Buffer spring not retained.

LaserHH

So I finally got most of my parts in and I have an issue. The buffer spring retainer simply can’t be retained by the buffer tube even when I have it screwed in as far as it will go. I did buy a mil spec lower kit so I have no idea how this is a problem. Everything else fits great besides mags; they’re a little tight and the trigger pull is pretty hard -harder than another ar I have with an aluminum lower. I’m working moving the hole back about two millimeters to account for this issue but Tim if you could release the lower as a step file WITH the textured grip that would be great.

Any input from anyone is helpful!

undeadchew

LaserHH I personally wouldn't bother with the buffer retainer, however I have ran into a similar issue before and it's just due to the length or depth of the thread cut on the buffer tube preventing the castle nut from being adjusted far enough to the rear. My solution was to cut the threads back on the receiver extension so the castle nut could be adjusted properly.

Also if you need help applying a grip texture after you modify check this post out.
https://forum.hoffmantactical.com/d/19-group-project-help/7

LaserHH

undeadchew okay super thanks for that other forum post. That’s pretty much exactly what I’ve resorted to by just cutting both lowers and joining them later so that’s cool. But I’m gonna have to do something about the buffer retainer because it already popped out as I cycled the bolt and it ruined the spring. I’m pretty far into making a new model so ig I’ll finish and hope the buffer isn’t too far back that it hits the retainer when the bolt cycles.

LaserHH

Also do you think this lower is too short? It seems like it is to me but it’s hard to tell the difference from Tim’s assembly video and this one.

undeadchew

LaserHH For me if all the parts fit, and it functions then it's close enough to run. But for re calibration I would measure some areas in the model and cross reference your printed lower against it.

LaserHH

Yea I totally agree. But since I have to reprint anyway I figured I’d try to fix the sizing a little
Bit since post print the magwell was EXTREMELY tight. The biggest sizing issue that I’ve actually been able to measure was the outside of the magwell. Print calls for 35.5mm and I have an actual of 34.88. I haven’t really been able to measure other inaccuracies just because it’s a little hard to measure many of the surfaces so yeah. Another noticeable thing is the front takedown pin plates do not
Fit well. I have to shove them in. As you can see in one of those pictures how it’s sitting there at an angle.

PPA_FTW

What’s preventing the buffer tube from screwing in deeper?

undeadchew

PPA_FTW I believe not enough threads for the castle nut.

PPA_FTW

Oh weird. Just a bad buffer tube then?

undeadchew

PPA_FTW I wouldn't say "bad", it probably would have been fine on a mil spec receiver, it's just that the SL15 buffer tower is a bit wider in that dimension.
Milspec: 12.7mm
SL15: 16mm~

and the buffer retainer is nice and all, but after having one break on me and jam up my action, I omit the retainer on builds. Sure it makes re-assembly and maintenance a little bit more difficult but me knowing I removed a point of failure makes it a worthwhile compromise. Then if you wanted that ease of assembly back you could use a self contained buffer system.

LaserHH

undeadchew very interesting… I didn’t know it was realistically possible to put an upper on without the retainer but i guess that’s a valid option for when I have this issue again. And for anyone wondering this is a RTB lower kit and yeah there is about 3mm less threads on this buffer tube than a tube from a PSA kit which I have around. And this kit would work absolutely perfect on a mil spec lower.
I ended up giving up on modifying the lower to move the pin back as there was no way to move it back enough without the buffer contacting the retainer when the upper is on (which in that case it would either break the lower when the bolt cycles or break the retainer) so I got a dremel and just ground the last two threads down on the buffer tube nut so that I could turn it a little farther back than it should. This worked perfectly and there’s no visible changes to the kit when it’s all put together. It actually looks really sleek overall because there’s no threads showing behind the nut.

hoffmantactical

LaserHH Great solution.