View Full Version : Crack in my new lower (pics)
Hello all,
I'm not new to shooting but am definitely new to building AR's... this is the result of my first attempt, and I think I have a problem. I need some advice.
I just assembled a PSA LPK into a brand-new Aero Precision lower, and after I finished I noticed what appears to be a small crack along the edge of the forward "ear" that holds the roll pin for the bolt catch. I know this was not here before assembly as I inspected the lower very thoroughly at the store (Surplus Ammo & Arms in Lakewood WA). When I put the lower together, I secured it in a magazine well vise block and used a standard pin punch along with a small hammer to install the roll pin. I initially tried using the "vise grip" method but wasn't having luck getting the pin started, so I changed to using the hammer and punch. I have a factory-assembled BCM that I used for comparison throughout assembly and also consulted a pictorial instruction set I found on Arfcom.
Both ends of the roll pin looked the same to me, with neither more tapered than the other. I drove the pin in starting from the rear of the receiver. I'm not sure if that makes any difference but I've seen photos of it being done both ways. The pin was hard to get started, went easily through the bolt catch, and then became hard to drive again as it went into the opposite "ear" of the lower receiver. I thought I did fine as I put no big scratches in the receiver and the bolt catch functions properly. And then I saw the crack.
I know I must have done something wrong. Do you think this is a superficial "finish" crack, or is it going to propagate until the bolt catch "ear" eventually breaks off? Is there anything I can/should do about this? What did I do wrong, and how can I avoid this on future builds? Thank you all for your time and help.
702Shooter
10-02-12, 00:48
If you're going to work on or build your own, I would recommend purchasing yourself a set of roll pin starter punches.
http://www.brownells.com/.aspx/pid=20640/Product/ROLL-PIN-STARTER-PUNCHES
Is it a crack in the metal or just the outer anodizing? Hard to tell from the pics. Can you flake it off with your fingernail?
702Shooter
10-02-12, 01:00
Is it a crack in the metal or just the outer anodizing? Hard to tell from the pics. Can you flake it off with your fingernail?
Looks like damaged aluminum to me. Also damage around the hole on the rear side in the 3rd pic.
TangoSauce
10-02-12, 01:07
A tiny amount of lube doesn't hurt either.
TangoSauce
10-02-12, 01:10
And just a note, my buddy recently used a PSA LPK with a RRA lower (I don't personally recommend either but that's neither here nor there). He could not get his bolt catch pin started using two different LPKs. He managed to get his FFL to swap lowers, and he got it to work. Take that anecdote with a grain of salt, but it makes you wonder if there has been an issue with PSA LPKs of late. Likely not, but it's a bit curious to see this happen to two people within a week apart of each other.
Texas_Mike
10-02-12, 03:04
Hello all,
I'm not new to shooting but am definitely new to building AR's... this is the result of my first attempt, and I think I have a problem. I need some advice.
I just assembled a PSA LPK into a brand-new Aero Precision lower, and after I finished I noticed what appears to be a small crack along the edge of the forward "ear" that holds the roll pin for the bolt catch. I know this was not here before assembly as I inspected the lower very thoroughly at the store (Surplus Ammo & Arms in Lakewood WA). When I put the lower together, I secured it in a magazine well vise block and used a standard pin punch along with a small hammer to install the roll pin. I initially tried using the "vise grip" method but wasn't having luck getting the pin started, so I changed to using the hammer and punch. I have a factory-assembled BCM that I used for comparison throughout assembly and also consulted a pictorial instruction set I found on Arfcom.
Both ends of the roll pin looked the same to me, with neither more tapered than the other. I drove the pin in starting from the rear of the receiver. I'm not sure if that makes any difference but I've seen photos of it being done both ways. The pin was hard to get started, went easily through the bolt catch, and then became hard to drive again as it went into the opposite "ear" of the lower receiver. I thought I did fine as I put no big scratches in the receiver and the bolt catch functions properly. And then I saw the crack.
I know I must have done something wrong. Do you think this is a superficial "finish" crack, or is it going to propagate until the bolt catch "ear" eventually breaks off? Is there anything I can/should do about this? What did I do wrong, and how can I avoid this on future builds? Thank you all for your time and help.
You should be fine. The crack didn't completely penetrate the tab, or else it would have come off and moved in the direction the pin was being driven in. In addition, the force that was applied while driving in the pin is much greater than any forces that will be applied during normal operation of the rifle. Even when the bolt is locked open once a magazine is emptied during live fire, the majority of the catch's surface area is pushed forward by the bolt and rests flush in the recess. This will prevent any excessive force from being exerted on just the tab alone. Even hitting the paddle with the palm of your hand to release the bolt should not be an issue. At this point, it is strictly cosmetic.
A few observations.
This happens quite bit when using the wrong technique and tools.
1. Lube your pins before installing.
2. Using the correct punches (starters followed by roll pin punches).
3. I highly recommend getting a Magpul trigger guard and putting it in between the ears when starting your roll pin. It will help when starting the pin. Or you can get a piece of solid plastic or Delrin and make something to insert in between.
4. Use a nylon/brass hammer. Tap the pin until it is flush and then place the trigger guard of your choice in the right position and finish driving through. I use the starter punch until it almost hits the receiver. Then use your roll pin punch.
Are you sure the lower wasn't out of spec? I have seen it more than once.
And just a note, my buddy recently used a PSA LPK with a RRA lower (I don't personally recommend either but that's neither here nor there). He could not get his bolt catch pin started using two different LPKs. He managed to get his FFL to swap lowers, and he got it to work. Take that anecdote with a grain of salt, but it makes you wonder if there has been an issue with PSA LPKs of late. Likely not, but it's a bit curious to see this happen to two people within a week apart of each other.
everyusernametaken
10-02-12, 05:01
You should be fine. The crack didn't completely penetrate the tab, or else it would have come off and moved in the direction the pin was being driven in. In addition, the force that was applied while driving in the pin is much greater than any forces that will be applied during normal operation of the rifle. Even when the bolt is locked open once a magazine is emptied during live fire, the majority of the catch's surface area is pushed forward by the bolt and rests flush in the recess. This will prevent any excessive force from being exerted on just the tab alone. Even hitting the paddle with the palm of your hand to release the bolt should not be an issue. At this point, it is strictly cosmetic.
I agree. It looks like a minor forging flaw. It certainly isn't critical, as that post isn't subjected to significant loads. If I had already put in the effort to fully assemble the lower, I probably wouldn't bother with getting a replacement, provided there are no other flaws on that lower.
Who ever started the rumor that it's ok to install roll pins with Vise Grips or Vise Grip clones needs to be taken out behind the work shop and have things explained to his knee caps
Examine the defect with a 10x magnifying glass and a strong light
TangoSauce
10-02-12, 09:56
Are you sure the lower wasn't out of spec? I have seen it more than once.
There's a good chance of that.
It just seemed ironic that two people were having similar problems with the bolt catch using the same LPK. Given that a different lower fixed the problem, it'd be safe to say it was most likely a problem associated with the lower.
TangoSauce
10-02-12, 10:02
Who ever started the rumor that it's ok to install roll pins with Vise Grips or Vise Grip clones needs to be taken out behind the work shop and have things explained to his knee caps
Examine the defect with a 10x magnifying glass and a strong light
Most likely a candy ass afraid of scratching his lower.
:p
A few observations.
This happens quite bit when using the wrong technique and tools.
Did you see that he's talking about the Bolt stop and not the trigger guard?
crusader377
10-02-12, 10:14
It does look like a minor crack from the pictures you provided. It looks to me more cosmetic and doesn't look particularly deep. As long as you have full functionality of your bolt stop, I would just drive on and learn for future builds.
Heavy Metal
10-02-12, 10:48
IG, look at his pics, not the trigger guard but the Bolt Catch.
A few observations.
This happens quite bit when using the wrong technique and tools.
1. Lube your pins before installing.
2. Using the correct punches (starters followed by roll pin punches).
3. I highly recommend getting a Magpul trigger guard and putting it in between the ears when starting your roll pin. It will help when starting the pin. Or you can get a piece of solid plastic or Delrin and make something to insert in between.
4. Use a nylon/brass hammer. Tap the pin until it is flush and then place the trigger guard of your choice in the right position and finish driving through. I use the starter punch until it almost hits the receiver. Then use your roll pin punch.
Heavy Metal
10-02-12, 10:49
I agree, this looks like a forging burr and not an actual crack.
You should be fine. The crack didn't completely penetrate the tab, or else it would have come off and moved in the direction the pin was being driven in. In addition, the force that was applied while driving in the pin is much greater than any forces that will be applied during normal operation of the rifle. Even when the bolt is locked open once a magazine is emptied during live fire, the majority of the catch's surface area is pushed forward by the bolt and rests flush in the recess. This will prevent any excessive force from being exerted on just the tab alone. Even hitting the paddle with the palm of your hand to release the bolt should not be an issue. At this point, it is strictly cosmetic.
ICANHITHIMMAN
10-02-12, 11:09
Who ever started the rumor that it's ok to install roll pins with Vise Grips or Vise Grip clones needs to be taken out behind the work shop and have things explained to his knee caps
Examine the defect with a 10x magnifying glass and a strong light
Lol that's How I do it with channel locks and tape
To me it looks like a tear Its not critical and could be ground out a little and welded by the right guy if needed.
My bad I didn't see the pics cause I couldn't bring him up on my phone for some reason when I saw ear I was thinking trigger guard automatically.
Quiet-Matt
10-02-12, 11:43
I blew up the last pic and I also believe that its a forging flaw. What you are calling a crack appears to be annodized and there is no silver visible. Shoot it. If it ever does break turn it into a .22
Looks like a superficial gouge you scraped up from using vise grips or possibly from the hammer you used. Just my 2 cents. Vise Grips? Really? :confused:
Who ever started the rumor that it's ok to install roll pins with Vise Grips or Vise Grip clones needs to be taken out behind the work shop and have things explained to his knee caps
My kneecaps recall that I've used vise-grip, channel locks, and C-clamp on the trigger guard on various occasions and have found all three methods to work fine. What's your specific objection?
Vise Grips and their clones increase clamping pressure on a rising curve, not linearly which make them difficult to control when pressing pins. They also have sharp teeth which easily tear through tape. Both factors are a recipe for disaster and will cause damage to parts. Channel locks with their teeth are only a little better.
Compounding the problem is the builder who has little to no experience wrenching anything, sees some video on youboob installing pins with Vise Grips without clue as to how much damage can be done with one little slip
C clamps make good presses
Here is what I don't understand about the vise grip crowd. It's not hard to install the pin, if you simply get the right tool and use the right technique. Lube the pin, use a start pin punch and follow through with a roll pin punch. It literally takes about 2 minutes to accomplish this.
If someone is struggling with that then they sure as hell won't be able to installed the trigger guard, lower receiver extension or even a barrel.
I assembled the exact same combo for the 4th time last week with absolutely no problems. I think your method probably caused the damage.
IntenseImage
10-02-12, 16:57
Vise Grips and their clones increase clamping pressure on a rising curve, not linearly which make them difficult to control when pressing pins. They also have sharp teeth which easily tear through tape. Both factors are a recipe for disaster and will cause damage to parts. Channel locks with their teeth are only a little better.
Compounding the problem is the builder who has little to no experience wrenching anything, sees some video on youboob installing pins with Vise Gripswithout clue as to how much damage can be done with one little slip
C clamps make good presses
Wow I didn't realize you meant they used them to press the pin in. I thought you meant to hold the pin while tapping away on it!
I just built my very first lower and found everything was quite easy to install (30 mins while sitting on the bed watching TV)
Sent from my Galaxy Nexus using Tapatalk 2
Suwannee Tim
10-02-12, 17:32
It looks like a cold shut in the forging. Most likely harmless.
cthompson36
10-02-12, 18:04
i think the reason people use clamps/vise grips is not because they think it's easier, but its cheaper than getting new punches. I just used .99$ punches from lowes and worked fine for me....
I use all kinds of things to install pins and have never had a problem, but then again, after rebuilding transmissions and fixing cars for years guns seem pretty simple to me. I guess I have built up a good sense for when to stop before something bad happens.
I bought all the necessary AR tools before I bought my first rifle. Now that I have the AR addiction I am glad I did because I seemingly spend every spare dollar treating my disease.
As others have said, having the right tools makes life much easier and allows the avoidance of these situations.
I have assembled about 10 LPKs on Areo Precision lowers. I can tell you that they are notorious for having the finish chip off during installation. My advice is to just shoot it if it doesn't look like the ear is going to break off. Proper tools not only keep the chips, scratches and damage away, they also speed up the assembly process.
A question to the masses here.....
Do you install the bolt catch retaining pin from the front or the rear of the receiver?
I have tried both ways and I prefer to tilt the receiver upward, place a cleaning patch between the receiver and my pin starter, and hammer the pin in from the front.
IntenseImage
10-02-12, 21:37
Did mine from the front
Sent from my Galaxy Nexus using Tapatalk 2
Ok guys, thank you for the replies. Tonight (after agonizing over this all day long at the office), I tried DJSkinny's advice and picked at it with a fingernail and even tried a toothpick. Nothing flaked off, and the "edge" is definitely distinct enough to abrade the wood of the toothpick. I hope those of you who think it's just a minor cosmetic defect in the forging are correct, but I can't tell for sure. I highly doubt I would have any recourse in getting a replacement lower as my assembly technique would certainly be blamed for the problem. Fortunately this lower is intended for the range, but I just ordered a set of roll pin punches (Amazon) and a set of starter punches (Brownell's) to help me out the next time I do this.
MistWolf: As far as the Vise Grip idea goes, I got the idea from the Build it Yourself section on Arfcom where it was presented as an alternative to the "scratch prone" method of using punches. Clearly this was not the right way to do things. Does anybody think the simple fact that I used a flat-ended pin punch instead of a roll-pin punch caused the problem? If the surface crack occurred during the driving-in of the roll pin, I'm not sure how using a proper roll-pin punch would have helped the situation. Maybe the crack happened when I was messing with the taped-up vise grips. :rolleyes:
ICANHITHIMMAN: How could this damage be repaired? Is it even worth pursuing? This lower was intended for the range. Certainly any repair attempt would require refinishing. I'm not going to go hacking at it with my Dremel. ;)
TangoSauce: I did coat the pin with oil before I tapped it in with the punch. Tonight I went through my spare parts bin where I found a brand-new bolt catch roll pin from Riflegear. I compared it to the bolt catch roll pin from another new PSA LPK I have, and I found that the PSA roll pin appeared to be slightly larger in diameter. I can't say that this had anything do with my problem, but the Riflegear pin appeared to be "neater" and better made. Interesting.
So, I intend go ahead and shoot this rifle at the range and hope it's OK. Should the bolt catch ear fail, I might put a dedicated 22LR upper on it. I'll never try another bolt catch without the proper punches, that's for sure. If anybody has any more advice or suggestions, I'd appreciate it. Thanks again.
Mule
I don't believe it. I just looked through photos of my lower that I took the day I brought it home. BEFORE I ever installed an LPK. In the attached photo, I'm pretty sure I can see the crack/flaw! If I'm right, then it really is a forging defect that I should have caught in the store. This was my first stripped lower so I didn't really know what I was looking for and I guess I just missed it. :(
I spoke with the staff at SA&A today and they asked me to bring it in so they could have a look at it. I'll do that later this week. With any luck, I can get in contact with Aero Precision (a local company) and hopefully get a replacement.
What do you guys think? Am I seeing things?
I don't believe it. I just looked through photos of my lower that I took the day I brought it home. BEFORE I ever installed an LPK. In the attached photo, I'm pretty sure I can see the crack/flaw! If I'm right, then it really is a forging defect that I should have caught in the store. This was my first stripped lower so I didn't really know what I was looking for and I guess I just missed it. :(
I spoke with the staff at SA&A today and they asked me to bring it in so they could have a look at it. I'll do that later this week. With any luck, I can get in contact with Aero Precision (a local company) and hopefully get a replacement.
What do you guys think? Am I seeing things?
Looks like a flaw to me. None of my lowers (including the SA&A lower I just picked up yesterday have that). Make sure to take your pictures with when you go down there... Good luck!
Justin
ICANHITHIMMAN
10-04-12, 06:10
To repair it would take the work of some one skilled with welding aluminum. Its not hard and a lot of guys can do it, but to do a good job is another story. Where most guys fail is in surface prep aluminum has to be clean and I mean real clean or you end up with a bad weld. Refinishing would be required but with so many options out there is relay quite easy. Heat treating is a non issue in this case due to the parts intended purpose.
If It were mine I would grind out a small area and fill it back in with weld. But if it is not effecting anything best leave it be. If it really bothers you hit it with some sand paper to flatten it out and add Krylon. Painted guns look better anyhow.
They way to cure this problem is as follows:
1. Throw the cracked lower away with the PSA LPK.
2. Buy the proper tools.
3. Buy a quality LPK (GandRTactical ones, LMT, Colt, etc.).
4. Write "I ****ed up" 10 times with your own blood.
5. Order a new lower.
6. Assemble properly and consider this a lesson learned.
Heavy Metal
10-04-12, 10:14
I would ignore it and drive on.
It is not in an area where it has any structural effect.
I am confident you will never have an issue with it.
They way to cure this problem is as follows:
1. Throw the cracked lower away with the PSA LPK.
2. Buy the proper tools.
3. Buy a quality LPK (GandRTactical ones, LMT, Colt, etc.).
4. Write "I ****ed up" 10 times with your own blood.
5. Order a new lower.
6. Assemble properly and consider this a lesson learned.
Funny.
OP, it sucks that your lower isn't coming together as you hoped. BCM prebuilts aren't that much more expensive but at least you can choose to order one with or without a blemish! :)
Problem solved! I called AeroPrecision and spoke with their quality control about the defect. They called SA&A and spoke to them on my behalf. A few minutes later Aero called me back and said that if I just brought the lower down to SA&A they would exchange it for me. As it turned out, SA&A did not have any more Aero lowers in stock and didn't seem to know when they would get more. I accepted a new (Aero made) lower with the SA&A rollmark on it in exchange. Charlie at AeroPrecision and Chester at SA&A were both extremely helpful in getting this resolved. I'm very pleased with the customer service I got and will definitely do business with these guys again.
I installed my LPK into the new SA&A lower tonight using my new set of proper roll pin punches and a little bit of grease on the pins to help things along. It worked out great... having the right tools made a big difference. Thanks to all for your help. :D
Good for you man!I followed your thread from the start since first posted to see how it turned out and I'm glad to see they (aero-precision) took cake of the problem for you!Thats good to know when a company steps up to the plate!Some of the 'best' AR companys out there would tell you that you have to 'pay' for their 'mistakes'.Anyway, also good to see that your lower went together smoothly.The 'propper' roll pin punches do make a world of differance when it come to quality craftsmanship and gettin' it put together right the first time!Have a good one!
Good to hear SA&A stepped up to the plate as well. I've been there several times to buy tools, parts & ammo.
Now get her built! We expect photos and a range report to soon follow
Here is what I don't understand about the vise grip crowd. It's not hard to install the pin, if you simply get the right tool and use the right technique. Lube the pin, use a start pin punch and follow through with a roll pin punch. It literally takes about 2 minutes to accomplish this.
If someone is struggling with that then they sure as hell won't be able to installed the trigger guard, lower receiver extension or even a barrel.
+1 on this technique, this what I used and if I worried about the the finish I just put tape down under the pin
Pistol Shooter
10-07-12, 16:23
Problem solved! I called AeroPrecision and spoke with their quality control about the defect. They called SA&A and spoke to them on my behalf. A few minutes later Aero called me back and said that if I just brought the lower down to SA&A they would exchange it for me. As it turned out, SA&A did not have any more Aero lowers in stock and didn't seem to know when they would get more. I accepted a new (Aero made) lower with the SA&A rollmark on it in exchange. Charlie at AeroPrecision and Chester at SA&A were both extremely helpful in getting this resolved. I'm very pleased with the customer service I got and will definitely do business with these guys again.
I installed my LPK into the new SA&A lower tonight using my new set of proper roll pin punches and a little bit of grease on the pins to help things along. It worked out great... having the right tools made a big difference. Thanks to all for your help. :D
Good deal, glad it worked out.
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