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Posted: 6/22/2013 7:02:37 AM EDT
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Hello Everyone. I was hoping my first post would be of my completed build but I'm having a snag. I bought a lower (not sure if I can or should mention the company). Just about everything went pretty smoothly until I tried to put the completed upper (came off a Bushmaster) on the completed lower. The only way I could get the rear takedown pin (RTP) in was with a rubber hammer (with a decent amount of force). Then the only way to get it out is with a punch and a hammer.
I have emailed the company I go the lower from (Thursday morning) but I haven't heard anything back from them. It's only been one full business day so I don't see a problem so far with their response. I asked them if they have encountered other lowers with the same issue. Being new I searched to see if maybe there are different sized RTPs. Everything seems to point to the same size. I took out the spring and detent to see if there was a hang up. This made no difference. I lubed the RTP, lower and upper before installing it and there is still plenty of oil there. I decided to put the RTP in from the opposite (left?) side to see if there was a hangup from that side. Turns out the RTP goes in smoothly until it hits the right side. It seems like the regular entry hole is just a little off. Is there any fix for this? Has anyone encountered anything similar? I am opened to any suggestions. |
| If its a rock river lower, its pretty common that it be tight. I heard somewhere that they suggest knocking it loose with a mallet for first few times and it will eventually loosen up. If that doesn't work I've heard of people removing a bit of material with emery cloth. |
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If its a rock river lower, its pretty common that it be tight. I heard somewhere that they suggest knocking it loose with a mallet for first few times and it will eventually loosen up. If that doesn't work I've heard of people removing a bit of material with emery cloth. It's not Rock River. Would it be ok to mention the company here? If I were to remove material where would I do that from? From the lower or the RTP? It looks like some of the anodizing has already come off the lower from putting the pin through the first time. Something I'm not extremely excited about. |
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Quoted: Quoted: If its a rock river lower, its pretty common that it be tight. I heard somewhere that they suggest knocking it loose with a mallet for first few times and it will eventually loosen up. If that doesn't work I've heard of people removing a bit of material with emery cloth. It's not Rock River. Would it be ok to mention the company here? If I were to remove material where would I do that from? From the lower or the RTP? It looks like some of the anodizing has already come off the lower from putting the pin through the first time. Something I'm not extremely excited about. If the hole in the lower is tight then just polish it up a bit. Generally they will wear in overtime. Yes you can mention the company. |
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I don't think I'd worry about it as long as I didn't have to beat the sh!t out of it to open it.
Lube it. Get a Delrin Pin Pusher instead of a steel punch and use it. The pin is steel and the receiver is Alu....it will break in with use. Doesn't really matter whose receiver it is. Tolerance stacking happens. |
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The maker is Aero Precision. I didn't want it to look like I was coming on here to talk bad about a company and I didn't know what the policy was for this site.
As to having to beat the mess out of it... that's about how I'd describe it. I have a friend close by who is pretty experienced with AR's. I think I'll leave the RTP out of it for right now. I won't have a chance to shoot it until I see him anyway. I think the right side hole is just a little too far back and not lined up right. Even without the upper attached it's hard to "release" the RTP. Like it's stuck once it's put in. I don't want to do any damage. Thanks y'all for the help. I'll keep you updated. |
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This might sound silly. But did you try to put the rear one in first, then the front one? Even without the upper attached it's hard to "release" the RTP. Like it's stuck once it's put in.This sounds more like a sharp detent pin to me. It doesn't sound silly. I'm totally new to this. Anything is possible. But to answer... I put the front on first. |
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This might sound silly. But did you try to put the rear one in first, then the front one? Even without the upper attached it's hard to "release" the RTP. Like it's stuck once it's put in.This sounds more like a sharp detent pin to me. It doesn't sound silly. I'm totally new to this. Anything is possible. But to answer... I put the front on first. Well then give it a try. Also refer to the IM I sent you about the detent pin. I've had some that were so pointy I could hardly get then to move at all. It's also not real bad to have a pin be tight, when assembled. That you might have to nudge Tap on a little to get then started. A little 3/16 piece of dowell rod or plastic and a little tap isn't bad. The more it goes back and forth, the easier it will get. 
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The maker is Aero Precision. I didn't want it to look like I was coming on here to talk bad about a company and I didn't know what the policy was for this site. As to having to beat the mess out of it... that's about how I'd describe it. I have a friend close by who is pretty experienced with AR's. I think I'll leave the RTP out of it for right now. I won't have a chance to shoot it until I see him anyway. I think the right side hole is just a little too far back and not lined up right. Even without the upper attached it's hard to "release" the RTP. Like it's stuck once it's put in. I don't want to do any damage. Thanks y'all for the help. I'll keep you updated. Pretty unlikely the holes are actually misaligned, as they're n a jig when drilled. But I suppose anything is possible. Never work on the expensive part (receiver) if the job can be accomplished working on the cheap part (pin). But before you do, put it together and shoot the hell out of it. From everything I've heard and read, it is very likely it will loosen up on it's own. Years ago, I had an SP1 that was very difficult to open via the RTP. It did in fact fix itself with use. I now currently have an M16 A1 clone (surplus upper w/ retro repro lower) that has the same problem. I originally needed a mallet/punch to close/open it. After working it many many times this way, I now can (barely) close it by hand. Still need the punch to open it currently (picked up a Delrin one per Direct Drive's instructions from my own thread, thanks!). But I've not even fired it yet, and fully expect it too will loosen with use. Also refer to the IM I sent you about the detent pin. I've had some that were so pointy I could hardly get then to move at all
Negative on the detent pin. If you read higher up in the thread, he already removed the pin and spring with no change in results. The tight fit and difficulty opening is not at all uncommon (though not a standard either). It is simply something encountered occasionally when mixing standardized parts from several (or even the same) manufacturers. The fact that specific parts (see here) are made for this condition are evidence of it's commonality. If you let it, it should simply cure itself with use. |
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The maker is Aero Precision. I didn't want it to look like I was coming on here to talk bad about a company and I didn't know what the policy was for this site. As to having to beat the mess out of it... that's about how I'd describe it. I have a friend close by who is pretty experienced with AR's. I think I'll leave the RTP out of it for right now. I won't have a chance to shoot it until I see him anyway. I think the right side hole is just a little too far back and not lined up right. Even without the upper attached it's hard to "release" the RTP. Like it's stuck once it's put in. I don't want to do any damage. Thanks y'all for the help. I'll keep you updated. Sounds like the start of your troubles is in the detent system. 1) OK, it's an Aero Precision If you used the set screw spring retainer and did not cut the spring to allow for the lost spring space, you could be having "coil binding" or simply too much spring pressure on the detent. 2) If you used the set screw, shorten the spring equal to the length of the set screw. 3) Grease the detent channel. |
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1) OK, it's an Aero Precision If you used the set screw spring retainer and did not cut the spring to allow for the lost spring space, you could be having "coil binding" or simply too much spring pressure on the detent. 2) If you used the set screw, shorten the spring equal to the length of the set screw. 3) Grease the detent channel. Finally received the 4-40 x 1/8" set screw and put it on my Aero Precision lower. After trimming the spring to accommodate the set screw length the rear takedown pin, although never that difficult to push, does slide somewhat easier. (My lower and upper are both Aero Precision) I can adjust the spring tension somewhat by setting the screw deeper or backing it out a little. This might help. |
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I had same Issues with the upper/lower fitment being very tight with several brands (usually with the rear takedown pin/lug)...what I usually do is trim down the rear takedown
lug of the upper receiver with a medium cut ceramic stone or fine cut swiss file depending how much needs to be taken off. Then once everything is fitted correctly, take some alumnahide or similar finish spray and re-finish the area that was worked on to get it back to the original look... Aero Precision uppers/lowers are known to be cut with tight tolerances, so this is fairly common for this to happen with their brand (and Including other brands they manufacture for). Overall, I believe they offer a very good value with their products, so don't be discouraged, I have not seen any of their products so far that is/has been out of spec. to the point it where it won't function properly as designed (although that does not mean it can't happen). Good Luck. |
| I have a Rock River upper that fits either of my Essential Arms lowers perfectly, but my Aero precision upper is really tight on one of the EA lowers and a perfect fit on the other. Just have to work it in and out a bunch to loosen it up. I consider that normal. |
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The maker is Aero Precision. I didn't want it to look like I was coming on here to talk bad about a company and I didn't know what the policy was for this site. As to having to beat the mess out of it... that's about how I'd describe it. I have a friend close by who is pretty experienced with AR's. I think I'll leave the RTP out of it for right now. I won't have a chance to shoot it until I see him anyway. I think the right side hole is just a little too far back and not lined up right. Even without the upper attached it's hard to "release" the RTP. Like it's stuck once it's put in. I don't want to do any damage. Thanks y'all for the help. I'll keep you updated. Sounds like the start of your troubles is in the detent system. 1) OK, it's an Aero Precision If you used the set screw spring retainer and did not cut the spring to allow for the lost spring space, you could be having "coil binding" or simply too much spring pressure on the detent. 2) If you used the set screw, shorten the spring equal to the length of the set screw. 3) Grease the detent channel. No, it is not. If you read his first post completely, he states "I took out the spring and detent to see if there was a hang up. This made no difference." Detent not the issue at all. |
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The maker is Aero Precision. I didn't want it to look like I was coming on here to talk bad about a company and I didn't know what the policy was for this site. As to having to beat the mess out of it... that's about how I'd describe it. I have a friend close by who is pretty experienced with AR's. I think I'll leave the RTP out of it for right now. I won't have a chance to shoot it until I see him anyway. I think the right side hole is just a little too far back and not lined up right. Even without the upper attached it's hard to "release" the RTP. Like it's stuck once it's put in. I don't want to do any damage. Thanks y'all for the help. I'll keep you updated. Sounds like the start of your troubles is in the detent system. 1) OK, it's an Aero Precision If you used the set screw spring retainer and did not cut the spring to allow for the lost spring space, you could be having "coil binding" or simply too much spring pressure on the detent. 2) If you used the set screw, shorten the spring equal to the length of the set screw. 3) Grease the detent channel. No, it is not. If you read his first post completely, he states "I took out the spring and detent to see if there was a hang up. This made no difference." Detent not the issue at all. Why yes, it most certainly is. If you read post #7, you would see that the following was stated.... " Even without the upper attached it's hard to "release" the RTP " Very likely we have a compound problem at work here, starting with the detent system.
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Why yes, it most certainly is. If you read post #7, you would see that the following was stated.... " Even without the upper attached it's hard to "release" the RTP " Very likely we have a compound problem at work here, starting with the detent system.
Direct, you are correct. I have two issues that could be compounding the issue. Issue number 1 - I can't get the RTP in or out without a hammer. There is no pushing it in or out. I had read the detent could be an issue so I tried taking that out with no change. Once the detent and spring were out I tried the RTP on the opposite side just to see. It was snug but went in fine until it hit the right side. Then I would have had to hit it with a hammer to get it to go all the way. From the right side it's that way from the beginning. This is what made me think it was just the hole on that side. But if the holes are drilled at the same time then maybe it's just TIGHT tolerances and more anodizing on that side. Issue number 2 - After I discovered that it went in find from the left I decided to see what it was like without the upper attached. This is when I discovered that it takes A LOT of force to get the RTP out even without the upper attached. I'm not sure how much Issue 2 is affecting Issue 1. Again, total noobie to this. Once I take this to my friends house I'll report back. You guys have been very helpful. I appreciate it. You've also helped me feel at ease with this lower. I was slightly afraid something was wrong with it. I guess in the grand scheme of things it's better for it to be snug than loose. |
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I didn't see where you mentioned the manufacturer of the LPK. I just picked up an upper/lower set off Gunbroker that came with an LPK. The LPK was a very low end POS.
Other issues aside, the forward pivot pin would not pass through both the upper and lower. I even pulled the one out of my PSA/J&T set and checked in it. Same problem. I checked the pin with a caliper and the end of the pin was flaired a couple thousandth. Most of that kit will be going into the trash and I will be getting a kit from J&T. I would return the LPK but the auction made no claims as to the quality of it. Still got a good deal on the receivers tho. 
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Sounds like that takedown pin is not playing well with the lower. Aero makes good parts; mine is exceptionally nice, and everything fit fine in it. That pin should slip in and out of the lower (without the detent installed) very easily, and I seriously doubt that Aero managed to put out ONE lower with a funky takedown pin hole. Both the pivot pin and the takedown pin are spec'd at a touch below 0.250" in diameter, and the holes in the lower are spec'd at exactly 0.250" in diameter. That pin you have most likely has a burr in the detent channel, or some other dimensional flaw that keeps it from going in easily. I'll bet that if you try another takedown pin, the new one will work great.
The takedown pin is $5.50 at Citizen's Armory. They ship things pretty quickly, and for less than $2. |
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Someone mentioned this in an earlier post but I want to repeat it because its important.
Always make modifications to the cheapest part. In this case, it sounds like the receiver hole could be undersized or the take down pin is over sized. So don't make the receiver hole bigger, make the pin smaller. Better yet, just shoot it, and work the pin in and out a bunch, and see if it won't loosen up on its own. |
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While I did read the above posts I may have missed it. Did you measure the RTP with a caliper if you have one? Also have you tried another pin? Your front pin will fit the holes just not seat correctly. Have you tried the pin from both sides? Just to see where the hang up is. Depending where you are I am sure there is someone here that can get you a new RTP if not let me know. I might have one in my parts box.
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Someone mentioned this in an earlier post but I want to repeat it because it’s important. Always make modifications to the cheapest part. In this case, it sounds like the receiver hole could be undersized or the take down pin is oversized. So don't make the receiver hole bigger, make the pin smaller. Better yet, just shoot it, and work the pin in and out a bunch, and see if it won't loosen up on its own. I agree with this but I would like to also point out that if it a tolerance issue with a cheap part, swap them out. No reason to spend hours fitting a pin that you can change out for free or a few bucks. |
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An issue not being addressed is the quality of the LPK. There's a lot of chinese garbage out there being passed off as mil spec.
The POS kit that I have has a lousy finish (looks cheap and chipping off) and poorly fitting parts. If it's a name brand then maybe it's just the pin. If it's not then you might want to reconsider using the major parts (FCG). The POS kit has at least twice the trigger pull as the J&T set. I was lucky to have something to compare it to. If you know anyone else that has a spare pin you could try, that would be the first thing to do. Don't worry about mentioning companies here, if it's out there then there are a bunch of people on here that have tried it and would love to comment on how good/bad they are. That is what a forum is all about: sharing information. In this case we know that Aero has a history of making good lowers. Let us know who made the LPK and anyone that has experience with the maker can let you know if it's a good one. |
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An issue not being addressed is the quality of the LPK. There's a lot of chinese garbage out there being passed off as mil spec. The POS kit that I have has a lousy finish (looks cheap and chipping off) and poorly fitting parts. If it's a name brand then maybe it's just the pin. If it's not then you might want to reconsider using the major parts (FCG). The POS kit has at least twice the trigger pull as the J&T set. I was lucky to have something to compare it to. If you know anyone else that has a spare pin you could try, that would be the first thing to do. Don't worry about mentioning companies here, if it's out there then there are a bunch of people on here that have tried it and would love to comment on how good/bad they are. That is what a forum is all about: sharing information. In this case we know that Aero has a history of making good lowers. Let us know who made the LPK and anyone that has experience with the maker can let you know if it's a good one. Very true, I am only using US parts these days. To much junk coming in from oer seas. |
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Sounds like that takedown pin is not playing well with the lower. Aero makes good parts; mine is exceptionally nice, and everything fit fine in it. That pin should slip in and out of the lower (without the detent installed) very easily, and I seriously doubt that Aero managed to put out ONE lower with a funky takedown pin hole. Both the pivot pin and the takedown pin are spec'd at a touch below 0.250" in diameter, and the holes in the lower are spec'd at exactly 0.250" in diameter. That pin you have most likely has a burr in the detent channel, or some other dimensional flaw that keeps it from going in easily. I'll bet that if you try another takedown pin, the new one will work great. The takedown pin is $5.50 at Citizen's Armory. They ship things pretty quickly, and for less than $2. I actually picked one of their lowers recently to build an entry level plinker for my son. Something good for him to learn on. That being said do you know of particular LPKs that work best with the APs? I've always heard that some work best in others and some suck wind too. I don't want to buy a load of crap just to save a few bucks. I also don't feel like dumping for a ST Enhanced LPK like I have either.. He's 7. |
| i have yet to get a bad LPK, though the feel of a stock trigger in any random LPK will vary. I've used DPMS, Palmetto State, Stag, and others, all with good results. I have never bought a kit from a gun show table that wasn't definitely correctly packaged for the name and price associated with it, though. |
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The maker is Aero Precision. I didn't want it to look like I was coming on here to talk bad about a company and I didn't know what the policy was for this site. As to having to beat the mess out of it... that's about how I'd describe it. I have a friend close by who is pretty experienced with AR's. I think I'll leave the RTP out of it for right now. I won't have a chance to shoot it until I see him anyway. I think the right side hole is just a little too far back and not lined up right. Even without the upper attached it's hard to "release" the RTP. Like it's stuck once it's put in. I don't want to do any damage. Thanks y'all for the help. I'll keep you updated. Sounds like the start of your troubles is in the detent system. 1) OK, it's an Aero Precision If you used the set screw spring retainer and did not cut the spring to allow for the lost spring space, you could be having "coil binding" or simply too much spring pressure on the detent. 2) If you used the set screw, shorten the spring equal to the length of the set screw. 3) Grease the detent channel. No, it is not. If you read his first post completely, he states "I took out the spring and detent to see if there was a hang up. This made no difference." Detent not the issue at all. Why yes, it most certainly is. If you read post #7, you would see that the following was stated.... " Even without the upper attached it's hard to "release" the RTP " Very likely we have a compound problem at work here, starting with the detent system.
Oops, guess I missed that  So it does indeed seem to be a compound problem (multiple issues). Unless maybe? it is indeed the takedown pin itself. Thinking about it, never thought about trying a different tdp on my M16 A1, and I should have.
GHPorter, thanks for reminding me of Citizens Armory and the link. Could have recently saved me a small fortune in shipping on small parts if I'd remembered them sooner. As it is, a spare tdp seems like a great piece to add to my growing list of spares, so I ordered one, and a few other bits (plus a Glock take down tool). Shipping still only totaled $1.95, what a refreshing deal! |
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I just ordered an LPK and the rest of the upper parts I need from J&T.
Everything on the rifle that I have fit perfectly and the trigger was nice and smooth with little creep. Not bad for a GP FCG. Last part I'll need will be a bolt...gotta free up some funds for that next month. Maybe a 4th of July sale. That and make sure the wife doesn't see the two of them together... 
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