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  #1  
Old 10-21-2012, 9:28 AM
drg-racr drg-racr is offline
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Default Just turned some mill handles on my Quentin AR10 80% lower....pics

I received my Quentin Defense anodized AR10(LR308) lower on Friday and I spent half the day at work on a handmill finishing it up. I am really happy with it. The anodizing looks fantastic. I am having one little issue with my safety detent hole or the thickness of the receiver. My receiver is thicker than a AR15 one and it is causing the safety selector to bottom out when the spring and detent are installed causing the selector to scrape tightly against the face of the receiver when turned. I tried 2 right handed selectors and neither would work but a left handed Stag selector does work. When I get my 308 lower parts kit if it doesn't fit I will have to modify it a bit for clearance. I used the dimensions off of the Colfax website for their LR308 lower and it worked out great except for one little thing. Quentin must not put their safety selector detent hole in the same spot as Colfax...mine is slightly offset in the safety selector bore I machined causing the selector to not point straight up or straight to the side as shown in the pictures. It still works properly though. If I could do it over again I would center the safety selector hole over the detent hole and dimension the hammer and trigger holes from that point. Its not off much..maybe .010-.015. I may end up making my own selector so I can get it pointing perfectly straight. I installed the trigger out of my Armalite National Match rifle and everything works great. Many thanks to the people involved in the group buy...couldn't be happier!















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  #2  
Old 10-21-2012, 9:48 AM
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Sucks about the detent hole being off. I haven't assembled any of my QD lowers so I haven't check mine. Might want to do that to check.
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  #3  
Old 10-21-2012, 2:22 PM
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Safety is on the wrong side
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  #4  
Old 10-21-2012, 2:26 PM
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I explained in the original post that the only one I had on hand that would work without rubbing the side of the receiver was a Stag left hand safety...that was in when I took the pictures.
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  #5  
Old 10-21-2012, 8:18 PM
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Are 308 and 223 safety switches the same? I would think they would be different because of the thickness difference of the receiver
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  #6  
Old 10-21-2012, 11:05 PM
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This will be a lot of work- but you could weld up the detent divots in the safety and re-cut them with a slight offset. Probably easier than trying to mess with the receiver holes!

-Dave
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  #7  
Old 10-22-2012, 3:37 AM
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I'll be able to make some small modifications to the selector detent slot to get it pointing where it needs to.
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  #8  
Old 10-22-2012, 4:20 AM
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Drill and ream the detent hole to the next nearest size up. (I don't have a print in front of me) I think it's .156" Turn a small aluminum insert to .157 and hammer it in place. Then redrill on center.

No welding involved no custom parts to make just one pin and some drilling and reaming.
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  #9  
Old 10-22-2012, 7:10 AM
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When my selector hole was off, I bought a 65 degree selector and it became a 45 degree selector. Works for me!
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  #10  
Old 10-25-2012, 9:10 PM
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Drill out the left side hole, and run a ambi selector that has removable selectors, such as the BAD or similar.

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  #11  
Old 10-26-2012, 8:57 AM
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I am concerned that the QD .308 piece is off-spec, as I have one that I have yet to assemble.

Would you say the issue is the lower not being in spec?
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  #12  
Old 10-26-2012, 1:06 PM
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As far as the safety detent hole front to back...you just need to make sure you center your .375 safety selector hole over it. I'm not sure why Colfax and Quentin Defense are different on this location since its the same DPMS pattern. As for the side to side location of the detent hole on my AR10 receiver it needs to be moved over towards the center of the receiver .015-.020. Some safety selectors may work but my two right handed ones are held tightly against the side of the receiver by the detent/spring pressure trying to pull it farther in to center up the detent. When I look down the detent hole with the safety slid all the way in I can see that its not quite in far enough. A lathe with a long groove tool will be able to give a little more clearance on the backside of the safety selector...
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  #13  
Old 10-26-2012, 1:09 PM
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That Ambi selector idea is a good one....
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  #14  
Old 10-26-2012, 1:23 PM
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At a build party we had the same issue. The QD is different from where you get your reference points for drilling the side holes.

For future builds, take the point from the safety spring hole with measurements from the rear take down pin. Use those two know points and adjust your alignment from them.

If your front pins are too close to the mag-well your lower trigger hole (bottom) will have to be enlarged to allow proper pull, as well as the misalignment of the safety selector.
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  #15  
Old 10-26-2012, 1:27 PM
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Luckily mine works properly...at least with the Armalite NM trigger.
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  #16  
Old 10-26-2012, 5:08 PM
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Quote:
Originally Posted by drg-racr View Post
Luckily mine works properly...at least with the Armalite NM trigger.
That's a good thing.. Have you tried to put a standard trigger in?
Good luck with your solution for the safety.
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  #17  
Old 10-26-2012, 9:53 PM
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sounds like you were a little off with the hole your drilled to me i have done quite a few ar10 qd lowers now and not one of them are off. actually the thickness on the 15 and the 10( fire control group) are the same on the dpms platform. unless your measuring a t.m. and they hve that lip on the top.

what jig did you use on this project? unless you mod the t.m. jig there is not one avail. on the market that i know of.
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  #18  
Old 10-26-2012, 10:38 PM
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Quote:
Originally Posted by SERIAL SNIPER View Post
sounds like you were a little off with the hole your drilled to me i have done quite a few ar10 qd lowers now and not one of them are off. actually the thickness on the 15 and the 10( fire control group) are the same on the dpms platform. unless your measuring a t.m. and they hve that lip on the top.

what jig did you use on this project? unless you mod the t.m. jig there is not one avail. on the market that i know of.
Of course I was a little off on the selector hole. What do you think this whole threads been about? I put up the original post to help out anyone else that may want to machine there own and would like to read about issues they may run into. My hole location is only causing the safety selector to point slightly off. The issue I had no control over is with the thickness of the receiver or QD not accounting for the extra thickness of my receiver when the detent hole was drilled. My Armalite AR15 receiver is .860 thick, a TM AR15 receiver I have is .880 thick and this QD AR10 is .917 thick.

I used the blueprint off of the Colfax website..it is for their 80% DPMS style lower. I didn't use any jigs, just dimensions. I asked on this site and didn't get any info on hole location dimensions so I went with the Colfax print figuring one DPMS receiver would be dimensioned the same as another...not the case. So if the whole AR10/DPMS LR308 differences weren't confusing enough there now seems to be different DPMS hole locations from one brand lower to another. But as long as you center your selector hole over the predrilled detent hole as stated above, you won't have any problems...but that has nothing to do with the safety pulling tight against the face of the lower.
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  #19  
Old 10-29-2012, 7:17 PM
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Hey i was wondering if you have a problem putting on the upper? Mine is dpms and the bolt catch is kind of in the way.
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  #20  
Old 10-30-2012, 5:00 PM
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It may be a while before I buy an upper..hopefully there isn't any problems with the bolt catch.
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  #21  
Old 10-31-2012, 4:18 AM
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Quote:
Originally Posted by jamesob View Post
Are 308 and 223 safety switches the same? I would think they would be different because of the thickness difference of the receiver
Yes, they are the same. The parts that are different are the takedown and pivot pins, the bolt catch, and the magazine catch.
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  #22  
Old 11-03-2012, 7:08 AM
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I got my DPMS lower parts kit and put the lower together. The mil spec trigger works great and I am actually really happy with the feel of it. The safety did not fit properly and was pressed hard against the face of the reciever when the spring and detent were installed so I had to machine .015 off of the backside of it as shown in the picture. I thought it would be easy to take .015 off of it but it turned out to be very difficult. The safety is heat treated and was harder than hell. I had to use some pretty stout carbide groove inserts to turn the material off and I had to re-sharpen the edge a few times. I'm hoping all of the AR10 80% lowers from this group buy are not like mine with this side to side detent location because it will cause some headaches for people.

AR&420
"Hey i was wondering if you have a problem putting on the upper? Mine is dpms and the bolt catch is kind of in the way."

I don't have an upper yet so I can't say if the bolt catch will be in the way but I did notice it doesn't have as much range of motion as my AR15's bolt catch's do.

I also tapped the rear takedown detent hole with a 4-40 tap so I could capture the spring and detent with a 1/8 long 4-40 set screw...one less thing to worry about losing when the grip is removed(or the buttstock on an AR15). You do have to shorten the spring a little bit to get it all to fit in the hole with the set screw. I have done this to all my AR's.








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  #23  
Old 11-03-2012, 7:28 AM
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Wow, those issues kind of suck.

For the selector, the best method would be to use a gauge pin in the detent hole so you can edge find to get your x value in line with the detent. Next time I guess.

The receiver width problem sucks. I think you did just about the only thing you can.

Good job on the pocket, it looks nice and clean.

I'm building an ~LR308 as well but mine is a TM10. The only problem I had was a slightly small BHO plunger hole which I solved by chucking my plunger in a Dremel and sanding the o.d. to fit. My upper is going to be a TM10 as well so I'm expecting no issues between the upper and lower.
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  #24  
Old 11-28-2012, 8:42 PM
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Sorry for old thread. but also having issues with the QD lower.

I just finished milling out my QD 308 lower today with a TM jig. Trigger and selector holes are where they're suppose to be according to schematics, but the detent hole is at least .040 off center of the selector. My selector fits fine and isn't tight against the receiver but it points no where near where its suppose to. not too happy about this...
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  #25  
Old 11-28-2012, 9:02 PM
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I haven't started working with mine yet, but I am concerned as this brings to three the number of people I am aware of who are having this issue.

Isn't there a spec for the DPMS/LR-308? It should be a simple matter to find out if these lowers are in/out of spec.
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Old 11-29-2012, 3:35 AM
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I have finished my LR308 build and have about 80 rounds through it. I had a few other problems come up with the QD lower since my original post. I was going to start a new thread soon and talk about the issues I had and how I fixed them. I'll try to post it in the next day or two and I will add the link to this thread. I'm pretty sure everyone that purchased one of these lowers will be having some of the same issues I did with the QD dimensioned 308 lower.
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  #27  
Old 11-29-2012, 6:55 AM
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Drg-racr,

When you drilled the hammer, trigger, selector holes; did you do that before milling out the FCG pocket, or after? Did you drill undersize and then ream them out, or was just a drill accurate enough? I've been reading up on 80%, seen a couple of different methods. Your part looks very clean and you have the ability to figure out what was different about the dimensions and what to do to fix it. Rare skills in Kali...
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Old 11-29-2012, 6:59 PM
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Mindwreck....Sorry to hear about your detent hole offset. That will cause you problems, mine was about .025 offset and the safety was pointing off far enough that the trigger would not work properly. I just made a new thread showing how I fixed mine and I think it may be about the only way you can fix yours. I'll post the link in this thread.

Klewan....It is best to drill the trigger/hammer/safety holes before you mill the FCG pocket. A lot of lowers get drilled to size and it works just fine but I do drill a little undersize and ream the holes on mine.
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Old 11-29-2012, 7:04 PM
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Here is the link to the new thread were I go over some of the issues I had with my QD 308 lower and how I took care of them.

http://www.calguns.net/calgunforum/s...d.php?t=650441
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  #30  
Old 12-05-2012, 6:44 PM
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Quote:
Originally Posted by klewan View Post
Drg-racr,

When you drilled the hammer, trigger, selector holes; did you do that before milling out the FCG pocket, or after? Did you drill undersize and then ream them out, or was just a drill accurate enough? I've been reading up on 80%, seen a couple of different methods. ...
And his name was BINGO!
I made this mistake 'directing' a friend on milling his lower. He drilled the hole after the FCG pocket was milled, upon my direction. The drill bit deflected off the right side causing the hole to walk .015". My friends selector looks and acts just like yours looks.
I showed this to Larry at Colfax Tactical. He pointed out his instructions that the SS hole should be drilled first.
If you ever find something odd when machining Colfax's lowers, get with Larry and he will review it, and make any needed corrections to the instructions.
With Larry in Redmond OR., now, and fully machining lowers I am confident he has everything worked out.
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  #31  
Old 08-30-2013, 11:36 PM
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Yes, this is a necropost.

Just want to warn some fellow QD 80% .308 buyers that even if you follow the official QD print that says the selector hole is 6.160" from the center of the front pivot pin, your selector detent can still be off center!

Or at least mine was. In my case, the detent hole is 0.016" too far forward, unlike yours which is too far back...

Mine may be close enough that I'll just live with it. But the warning's out to anyone else: measure your .308 lower before drilling!

BTW, I did drill my holes prior to milling out the pocket, so it is not a case of the slight walk that WARDOG described.
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  #32  
Old 09-21-2013, 12:31 AM
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Quote:
Originally Posted by dchang0 View Post
Yes, this is a necropost.

Just want to warn some fellow QD 80% .308 buyers that even if you follow the official QD print that says the selector hole is 6.160" from the center of the front pivot pin, your selector detent can still be off center!

Or at least mine was. In my case, the detent hole is 0.016" too far forward, unlike yours which is too far back...

Mine may be close enough that I'll just live with it. But the warning's out to anyone else: measure your .308 lower before drilling!

BTW, I did drill my holes prior to milling out the pocket, so it is not a case of the slight walk that WARDOG described.
I ran into the same problem with the detent hole slightly forward of the selector hole. I used the QD drawing from Aimsmall also, and just thought my DRO was slightly off. I went ahead with the build and everything went together without any issues. I still need to take the gun out to the range and do a functional test.
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  #33  
Old 09-26-2013, 10:30 AM
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You too, huh? It sounds like you got lucky, though, with the holes close enough together to be safe...

Well, I've got good news. I spoke with Quentin Defense after getting their contact info from Aimsmall. After some disagreement about whose drilling was off (their measurements contradicted my two machinist friends' separate blind measurements--no way of knowing who's really right without taking more measurements), they were very kind to simply eat the cost of the bad one and send a brand new 80% to me.

Thanks to Abby for the replacement and to Eric for taking the time to measure!
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  #34  
Old 11-24-2013, 1:16 PM
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I live in burbank does anyone around my area know how to mil out an 80% lower. I'm buying an AR10 80% and would like help with it.
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  #35  
Old 11-24-2013, 2:05 PM
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Quote:
Originally Posted by SERIAL SNIPER View Post
sounds like you were a little off with the hole your drilled to me i have done quite a few ar10 qd lowers now and not one of them are off. actually the thickness on the 15 and the 10( fire control group) are the same on the dpms platform. unless your measuring a t.m. and they hve that lip on the top.

what jig did you use on this project? unless you mod the t.m. jig there is not one avail. on the market that i know of.
Disagree. Had same problem with the QD308 and the selector scraping on the LH side of the lower.
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