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Discussion Starter · #1 ·
Is there any problems with the series 80 being milled for the BC#1 or #BC#2 sights or clones?
 

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Because of the location of the firing pin safety hole on the '80 series guns, the Bo-Mars are normally installed somewhat to the rear of the slides without the firing pin safety. Depending on the 'smith, usually about .080 to .125 rearward of the pre '80 series guns position, which means they overhang the rear of the slide somewhat.
 

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Discussion Starter · #3 ·
so just what does that require? does the frame have to be welded up in the old dovetail area or is enough stock removed in the BC#1 cut for it?
any pics of a BMCS on a series 80 on line anywhere?
 

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Gunsite Raven: On the package that the BoMar sight comes in it states: "NOT DESIGNED for Colt 1980 & 1990 series and other models with firing pin safety lock if used for combat MELT-DOWNS." In other words, if you mount it "high" on the slide and do not cut the sight in then it will be ok to use it, along with a very high rear sight and a lot of overhang to the rear. This type of install is usually done by modifying the existing factory dovetail to accept the BoMar and does not entail milling down into the slide and therefore would not create an issue with the plunger hole - a new and very high front sight is also needed to make this combination work. It does however give you a much longer sight radius if that is something you are looking for.

That being said, the BoMar you are talking about can be installed on the 80 Series slides as long as you pay attention to where the safety plunger hole is or you will mill into it. You need to really pay attention to dimensions when doing this project as slide dimensions will vary as will the BoMar sight bases. These variations may not be huge but should be taken into account. The cuts for the dovetail are the same for the BMCS and the BMCS-2 sights. The BMCS-2 has a self-contained elevation screw and a thicker body that will sit higher on the slide than the BMCS. The BMCS-2 does not require the drilling/tapping of the slide but does require an even higher sight normally than the BMCS does. I much prefer to use the BMCS BoMar when making a sight change.

Normally, the standard sight cut that Colt puts in their fixed sight slides is right at .100" deep. The first cut in installing the BoMar sight is to mill off a flat that is .100" deep, so as you can see this is normally no problem getting the original sight dovetail out of the picture. Some times you will have to go .001" to .002" deeper to clean it out totally but that should not prove an issue. The NORMAL locating cut on a non-80 Series slide is 1.000" back from the breech face. On an 80 Series slide I will make the first .100" deep cut starting at 1.100" to 1.110" from the breech face. With some careful measuring of the location of the safety plunger hole from the breech face you can get an idea as to how much clearance you will end up with when cutting the slide for the blade body to sit down in - there will not be an "excess" amount of clearance but certainly enough to miss the plunger hole.

Once I make my .100" deep first cut at 1.100" to 1.110" back from the breech face I will then make a cut starting at about .340" to .350" back from the step down left by my first milling pass. I will make this cut 0.98" deep and .270" wide. After I have this slot cut into the slide I will then take the dovetail cutter and after centering it in the slot will take the additional .002" of depth out while making the initial dovetail cut in the slot. Once the basic dovetail is cut you will have to confirm your dimensions to the actual sight being installed as they do vary somewhat. The dovetail cutter is slightly undersized so what I do is move the cutter approximately .002" to the left and right of the initial cut and check the sight for fit. When I get it to the point I can almost get it into the dovetail I will then take my 60 degree file and touch up the sight dovetail just a tad as well as the milled slot. I am happy with the fit when I can gently tap the sight body into position for a nice snug fit.

Once I get the sight body fit to the dovetail I then scribe carefully where I want to make the hidden leaf cut for the adjustment body to sit down into. I use an edge finder to find the exact center of the slide and then match the sight body up with this center line to insure proper left to right placement. I then mill out the hidden leaf area to a size that will just accept the sight adjustment body with no interference. By doing what I have quickly described above I have been able to avoid milling into the safety plunger hole in the slide and the sight overhang at the rear is not too bad. The rear of the blade usually ends up just about even with the curved end of the slide and does not look to badly at all - certainly much better than the original sight or the very high mount method of mounting the BoMar. Once the sight is milled in to my satisfaction I will then properly locate the hole that needs to be drilled for the adjusment screw. Once located a #31 drill is used to drill through the slide and into the firing pin channel - NOTE: do remove the firing pin and spring before doing this part. A 6-48 tap is used to thread the hole and then the inside of the firing pin hole is cleaned up with a small swiss file so there are no burrs. I drill and tap the hole on the same machine with no movement of the table so that everything is done on the same plane to avoid getting anything canted or out of sorts. I use a two flute plug tap for threading this hole. Also, the firing pin stop plate must be milled down for the sight adjustment body to clear and this is normal for both standard slides as well as the 80 series slide. The front sight blade will also have to be changed out when adding the BoMar BMCS rear and normally a .210" high sight is used with a .125" tenon. On a normally installed BoMar, the right side of the hidden leaf cut has a little cut-out area made into it for an aid in getting some clearance for a screwdriver when making windage adjustments. On the 80 Series installs this hidden leaf wing is somewhat shorter than on a "normal" install and I do not put this little cut-out area in as it would remove too much of the hidden leaf in my opinion and make it look somewhat odd. There generally is not an issue with making windage adjustments by not putting in this little relief area on the 80 Series cuts.

If you would like, send me your email address and I will send you a PDF file of a drawing I have made showing the layout for the BoMar sight cut with notes talking about the 80 Series slides and the safety plunger hole. Please note, this drawing is a reference drawing and while the numbers indicated are very close to what I currently use they do vary from project to project so do keep this in mind. Measure, measure, measure and then cut after you have checked one more time.
 

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Good post,

I wonder if there is any "Bo-mar" style sights that can be installed on a series 80 that allows as low a mount and keeping the sight blade even with the slide...like a series 70?

I thought I saw "pictures", which can be deceiving, of series 80 guns with a low mount, and the sight blade even with the slide.
Perhaps, they removed or will not use the plunger system so it doesn't matter??
 

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Discussion Starter · #6 ·
Bullseye45acp

Bullseye45acp
Thank you vary much
that is the most through reply to a post i have ever received anywhere on any board.
Your generositie with your time and knowledge will not go unnoticed.
Thank you again!

Irishlad

<<"I wonder if there is any "Bo-mar" style sights that can be installed on a series 80 that allows as low a mount and keeping the sight blade even with the slide...like a series 70?">>


Me too.
 

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How about mounting like the Springfield Operator TRP with the blade located before the end of the slide?? moving the dovetail cut closer to the breachface rather than further away? Is it possible to do that on a S80?
 

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Isn't it possible to drill the sight dovetail, so the S80 plunger works normally? That is, put the sight in the normal low-mount poistion, and drill a hole in the sight that corresponds to the plunger hole in the slide?
Colt sold a run of M1991A1s with Bomars and Videki triggers, a couple of years ago, and they had the sight set rearward, as noted above. The Special Combat has the same mounting, so there is probably a pic of that somewhere on the forum or at the Colt website.
 

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Yes, certainly the Bo-Mar sight can be mounted in just about any manner you want to. If you mount the Bo-Mar using the standard commonly used dimensions on an 80 Series you will cut into the safety plunger hole and it will be exposed in the right front corner of the hidden leaf cut. If you do not do a hidden leaf cut the hole will be exposed and easily seen under the main sight blade body. The series 80 parts can certainly be removed and the sight mounted in the standard position and will pose no issues if you are not planning on using those parts again. Putting the Bo-Mar sight on the series 80 pistols properly will not only provide the current owner the option of putting back the original parts if so desired but will also give possible future owners this same choice. If one is not concerned about having the safety plunger hole exposed in the sight cut where the main sight body resides then by all means do so, however the Bo-Mar BMCS when mounted in such a manner that the plunger hole is not exposed does not hang back over the slide in an unusual or odd looking manner. As I stated earlier the back of the sight blade is about even with the curve of the back of the slide or just slightly ahead of it - not at all unpleasing to the eye. While it certainly is not going to look like one mounted on a Baer, Caspian or other type of 70 series style slide it will still look quite nice especially if the hidden leaf cut is executed which in my opinion is the only way to do these type sights.

The cutting of the sight dovetail does not cause any problems with the safety plunger body regardless of using the standard Bo-Mar mounting dimensions or when using the modified mounting dimensions for the series 80 slides. It is the cut at the rear of the slide that will cause the safety plunger hole to become exposed when milling out the area inside the hidden leaf for the main sight body to reside. If the dovetail portion of the sight were located directly over the plunger hole then you could certainly cut into the sight dovetail to a point and get the plunger to work again, however the hole will appear in the slide under the movable sight leaf main blade body and there is not way to make that arrangement work. Also, if you moved the dovetail back far enough to redrill for the plunger hole then the sight would hang off the back of the slide by a whole bunch and not look very good at all. The bottom of the cut under the main sight body generally runs about .250" maximum depth from the rounded top part of the slide so as you can see it is quite a deep cut and if you measure the depth of the safety plunger hole you will find that it goes very near the top of the slide. If you remove the metal for the sight blade body it the normal dimensions you will have a hole exposed about the size of the safety plunger.

There are any number of choices one can make when deciding on how to mount this type of sight on the 80 series slides. As long as the owner is fully aware of what they are going to have as and end product then by all means the mounting of the sight can be done in one of several ways. Personally I like doing the method I described on the 80 series thus allowing the current or future owner of the pistol an option they may or may not want to exercise with regard to the system safety while providing a low mounted sight system that is pleasing to the eye. I am by no means saying that my way is right or wrong, better or worse or anything else - this is the way I do it and have found it to work quite well.
 

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Bullseye45acp,

Thanks for the info and taking the time to describe it in detail.
I'm sure your way looks very good. Sounds like a lot of detailed work, not something for the "local" gunsmith by any stretch. :)
 
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