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Posted: 4/26/2013 11:48:33 AM EDT
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Guys, was working on (my first build, hopefully not my last) a retro build I've had half of forever (M16 A1), finally got all the parts together to finish it. Was installing an RRA LPK into a Nodak Spud retro lower, and had to stop at the trigger pin insertion. Watching videos, I know it should not be that tough to get in, but I managed to get it into one side of the receiver, and nearly flush with the inside of that hole, but no further. Even whacking judiciously with a plastic mallet (harder than I should have needed to), it would not budge further.
I now need to go to purchase a decent punch to remove the pin (taped vice grips have already marred it slightly, while not budging it even a mic). Question is now, the best way to fit the parts. I'm thinking micro file the inside diameter of (all four) holes in the receiver, seems like the easiest route (I have a round micro file on hand, of course I will need to go slowly and carefully for sure or I could ruin the receiver). Or, should I try taking a little off the pins somehow (emery cloth??)? One (hopefully last) question, is there a decent touch up finish for the AR receivers? I managed (even with the vice grips taped up) to scrape a small spot on one of the ears holding the mag catch roll pin- would like to at least get it not to be so shiny (finish doesn't need to be perfect, but I'd like to match somewhat). Hoping for some sage advice from those more experienced than I, thanks in advance! |
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Oil the trigger and hammer pins, go slow, and jiggle it. I usually can get a full trigger group installed in about 5 minutes but yesterday I was trying to install a Geissele SD-E in a Sig Sauer 516 lower and I had to take a break after about 50 attempts.
One thing you should definitely do is insert the trigger and hammer pins by themselves in the receiver holes. place them all the way in so that they are fully seated, to ensure that you are not dealing with an out-of-spec issue. The trigger should go in with little to no issues. Take the selector out if you want to make some more room in there. Lining up the hammer with it's loaded spring can make your thumb sore fairly quickly if you don't get the hammer pin installed in the first few attempts. Do not bang on the pins with a hammer! all that will do is cause very hard trigger pins to destroy softer aluminum. |
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Oil the trigger and hammer pins, go slow, and jiggle it. I usually can get a full trigger group installed in about 5 minutes but yesterday I was trying to install a Geissele SD-E in a Sig Sauer 516 lower and I had to take a break after about 50 attempts. One thing you should definitely do is insert the trigger and hammer pins by themselves in the receiver holes. place them all the way in so that they are fully seated, to ensure that you are not dealing with an out-of-spec issue. The trigger should go in with little to no issues. Take the selector out if you want to make some more room in there. Lining up the hammer with it's loaded spring can make your thumb sore fairly quickly if you don't get the hammer pin installed in the first few attempts. Do not bang on the pins with a hammer! all that will do is cause very hard trigger pins to destroy softer aluminum. Thanks, but I guess I wasn't clear enough. There is DEFINITELY an out of spec issue. The pins and holes already were well oiled with CLP. and even without the internals (tried as you suggested before posting, the holes are simply too small or the pins are too big), it's not happening with or without the hammer. It was work even getting the one pin started, and took the hammer to do so. Again, it is barely into the hole, and is lodged there (will need a proper punch now to remove it from the other side, while of course properly supporting the receiver). The receiver being softer than the pins is why I felt it may be best to carefully work the holes with a round micro file. And yes, I DID try both pins, and both holes from both sides. Definitely NOT a match, though very, very close. Thanks for your input, I appreciate your response. |
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Gotcha... I would try a different set of pins before permanently altering my lower. DO you have another rifle laying around that you could borrow the FCG from? Also, what brand is the lower?NM, you mentioned it. Well, that IS something I hadn't considered. I do have a factory RRA and a Colt I could try those. One other thought I did have, I have an extra RRA LPK, I will try those pins first to see if they are different (shouldn't be, I strongly suspect the issue is with the receiver, though TBH we are probably talking only a couple of thousandths- was able to barely get it started as is, and had no issue popping it back out with a light hammer and a proper (3/32") pin punch (though I did have to hit it moderately hard). |
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Guys, was working on (my first build, hopefully not my last) a retro build I've had half of forever (M16 A1), finally got all the parts together to finish it. Was installing an RRA LPK into a Nodak Spud retro lower, and had to stop at the trigger pin insertion. Watching videos, I know it should not be that tough to get in, but I managed to get it into one side of the receiver, and nearly flush with the inside of that hole, but no further. How do you get a pin flush with the inside of a hole ? I now need to go to purchase a decent punch to remove the pin (taped vice grips have already marred it slightly, while not budging it even a mic).
This has fail written all over it. Vice Grips to install a trigger pin ? If you can't push the pins in by hand, you should only have to tap lightly with a plastic faced assembly hammer. To remove the pin use a delrin pin pusher and don't beat the sh!t out of it with a hammer. Question is now, the best way to fit the parts. I'm thinking micro file the inside diameter of (all four) holes in the receiver, seems like the easiest route (I have a round micro file on hand, of course I will need to go slowly and carefully for sure or I could ruin the receiver). Or, should I try taking a little off the pins somehow (emery cloth??)?
Don't alter an expensive part (receiver) to accomodate a possible out-of-spec cheap part (pin). Chances are great that your RRA pins are oversize....check them with your calipers. One (hopefully last) question, is there a decent touch up finish for the AR receivers? I managed (even with the vice grips taped up) to scrape a small spot on one of the ears holding the mag catch roll pin- would like to at least get it not to be so shiny (finish doesn't need to be perfect, but I'd like to match somewhat).
When using that n00b method of taping up pliers for installing AR pins and the resulting scratches/gouges bother you, have a bottle of this handy... 
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How do you get a pin flush with the inside of a hole ?
Let me re-word it to be more clear. I got the pin all the way through one hole (or nearly so) to (almost) the inside of the receiver. Near flush. BUT, this required FAR more force than it should have, and it wasn't getting any less. Continuing in this manner, that had fail written all over it. This has fail written all over it.
Vice Grips to install a trigger pin ? If you can't push the pins in by hand, you should only have to tap lightly with a plastic faced assembly hammer. To remove the pin use a delrin pin pusher and don't beat the sh!t out of it with a hammer. The vice grips were an attempt to remove the stuck pin (as I stated in the post above). And with a proper sized pin punch, and supporting the receiver properly, there was little danger of damage to remove it (and it had been done successfully and posted above before you posted this). But thank you for the heads up on the Delrin pin pusher, I'd not seen these. Don't alter an expensive part (receiver) to accomodate a possible out-of-spec cheap part (pin).
Chances are great that your RRA pins are oversize....check them with your calipers. You are correct here, and they were in fact oversized (no calipers or micrometer here, though if nec. I'd have obtained a set- compared to those of my Colt, I can see a very slight difference in size). With the suggestion from PFran42 above, I did try other pins. My other LPK from RRA had the same size pins, and would not fit. My new Colt 6920? I partially removed the trigger pin and it did fit, though snugly, into the Nodak Spud receiver. I also tried the RRA pins into the Colt lower, and they also fit. Rather than swap them out, and mess with a factory original (and brand new) Colt, I followed the suggestion of GoRebels above, I went to the KNS website. They sell pins in 3 diameters, smallest is .154 and next is .155. I suspect the RRA pins I was shipped are near the larger diameter. Won't take much for them to fit in my NS lower like I said, but I would rather buy pins than alter the receiver. Ordered a couple sets of the .154 pins (hopefully these will fit, if not I'll explore other options). So the build is off for several days to a week (or whenever the pins arrive Priority Mail). When using that n00b method of taping up pliers for installing AR pins and the resulting scratches/gouges bother you, have a bottle of this handy...
The "n00b" method you refer to was obtained in the build guide in this Forum. Idea was to use the vice grips as a makeshift press (not for the trigger pin, but the magazine catch roll pin). Thank you for the reference to the B/C Aluminum Black, should be just the thing.
WRT working with pins, softer and harder metals, etc., I'm no noob at all. I am a Carpenter who often works as a Millwright (same Union). Most recently on a turbine in a nuclear power facility. Yeah, much bigger components generally, but the same principals. And much more costly if one screws the pooch. Thanks to all who've responded, I appreciate each and every response. Will report back when the new pins get here, and I (hopefully) move forward with the build. Still don't have my BCG anyway (could drop in one of the others, but I want to take all three out to the range and shoot them all complete, no borrowing parts). Will post pics in the pic threads when I'm done. Thanks again. |
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Get a digital caliper...they're cheap now...under $20.
The Delrin pin pushers are good because they don't tear up the annodizing around the hole and mark up the pins like a steel punch will. Midway has them. I'm not into the "plier method" as you can tell. A roll pin punch set (Grace @ Midway) and a roll pin holder set (Brownells) are good investments if you are going to build any more. I'm a Union Carp as well....Local #156 Oregon City. 
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Don't alter an expensive part (receiver) to accomodate a possible out-of-spec cheap part (pin). Chances are great that your RRA pins are oversize....check them with your calipers. I had the same problem with a Rainier lower http://www.ar15.com/forums/t_3_4/607296_Rock_River_LPK_Trigger_Pins.html The pins are somewhat oversize, nearly .156 and worked fine in one lower. I managed to get them to work using the plastic end of a 4 oz Brownells hammer, but they barely fit. I could easily see them not working at all. |
| As recommended on a Midway video, I used a #23 drill to ck. out the trigger and hammer pin holes. It went in w/o any issues and I also dry fit the pins beforehand just to check. Probably not any earth shaking news there, but checking in advance just seemed like the logical thing to do. It's my first one and it went together without any issues. Beginners luck? |
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I would try reaming them out with the corect size drill bit. I'm not exactly sure of the correct hole size but if the pin size is .154 diameter, I would think a drill bit size of .152 - .153 would be right there in the ball park. A .152 diameter drill is a #24. If you don't have a machine tool distibutor local to you, you might try MSCdirect .com , useenco.com , Grainger, Harbor Freight or even McMasterCarr.com.
I'll check back later and if you still can't find anything maybe I can grind up a nice little carbide reamer for you. LOL! Later, JJ |
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Make sure your safety is in the fire position..it will allow you to move the fcg around to align the the pins.. Thanks, but I hadn't installed the safety yet (good point though!). Quoted:
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Don't alter an expensive part (receiver) to accomodate a possible out-of-spec cheap part (pin). Chances are great that your RRA pins are oversize....check them with your calipers. I had the same problem with a Rainier lower http://www.ar15.com/forums/t_3_4/607296_Rock_River_LPK_Trigger_Pins.html The pins are somewhat oversize, nearly .156 and worked fine in one lower. I managed to get them to work using the plastic end of a 4 oz Brownells hammer, but they barely fit. I could easily see them not working at all. Thanks, I am pretty sure I'll be building more. Plus always love a good excuse to buy more tools! Yeah, having read your thread, I think mine were even a bit tighter than yours. I can easily see destroying the receiver if I'd persisted in trying to install them in the Nodak Spud. I'm guessing it's the sum of two companies trying to keep tight tolerances in the finished product, but each not knowing how tight the other's tolerances were. I doubt the freezer idea mentioned in your thread would have worked in my case (thought about it and decided not to try it) though the drill/sandpaper method on the pins would have.Drill bit by hand probably would have done it for me (as would the small round file), but I'd just rather drop in a manufactured part without fitting (great to hear I'm not alone, from all the replies in your thread, it is clear that RRA pins have been running large at least in a significant number of cases).. Thanks again to all who replied, looking forward to posting pics of the M16 A1 when completed. Also looking forward to having it as a replacement for my SP1 I am still kicking myself for selling years ago. |
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Ah, more good replies! The disconnect spring, I hadn't even installed it yet (was going to do so after I eased the pin a bit into one side of the trigger, which never happened- as I already knew it was at least a bit tight.
The drill bit would almost certainly do the trick, and plenty of vendors here in the Detroit area to pick one up from.. But for now, I've already spent the money on the new pins. If I get impatient, I'll keep this option in mind. Thanks for the offer, but I think I've got this one covered. Hoping to have the pins by Thursday. |
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Ah, more good replies! The disconnect spring, I hadn't even installed it yet (was going to do so after I eased the pin a bit into one side of the trigger, which never happened- as I already knew it was at least a bit tight. The drill bit would almost certainly do the trick, and plenty of vendors here in the Detroit area to pick one up from.. But for now, I've already spent the money on the new pins. If I get impatient, I'll keep this option in mind. Thanks for the offer, but I think I've got this one covered. Hoping to have the pins by Thursday. No worries, my foot is buggered up right now so I can't even go out in the shop to check. LOL! A high speed drill bit that size should really only be around a couple bucks. I'm curious now, I guess I'll have to take one or even two of my lowers into work and check the hole size(s). 
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Maybe there could possibly be a thicker hardcoat anodize on the lower. A Type III hardcoat anodize typical thickness range is between 0.0005 in. to 0.0045 in. per MIL-A-8625F
MIL-A-8625F Section 6.10.1 Surface dimension of parts. On specifying the thickness of coatings, especially for the Type III coatings, allowance must be made for dimensional increase. Both a machining dimension and a coated dimension, equal to one half of the thickness of the applied coating, can be expected for each surface coated due to surface growth. For example, for a 0.004 inch (4 mils) coating on close tolerance parts, a pre-machining allowance of 0.002 inch (2 mils) per surface must be made prior to hard coating. If close fits are specified in design drawings, buildup in thickness caused by anodic coatings, especially Type III, may result in interference on assembly. http://www.wbdg.org/ccb/FEDMIL/a8625.pdf |
Recommended viewing.... http://www.brownells.com/.aspx/lid=11004/learn/ |
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I didn't notice if this was asked: Are you sure it's not a large pin Colt LPK? Colts from 1990 to 2009 used larger trigger pins and they still sell large pin LPKs. The large pin dimension is 0.169 inches, whereas the standard pin dimension is 0.155 inches. Well, the LPK is RRA (both of them), it was a factory new Colt 6920 that I used for comparison. And I'm certain the difference isn't as great as .169 to .155. The pin actually went into the hole (just barely), but only by being driven with far too much force. And it wasn't interested in going any further. |
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Maybe there could possibly be a thicker hardcoat anodize on the lower. A Type III hardcoat anodize typical thickness range is between 0.0005 in. to 0.0045 in. per MIL-A-8625F MIL-A-8625F Section 6.10.1 Surface dimension of parts. On specifying the thickness of coatings, especially for the Type III coatings, allowance must be made for dimensional increase. Both a machining dimension and a coated dimension, equal to one half of the thickness of the applied coating, can be expected for each surface coated due to surface growth. For example, for a 0.004 inch (4 mils) coating on close tolerance parts, a pre-machining allowance of 0.002 inch (2 mils) per surface must be made prior to hard coating. If close fits are specified in design drawings, buildup in thickness caused by anodic coatings, especially Type III, may result in interference on assembly. http://www.wbdg.org/ccb/FEDMIL/a8625.pdf My initial thoughts ran to coating thickness as well, and this may be the case. That's why I was initially thinking micro rat tail file (the suggested drill bit is a better option I suspect). I saw your post in jratc's thread also after he linked it here. Good of you to add the info, it is good to have. I still will wait for the new .154 pins to see if they just slip in. If not, I'll either alter the pins (drill and sandpaper method mentioned in jrtc's thread) or carefully open up the receiver hole just slightly (while I'd lean towards modifying the pins before the receiver, there is the thought that if they are undersized for a definitely standard pin, it might be best to open them up). I know this- the Colt pins in my 6920 fit the Nodak Spud receiver as is (though tighter than the Colt lower). And the RRA pins fit the Colt lower (though tighter than stock). Yes, I could have just swapped them out. But I didn't want to mess with a factory fresh Colt (mixing parts) and I am still waiting for my ordered BCG for the build anyway (hopefully this week). And with others having the issue with the RRA pins (see also the thread by jrtc here), I think it's a safe bet that we have here a combination of oversize (RRA) pins (which did fit the Colt, though tight) and very tight tolerances on the lower (Nodak Spud- which did accept the stock Colt pins). I am pretty confident the new pins from KNS will install easily, without modification to either part. |
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http://i197.photobucket.com/albums/aa166/redtazdog/AR-15-Fire-Control-Group.gif Recommended viewing.... http://www.brownells.com/.aspx/lid=11004/learn/ Thanks, great stuff there! |
| One more tip: use a "slave pin" to hold the disconnector in its position while inserting the trigger pin. It turns out that a trigger guard pin works pretty well for this. Doing it this way lets you see the trigger/disconnector as they are assembled, and you can verify that they are correct and that the disconnector moves correctly. Kind of a big deal... |
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One more tip: use a "slave pin" to hold the disconnector in its position while inserting the trigger pin. It turns out that a trigger guard pin works pretty well for this. Doing it this way lets you see the trigger/disconnector as they are assembled, and you can verify that they are correct and that the disconnector moves correctly. Kind of a big deal... Thanks, actually the Brownells videos linked above (just watched, great stuff!) showed using a punch as a slave pin for assembly. I plan to try that, being as I have a new set of pin punches 
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One more tip: use a "slave pin" to hold the disconnector in its position while inserting the trigger pin. It turns out that a trigger guard pin works pretty well for this. Doing it this way lets you see the trigger/disconnector as they are assembled, and you can verify that they are correct and that the disconnector moves correctly. Kind of a big deal... Thanks, actually the Brownells videos linked above (just watched, great stuff!) showed using a punch as a slave pin for assembly. I plan to try that, being as I have a new set of pin punches Being as I'm admittedly a little anal about dinging the finish around the trigger pin holes, I use the Delrin pin pusher for the slave pin. Generally leaves no trace. For the bolt catch roll pin I use a drill bit shank of the correct diameter for the slave. It is taped lightly to the receiver so that it stays with the roll pin while it is being chased out. Prior to driving, this arrangement also allows for proof testing the bolt catch for correct function.....critical step. |
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I'd like to thank all of you who took the time to read and/or answer this thread. It was a HUGE help to me in completing this, I appreciate especially those who've shared their knowledge and added to mine (and others as well).
Update here guys (can't seem to edit the thread title now), my RRA BCG from PK Firearms arrived on Tuesday, the new .154 pins from KNS arrived yesterday, and I completed the build (my first) last night. The pins slipped right in as they should (semi snug fit, not loose, but no hammer required). The KNS pins are unfinfished, so I have bright metal to darken (more incentive to find some Aluminum Black from Birchwood Casey, I have read it works on steel too). Plus I need to touch up my mark on the bolt catch pin retaining ear (earlier in the thread, I erroneously stated I'd marred the magazine catch, didn't catch it until later). And there are some old handling marks on the surplus upper I need to clean up (already darkened, but badly- I'll see what I can do to improve on that). Only issue from last night was getting the takedown pin to close. Functions fine in the lower alone, and the two receiver halves go together nicely, but the pin didn't want to close all the way. After checking to be sure it wasn't hanging up on the inside of the lower, a few light whacks with a rubber mallet got it to close. Required a punch pin and hammer to open. Working a few times, it got easier (can now close the pin completely by hand most times, still need the punch/hammer to open, but less force required). After some research, it appears this is not an uncommon thing (several threads here and elsewhere on it found with Google) and working it a bit more should make it better (shooting might help too). If nothing more, a bit of very mild working (probably mostly finish) should fix it. But I'll try to "wear it it" first. BTW, this was my first build. Bought the complete upper assembly (surplus Colt M16 A1) 6 to 8 years ago (?!). Can't believe I let it sit for this long uncompleted (my RRA Entry Tactical has had something to do with that no doubt ). But I won't be that long for my next (receiver for my AR15 pistol build is on order, along with the buffer assembly and BCG, already have the spare RRA LPK, plus KNS hammer and trigger pins- just in case).
Waiting for the USPS today to bring my Midway order, a cheapish, sort of retro looking case in OD (thought it fit the personality of the rifle- and at $19.99 for the 42 inch, how could I go wrong?). Check these out, they are a bargain if even half decent. I'll get more pics into the Retro Forum after the case is here and I've touched up the finish. For now, here's a "blast" from the past! 
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The fit between upper and lower will smooth out in time, and they will lock up very nicely. It is a Good Thing for the takedown pin to be a bit tight at first; it leads to a more secure, less rattling fit. Some people feel that their rifles are less accurate if there is play between upper and lower, but whether that has any basis in fact is debatable. It is at least distracting when they don't hold tight together, so a tight fit is good.
Great looking rifle! |
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