P in this thread sees a lot of time in the woods), the carbon steel shim could start to rust beneath the sight. Is it even a concern? Maybe hit it cold bluing?

I've seen brass feeler gauges, but I don't believe they are usually nearly as thin as steel gauges.

I'm also going to wander down to the manufacturing area to see what sorts of shim stock leftovers or scraps the technicians may be willing to let me have.

View Quote

It's going to rust, cold blue will help but sooner or later it will rust. The best method is to peen the dovetail back if it's wallowed out like the video I posted or peen the sight. If I was going to introduce foreign matter in there I would put silver solder on the bottom of the sight to build it up and file it to fit.

Posted: 7/17/2018 9:07:52 AM EDT

[#19]

you should be able to find stainless and brass shim materials in the machine shop if they let you have some

Or at places like McMaster

https://www.mcmaster.com/#stainless-steel-shims/=1dr2wmw

Posted: 7/17/2018 2:44:30 PM EDT

[#20]

Quote History

Quoted:
you should be able to find stainless and brass shim materials in the machine shop if they let you have some

Or at places like McMaster

https://www.mcmaster.com/#stainless-steel-shims/=1dr2wmw

View Quote

A definite yes on the stainless from the shop. It's a aerospace manufacturing facility, so shims should be stainless, probably 316 or 17-4. I'm guessing they have a bin of shims along with the bins of other hardware that are leftovers.

[ARCHIVED THREAD] - How to fix front pistol sight too small for dovetail?

Armory » Gunsmithing

Warning

Confirm Action

About AR15.COM

Stay Connected

Newsletter

Contact Us