I did two 80% lowers today on a router jig that I just bought and I screwed up both. The fire control pockets on both are too deep. On my caliper they both read 1.29 inches. I believe they're supposed to be 1.25 inches. Are they toast as is? It seems I will have less than half of the thickness that I'm supposed to have on the bottom. I'm worried that the trigger spring will be affected. They looked great until I checked the depth. What a downer. Thanks.

They'll work

Yep, should be fine. You could always get extre power springs if you are worried.

It's an A1 retro project with all Colt parts so I'm hoping to keep it as true to form as I can. Unforunately they're expensive Nodak retro 80's.Thanks for the replies.

Absolutely no problem at all, put them together and shoot them

So far I feel better reading all your replies. I've been kicking myself over it all day.

In the final analysis, the floor of the FCG well is only used for one thing - providing a surface for the trigger spring to work against. It also helps keep too much crud from entering the well from below.

I tried to search similar threads here and elsewhere and I see guys worrying over a couple of thousandths........I blew right by that like it was standing still. I'll take it as a learning experience I guess.

I wish my problem was the same as yours.

During the last cut the router bit kicked back. I did not notice that it also caused the depth of cut to change.

I started to cut again and it was obvious there was something wrong with the cut.

I pulled the lower out of the jig and at the rear of the hole cut for the trigger, it was cut way too deep.

Looking closer, that area was a little thicker than the side of a soda can!

From the bottom it looked normal, but it flexes with slight finger pressure!

My plan is to build up the bottom with JB Weld or something like that and machine the bottom to spec.

I have nothing to lose!

Actually, the floor plate thickness is pretty critical and .040 is quite a bit. You have to remember that the trigger pins are what's holding the trigger in place and if the bottom of the trigger is not tight to the floor then it will rock and that's not good. However, all is not lost, just mix up some two part epoxy and add some of those aluminum shavings you're covered with to it. It should be the consistency of peanut butter. Fill it in and let it harden for 24 hours and re-mill it.

That's kind of what I was afraid was gonna be the case. I have a ton of money in parts and I really was hoping to avoid rigging these particular builds. My own fault entirely though.

Put them together and shoot them a lot of pockets have been milled two deep over the years including the actual guns that Colt have made.  There are many people that have milled them a bit to deep and are still running them just fine, I have seen guns that have been partially milled all the way through the bottom in places that are operating just fine.

Put one together and shoot it for a while and see how it goes, I am 100% sure you will have not problems at all.

I think you will be fine, test it out anyways.  That's just a bummer on the lowers since they were from NDS.  Quick question did your safety hole line up with your safety detent so that your safety isn't sitting slanted?  Reason I ask is my buddy got some 80% from RightToBear both anodized and unanodized and the unanodized ones safety was off enough it sits crooked.  Was wanting to buy a few myself to have engraved but am afraid to sink $100 in each of them and end up with safetys that look like crap.

Also did you use the 5D Jig or one of the others?  One other thing I noticed on the 5D Pro jig is the trigger cutout hole is HUGE!  The first one looked so bad after that we decided just to use dremel/files to finish the hole out so it wouldn't be so large.  Probably wouldn't bother most but I have no idea why they made such a big trigger hole.

A random idea I just thought of, if you had issues with your trigger pins walking out due to not enough force applied from the spring a quick fix would probably be to have someone with a lathe put you a tiny little notch in the trigger pin so you can install a little C Clip on it so it won't be able to come out.  Would make it harder to uninstall a trigger but I think it would work to keep it in place and someone with a lathe could do it in under a minute.  It would also be invisible from the outside and barely visible looking inside the receiver unlike those ugly anti-walk pins others use with the screws and stuff.

Edited to add - one more thing, how was you planning on finishing these out?  Sending them off to be anodized somewhere or painting them?  If you do decide to go with paint use MolyResin Gray-Black Flat, it is the appropriate color for the old XM Gray and looks great.  I am probably going to get the stuff to do it myself this month but would like to eventually get my own anodizing setup to do my own.

As long as you don’t go through the bottom, they are GTG.

You could always get a self-contained fcg like a POF trigger.

Does anyone make a self containing FCG that has the right appearance?  Serious question, as I don't think I have seen one.  The inside wouldn't matter of course but the outside would.  When doing a retro build it would look a little funny to me to have a different style trigger then stock especially after going all out on the lowers like the OP did.

I didn't get to drilling the holes yet. I planned on using Norrells greyish flat black. I was going to electro etch it myself. I used the 5d Pro and my drill press. I never did one before so I bought a cheap lower to practice on at least once before I messed with the expensive NDS lowers. That came out great but as you mentioned the trigger slot was huge. I got into trouble because I was trying to remedy that. I was gonna mill the correct size trigger hole on my own.

I took the measurements of the finished pocket of the cheap one and set my drill press stop at that depth and drilled the starter hole. Then I used a bigger mill in my drill press to plunge to that same depth to have a big enough hole to start the router in. The drill bit doesn't leave a flat hole at the bottom and I didn't want to start the router touching any material so I milled the bottom of the hole flat. Everything was fine until I got to the last pass. the mill hole was wide and just a touch too deep.I set the router depth hard against the final stop. I think either I misjudged how deep I was setting it or maybe the depth lock slipped.

I just don't have enough experience at it and I was trying to be perfect and I messed up. A brain fart and it cost me. I'm really disgusted with myself as I should have just followed the directions exactly and lived with the large trigger slot.

I was trying to make really nice SP1 type and I bought a bunch of new semi Colt parts from SA. They weren't cheap and it's not an option to not use them. Thanks for the replies.

My bet is on no affect at all.  Everything should be fine.  It won't be thin enough to fail.  Not enough difference to make the trigger return spring tension weak (the only thing thst should make contact with the floor) and nothing else matters or depends on this dimension.   Everything else is just clearance.

Why they make it that large I have no clue... but if you want to make it look right in the future you can do what we did.  It isn't as easy as it would be if they made it the correct size to start with and will probably take you about an hour or so to do one your first time but after you get the hang of it it's so much nicer then the gigantic hole.  You will need a stock receiver to reference from as you eyeball it... I guess you don't need one but it helps.

Don't worry about not drilling through the bottom, the original bit that drills all the way through isn't too big, it's the router moving sideways afterwards that makes it too large.  So just go ahead and drill all the way through the bottom like it says to do but once you mill out the FCG pocket do not mill out the trigger hole with the router.  Get you a good set of mini files which set me back about $4-5 at Wal-Mart.  There isn't much need in taking anymore off the sides since it's about perfect on width, but it obviously needs to be about twice as long with material taken from the front and back.

To achieve this I mostly used the completely round file, and a file that was flat on one side and rounded on the other.  With these 2 files you can get it to pretty much perfection with a little bit of work.  It is just one of those things you have to try first before you get down completely but even your first one will turn out much better then the 5D hole.  A really good way to speed this up is to use a dremel for a large amount of the cutting.  I found the best bit to use is the one that is completely metal like a drill bit but is smooth until the end where it has a spiral/end mill looking cutter.  These are common and usually included with most dremel tool accessory kits, and I believe sold seperately at Wal-mart as well.  This will cut your time back to about 20 minutes after you get the hang of it - do 90% with the dremel and the rest with the small files.   It helps to have a trigger handy during the fitting so you can drop it in and see how it fits, and after it goes in to see how much room is in front and behind it.

It really would be much nicer not to have to do this though, does anyone have any idea why they made it so large?  I have asked myself this many times.  I have never seen a factory lower come close to that size so it isn't trigger compatibility.  It also isn't about having enough material removed for the router to get started either because the trigger hole isn't completely milled out until that last action.  My initial fix was going to be making some plugs to fill in the 3rd section of the jigs guide and then opening up those new plugs to the correct size so that I could use the router in the future but I haven't gotten around to that yet - maybe after I get a milling machine.

A question. I'm very far from an expert on the effects of out of spec issues. I'm far from an expert on these rifles. What would be the ramifications of the trigger spring being weak or the legs being not positioned as they were designed in a worse case scenario? A few opinions have been mixed so I'm curious about the reasoning behind the opinions. Thanks again for all of your input, it's helpful. I like to learn as much as I can about things I'm interested in from people with experience. I've taken on a lot of things on this project for the first time, jigs, Norrells, air brushes, electro etching....all processes I have no prior hands on experience with.

The trigger's range of motion is defined by its interaction with the hammer up front and the selector in the rear. Once assembled, the selector prevents the nose of the trigger from dropping too low when it is pressed, and the hammer prevents the nose from rising too high, regardless of whether the floor of the FCG well is there. If the trigger spring is not present or not functioning properly, you may have to push the trigger back forward manually to get it to release from the disconnector and reset after each shot.

Thank You

I am right there with you, I plan on getting some stencils this month to try etching.  I also want to get a Norrells set up to do my own painting, I just wish I knew more about what all I needed.  I have an extra propane gas stove in the garage I can get a propane tank for so curing should be set, as well as a smaller/mid size 25 gallon air compressor.  From the little reading I have done it seems like people say you need at least 25-50 foot of line between your compressor and airgun, as well as a couple filters in between.  At the same time I see people use these cheap cans of air without a compressor from Testors for $15-30 or so and have fantastic results.  I was looking around on ebay and found some units that supply air to an airbrush and work as their own compressor for around $50 - any advantages over a regular compressor I have no idea.

To answer your question above, I am fairly sure the spring is just to keep the trigger in place where it is suppose to be and to put pressure on the pin that goes through the receiver so it won't fall out easily.  The hammer spring is your important spring, and surprisingly is the only one that really changes your trigger pull weight as well.  So as another poster above said I'm pretty sure about the only problem you might have is the pin being a little loose from lack of spring tension on the trigger but I doubt it will hurt anything and if it does there are ways you could fix that.  I am no expert on this area though so others will be able to answer your questions better, just thought I'd throw my 2 cents in.

If you do any modern builds check out the  Hiperfire EDT2 trigger, sadly it isn't a perfect match for looks to the stock trigger so I won't use it on clone builds but right now you can get them for $54 shipped from OpticsPlanet with a 10% discount code and they are amazing triggers for the money.  Really night and day between stock triggers and it for me.  I just bought one a couple months back to try and plan on stocking up on them before these older models are sold out and all they have are the newer ones at the normal $90+ price.

I'm not sure about any of it either but I think ideally the Norrells should be warm and I've seen the small cans of compressed air freeze up with sustained use. Again, that might not be the case or an issue as others seem to have had success with that method. I bought an air line with a built in dryer for using the air brush, I guess it can't hurt. I have a small compressor. I also discovered my oven is in no way going to keep a steady 300 degrees. I put some thermometers in there and it fluctuates a minimum of 50 degrees either way when it comes on and goes off. It also reads way over 300 according to the thermometers even though the oven says it's at 300. I don't know how to compensate for that yet. I understand if it's too hot or you keep it in too long it makes the color turn greenish.

For the etching you need a power supply with leads, solution and a bunch of Q-tips....and of course a stencil. It's a little tricky at first gauging how deep your going. I would practice on something first to get the hang of it. getting that stencil on straight is also a bit nerve racking as you only get one shot at that.

Forum says I'm limited to 200 words so I couldn't finish rambling in my last post.

But, I have been researching all this for awhile and thought I was doing fine until my bonehead move on the lowers. I hate the thought of having to start over with new expensive lowers as at least for me routing them out is a tedious stressful process. On one of the cheap first ones I tried all was going well until the router hit a spot it didn't like towards the end and got a little unhinged in there. I got complacent as all was going so smoothly. I learned from that and did 2 perfect ones and then proceeded to load myself with uncertainty by milling the pockets too low. I try to keep concentration high and hold that router tight but that's tiring after 2 in a row. When turning it on for a new pass hold that sucker tight and try not to let it be touching anything. I don't even know how much money I have spent on all original Colt A1 parts and tools for this project as I'm a perfectionist. I'm just bummed out about the uncertainty of what I did by milling too low. Even if it works I know it's there and that bothers me to no end. I guess the moral of the story is if your new at it and try to get too fancy and not follow the instructions you have to live with the consequences.

Seen a lot of info about the way the triggers work on these things so let me explain. The trigger and the Hammer are totally dependent on the placement of their pins. The amount of over travel and length of pull is what is affected by the floor depth. If you want to get the most out of your trigger then correct the floor plate issues, it's so easy. If you don't want to use the JB weld or my Epoxy fix then go to your local auto parts store and buy a set of sacrificial feeler gauges and cut to fit.

Thanks for the info. I'm sure I could fix this but with all the dollars I have tied up in the parts I just don't want the receivers to be what I would consider hacked back into spec. Maybe I will do as you suggest and repair them for some other future project and just bite the bullet and start over with new Nodaks and finish them as per the jig instructions not worrying about the giant trigger slot. Or take the advice of a previous poster and address the trigger slot in the way he suggested. I will never be happy with these 2 particular lowers knowing that the floors were built back up. Thank you all for your input, it is appreciated.

Well there are companies around that actually sell powdered aluminum that can be mixed with epoxy, if you mix it heavy enough, and then spread in the well, let set up hard for a few days and set your depth correctly, you could re-mill the pocket and finish with your choice of finishes, it would not be visible.  With some of the newer formulas of epoxy, it would also be stronger than just the aluminum and there would be no shame at all.

No Daks are expensive and they take a long time to get, I would not be able to wait.

Yes you are right they are expensive! No wait on 80% lowers from Nodak though.

After the hammer drops, maybe the trigger would have a little over travel, I'm not even sure if the trigger is limited by the floor depth or the selector?
OP: how thick is the floor at the trigger hole?
I'm sure you'll be fine. You're not even going to notice. I'd try this lower and see for your self before you go pouring jb weld or whatever in there. How hard is it to install the fire control group, slap on an upper and dry fire it a few times?

I haven't gone any further since I milled them yesterday. I didn't do the trigger slots yet. From measuring the outside depth of the receivers and subtracting the inside depth of the pockets it appears the thickness of the bottom of one is .0375, and the other is around .0425. I'm definitely going to complete them but I don't know yet if I'm going to use them for these 2 builds.

That's simply incorrect. The selector prevents the trigger from touching the floor when pressed. The hammer prevents the tail from dropping in the back.

When you say you bought an air line with built in dryer, is that something you hook to your compressor or is it a separate unit that supplies it's own air like I seen on ebay?  Just curious about this since I plan on buying a setup in the next couple of weeks to do my painting.  I need to figure out what all I need for sandblasting as well but that looks fairly simple, I believe I can make my own blast cabinet out of a tote pretty easily and then just get a cheap blasting gun for $10 or so and blast media.  Not sure if there is really anymore to it then that.

That really sucks about your temperature on your oven as well.  Is it electric or gas?  Just wondering if one is better at consistency then the other since I have an extra gas range in my garage.  For just doing receivers a little toaster oven would probably be plenty big enough on the upper and lower.  Either way I am sure it will look great in the end even if you do have it a little higher temp or keep it in longer the slight green tint can look factory as well since we see so many variations in colors.  The hardest thing about that setup would be doing an upper and then doing a lower a few months later and trying to match the color, if you didn't have it down exactly it may mismatch slightly.  Not a big deal there either really, most surplus M16's never matched anyways.

I wouldn't scrap my builds because of the bottom being too thin, it isn't something you can see from the outside so even if you did have to build it up which I see no reason for it would still look great on the outside.  And even the inside would look great after you painted it with some Norrells.  The trigger hole being gigantic would bother me way more then having to build up the lower on the inside since it is actually visible and throws the look off for me.

I’m with the group that thinks this will affect your build not at all. We are talking about 4 hundredth of an inch here. That’s a hair more than the thickness of a credit card. The angle of your trigger spring will hardly be affected.
If it really bothers you cut a piece of .040 aluminum sheet to fit the bottom of your FC pocket and drop it in.
A slight downward bend on the tips of the spring legs might be another possibility?

On the air hose, it's sold by Badger who makes the airbrush. It's just a 10 foot long braided air hose with a built in water trap that connects your compressor to your airbrush. That was the brand of airbrush mentioned on Norrells website so that's the only reason I bought it.

The oven I'm talking about is the gas oven in my kitchen. In researching that it seems all standard kitchen ovens work the same way, they don't keep a constant temperature. They all drop to a certain point below what they're set to and then come back on and go over what they're set to. They cycle like that continuously. A lot of ovens aren't accurate to what they say on the dial either. I would check your oven with a separate oven thermometer...you might be surprised at what you find.

The other thing I need to do is look into my router depth lock and see if there is a way to tighten it up. I believe that was the main cause of my issue. I don't know what I'm gonna do with these lowers yet. I'm kind of a perfectionist so it bothers me what happened. I will finish them for sure but maybe keep them in stock for something in the future. With all the money I have in Colt parts I might just give it another shot now with some of the experience I've gained. I probably should have done a few more cheap ones before jumping to the Nodaks.

As someone else said earlier I should have just drilled right through the bottom. I didn't realize the 21/64 bit was so close in size to the size of a standard trigger slot. The big slot that the jig made on the first one I did threw me off. Next time I'll just drill all the way through and skip the third step on the jig and address the slot myself.

My initial fix was going to be making some plugs to fill in the 3rd section of the jigs guide and then opening up those new plugs to the correct size so that I could use the router in the future but I haven't gotten around to that yet - maybe after I get a milling machine.

That seems like an excellent idea.

I didn't have anything laying around that would suit this and in a pinch I tried some cheap scrap wood and it didn't turn out so well and that is when I decided just to use the small files to finish it out and the small files do a wonderful job but is a little slower.  Without a milling machine it will be a little harder to make a plug for the jig and after I get a milling machine I will probably just do the trigger opening with it, or machine a few of the plugs and hand them out to everyone with 5d Jigs....

Also if you haven't drilled the hole completely through your receiver for your trigger hole yet I'd say it would be best to do that before trying to file anything as it makes a great reference and completes over half of it for you.  And go ahead and drill out your safety selector hole and trigger pin holes they are relatively easy and it will allow you to fit the trigger as you are filing out the opening for it.  I found the best way to do this is either with a drill press where you can put a little bit of force on it or if you have to use a hand drill to put it on something at about knee height that way you can slightly bend over and put a lot of pressure on the drill but be able to keep it straight as well.  Without the pressure the holes take a long time to cut, especially the safety hole.  With pressure or a drill press they only take about a minute or two on the safety and less on the trigger ones.  One other thing you will likely find that your safety hole is too tight for your safety and you will need to take a piece of sandpaper and wrap it around a drill bit and go around the safety holes a few times with rough grit and then fine grit to smooth it up.  It also helps if you go around the safety itself and smooth it up the same way.  The trigger pin holes come out the perfect size so far from my findings and are plenty tight.

Thanks for the info on the ovens, that really sucks as I have that spare gas range and was really planning on making it work.  I am still tempted to figure out a way to make it more precise, and if not I will likely try using it anyways.  In your reading did you find that electric toaster ovens were the same way?  I doubt it would help very much but if you spent a few dollars on some insulation to put around your stove on the sides/back etc. I bet it would keep the heat trapped inside for a longer period and therefore be able to maintain a steady temperature for a longer duration.  Over the years I have seen so many people use their household oven for baking the finish so I figure the results aren't as bad as you might think, but it would be nice to be able to do it right.

I will have to look into that air setup, how much did it cost you for the hose and filter?  Really hope you can get around to everything soon I'd love to see some pictures as you do them if you feel like sharing.

The hose was $23 online. It's probably not necessary but I figure it can't hurt. I don't think the oven is gonna be that critical as I see a lot of people do them in their kitchen oven and are real happy with it. I just know my oven always overcooks food so that's why I decided to look into it. I'm going to set mine at 287 because after testing it out that seems to hold it closest to 300 on my particular oven. I'm really not sure how critical being at exactly 300 is with Norrells but I figure the closer I can be the better.

I have used my oven with Norrell's and other finishes on old boat parts I restore and the flux in the temp has not cause a problem at all, but do be aware, the odors can be a problem when you are curing the different finishes.

My air bush I bought at Harbor Freight and I have never had a problem with it, I have a small couple gallon compressor that is noisy but works just fine for spraying, you just need to be able to maintain the air pressure and make sure you have no oil or water in the lines, it really does not take expensive equipment to spray these finishes, but you do need to make sure and clean things correctly after you are done, or you will gum up tips and such.

Also, no matter what set up you use, get a good quality respirator, when using those small air brushes, the particles are so small you won't even realize you are inhaling them until it is to late.

Thanks, $23 sounds great if that is all I need.  I thought if I used the compressor I was going to have to order 25-50 foot of copper line with a couple filters put in place so I wouldn't have to worry about the water buildup in the line.  I am not worried about having the best equipment at the moment, I just want something that works and I can have fun with and refinish some guns/parts I have.  I may eventually get some Cerakote as well but for most things Molyresin looks to have a better surface finish look to it and is more natural looking for standard firearm finishes.

I didn't know Norrells had any info on their page about what airbrush to use, I will have to go read up a little on it.  I also would like to get a small sand blasting setup so I can blast things before refinishing to make it easier.  I have heard with a small compressor like mine with 25 gallons I won't get much blast time before it starts back up again but I am not going to be doing much and don't care to wait as long as I can get it to work.  I have tried googling what parts do I need for a cheap paint setup and sand blasting setup but most of what I come up with is completely unrelated or people spending hundreds of dollars or even more on equipment that I just don't have at the moment.  I'd love to find a place that had an equipment list of all cheap but usable equipment to get me up and going.

Blasting is the biggest pain to set up to work well. It takes up a lot of space if you just have a garage. You also need a stout compressor. Having the ability to blast open up a lot of options such as parkerizing and surface prep for sprayed on finishes like Norrells. I wish I had the room for a nice setup.....it makes everything easier. I did a lot of car restoration and media blasting is the ticket for all sorts of projects.

I don't think you'd need a very big area for gun work when it comes to blasting?  You can make your own little blast cabinet out of a tote with a piece of clear plexiglass glued/screwed onto the top and gloves built into the sides for probably under $50 and the tote can be whatever size you want.  I plan on building one big enough to hold barreled actions but you wouldn't need one that big for just AR work, 22" or so wide would probably be plenty.

But the compressor is definitely the big problem I believe mine is only 25 gallons but I don't remember what CFM.  I plan on getting a bigger compressor sometime later this year but that is down there on my list of things at the moment.  Even with a small compressor I don't think it would be too bad to blast a receiver sized object?  Then again I have never done it but if I can get a receiver blasted in an hour or two I will be happy for now until I can upgrade compressors.

Space isn't really an issue for me anyways and eventually I'd like to have my whole garage outfitted with a gunsmithing shop of my own.  First up on the list is an older Bridgeport milling machine, and then hopefully a lathe to do barrel work.  And of course the painting setup, and a parkerizing tank which I have found online for about $150.  And lately I have been looking into anodizing a little more as well, nobody offers the retro Gray colors and I'd love to be able to do my own.  I know it would take a lot of effort but after getting it dialed in fairly close it would be so much easier to get the correct looking parts for builds.

You're overthinking this. This is simply not an issue. Assemble your rifles and enjoy them.

I probably am, I'm just not really that familiar with how critical certain dimensions are. Then when there is a mix of opinions from people who know more than me I really start to overthink it. I'm known for overthinking though lol.

The best way to figure it out, put one together and throw a few hundred rounds through it and then take down and inspect it.

I definitely will. The decision is whether I want to pour all my expensive Colt parts into them and etch and Norrell them or just save them for a future cheaper project. I would rather do all that retro work on something I'm positive is 100%. Decisions.....

Circuits is dead on:

The floor keeps dirt out and is a contact surface for the trigger spring. A .04" difference in floor height will have virtually no effect on the preload of the trigger spring. Actual trigger movement is constrained between the safety and the hammer.

If you're dead set on "proving" the lowers, build them with run of the mill standard parts, shoot the crap out of them until you're comfortable and then build your clones with the Colt parts.

One nice thing about LPK's they can be installed and they can be taken out, it seems like a pretty simple thing to me.