Fitting an M&P rear sight

[Dos Cylindros]

Guys, I need just a bit of advice. I have to 10-8 rear sights inbound to replace the rear sights on my full size M&P 45 and my M&P 45c. I have the MGW M&P sight pusher to do the install and I understand the mechanics involved (the striker block, spring and cap that rest under the rear sight). My only question is, I know I am probably going to have to do a little fitting on the rear sights to get them in easily and there in lies my question.....where do I file? Do I file the base of the sight (the bottom of the dovetail), or do I file on the angled surfaces that match up with the angled cuts on the slide dovetail?

Any pointers would be much help, I am confident I can do this myself as I have been tinkering with guns for most of my adult life, I have just never had to fit a rear sight.

[lcfuller]

I just had to take a few passes on the bottom of the sight to fit. Just put the file flat on the work bench.

[spamsammich]

Ditto. Take a few passes with a flat file and check fit often. It will be a tight fit, which I consider a good thing. You'll enjoy that rear sight, I find it to be just as good as the Heinie straight 8s I have on my G19 but the plain black field is less confusing to my eye.

After the file, if you have a really flat Arkansas stone or a flat granite slab, run the sight on the stone to polish up the bottom surface and get the file marks down some. Hilton recommended using cold blue on it if I wanted, but regular application of a oil is enough to keep it happy.

[spamsammich]

Looking at my emails, it seems that I took down the front bevel rather than the bottom of the sight. I took about 0.005" off the front with the file and then smoothed it out with a stone. In hindsight, I think it would be easier to get a more uniform cut with the file if I worked the bottom surface.

[Dos Cylindros]

OK, so bottom of the sight seems like the best idea even though for the life of me my brain can't process how that would make the sight fit. Thanks for the imput so far guys, keep it coming if anyone has any further advice.

[C4IGrant]

Try to install the sight without any modification first (as it might just fit). Ameriglo sights are this way.

Install the rear sight and wiggle it until it is holding the striker block spring and disc. Then take a small rubber hammer (or any type of hammer that will not harm the sight or the slide) and tap it in. A lot of times, this will get the sight halfway in and won't leave any marks on the sight. Then continue on with the sight pusher.

If you do not get anywhere with the hammer, then you will most like need to take some off the front edge (and maybe the back edge as well).



C4

[spamsammich]

The most important thing is to go slow and test fit often. As Grant pointed out, you want to be able to get the sight in half way. I almost cut too much off the front, I was able to beat on it with a delrin rod and hammer to get it to fit the rest of the way without a sight pusher. Luckily, I didn't have to monkey with it once I found mechanical zero. At 25 yards it was POA-POI if I did my part.

[Dos Cylindros]

OK guys, thanks for the info. Can't wait for my 10-8 rears to get here as I had them on one of my 1911's, and loved them.

[Dos Cylindros]

I have a metal file, but would sand paper give the same result?

[spamsammich]

Not unless you have a good sanding block. You want the cuts you make with the file to be flat and even.

[TomMcC]

I use an old hand held mirror and some 320 sandpaper. But any piece of of flat metal or glass will do. The sight should not go beyond half way (a little less is better) in the dovetail with very firm finger pressure. Once it is that far you can mechanically drift it the rest of the way. Sand only the bottom of the sight dovetail. Test often, if the sight goes into the dovetail with finger pressure right off the bat, no sanding is needed. That's my method, hope it helps.

[Dos Cylindros]

Once again guys, thanks for the help. I'm sure I have a good handle on the mechanics of this so I will give it ago as soon as they arrive.