How to make your 20% look 100%.

Contribution from Racer 88


I’m just a noob when it comes to building guns. But, I’ve been working with my hands in some fashion for my whole life (coming up on 58 trips around the sun). And, I rather enjoy teaching and demonstrating techniques I have found helpful in my professional and other endeavors. So, it wouldn't be long before I did the same in this facet of the firearms experience! 😎


How I got here.

After shooting a friend’s P80 build at the range, I bought my first P80 frame about 2 years ago with the idea that MAYBE some day I’ll build a gun. And, there it sat in my closet. The recent political saber-rattling about “ghost guns” compelled me to get my ass in gear. The President, himself, said that anyone can, “just order a kit through the mail, and in 30 MINUTES have a working gun!” Well, hell… I can surely spare a half hour to have my very own “ghost gun!” 😉


So, I dove into the P80 pool… DEEP. When I decide to pursue an interest, I jump in with both feet. I gotsta know EVERYTHING. And soon!


Luckily, I stumbled across an MGB video on Youtube. At first, I thought “Damn, this guy is long-winded.” But, wait… who ELSE do I know like that? 😉 Then, I realized he’s a perfectionist, even when perfection is not required. Who else do I know like that?? It takes one to know one! He’s speakin’ my language! From there, I found this MGB forum and a truly fine group of helpful and friendly people.


OK… let’s get on with the subject at hand: How to finish a frame that doesn’t look like you turned a rabid rat loose on it after binging on bath salts.


Be kind to the plastic!

One thing I’ve learned about working on plastic, or POLYMER if we are feeling sophisticated, is that it’s not like working on hard materials such as metal or even wood. It’s SOFT. So, abrasive and cutting instruments will remove material very quickly. Furthermore, plastic is “grabby.” It will grab that rotary instrument and PULL it in. Cue Homer Simpson’s, “D’OH!”


Another property of plastic is that frictional heat will MELT it. Electric motor-powered tools have a lot of torque. They don’t stall if you press hard. They keep going, and the friction will QUICKLY generate heat. A lot of heat. And, plastic no likey heat. Ask me how I know!


I was polishing the shelf with a felt spear point like in MGB's video.

Whoops! Too much pressure! Had to trash the housing. (You can skip polishing the housing altogether, IMO.)

Another challenge of using rotary tools on small movable items is chatter. Chatter can happen when the tool AND the material or item being worked on are not being held steady in relationship to each other. It makes for a choppy, boogered up surface.


The Dremel tool is ironically quite unwieldly for something that is designed to do fine intricate work. It’s heavy. It’s fat and cannot be gripped like a pencil or paintbrush. It’s like trying to conduct an orchestra with a baseball bat instead of a proper baton.


Using a much narrower and lighter flex-shaft handpiece attachment for more delicate procedures helps with that issue. However, both the Dremel and flex-shaft have the additional burden of an electrical cord or cable shaft, which add weight and torque while holding and using the respective tools. This causes hand fatigue (yeah, it’s a thing), which makes for shaky work.


So, you’ve got a rather vulnerable piece of plastic in one shaky hand being subjected to a heavy high-speed high-torque rotary cutting instrument in the other shaky hand. This piece of plastic is destined to become a device intended to contain an explosion that hurls a piece of deadly metal downrange with PRECISION. If you fuck it up, at BEST it won’t work. At worst, someone could get hurt, including you.


Take control !

How do we avoid all that? With CONTROL. You’ve got to have control over the tool and the material you’re working on. Similarly, in precision rifle shooting (another passion of mine)… The more points of contact you have between the firearm, your body, and the ground (or other structural foundation), the steadier everything in the “system” will be.


Where to start? First we need to lock down the frame. For obvious reasons (I hope!), clamping it directly in a vise is a no-go. I picked up a nifty and rather simple device called the “Ergo Mast.” It’s a $15 piece of plastic molded to fit into the mag well of your frame. It also has a notch to lock into the magazine catch. But, even without the mag catch installed on your frame, the Ergo Mast will steady the frame very nicely. The Ergo Mast can be secured to your bench top via their own optional base, which is bolted to the bench.