Building 1911s on 80% frames - Share yours, ask questions


If you have a good jig and steady hand a power drill will work, but again, you dont have to worry about it since you are in Texas.

A Caspian Foster frame will be what you need.

But it is only worth it if you want to do this for the experience and to be able to say that you built that gun. It will be super difficult to get all the parts and tools cheaper than buying a GI spec (especially a used one).

Invest in a good caliper. For frame to slide fitting that will be the most important tool.
Also get a Jerry Kuhnhausen 1911 Shop Manual vol 1 and 2 books. At least vol 2.

You could buy a kit mentioned above for all the parts or buy parts “one at a time” as you build along.

My process is as follows:

  1. Inspect the frame (much more important for 80% than a Caspian) for symmetry and spec.
  2. Inspect the slide. Slides can be “defective” even when you buy from reputable makers pretty often.
  3. Measure the slide and fill out a worksheet like this one :
  4. Messure the frame and fill out the worksheet.
  5. See which dimensions to address. Shoot for .001" clearance.
  6. Test fit the barrel to the slide. Check for locking lug engagement, bushing fit, etc. I prefer to use gunsmith fit barrels, but if you go with a “drop-in” it may be easier.
  7. If the slide checks out, start reducing the dimensions on the frame rails to match the slide.
  8. Fit the frame to slide. Better to not lap, but a couple of back and forths with a very high grit lapping compound will not hurt. (I am talking 1200 grit).
  9. Assuming the barrel is drop-in, verify the link size is good… hopefully it is, but I don’t use drop in parts… you do this by performing a modified Schuemann Timing Test. (I can explain this in detail later)
  10. Test fit grip safety and thumb safety (thumb safety has to be NEW). Grip safety must be able to touch the rear wall of the frame with its bottom.
  11. Test fit the trigger. If drop-in and it fits, good, if not, fit the trigger pad to the frame (top and/or bottom of the pad, making sure the trigger bow is staying horizontal)
  12. With trigger installed, fit the grip safety to the rear of the trigger bow if needed. The grip safety must be able to move its trigger stop arm behind the trigger bow from fully engaged position with the trigger all the way forward.
  13. Install the sear, disconnector and hammer. Make sure the disconnector head can move freely up and down in the frame. I assume you will be using a drop in set.
  14. Fit the thumb safety to the sear with cocked hammer.
  15. Assemble the rest of parts and test the function of everything using snap caps.
  16. Address any issues.
  17. Recheck and repeat until everything is 100%.
  18. Test fire with 1 round in the magazine. If something doesn’t work, stop and find the issue. Fix, repeat the test. If gun fires, round ejects and slide locks back, check the gun over and if everything is good, proceed.
  19. Test fire with 2 rounds in the magazine. Same thing as above.
  20. Test fire with full 7 round magazine. Same thing as above.
  21. Finishing touches.

Sorry, this is assuming you go for drop-in parts. That means a whole lot of hoping that they are all in spec.

Better to take it one step at a time, ask a lot of questions and not to hurry.
Hope this helps.

P.S. get the books first.


Good stuff, thank you for that post. I’m sure I am not the only one who will benefit from it.

A few questions if you don’t mind good sir.

edit I think I figured it out, it has a serial number so I need to ship it to an FFL. What 80% frame source would you recommend if I decided to go that route? The $150 Caspian foster frame is very appealing… I suppose that would be a great place to start before doing an 80%.

  • Also, would you recommend carbon, aluminum or stainless frame (receiver) / slide?
  • What are the advantages and disadvantages of drop-in parts besides the convenience?
  • If budget minded for the first one what parts kit (or individual part suppliers) would you recommend?
  • Lastly, I really liked the compensator you cut / drilled in to the slide on one of your builds (Build 5, “Bob”), is that something that can be done to one of these Caspian slides or do I need a custom slide for me to attempt it on another build?
  • Oh, can I use anyone else’s slide instead of Caspian? Like for example, could I get an old WWI/WWII GI slide and use it on this build?

Trust me, people will get annoyed at me because I always ask a bunch of questions because I want to get stuff right.


I, for example, cannot buy a frame only in CA. We have a roster of certified handguns here. A frame is not a handgun that meets the approved criteria. So 80% was the way.

I have used 1911builders frames mostly, VytamenC is the second source. In reality many different carriers are using the same supplier, so the frames are likely to be all the same quality or close to each other.

I prefer steel to aluminum and stainless steel to carbon steel, though carbon is a better choice overall. Stainless is just something you can leave “unfinishied”.

There is really no such thing as Drop-in when it comes to 1911s, but generally drop-in parts will require little to no fitting in some cases. The flip side of that is that tolerances stack and some parts may fit looser in one gun than the other. Or they may simply be out of spec for the other parts. Gunsmith fit parts are generally oversize in all the needed dimensions where precise fitting can be achieved. But then you need more tools.

Wilson combat parts are decent. I have never tried those kits Robert linked (but have seen people build on those and it seems they work).

On the “Bob” build I used a Schuemann Hycomp barrel. I have heard they may be out of business but you can try to see if they still sell barrels. Any slide can be cut for those barrels.

I have used a couple of TR-enabling slides (very good prices) and they seem to work.

The frame is fitted to the slide, not the other way around, so you can start with any decent slide (that is good overall) and fit the frame to that slide. Be careful with WW1 slides. If I remember correctly some of those were left soft. I dont remember where I have read it, or if it was WW1 slides…


Oh, and you will need to make sure to get a standard or unramped barrel if you go with a standard frame. Or if you go with a frame that is cut for a ramped barrel you will need to get a barrel that has that ramp.

You have 3 choices in frame cuts:

Clark/para (aka C/P, and schuemann uses Clark/Para/Lissner on their barrels)
Nowlin/Wilson (aka N/W or W/N).

Frames cut for C/P need to be modified slightly to fit C/P/L barrels.


Just remember… there are no stupid questions, but there are a lot of inquisitive idiots.

Ask away my brother, ask away.

Doing a build (80% or otherwise) you will learn a lot and have a better appreciation of firearm building.

@Mosinvirus is the man to learn from.



General 1911 tools and smiffin’ videos.


@Mosinvirus are you doing your own stamping and engraving in yours or are you out sourcing


I went with a local laser engraver option. Quick, clean, and sharp. Can’t beat that.


I’ve been wondering about that for a while
When you were able to build in ca
Was this required by the state or just a personal preference


Build 6 “RaMmeR” playlist is below:


I engraved as a personal preference. Now it is required anyway.
I figured that if I ever got pulled over and my guns got inspected by CA LE, without engravings they would have more questions than with. Also it would be easier to reference stolen or lost firearms if they were serialized.


I agree
Was t sure if it was a requirement


Well, back then when I had mine engraved I chose to engrave using my Channel Name. CA rules now dictate that the markings must include legal names.

So I had to go back to the engraver and put my legal name on the frames as well. This sucked because I did it right through the finish (melonite, Ion Bond, Parkerizing, etc).


That’s unfortunate I always thought it was awesome that you had your channel name on them


The channel name is still there.
I engraved my legal name slightly more to the rear, over the right grip panel. It was an additional engraving, not a replacement.


Hi I thought I would ask for an opinion on my 1911 build. Its sa frame, Rock Island slide and fusion bull barrel in 38 super. I think I would like to port the slide. I seen MV do this with a file, I don’t have mill so its the file route. Opinion, think I should try, any tips advise. This is where I’am at now with the build.


I would buy a cheap slide or one of the sarco kits
To experiment if that’s the slide Your going to use for your build
I have gotten a few frames and 3 slides to experiment with
I haven’t started that project as of yet I’m waiting for winter to really settle in here so I have a excuse to be in the shop all the time

Unfortunately 1911 parts are not cheap I got lucky with my experimental slide someone gave is a 1911 in a plastic bag all in parts at the shop I work at and said his wife broke it and he wasn’t allowed to have guns anymore and could we dispose of it for him
I took the bag for experiment


Damn Your frame looks a bit beat up lol
Did you have to deck the sa frame?
I’m sure @Mosinvirus will be along shortly to chime in


100% go for it, live and learn!