Drilling scope mounts

I am an owner of a small machine shop that deals with industrial customers. I have never done any gun modifications, although I am an avid hunter, and have several firearms.

I received a call out of the blue wanting to know if I could drill and tap a receiver for scope mounts. Now, I believe I have the skill for this, but really am not set up for doing it, and would be more of a PITA type of job for me anyway.

This did bring a couple questions to mind though.

First, doing a private party transaction like this, modifying an existing firearm, what would that laws be? Would I need a permit of some sort? I am rather clueless as to this, so enlighten me.

Second, as a guess, what would a normal gunsmith charge for such a task, IE drilling and tapping (6-48) 4 holes for scope mounts? I gave an estimated guess at this, and of course the customer about choked. I really can't do much with an hour, by the time you talk to them, set-up, do it, billing, ect. But it did bring out my curiosity of what someone in the field that does it often charges.

At the moment I really don't have the time or want for this kind of work, other than if it were my own firearms. If having to have a permit to do this, it would more or less just give me an excuse to potential customers as to why I am not even interested, lol. On the other hand, I know of no gunsmiths in the area, as I have asked gun dealers of who I could take things to, with a resounding "nobody around here" answer.

Pat

Hi Pat,
If a customer were to leave the gun in your possession ( he goes away) you would have to have a federal firearms license. If he stays there the whole time, it's not required. At least by the feds. Your state may have different rules.
Foster did (may still) make a jig for drilling receivers for scope mounts and some types of iron sights. I used one many years ago and was happy with the thing. Far as pricing, if there are no smiths in the area, you probably could charge a premium for services like this.
Like any other firearms advice you get on the internet, the onus remains on you to find out the facts of the law. I know a couple of gunsmiths that have quite a good relationship with the ATF, I've also been present when that wasn't so much the case. Good luck with your endevor!

Lowell

For what it is worth, I sent a benchrest gunsmith a custom action about 10 years ago to build a complete benchrest gun for me. I wanted the scope mount holes to have the same hole spacing as a Remington action.

The price for drilling and taping was $15 per hole. (Although the entire bill was over 2k.) I don’t know what he would have charged if he was just tasked with the drilling and tapping the scope mounting holes. But when he quoted the price, he knew exactly how much he charged for such a job, and he was a very well known smith. So I guess that was standard.

Fifteen dollars seemed kind of inexpensive to me ($45 for 3 holes) and that was 10 years ago.

Actually, my understanding is that you would need an FFL (federal firearms license) only if the customer were to leave the gun overnight. According to Brownell's the national range for drilling and tapping is $20 to $45 per hole. Hope this is helpful to you.

PS: The drilling jig is made by FORSTER.
FORSTER : UNIVERSAL SIGHT MOUNTING FIXTURE & COMPONENTS - World's Largest Supplier of Firearm Accessories, Gun Parts and Gunsmithing Tools - BROWNELLS

Scroll down to the "Fixture."

I never paid more than $10.00 a hole but dealt with gunsmiths that had fixtures for the job.You have no fixtures then to set up and your time and all you got to do it by the hour,I since bought drill and tapp fixtures and dont have to deal with haveing someone do the job.As long as that person is present and does not leave you are ok,but would check state laws for your state to be shure,it would be your butt in the meat grinder if your laws in your state say diferent.Let him find a gunsmith would be what I would do

I dont use a jig, setup in a Bridgeport with a good DRO and it is easy. I do have blocks for holding the different receivers. If the receiver is case hardend you will have to grind thru or start with a carbide drill.

Well everyone is a gunsmith! They just don't have time to do it right now. Triage is 30 minutes, egress is 30 minutes, the job takes an hour if you dial it into the mill, 30 minutes if you have a site jig set up on a drill press. I charge $100.00 for one hole or four it doesn't matter. Iron sites $175.00. That is just labor for the holes drilled and tapped. It works out to $50.00 an hour which is the minimum you can probably charge if you are paying rent, electric, equipment, consumables, phone etc. Of course I do the actual work for free because I love my job so f****** much.

emt2688 said:

I am an owner of a small machine shop that deals with industrial customers. I have never done any gun modifications, although I am an avid hunter, and have several firearms.

I received a call out of the blue wanting to know if I could drill and tap a receiver for scope mounts. Now, I believe I have the skill for this, but really am not set up for doing it, and would be more of a PITA type of job for me anyway.

This did bring a couple questions to mind though.

First, doing a private party transaction like this, modifying an existing firearm, what would that laws be? Would I need a permit of some sort? I am rather clueless as to this, so enlighten me.

Second, as a guess, what would a normal gunsmith charge for such a task, IE drilling and tapping (6-48) 4 holes for scope mounts? I gave an estimated guess at this, and of course the customer about choked. I really can't do much with an hour, by the time you talk to them, set-up, do it, billing, ect. But it did bring out my curiosity of what someone in the field that does it often charges.

At the moment I really don't have the time or want for this kind of work, other than if it were my own firearms. If having to have a permit to do this, it would more or less just give me an excuse to potential customers as to why I am not even interested, lol. On the other hand, I know of no gunsmiths in the area, as I have asked gun dealers of who I could take things to, with a resounding "nobody around here" answer.

Pat

Click to expand...

Several years ago, when I was young and stupid (as opposed to old and still stupid) I used to set up a Bridgeport clone, drill and tap the reciever to fit whatever bases the customer brought me, and send him down the road for $35. Then I encountered my first 03A3. Harder than the hinges of hell. Price didn't go up, I just quit doing 03A3s. If I were to do a drill and tap job today (which I wouldn't, due to the licensing requirements), I wouldn't do it for less than $15 per hole, likely higher, due to the liability questions. Only guns I'll touch these days are MINE!

Most full time machinests in job shops are more than skilled enough for basic gun work. Many run circles around "gunsmiths" in this area. The main issues are related to the law, firearm specific knowledge or having the special tools.

Scope mounts are about as basic as it comes. Work of this type has three issues -
First, if you dont have a licence, the customer has to hang around. If he leaves, you get into that transfer thing that is a big no no without a licence and your insurance company may take exception to non employees in the shop. This is a clasic catch 22.

Second, Unless your farmilear with the gun, you may lose your ass on a hard reciever. Break off a tap or shatter a few bits and the job is not profitable. So many guns made so many places, the only chance anyone has is experiance. Forums like this are a good way to avoid that kind of SNAFU by drawing on the experiance of others. Definately ask about the particular make and model before starting in if you are not sure.

Third, The gun has to be stripped down in most cases before the drill and tap work starts.
Do you have the right tools for that. You know, all the little hollow ground screw drivers and brass punches to keep from buggering the screw heads and dinging up the pins. What are you going to do when that little spring goes "poing" into the chip tub. Again, experiance and the right books to let you know how to do the tare down on an unfarmilear piece.

Think about it, how comfortable are you with the public bringing guns into your place of business, expecting you to stop your regular work and deal with there problem imediately (just try to get them to keep an apointment). Then you have the billing - can you take a credit card. Sounds like a PITA if your not licenced and set up for that kind of business.

I suppose some one should have mentioned that you can't just put the action in the mill vise and drill 4 holes. A lot of action threads are cut with taps or a great deal of time and thought was not spent getting the threads straight in the receivers. Of course the action is generally pointing in one direction and the barrel in another. If you dial in the receiver and drill and tap it you will soon find that it won't bore site and then a lot of shimming comes into play or the TIG machine comes out. Neither is desirable. The best way I have found to date is to clamp V blocks to the bed of the mill and get them lined up and indicated in. Then lay the barrel into the V blocks and clamp it tight. The receiver end is going to be higher because of the taper in the barrel so the head on the mill will have to be twisted over a bit to get straight holes into the receiver. You will have to shim up the V block on the muzzle end if you can't tilt your mill head. I grew out of pulling the mill apart when I had to do my first one in school at CST that way just to learn how to do it and went up to the tool room and dumped $500.00 on a Forester Site Jig. Oddly enough once a year I get caught by some freaky gun that will not fit into the Forester and I have to strip the vise and dividing head off of the mill and go at it old school. I have always meant to build a height adjustable V block for the chamber and and then just use the dividing head to hold the muzzle and after 30 years its still on my to-do-list. I have thought about it a lot but its just to simple and easy to do so I haven't bothered yet. If a project takes less than a day I have motivational problems.

ADD TO POST

I should have mentioned that the Forester site jig and many others aligns the holes to the barrel. It uses a miniature V block affair just like I have described for the mill. A lot of people never notice that the barrel and receivers are often pointed in different directions because the jig cunningly takes this into consideration without telling you.

DJA said:

PS: The drilling jig is made by FORSTER.
FORSTER : UNIVERSAL SIGHT MOUNTING FIXTURE & COMPONENTS - World's Largest Supplier of Firearm Accessories, Gun Parts and Gunsmithing Tools - BROWNELLS

Scroll down to the "Fixture."

Click to expand...

That's it, pardon my gaffe. Good piece of kit. One of the above posters has run into some apparently "strange" builds where the axis of the bore is not aligned to the centerline of the receiver. I won't say it doesn't happen, but it should be rare. The remarks about hard metal, surface hardening particularly in old mil surplus actions is spot on. They'll snap a carbide drill in a heartbeat if you're not expecting it. Glass hard surface, butter just under. If you know it's going to happen and change bits accordingly, it's just a PITA. If you don't allow for it, snapped off drills will surely ruin your day. Have to admit I'm sorta' glad I'm not doing that anymore.

Lowell

L Haney said:

One of the above posters has run into some apparently "strange" builds where the axis of the bore is not aligned to the centerline of the receiver. I won't say it doesn't happen, but it should be rare.

Click to expand...

i bet it is pretty common on mass produced rifles. i would never count on the outside of the receiver to perfectly coaxial to the bore or the barrel or even the receiver bore.

300sniper said:

i bet it is pretty common on mass produced rifles. i would never count on the outside of the receiver to perfectly coaxial to the bore or the barrel or even the receiver bore.

Click to expand...

Perfectly? No, but well within the adjustment range of irons or scopes. If you have to resort to shims or milling then the firearm was suffering from assembly/manufacturing issues before you started. Bear in mind old military rifles were never intended for "drop on" scope mounting and the top surfaces of the receiver were not planar to start with.

now for my .02 and not a word about how or were to drill the holes for the front of the mount on a bolt gun ? like not in the locking lug ! but if your one that must[i don't] then not to close to edge [locking lug face]

Thank you all for the replies.

It pretty much confirms my gut instinct to stay away. I didn't initially say no, but told the man that I wasn't set up for it, and he would eat the costs of the taps (didn't know if a plug tap would do, or would need a bottom tap) plus a guestimate of at least $100, but would have to see it first. I am glad that turned him off and he replied he had a "machinist neighbor"

I envisioned it to be one of those 30 minute jobs that takes 3-4 hours drilling out busted taps with carbide, or worse.

In the future, I can pull out the don't have a FFL license card.

emt2688 said:

Thank you all for the replies.

It pretty much confirms my gut instinct to stay away. I didn't initially say no, but told the man that I wasn't set up for it, and he would eat the costs of the taps (didn't know if a plug tap would do, or would need a bottom tap) plus a guestimate of at least $100, but would have to see it first. I am glad that turned him off and he replied he had a "machinist neighbor"

I envisioned it to be one of those 30 minute jobs that takes 3-4 hours drilling out busted taps with carbide, or worse.

In the future, I can pull out the don't have a FFL license card.

Click to expand...

That last one is probably your ace in the hole. Or should be. Nobody with any brains wants to get crossways with the feds. Let the folks with the license recover some of the cash and headache they've already expended.

1yesca said:

now for my .02 and not a word about how or were to drill the holes for the front of the mount on a bolt gun ? like not in the locking lug ! but if your one that must[i don't] then not to close to edge [locking lug face]

Click to expand...

Sorry! Most drilled holes for these mounts, especially on rifles that were not intended for optics, are done "free hand", as far as the location of the front mount. The center of the front scope base would usually be situated half way from the front of the open area to the face of the receiver. This just looks "balanced". Often these holes are drilled and tapped blind, as there is no reason for full penetration. I've yet to see a gunsmith that let these screws protrude into the area of the locking lug rotation. Three full threads of engagement are sufficient for these fasteners. Heavy recoiling guns may need additional screws to prevent shearing.

Lowell

300sniper said:

i bet it is pretty common on mass produced rifles. i would never count on the outside of the receiver to perfectly coaxial to the bore or the barrel or even the receiver bore.

Click to expand...

And I would never count on the outside if the barrel to run true to the bore either ;-).

checking some common barrels nothing is perfectly true to the bore, not the threads, not the bolt counterbore, not the outside of the barrel.