newer style 80% spec question

[goober]

i never look at the clock when im machining so you guys could be right. It might only seem like 10 mins to me but is 30 in reality. I'm also a newbie to machining so dont burn me too hard

hey no worries... just sayin'
(and i'm a completely untrained DIY hack myself, if we're worryin about qualifications here )

[savs2k]

hey at least we can say we build it ourselves instead of buy it ourselves.

[Grumpyoldretiredcop]

I had a little bit of free time today so I decided to get back to work with the lower. It looks like it'll fit. I realigned everything to get it in spec. Ugly wall but hey it should work. So anyone who screws up by not reading directions at least once like me.... you can still fix it. I still need to do the trigger slot and trigger/hammer pin. Then i'll know if it's functional. I did a test fit and my upper has some slop to it. The milling adapter plate slot is a bit wider then it should be. I'll figure out a way to stop the play but its not bad i've had worse on lowers/upper i've bought. Anyways here is a single picture update. Thanks for the help guys.

My first lower doesn't look too different from yours, still passed functional checks and functioned correctly when assembled/testfired. As long as the cavity width is in spec, the hammer spring will bridge the grooves in the cavity wall and keep the hammer from walking.

[Acorn556]

If it were me.....after doing two and making it a learning experience.....I'd finish the whole process just so you see where ELSE you could screw up.

[goober]

If it were me.....after doing two and making it a learning experience.....I'd finish the whole process just so you see where ELSE you could screw up.

absolutely. even if the mistake you make first is so bad that there is NO chance of salvaging the piece and producing a functional product, use it as a canvas to practice all the other ops you need to do.

[fabguy]

absolutely. even if the mistake you make first is so bad that there is NO chance of salvaging the piece and producing a functional product, use it as a canvas to practice all the other ops you need to do.

That is VERY true, Do that with everything and you'll be amazed at how good you get. Practice practice practice. Now we have kids

[woodey]

I would mark the lower with Dykem and mark out what the FC cavity should look like and see if I could make it work. Looking at the small drill holes and then the divot of the larger one, it appears that the small drill holes may not be out to the final dimension, but since I haven't done a "drill out the FC cavity" build, I don't know.

After see a few of these built in my shop I think the layout before you start is key to a good job. Using Dykem blueing or black marker & scribing parell line on top that you can see when the jig is on is the trick. The CNC jig is loose & needs to be fitted to the receiver.

[savs2k]

actually what i learned

1. read the instructions at least ONCE
2. dont scratch your *** while working

The one i screwed up in this thread was my first attempt at the solid firing control pocket. I use mills and cnc vertical mills but didn't want to bring a lower in to work on it at someone else's shop. So trying to mill on a drill press is crappy idea but hey it works. I only screwed up because i was lazy TWICE. But everything is almost done on the new lower. I just need to do the hole for the trigger and i'm good to test. I tried a test fit for the hammer and trigger with the spring and pin earlier today. It looks promising. I still need to find a way to reduce the slop in the upper though. The rear pocket hole is slightly too big. I believe it's still in spec but I don't like the play at all. I'll probably do the trigger after dinner and let you guys know the result.

[goober]

After see a few of these built in my shop I think the layout before you start is key to a good job. Using Dykem blueing or black marker & scribing parell line on top that you can see when the jig is on is the trick. The CNC jig is loose & needs to be fitted to the receiver.

i don't know if i'd call the CNC jig "loose", but yes, measure thrice cut once is always a good axiom.
the TM jig does appear to have somewhat better positive alignment of the FCG pocket milling guide plates.

[woodey]

Well maybe not loose, but it can be canted several degrees out to the left or right if your not aware of it & watching out. I think there holes on there milling plate are large to acomidate several differant lowers from milled to forged. Where the TM jig is made for there lower only, not even having all of the differant holes in the jig but only the two holes that need to be drilled on there lower.

[savs2k]

Well maybe not loose, but it can be canted several degrees out to the left or right if your not aware of it & watching out. I think there holes on there milling plate are large to acomidate several differant lowers from milled to forged. Where the TM jig is made for there lower only, not even having all of the differant holes in the jig but only the two holes that need to be drilled on there lower.

thats exactly what got me in this situation. When I run something on a cnc the finish product will NEVER now then or ever be as loose as the adapter plate. I would have designed it to a tighter fit to the jig its self. But I didn't make it and still bought it and love it so I can't complain too much. It was my own laziness that got myself to screw up my lower and I very much admit that. If I had properly read all of the instructions instead of looking at the tools and pictures I would have done it right the first time.

[savs2k]

as promised I put everything together and did a function test with a snap cap. Looks good right now. The trigger is a little loose left to right because of the wall dimensions being screwed up from misplaces 1/8 drill holes and the upper is slightly loose. Not bad or unusual, it just bugs me. I'll be taking it out to the range tomorrow hopefully for a test and to zero my eotech.