Drilling and tapping receiver on Maverick 88

[RadekSkylark]

Hello, everyone!

Recently I bought myself a used Maverick 88 Security 18,5" (5+1) 12 gauge shotgun in a decent condition.

I was thinking that it would be nice in the future if I could add some red dot sights maybe, but this shotgun doesn't have a rail on the receiver. I've found out that there are some screw-on options from different manufacturers (which are rather bulky), but they cost a lot and the shipping (you can see the struggles with it in my other post on this section of the forums) is a huge problem.

Considering this, to me, it seems more worthwhile to drill and tap the receiver in the same manner as on Mossberg 500, so that all its accessories can be fitted on my shotgun as well.

The question I'm having is whether this is doable (as in safe, considering how this shotgun works as well as thickness and strength of the receiver)? Can someone please share on experience with this?

Also, I don't have dimensions for the location of these holes (as for Mossberg 500) so that I could "position" them correctly, and the drills/thread size. So, if it is OK to drill/tap, it would be really nice if someone with Mossberg 500 could chime in with dimensions on the location of the original holes (I presume they are centered on the receiver with regards to the longitudinal axis of the shotgun, but I'm not sure on the dimension from the front size of the receiver as well as between the holes, and the thread size as well).

Thanks

 

[BoBo522]

Disclaimer: My conclusions are speculative but I believe the reasoning is sound.

The receiver is essentially identical to any other 500-series receiver in terms of thickness and composition, with the notable difference being the absence of a cutout for the tang safety (Maverick uses a cross-bolt safety in the trigger assembly). I don't believe you should have any concerns about the strength of the receiver or its ability to be modified in this way.

I don't have the dimensions, but you can probably solve this one easily enough if you get the pic rail you want to install and use it as a template. It should be longitudinally centered on the receiver, in the vicinity of the "vestigial grooves". Thread size - total guess, I think it might be 8-40 but I'm not entirely sure.

Good luck with your modifications!

 

[RadekSkylark]

Hello there!

Yeah, that's a great idea to buy a pic rail and use it as a template.

Do you think it is something one can do by himself on a press drill without involving a gunsmith, or would you say rather not (my hands grow from the correct part of my body).

 

[herrwalther]

If you feel comfortable drilling blind holes (partial holes that don't go through to the inside of the receiver) I would say go for it. That is the hardest part of D&T for any top rail, in my opinion. Finding the center, laying it out, etc is the easy part. You can save yourself some work by getting an OEM Mossberg 500 rail to layout the hole locations, just make sure it is center. 5 minutes on Google says the thread pitch for Mossberg top rails has been 8-40 for the past 20 years or so.

 

[RadekSkylark]

Oh, so those need to be "blind" holes? That I didn't know. It does make everything way more complicated, as I presume the thickness of the receiver is quite limited (presume something around 1/8", maybe a bit more?)

The problem with gunsmiths locally is that I don't fully trust them. Consider that we don't have that many guns around, so there are only maybe 2-3 gunsmiths locally, and the total amount of work to be done is somewhat limited, so they definitely don't have the same level of experience as gunsmiths in the US. So I'm really not sure whether these gunsmiths can actually do such "general type" of machining (like drilling a blind hole) way better than I myself could with some relatively decent tools. What I do know is that they'll charge me at least 110$ for those holes drilled/tapped.

 

[twofewscrews]

From Mossberg regarding screw size and torque values:
We would use 8x40 on our drilled and tapped models and with those small screws I would just go hand tight if you really want to torque them to 12 inch pounds.

I also have a Maverick 88 that I added a UTG 590 Optic Mount to so I could use a scope/red dot at will. The UTG 590 requires no permanent modification or gunsmith to install, but given your shipping restrictions it might not be a viable option for you. If you do go this route or a similar route one thing to keep in mind is that it adds a bit of rise to the optic which might require you to add some kind of cheek riser to use with scopes/red dots. If you're familiar with Kydex you can fashion one for yourself for less then 5USD plus a heat gun, if you don't already have one, and the cost of bolts to secure it to the stock. Given that I'm in the US I bought a pre-made Kydex Cheek Riser off of Amazon and used a heat gun to make it fit properly. The Side Saddle (shell holder thing is optional). The cheek riser is thin enough (.08 inches or 2.03mm to the comb) that it doesn't interfere your cheek weld.

I added some pics to show you roughly what this would look like.

Good Luck.

 

[RadekSkylark]

I've searched for similar parts like the UTG 590 optic mount but haven't found any that would ship to Latvia, which is why I'm considering the drilling/tapping.

 

[snowman357]

Why blind holes its not in the area of the chamber, yes dont have the screws so long it hits the action. probably not a lot of metal there using all of it would be better, but its not my gun. I would try a side saddle mount first, if you drill and tap use aluma tap oil, thickness of receiver should be at least the diameter of the screw you are using as a rule of thumb.

Side saddles with rail:

 

[herrwalther]

Why blind holes its not in the area of the chamber, yes dont have the screws so long it hits the action. probably not a lot of metal there using all of it would be better, but its not my gun. I would try a side saddle mount first, if you drill and tap use aluma tap oil, thickness of receiver should be at least the diameter of the screw you are using as a rule of thumb.

I prefer using blind holes whenever possible. Most people who do D&T themselves will get the wrong length screw, drill through to the receiver, and have screws interfering with the action. Best case it scratches the top of the bolt.

 

[snowman357]

I prefer using blind holes whenever possible. Most people who do D&T themselves will get the wrong length screw, drill through to the receiver, and have screws interfering with the action. Best case it scratches the top of the bolt.

If you cant put the proper length screws in place then yes do blind holes.

 

[RadekSkylark]

Guys, can you please clarify - as I understand there are a total of 4 holes in the receiver of Mossberg 500 and 2 of them are just above the extraction port (thus, the chamber, or is the chamber on a shotgun the part just in front of the extraction port, basically, at the start of the barrel?). Please, correct me if I'm wrong, but if that's the case, then 2 of the holes are in the chamber?

Anyways, if I would drill 4 through holes and tap them in the exact location as on the 500, I could either find the right size bolts (or cut them shorter to the exact length needed, or at the worst case order some bolts to be made in the machine shop, if purchasing bolts that are made for the 500 is not possible) so that they don't protrude (or protrude just a bit) into the receiver, or if this is not possible, try and make blind holes? To be honest, though, I can't see the case of "not finding the correct length bolts" as the criterion for deciding between through/blind holes, cause if you have blind holes you still have to have bolts so short that they'll actually fit and be tight enough for the rail to be attached (the same bolts will still work in through holes).

So, to me, it seems that the question of through/blind holes is a question of whether it is OK for the receiver to have "open" holes in terms of gases escaping the chamber area or something of that sort, basically, a question of functionality but not regarding the bolts themselves (considering that they're the correct lenght).

 

[twofewscrews]

Guys, can you please clarify - as I understand there are a total of 4 holes in the receiver of Mossberg 500 and 2 of them are just above the extraction port (thus, the chamber, or is the chamber on a shotgun the part just in front of the extraction port, basically, at the start of the barrel?). Please, correct me if I'm wrong, but if that's the case, then 2 of the holes are in the chamber?

You're correct that the chamber of is basically the start of the barrel. The holes will be (should be) over the ejecting port.

Anyways, if I would drill 4 through holes and tap them in the exact location as on the 500, I could either find the right size bolts (or cut them shorter to the exact length needed, or at the worst case order some bolts to be made in the machine shop, if purchasing bolts that are made for the 500 is not possible) so that they don't protrude (or protrude just a bit) into the receiver, or if this is not possible, try and make blind holes? To be honest, though, I can't see the case of "not finding the correct length bolts" as the criterion for deciding between through/blind holes, cause if you have blind holes you still have to have bolts so short that they'll actually fit and be tight enough for the rail to be attached (the same bolts will still work in through holes).

So, to me, it seems that the question of through/blind holes is a question of whether it is OK for the receiver to have "open" holes in terms of gases escaping the chamber area or something of that sort, basically, a question of functionality but not regarding the bolts themselves (considering that they're the correct lenght).

Through holes will not affect the function of the gun assuming of course that the screws are the correct length and do no interfere with the bolt. The chamber is in the barrel not the receiver.

This vid will show ya how the holes will line up on the receiver. Not the best vid but it'll do:

 

[RadekSkylark]

Oh, great, cause through holes I definitely should be able to do myself, just got to get the drill press and the rail to set out the holes on the receiver. The hardest thing probably is the setting out of the holes to be "exactly" on the longitudinal axis of the barrel (have no idea at this point how to set that out precisely, to be honest).

 

[herrwalther]

Oh, great, cause through holes I definitely should be able to do myself, just got to get the drill press and the rail to set out the holes on the receiver. The hardest thing probably is the setting out of the holes to be "exactly" on the longitudinal axis of the barrel (have no idea at this point how to set that out precisely, to be honest).

Finding where to drill is the easy part. Just don't overthink it. The top of your receiver should be serrated. This is a common milling method to reduce glare when looking down the receiver at the front bead. You will be drilling in this area for the mount. You can use layout fluid or even a silver Sharpie marker to highlight the area to make the process easier. Use calipers to measure the width of the serrated area at each screw hole using the Mossberg base as a template. Divide that number by 2 to get the center. Then use a center punch to put a start point for the drill right where it needs to be for all 4 holes. Make sure your bench vise on your drill is level both ways before drilling. Otherwise you will have crooked screws holding your rail on.

EDIT TO ADD: If you use the Sharpie, it will come off with Acetone when you are done. Acetone also removes all oils and grease. So make sure you relube everything after.

 

[RadekSkylark]

Thanks, good ideas that should actually work.