Personally I think those are bad instructions for a number of reasons, the biggest being that the jig is apparently nowhere near concentric left to right

You and me both. I have a $100.00 poly paper weight.

 

From what I've seen and read, JMT is one of the more serviceable poly lowers out there, but they screwed the pooch on the jig/instructions...

You could drill the holes out oversized (all from the same side...) and add some bushings.  Either epoxy them in or just get some anti-walk / KNS pins to make sure they don't slip out of the lower.

I called JMT late yesterday afternoon, explained the canted holes, and was immediately connected to Scott, one of their technicians.  His first questions were; 1) How long ago did I order the lower?, and 2) what color is the jig, grey or grey/tan?  He stated that they had recently changed their jigs, apparently to deal with this issue. Not sure what the 'new' jig color is but mine was light grey.  According to him they only receive hole location complaints from 4 or 5 people out of 2,000.  I told him that those 4 or 5 people must all be on this forum, (in a friendly way).

He also said that on some occasions the person doing the drilling would clamp the jig in a shallow vise too tightly and distort the lower half of the jig. He also stated that the old jigs could cause the lower to be lose inside the jig, but mine fit very snugly on both sides.

After discussing my machining prowess, and the jig pilot holes being .015" off from side to side, Scott asked me to ship it back with the jig as he wanted to evaluate the problem.  Having nothing to lose but a useless block of plastic at this point, I sent it off this morning priority mail, so I hope to hear something from them by the middle to later part of next week.  Scott assured me that I would be taken care of - hopefully not by a black helicopter at 3am.

My suggestion to others with this problem is to check the pilot holes on both sides of your jig.  Do so by running a smooth file over the top of the two-sided jig (with top plate off) to be sure there are no  casting burrs.  I simply used a dial caliper and measured from the top of the holes to the top of the jig.  If the holes are off, do not do any machining until you contact JMT.  If your lower is completed and defective, still call JMT to let them know that there seems to be more than 4 or 5 out of 2,000 people experiencing this problem.  They do seem to be reputable folks and genuinely interested in making this right.

This whole issue looks to be the fault of drilling from both sides, especially when the jig is defective.

Grey jig here... Thank you for this info. I will check my jig and get in touch with them.

 

My lower had all those problems plus the hole for the mag release was to big and the take down pin holes seem to be overdrilled. I would not recomend this lower at least untill they get the bugs worked out. I am going to contact them on monday and discuss the issues.

Schultz

so are the Grey jigs the old or new?  Mine was all grey?

I was one of the first to order these when they hit the market.  Mine all had the grey jigs, all were drilled according to the instructions (flip them after drilling 3/4 thru), and the trigger pins were all crooked.  I fixed the problem by taking a Dremel and widening the notch on my selector- 2-minutes of fitting and they work beautifully!  Several hundred rounds thru each without a problem.  I waste finitely not impressed with the product though and wouldn't buy another one- might as well go with aluminum.

I too have purchased this part from Rainier, and luckily read this before I drilled.

I'm seeing the problem being the jig (grey); assembled without the lower, there is a noticable out of square between the top and side of the jig. Assembled with the lower, this looks much better, but I strongly suspect that the unit continues to be slightly out of square.

I have sent a message to JMT about it, and will probably call later when West-coast time catches up. The lower itself looks great, but I'm not poking any holes until I hear from them because I have no confidence in the jig given what I've read here.

I have no problem doing full layout on the lower itself and drilling/milling sans jig, or even modifying the jig to where I am confident of it's fit, will keep your posted.

Let me just follow up with a shout out to Rainier Arms for great service and quick shipping, and to JMT for the lower itself, it look like a great product.

Scott, (the technician at JMT), called me late yesterday and said he had used my grey jig I sent back to drill a couple more lowers and had the same issue with crooked holes - when drilling from both sides.  He drilled one all the way through from the right side only and it turned out perfect. He's trying to determine why the holes in the jig won't line up on both sides on some jigs but not others, but I don't really care, because when I get my replacement it'll be drilled from one side only.

I do like the lower, and will be looking forward to seeing it completed correctly.

Hey fellas, long time lurker, first time posting. I've been following the comment threads on here ever since I got my lower, so I thought I'd toss in my experience.  I forget who said it, but drilling the hammer and trigger holes from one side is the way to go, mine came out dead nuts on, no issues. I spoke with Scott out at JMT today and they're actually revising the instructions to reflect that.  Another thing I learned from him is that they do pay attention to this thread (and others) and all of you are contributing to making their product better, I wish more companies were as plugged in to their customers as they are.  Anyway, I finished milling my first JMT lower yesterday, now it's nearly ready to go to the range.  I still need to tighten everything down, stake a couple thingies in place, lube her up and all that fun stuff, but I couldn't be more excited about how it's turning out.  Pics anyone?  http://imgur.com/a/wzZLj#0
http://i.imgur.com/5pwnAQA.jpg
http://i.imgur.com/Bo65d3p.jpg
http://i.imgur.com/c8mawJm.jpg
http://i.imgur.com/FETKwLy.jpg

Please post a range report after you run some rounds through that. Nice looking rifle too.

Looks sweet, hopefully it performs as well as it looks.

Tagging just to stay updated. I want to give this a try.
But not until all the bugs are worked out.

I have seen comparisons of the EP and Polymer80 but not between the P80 and the JMT.
It seems the P80 is better than the EP but I didn't like the thin mag-well of the P80.

Im gonna sit here on the fence a while yet.

From which side are you drilling all the way through?

I'm glad I could make a monetary contribution to their quality control

Drill from the side of the jig with the JMT logo and hole diameters on it.

Did you buy the lower with that finish or did you paint it? If so, what did you use? It looks great.

for those with a JMT paperweight, has anyone ever considered an epoxy based weld system?  JB weld comes to mind,  I've done some really stupid things in the past to polymers, fixed with JB weld and then went on playing, it might work especially considering that most of the parts and holes wont be dealing with pressures, just vibrations

That's the original color right out of the box, you'll be seeing JMT announce all the new colors pretty soon.

Hi Everyone,

I am a long time reader and first time poster.

I felt I had to post to tell you that I built an AR with a JMT lower (grey jig) and it is performing absolutely 100% flawlessly.  The amount of compliments I get at the range is amazing.

I have never done anything like this before, but I have done a lot of woodworking in the past 20 years, so doing precision setups is something I am used to doing.  Really all this is is precision drilling and mortising.

I have seen the problem with canted or off angle holes many, many times in woodworking, when doweling or mortising.

The problem almost every time was that people (sometimes me) leveled the piece with a bubble level, but didn't square the piece to the drill bit.  The thing is that while the piece may be level to the floor (really to the earth), the drill press may be slightly off angle and that will produce an angled hole.

When dealing with this much precision, a bubble level is virtually useless.  You need to square the bit to the jig with a small, quality, machinists square, and assure it is square from 4 sides.  Not doing that, and using a bubble level is a sure way to get angled holes.  Also, you need to check and recheck that the bit is centered in the jig hole.

While I don't doubt that some of the lowers or jigs may have manufacturing defects (something that happens in virtually every manufacturing process), I think that a lot of the canted holes are more user error than manufacturing defect.  I think this mainly because I have seen the same thing happen for over 20 years.

I don't want to offend anyone, or cause trouble, and if I'm wrong and you squared the piece to the bit, please disregard this post and call me Sally.  

But I am amazed with the quality of the JMT lower and wholeheartedly recommend that people buy it.  I experienced fantastic service from JMT, I ordered it on a Saturday and had it in my hands on Tuesday! I have hundreds of rounds through it and haven't had one FTF or misfeed.

What's the pay like at JMT nowadays?

 




 

I wouldn't know, All I know is that it worked for me, and I have seen the same problem in woodworking dozens of times... and the pic godrilla47 posted shows him using a bubble level to set up the jig.  But I guess it must be a coincidence.

Believe me, or don't, I don't care, and I thought about not posting because I would look like a shill.  I'm not.  I just think JMT deserves some support from a very satisfied customer... One who has made the same kind of mistakes they are being blamed for.

http://imgur.com/34U12as

Regardless of what they are or aren't being blamed for, their prescribed method to drill the fire control group holes is not the right way if you want them to be in position and concentric.

When the only thing you have to index on is a plastic jig with possible tolerance issues, you shouldn't be drilling from both sides in two setups, when it's completely possible to drill the holes from one side.

Long time lurker, first time post... wait nevermind

Got the kit with the light gray jig from Rainier today.
Haven't drilled any holes, but I transfer punched them one each side.  Measuring from the top surface, the safety hole measures 0.015" higher on the right side, the trigger holes are close enough to say they're equal, and the hammer hole is 0.010" higher on the right side.

Safety: 0.698L / 0.685R
Trigger: 0.933L / 0.935R
Hammer: 0.616L / 0.606R

I'll be drilling them from one side when I get around to it, any input as to which side would be best?

Edit:


Understatement of the thread here.

I think this is the appropriate response to drilling the holes from both sides:

Well neither one is really "right"
~0.020" difference in pin/selector locations can make a huge difference in trigger performance and feel.
If the tolerances stack up enough, you may not even get it to fire, or it may fire with the selector on safe.


For reference:

Leave me out of it, I did't post pictures so "lurkers" could coincidentally pick them apart. The process that's out of spec are the pin holes which I did on a drill press. The drill press was squared to the work rest and square to the work piece. The 3in1 I used for the milling process was in fact leveled and square to the work piece and I had no problem in that area function wise.

 

I really don't mean to pick anyone apart. I just have made the mistake of leveling but not squaring and have had angled holes because of it.

If you did square it then great.

I squared it meticulously, drilled from both sides, and it worked perfectly.

I would worry about runout drilling from one side, but if you have a good press and a straight bit, it should be ok.

It could certainly be that the holes in your jig are off, or that the ribs inside the jig angled the lower.

All I can say for sure is that mine works great.

I have personally milled two of these and I have spoken to Scott about the trigger pin holes. The first lower I milled, was the one you see in the video. It went perfect and the lower functioned excellent. I now have close to 500 rounds through it without a single failure.

The second lower is a different story. I machined it just last week, the trigger was canted ever so slightly not allowing the safety to sit flush and therefore the detent did not engage. After checking the jig out I discovered it was off .015 and therefore drilling the holes from each side caused the issue.

JMT is aware of the issue and has changed the jig so can only drill from the ejection port side. It is my understanding that all of Rainier Arms inventory is being switched out and all sales moving forward will have the new jig. For existing owners who have not yet milled their lower, simply drill the holes all the way through from one side. Make sure when you dot, DO NOT run into the next hole as it may can't the bit. If you have questions or concerns, you can contact JMT directly. I know in talking to Scott they are dedicated in supporting their customers and that this was an isolated issue on only s small batch of lower jig.

Hello, I am a not so long time lurker (no, really) and first time poster.  I received my JMT lower yesterday and will be drilling the holes with a press as soon as the lower parts get here.  I have never done anything like this, no carpentry, woodworking, or mechanical or machining work of any kind.  I am not in any way what you would call mechanically inclined.  I just really want to do this the right way and eliminate any possibility of user error.  If the jig sucks, that's fine.  I guess I'll just learn about using JB Weld next if I have to.

I am not sure what you are referring to in your post though.  What do you mean by "Make sure when you dot"?  I am not familiar with this term.  Also, what should I be using to ensure this is level?

I have ordered a square and level tool http://www.amazon.com/gp/product/B002IVTN16/ref=oh_details_o02_s01_i00?ie=UTF8&psc=1  and a caliper http://www.amazon.com/gp/product/B000GSLKIW/ref=oh_details_o02_s01_i01?ie=UTF8&psc=1   Should I plan on using another specialized instrument to make sure the drill is perfectly perpendicular to the jig?

Thanks to ANYONE who can help with this.  I am looking forward to putting all this together.  I have ordered a good quality upper from PSA and only want to have a good, reliable AR-15 at the end of this.  This will be my first one.  Thanks for the help everyone!  :)

I think there was a typo in there.  He means don't drill all the way through the lower and into the far side of the jig, stop as soon as you're through the far side of the lower or the jig might kick the bit sideways and oval your pin hole.

You may not finish one with the INTENTION of selling it. If you complete it for yourself and then later decide you no longer want it, you may legally sell it. No serial number is required but if you do sell it someday,  it is recommended.

Thanks for the clarification.  Is this done by measurement alone or is there a different noise made when the drill bit reaches the jig on the other side?

Well with aluminum, you would feel it, not so easy with polymer.  If you've got an actual mill, use the depth stop on the quill.

Talked to Dan and Scott today at JMT and they have now changed the drilling instructions on their website to include drilling all the way through from the right side only.  They have apparently altered their newest jig to reflect this change.  I'll know what it looks like when it gets here Friday.

So, I have the JMT 80% lower and after reading this thread I realize that I am not in a position to confidently drill these holes with the press I have access to.  The one I am able to use (a friend's) is an old table top press but even a square with bubble levels shows that it isn't level.  I don't want to risk it with this press and I really wouldn't know where to start making it precise enough to drill these holes.

I see at Harbor Freight they have new table top presses for about $140.  If anyone is familiar with these, do you think it would be reliable to get this job done?  I don't mind buying a tool I may need again in the future (especially if this makes a good lower :)  ) but I don't want to spend the money if it isn't going to be precise enough.

Thank you guys ahead of time for the expert advice!

Level doesn't matter, as long as the spindle is perpendicular to your work piece.
If there is no adjustment in the head and you're out of square, you might consider an adjustable vise setup instead of a whole new drill.

happy time.  I just finished my JMT LOWER. Or should I say my second attempt. My first one was a complete failure.  Some of it my fault, but I still finished the project only to discover that by following the directions the trigger pin holes don't lineup.  Undaunted I gave it another chance.  This time I followed the new recommendations by drilling only from the right-hand side, and everything went in properly.  I used a large craftsman standalone drill press and a 3/8th end-mill. I checked to make sure my table was level before drilling out the side holes.  By far the best 80% polymer lower out there right now.  The lower fit well with all three of my standard AR uppers.  But was a little tight on my Rock River arms upper.  Next stop aluminum.  I ordered two different types of jigs.   And guys how about marking the jigs with a line to say how far to go back. Yes I know the directions give measurements but saying don't go to far back is not helpful.  But fast shipping and very solid lower.

I'm back to report a 100% success with the second lower JMT sent me. No cant and functioning 100%. The new jig will only allow you to drill from the JMT logo side all the way through. This solved any issue I personally had with the first lower being off.

I too have had total success with my JMT lower. Luckily  I read this thread first and contacted JMT with concerns about the drilling. Looks, great, and most importantly, the rifle works as it should.

WOW, JMT must be paying everyone!!!

Just kidding, I'm glad that the new jigs and instructions work better for you guys.

I'm thinking about maybe buying another and trying again. Same thing happened to mine. Canted holes.

Hey all- first time post, first AR build.

I ordered my JMT back in November and just got around to finishing it this week so I wanted to weigh in as this thread was super valuable to me.

I drilled my hammer and trigger pins through from the right side at the advice of what I read here.  No issues, everything is square and the LPK went in without issue and is functioning correctly.  I did note that the bit did widen the holes on the opposite side of the jig indicatiting that they were not properly aligned.  I am very gratefull I read this thread first.

I used a different method then most.  I used a drill press to make "pilot" holes to the appropriate depth simlar to the method used in aluminum 80% lowers.  I then used a dremel tool and cutting bit to remove the rest of the material.  Much more time consuming, but going slowly and constantly referencing my micrometer I was able to accomplish the task.  I did this because I did not have a vice for the drill press i was using and quickly realized that without one, using the end mill bit would be impossible.  I could have bought one, but I really did want to add another $100 to the cost of my lower.  The major advantage of polymer is that the dremel bit flies through it with ease.

At this point the LPK is in and working, everything is tight and nothing appears canted.  My PSA upper arrives this week and I will update with photos and a range report.  I would add that the lower looks great and feels solid.  I have every confidence in its construction and that it will hold up for a long long time.

(many folks argue about why one would use an 80% upper when you can pick up an completed aluminum one for $50.  I could care less about the pride of building it myself or the gov. taking it away...In October 2013 Maryland banned the purchase of AR recievers, I am very grateful to have this legal alternative.  There is no other way for me to legally build an AR in MD currently.)

Sincere thanks to all those who posted here, I would have ended up with a useless piece of plastic and lost 5 hrs of my life without your input.

JMT 80 Lower $99
PSA Enhanced LPK $89.00
PSA CHF Mid length 16" ($419 shipped w/ bcg!!)
Bravo Company Carry Handle $110.00
Magpul MOE hand gaurd $28.00
~$30 tools

< $800.00

^This^

Glad to hear that you machining went well, sorry to hear about your state :-(

I finally got around to machining the new replacement JMT lower they sent me, supplied with the new jig for drilling from one side only.  My drill press was perfectly square to the table just like the last time, only this time the holes came out perfectly level.  JMT's new approach to drilling the holes works.  I used brand new 5/32" and 3/8" drills bit and all my holes came out with just a slight interference fit.  Very nice.  All factory holes were of perfect size as well.

I went on to remove the bulk of the pocket meat with 3/8" and 1/2" drill bits, followed by careful finishing with a 3/8" 3-fluted HSS end mill.  I would suggest that maybe a 4-fluted end mill (recommended by JMT) might work a little smoother.  Pay close attention to rpms (1400-1800), and do not be in a hurry.  

The finished product mated to a Del-Ton upper perfectly, and my son is loving it.

JMT's lowers are a top quality product, their customer service is 2nd to none, and I would not hesitate to buy another.  It sounds as if others here have discovered the same thing.

OR... you could get a spot on Mil Spec lower (anodized, all correct, etc) for $50! Imagine that!

That's just "Plum Crazy"!