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Posted: 12/3/2013 7:56:12 PM EDT
Link Posted: 12/3/2013 9:41:12 PM EDT
[#1]
Since it is only 80% complete am I correct in assuming these lowers do not need to be shipped to an FFL?  Are you required to engrave a serial number?
Link Posted: 12/3/2013 10:32:51 PM EDT
[#2]
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Quoted:
Since it is only 80% complete am I correct in assuming these lowers do not need to be shipped to an FFL?  Are you required to engrave a serial number?
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80%'s are not "receivers" yet. YOU become the manufacturer when you complete it. Does not require FFL. But it's for YOUR use only (not for sale once completed). NFA rules still apply.
Link Posted: 12/4/2013 1:37:31 AM EDT
[#3]
For $95, I'll give it a go. Based on Rainiers reputation for quality this should be a decent polymer product.
Link Posted: 12/4/2013 2:29:01 PM EDT
[#4]
These are very cool, I'm glad to see people heading back to the drawing board for a stronger design. I'll be picking one of these up after Christmas just to show my support for innovation.

ETA: Anyone know the weight of a completed lower?
Link Posted: 12/5/2013 7:38:25 AM EDT
[#5]
Is this the same company as Polymer80?

NMD the two look similar, but there are differences, although it's the same idea.
Link Posted: 12/5/2013 3:48:27 PM EDT
[#6]
Link Posted: 12/5/2013 6:54:16 PM EDT
[#7]
Interesting.

Remedial 80% lower question: Are jigs ubiquitous, will it work on (virtually) any 80% lower?
Link Posted: 12/5/2013 7:12:35 PM EDT
[#8]
Link Posted: 12/7/2013 3:29:55 PM EDT
[#9]
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Quoted:


The jig is specific to the lower, as it is molded to the shape of the JMT.
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Quoted:
Quoted:
Interesting.

Remedial 80% lower question: Are jigs ubiquitous, will it work on (virtually) any 80% lower?


The jig is specific to the lower, as it is molded to the shape of the JMT.


What is the jig made out of ?
Link Posted: 12/8/2013 5:38:00 PM EDT
[#10]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


The jig is specific to the lower, as it is molded to the shape of the JMT.
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Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:
Interesting.

Remedial 80% lower question: Are jigs ubiquitous, will it work on (virtually) any 80% lower?


The jig is specific to the lower, as it is molded to the shape of the JMT.


How easy are these to finish up? You guys done a few?

What kinda round count should I start getting nervous at?

I already ordered one anyways.
Link Posted: 12/8/2013 8:09:31 PM EDT
[#11]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


How easy are these to finish up? You guys done a few?

What kinda round count should I start getting nervous at?

I already ordered one anyways.
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Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:
Quoted:
Interesting.

Remedial 80% lower question: Are jigs ubiquitous, will it work on (virtually) any 80% lower?


The jig is specific to the lower, as it is molded to the shape of the JMT.


How easy are these to finish up? You guys done a few?

What kinda round count should I start getting nervous at?

I already ordered one anyways.


I'd also like to know if these have been tested and how well they held up. Maybe Rainier has put them through the ringer?
Link Posted: 12/9/2013 7:08:03 AM EDT
[#12]
I hope to see someone do a video or step by step thread on this before I dive in.




Link Posted: 12/9/2013 8:28:02 AM EDT
[#13]
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Quoted:
I hope to see someone do a video or step by step thread on this before I dive in.

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There is a DIY video. Don't know how easy it will be without a drill press and other stuff. Seems not too bad though.
Link Posted: 12/9/2013 9:38:46 AM EDT
[#14]

Discussion ForumsJump to Quoted PostQuote History
Quoted:
There is a DIY video. Don't know how easy it will be without a drill press and other stuff. Seems not too bad though.
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Quoted:



Quoted:

I hope to see someone do a video or step by step thread on this before I dive in.







There is a DIY video. Don't know how easy it will be without a drill press and other stuff. Seems not too bad though.


Copy, thanks!



 
Link Posted: 12/9/2013 9:45:16 AM EDT
[#15]
NOW we might actually be getting somewhere.

And I don't even LIKE poly lowers...

The price could be a bit lower, as there are forged 80%'s out there for $80 from places like Tactical Machining, but that doesn't include a jig.
Will they offer a jig-less option in the future at some point, for those that already have one from this package deal, maybe saving a few bucks?
Link Posted: 12/9/2013 10:06:18 AM EDT
[#16]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
NOW we might actually be getting somewhere.

And I don't even LIKE poly lowers...

The price could be a bit lower, as there are forged 80%'s out there for $80 from places like Tactical Machining, but that doesn't include a jig.
Will they offer a jig-less option in the future at some point, for those that already have one from this package deal, maybe saving a few bucks?
View Quote


Yeah but this one is undetectable
Link Posted: 12/9/2013 10:15:25 AM EDT
[#17]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


Yeah but this one is undetectable
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Discussion ForumsJump to Quoted PostQuote History
Quoted:
Quoted:
NOW we might actually be getting somewhere.

And I don't even LIKE poly lowers...

The price could be a bit lower, as there are forged 80%'s out there for $80 from places like Tactical Machining, but that doesn't include a jig.
Will they offer a jig-less option in the future at some point, for those that already have one from this package deal, maybe saving a few bucks?


Yeah but this one is undetectable


There is steel reinforcement, apparently...
Link Posted: 12/9/2013 4:10:13 PM EDT
[#18]
What is the weight on a finished lower?
Link Posted: 12/9/2013 5:40:48 PM EDT
[#19]
Anyone put a bunch of rounds through one of these yet?

I've been looking for a way to shave off a few ounces so I can call my carbine "7 pounds" instead of "7 pounds 3.4 oz" just for bragging rights.
Link Posted: 12/10/2013 2:26:36 PM EDT
[#20]
Just ordered one I will post results.
Link Posted: 12/18/2013 5:01:17 PM EDT
[#21]
Any updates?
Link Posted: 12/18/2013 5:19:11 PM EDT
[#22]
Interesting.
Link Posted: 12/19/2013 6:56:52 AM EDT
[#23]
TAG
Link Posted: 12/19/2013 5:37:18 PM EDT
[#24]
The one I ordered has not got here yet. When it does I will give first impressions.
Link Posted: 1/14/2014 4:22:37 AM EDT
[#25]
I worked on mine this weekend.  Was very excited.  Key word is WAS.  After cutting out all the material and fitting and installing the LPK parts it wouldn't fire my 5.45x39.  Upon closer inspection the hammer was tilted to the left.  The hammer pin holes must not have lined up.  The reason I went with the JMT was the included Jig. Jig was suppose of prevent a newbie machinist from drilling the holes in the wrong place. Now I'm unsure what to do.  I would gladly purchase another because I was impressed with the apparent strength and design of the JMT lower but....with the jig I (?) still screwed up?
Link Posted: 1/14/2014 4:43:29 AM EDT
[#26]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I worked on mine this weekend.  Was very excited.  Key word is WAS.  After cutting out all the material and fitting and installing the LPK parts it wouldn't fire my 5.45x39.  Upon closer inspection the hammer was tilted to the left.  The hammer pin holes must not have lined up.  The reason I went with the JMT was the included Jig. Jig was suppose of prevent a newbie machinist from drilling the holes in the wrong place. Now I'm unsure what to do.  I would gladly purchase another because I was impressed with the apparent strength and design of the JMT lower but....with the jig I (?) still screwed up?
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Don't feel too bad, some people where I work cold tear a brick up with a feather.
Link Posted: 1/14/2014 3:46:41 PM EDT
[#27]
I did mine also my hammer ended up a little off also. I have not had a chance to try yet. I also noticed that the mag release button hole is a lot bigger than it needs to be and the button catches the edge. It would be nice to know if anybody else has these issues.
Schultz
Link Posted: 1/14/2014 4:07:28 PM EDT
[#28]
I plan on giving mine a try in the next couple of weeks. I will post my results.
Link Posted: 1/14/2014 4:28:38 PM EDT
[#29]
I like Polymer80's jig setup better honestly, but they don't have the reputation. I'm debating whether or not to try one of these for my first build coming up in the near future. I will be building a 2nd and possibly a 3rd so I may save this for my 2nd build.
Link Posted: 1/15/2014 5:27:10 AM EDT
[#30]
in for more reviews/problems
Link Posted: 1/16/2014 9:46:09 AM EDT
[#31]
Wanting a lightweight build for the wife utilizing a poly lower, the JMT 80% is on my short list of options, so I joined the forum primarily to participate in this discussion.  

drbs57: did you drill through from one side only?  And was your drill press table flat, level, and squared to the drill?  These would be the most obvious reasons for a tilted trigger pin hole.  Seems like if you set both jig halves on a flat surface about 1-1/4" apart and place and drill bit through the holes on both sides, the bit should look level to the table.  If drilled through from both sides, the holes wouldn't meet up in the middle if the jig was off.

Have you contacted JMT yet?  I am very interested in hearing what you find out, as there is very little feedback available online concerning these lowers.

Link Posted: 1/16/2014 2:02:03 PM EDT
[#32]
Yes. ..drilled holes only from on side.  Yes I attempted to have drill press level and square.  Last night I fitted in a POF trigger unit. I lined up the trigger hole and removed material to line up the hammer hole and sure enough one side had more oval shape than the other. But I got the Hammer plumb with the reciever. I filled in the gaps with JB Weld and calked it up to experience.  Guess I'll make it my dedicated .22 setup (if it fires tonight).  I really don't know how much ownership of the problem is mine or JMT.  I'm guessing it all me but because of the little bit of doubt I probably will not try another JMT.  I think I'll try a EP next...
Link Posted: 1/17/2014 3:27:40 AM EDT
[#33]
Thanks for getting back 57.  

Taking in what you said, it helps me a lot.  It appears that the problem you encountered may have been the result of not drilling from both sides.  There are variables with the potential of working against you if not addressed properly, especially if using an ordinary drill press in a home workshop (not sure what you used).  In the video the operator stresses leveling the table, which is fine and good, but what if the drill press itself is not sitting on a level floor/bench or plumb(?)  Then you have a level table and a tilted bit.  But even with the bit & table squared to each other, the arbor could have too much slop, (most do as they're not built to be ultra precision), causing the bit to wander through the cut.  Even though the lower isn't real thick, I can see why it is very important to drill just a little more than half way through from both sides.

I hope you can use the lower for your .22 build.  It could be saved for any build by having the oval hole professionally milled out on the bad side and an insert installed, or a custom stepped pin fabricated.

Still, its a little spooky not being able to find any other reviews from those who may also have first hand experience with a JMT lower.
Link Posted: 1/17/2014 2:08:57 PM EDT
[#34]
sry...I was misunderstood.  I drilled from each side.  I went back and checked for marring in the jig's pilot hole and there was none on eaither side.  So the jig did not line up for one reason or another.  That's why I'm not quite willing to take 100% responsiblity for the less than exciting results.  The safety and trigger holes ended up spot on, tight and true and they were drilled without any change in setup between the three (per side).  I'll report back after playing with .22
Link Posted: 1/17/2014 6:29:40 PM EDT
[#35]
I checked my jig also it appears that the hole in the jig was not lined up. I also did not like how big the mag release hole was drilled by the factory
Schultz
Link Posted: 1/18/2014 4:18:46 AM EDT
[#36]
That sucks, but as with fabrication, there is always aFix of some sort.  
For the record I wouldn't want to independently drill two holes that are supposed to align.... Always better to line bore.  Also easy to check alignment on a scrap piece of material first.

I hope that you are able to straighten things out ( no pun intended!)
Link Posted: 1/18/2014 10:39:25 AM EDT
[#37]
I purchased one from Rainier on sale for $89.95. I finished mine on a milling machine, actually a mini-mill. I watched the video posted on the JMT sight and printed out the PDF instructions. Followed the instructions including drilling the holes (hammer, trigger, safety) from both sides of the receiver. Everything turned out perfect. Holes are true and assembly with DPMS LPK went without a hitch. I was skeptical about the polymer thing but after completing this one, I really like it. Recently I changed out the stock trigger parts and installed a Timney trigger I had laying around. Now, I like it even better. I have tried it out on my 5.56 Nato 16" upper and a 300 AAC 16" upper without any problems. Used Pmags and Lancer L5 mags both without problems. Have fired at least 500rds and everything remains tight. Both upper receivers were built on MUR's. I know 500rds isn't very much but, it's a promising start. I would definitely buy another, so far I am a happy camper.
Link Posted: 1/19/2014 7:39:52 PM EDT
[#38]



Fresh out of the box, well packed with straight forward directions. I promptly went to the website as directed, watched the video and downloaded the instructions.






















Gathering the tools for the build.






















After realizing my 3in1 wasn't going to give me the clearance needed, I decided to drill the safety and trigger pin holes on my drill press. I made sure everything was leveled out before drilling, I encountered no issues.  






















Leveling out the receiver on the 3in1, I did notice the top cover of the jig gave a different level than the top of the jig. I went with the level of the top of the jig.






















Remove material, check depth of cut... again and again. The material was easy to cut and gave me no issues.



























Ready for the jig top cover and final plunge through for the trigger. No problems thus far. Just taking my time.  






















All done, total time 1 hour. I don't have a LPK handy, I'll post my functionality test when I get one.
















 
Link Posted: 1/21/2014 2:30:43 AM EDT
[#39]
Great pics!

What knife is that in the last pic?

Thanks
Link Posted: 1/21/2014 6:12:49 AM EDT
[#40]

Discussion ForumsJump to Quoted PostQuote History
Quoted:


Great pics!



What knife is that in the last pic?



Thanks
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I hope the pics help everyone out a little. The knife is one of my customs, I make blades.  

 
Link Posted: 1/23/2014 5:01:13 PM EDT
[#41]
Very nice blade. Great craftsmanship!
Link Posted: 1/24/2014 6:12:58 AM EDT
[#42]
Very nice.  The finish looks fantastic.  Obviously not your first rodeo.  You inspire me to try another.
Link Posted: 1/24/2014 11:30:22 AM EDT
[#43]
LPK on order, I will update when everything comes in.
Link Posted: 2/9/2014 10:23:07 AM EDT
[#44]

Have mine on the way and only have access to a drill press and am trying to find out if these can truly be done well using just a press or not?

This is my firs build of any kind and really have no desire to screw it up......

And tidbits from someone who has done a JMT would be appreciated!!
Link Posted: 2/18/2014 8:32:48 AM EDT
[#45]
My LPK came in yesterday... The hammer/trigger/selector are all off at the same angle causing everything to cant. I think I will try to face the hammer flat to the BCG, I don't know what else to do. Is this a jig issue?
Link Posted: 2/20/2014 9:56:02 AM EDT
[#46]
received one of this recently, had to take a razor blade to scrape away excess material to be able to fit the mag release catch in (lpk was a spikes tactical) still have yet to mill out the receiver. looking forward to seeing how it works.  quick question, instead of leveling out the drill press is it possible to use the jig with a bit through both sides to ensure the presses base plate is perpendictular to the drill angle?
Link Posted: 2/21/2014 2:28:11 PM EDT
[#47]
I started drilling my JMT lower today.  After hearing about the tilted pin holes experienced by others, I made absolutely sure that the table, drill press, jig and vise were all plumb, level, square and dead nuts on.  Followed the video step by step.  Drilled in slowly and carefully with brand new drill bits 3/4 of the way on both sides. But all three holes ended up canted .015" lower on the left than on the right.  It doesn't sound like much, but it is when trying to line up fire control parts to function properly in a lower that's less than an inch wide.  

Measurements of the jig itself show the starting holes vary .015" from left to right, which makes the jig the smoking gun.  Could it be cobbled to work? - probably, but which hole is the right hole?  And who really wants a cobbled together lower?

I really like the lower.  It's well built and sharp looking.  But this ain't gonna fly like it is, so I'll be getting in touch with JMT to see what can be done about it.  
Link Posted: 2/21/2014 5:53:11 PM EDT
[#48]
I guess I'll just add that I have canted trigger pin holes too.  The hammer pin holes seem fine.  I suppose it could be due to user error, but 1) I put the lower back in the jig and the holes line up exactly with the jig on both sides, and 2) I've since completed aluminum lowers with the Juggernaut Tactical jig and everything lined up perfectly, so I doubt it's my technique or an out-of-spec drill press.  

I wonder if I could epoxy the holes in the JMT lower and re-drill them with the Juggernaut jig?  I guess it's worth a try, as it's not really serviceable as-is so nothing would be lost if it doesn't work.
Link Posted: 2/21/2014 5:56:07 PM EDT
[#49]
So is this happening when people are drilling the holes from each side, or when drilling all the way through?  I've finished plenty of aluminum lowers, never used a jig, and I always drilled all the way through both sides in the same operation.  Never once had a canted pin hole.  Having to do multiple setups while trying to maintain location and concentricity is not a simple thing, especially if you're working with anything but an actual mill.
Link Posted: 2/21/2014 6:02:24 PM EDT
[#50]

Discussion ForumsJump to Quoted PostQuote History
Quoted:


So is this happening when people are drilling the holes from each side, or when drilling all the way through?  I've finished plenty of aluminum lowers, never used a jig, and I always drilled all the way through both sides in the same operation.  Never once had a canted pin hole.  Having to do multiple setups while trying to maintain location and concentricity is not a simple thing, especially if you're working with anything but an actual mill.
View Quote
The directions say to drill 3/4 of the way through, flip the lower and drill the other side using the jig as a guide. This is happening when doing as instructed.

 
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