Rear Takedown Pin Suddenly sticks

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  • Parallax-Free

    Banned
    BANNED!!!
    Apr 12, 2017
    309
    Balt. Co MD
    Hello MDS, I have a problem.

    I've had a 300blk from Hanover Armory for a few weeks now.

    I've taken it down many times adding lube to preferred surfaces, cleaning after shooting etc. The upper and lower have been separated many many times.
    I recently switched out the buffer tube and now the detent for
    the rear takedown pin gets
    firmly lodged into the back divot in the takedown pin when the pin is in the open position.

    I can pop the pin out easily enough, but when I try setting it back into the frame to reattach the upper its solid as a rock.
    I need to use a mallet each and every time. My palm cannot get the job done without risking injury or damage to the receiver.
    Every part that makes contact with the spring or detent is the exact same as before. I did not bind the spring either.

    When I first brought the rifle home everything worked fine. I've taken the receiver extension tube back off,
    double checked the detent and spring for damage, cleared the hole of any debris, lightly applied gun butter to ease the process and still I have this issue.

    Can anyone tell me why this would suddenly be a problem and how to fix it? I'm this close to taking tin snips and shortening the spring by 1/16 inch until it backs the heck off the pin properly.



    Thanks
     

    Bountied

    Ultimate Member
    Apr 6, 2012
    6,884
    Pasadena
    Hello MDS, I have a problem.

    I've had a 300blk from Hanover Armory for a few weeks now.

    I've taken it down many times adding lube to preferred surfaces, cleaning after shooting etc. The upper and lower have been separated many many times.
    I recently switched out the buffer tube and now the detent for
    the rear takedown pin gets
    firmly lodged into the back divot in the takedown pin when the pin is in the open position.

    I can pop the pin out easily enough, but when I try setting it back into the frame to reattach the upper its solid as a rock.
    I need to use a mallet each and every time. My palm cannot get the job done without risking injury or damage to the receiver.
    Every part that makes contact with the spring or detent is the exact same as before. I did not bind the spring either.

    When I first brought the rifle home everything worked fine. I've taken the receiver extension tube back off,
    double checked the detent and spring for damage, cleared the hole of any debris, lightly applied gun butter to ease the process and still I have this issue.

    Can anyone tell me why this would suddenly be a problem and how to fix it? I'm this close to taking tin snips and shortening the spring by 1/16 inch until it backs the heck off the pin properly.



    Thanks

    You probably forgot to put the little detent pin in with the spring and the spring is getting stuck in the hole on your takedown pin. I had this happen to me. I didn't realize the little silver pill guy fell out. Take it back off and make sure the detent pin is in there.
     

    Parallax-Free

    Banned
    BANNED!!!
    Apr 12, 2017
    309
    Balt. Co MD
    You probably forgot to put the little detent pin in with the spring and the spring is getting stuck in the hole on your takedown pin. I had this happen to me. I didn't realize the little silver pill guy fell out. Take it back off and make sure the detent pin is in there.



    Nope, the detent is in there. It's assembled correctly. I can't figure it out.

    It feels like the spring is too strong and is setting the
    detent too deep into the pin's rear divot. if that makes sense.
     

    Bountied

    Ultimate Member
    Apr 6, 2012
    6,884
    Pasadena
    Nope, the detent is in there. It's assembled correctly. I can't figure it out.

    It feels like the spring is too strong and is setting the
    detent too deep into the pin's rear divot. if that makes sense.

    Maybe take the spring out and cut a couple coils to lighted the tension? If it was fine before and now its not seems like something didn't go back right. What buffer tube did you install? I have had issues with the plate bending the spring and it not wanting to go in right.
     

    Parallax-Free

    Banned
    BANNED!!!
    Apr 12, 2017
    309
    Balt. Co MD
    Maybe take the spring out and cut a couple coils to lighted the tension? If it was fine before and now its not seems like something didn't go back right. What buffer tube did you install? I have had issues with the plate bending the spring and it not wanting to go in right.



    It's an anodized BLEM aftermarket tube. It fits snug, and the plate is flush with the receiver.
    The tube shouldn't be the problem, the spring is straight, the detent isn't deformed or anything.
    I appreciate your feedback. I'm going to wait a day and see if anyone else has suggestions
    before I cut the spring. I ordered a replacement part set, so if I don't manage to fix it,
    hopefully, that will.
     

    E.Shell

    Ultimate Member
    Feb 5, 2007
    10,242
    Mid-Merlind
    Pull the detent pin and flip it 180o and put it back in. Some pins have variations and will run easier one way than they will the other. While doing this, clean the bore with a pipe cleaner to ensure nothing is jamming the detent.
     

    Magnumite

    Ultimate Member
    Dec 17, 2007
    6,561
    Harford County, Maryland
    I realize you said the parts are not damaged but did you look at the end of the pin to makes sure it hasn't flattened? The detent in the pin is a rounded divot, could have gone sharp shouldered. The pin could be soft and have flattened. The pin could be seizing in the bore so scuffs around the perimeter of the pin would indicated that.
     

    Parallax-Free

    Banned
    BANNED!!!
    Apr 12, 2017
    309
    Balt. Co MD
    The Buffer tube has an extended lip that just catches the buffer retention pin. I really don't think thats the problem because the castle nut is flush with the retention plate which is flush with the frame. The Buffer tube shouldn't make a difference.


    I removed the spring and detent pin again, it had a bur on it that I didn't see before,
    I filed it lightly and polished it with some 3000 grit paper and cloth. It's working better, it's not as locked in. But still sticks pretty hard.
    I had to use my magnifying headset to see the bur on the pin so it's no wonder
    it passed my earlier inspections.

    I'll spend some time just popping it in and out until I get somewhere.


    Thanks everyone.

    Sent from my SAMSUNG-SM-G870A using Tapatalk
     

    K-43

    West of Morning Side
    Oct 20, 2010
    1,881
    PG
    I've gotten new pins with burrs or too abrupt a shoulder in the depression where the detent clicks in. Carefully use a riffler's file to "ramp" it a bit - cut a slight angle for the detent pin to ride up. Then you can polish the bejeebies out of it if you want.
    A little lube in the groove of the pin helps quite a bit. Q-tip a little grease or oil of choice on the inside while it's pulled out. Slicker is quicker. Yeah, the rhyming is lame but I couldn't help thinking it.
     

    Parallax-Free

    Banned
    BANNED!!!
    Apr 12, 2017
    309
    Balt. Co MD
    I've gotten new pins with burrs or too abrupt a shoulder in the depression where the detent clicks in. Carefully use a riffler's file to "ramp" it a bit - cut a slight angle for the detent pin to ride up. Then you can polish the bejeebies out of it if you want.
    A little lube in the groove of the pin helps quite a bit. Q-tip a little grease or oil of choice on the inside while it's pulled out. Slicker is quicker. Yeah, the rhyming is lame but I couldn't help thinking it.
    Rhymes work! Helps one memorize.

    Sent from my SAMSUNG-SM-G870A using Tapatalk
     

    bigjohn

    Ultimate Member
    Jun 29, 2007
    2,752
    Put a drop of oil in the detent hole and work it a few times. It's helped a few of mine
     

    yakfish

    Banned
    BANNED!!!
    Jan 27, 2017
    240
    Pull the detent pin and flip it 180o and put it back in. Some pins have variations and will run easier one way than they will the other. While doing this, clean the bore with a pipe cleaner to ensure nothing is jamming the detent.


    This. They have two ends, and each is shaped slightly different. The more rounded end goes in the pin, the pointy end meets the spring
     

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