I’m having a very annoying problem with my lower receiver. My bolt catch will fall off the back of my magazine follower, meaning my bolt never locks back and occasionally I get feeding failures. This happened with the factory bolt catch I had on before, and now with the new Phase 5 extended V2 I replaced it with. This lower didn’t always do this, but it has for quite a while, and I’ve only recently managed to figure out that this was the cause of the problem. My ASC mag is extremely bad about this problem, but Pmags do the same thing, just not as badly (differences in how much forward and backward movement of the follower is allowed in the mags). The bolt catch has considerable angular movement about the roll pin that holds it in place (and not about the axis you want it to have angular movement). Noticeably more than on the other lower I have from the same company. I installed a new roll pin with the new bolt catch, so that shouldn’t be the problem. I’ve seen where others have had a similar problem, and the fix is just get a bolt catch with a longer arm for the follower, but this has persisted across 2 different bolt catches, 1 of which did not always display this problem. What are some suggestions for how to fix this, because I’ve exhausted my ingenuity and patience for the problem. I honestly wouldn’t mind replacing the lower, it’s a cheap stripped lower I picked up years ago, and I have had my eye on a San Tan Tactical lower, but I hate ordering lower receivers and having to deal with a local FFL to ship it to, so I’d prefer to fix the one I have if possible. I’ll post some pics of what it looks like with ASC and Pmags.
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AR 15 Bolt Catch Problem-looking for advice
- Thread starter sjc929
- Start date
The first 2 show how much the contact differs when the follower of the ASC mag is fully forward vs. fully backward, and the third is the contact with a Pmag.
Maybe the "ears" (on the lower) that hold the bolt catch roll pin have somehow gotten spread out a little? That's a head-scratcher.
Edit: pics weren't up when I began composing my post. Looking at the lower, the ears look okay. The only other guess that I have is in regard to tolerance stacking... maybe the lower is riiiight on the edge of spec between the mag well and the bolt catch cut? I got nothin'.
Edit: pics weren't up when I began composing my post. Looking at the lower, the ears look okay. The only other guess that I have is in regard to tolerance stacking... maybe the lower is riiiight on the edge of spec between the mag well and the bolt catch cut? I got nothin'.
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Take a look at 13:10 in the linked video. SinistralRifleman demonstrates tuning / trimming the Bolt Catch spring. Might be worth giving that technique a try.
That is what I would guess is that the spring that is attached to the bolt catch is too strong and may need to be weakened or replaced. Does the bolt catch move up and down freely? There may be some copper fouling in the channel with the bolt catch?
rfmanning, that might be the solution. I seem to recall when I last had the bolt catch off that the detent was not flush with the receiver walls, so trimming the spring will be my next attempt at a solution, thanks.
maggitas the bolt catch moves freely, doesn’t seem to have any excess friction, even compared to my other lower that works fine. I don’t think there’s any fouling in the channel interfering with anything, but I’ll check when I remove it to cut the spring.
maggitas the bolt catch moves freely, doesn’t seem to have any excess friction, even compared to my other lower that works fine. I don’t think there’s any fouling in the channel interfering with anything, but I’ll check when I remove it to cut the spring.
Springs are cheap. Pounding your head against the (non-locking back) receiver isn't.
Occam's razor (or Ockham's razor) is a principle from philosophy. Suppose there exist two explanations for an occurrence. In this case the simpler one is usually better. Another way of saying it is that the more assumptions you have to make, the more unlikely an explanation is. Occam's razor applies especially in the philosophy of science, but also more generally.
Occam's razor (or Ockham's razor) is a principle from philosophy. Suppose there exist two explanations for an occurrence. In this case the simpler one is usually better. Another way of saying it is that the more assumptions you have to make, the more unlikely an explanation is. Occam's razor applies especially in the philosophy of science, but also more generally.
Purchase a 9mm bolt catch ( Colt pattern ) and trim it down to fit.
https://www.ar15.com/forums/ar-15/Pr...0--/66-479984/
Sure worth a try... http://www.primaryarms.com/cmmg-ar-9...rifles-90ca572
And.. a real Colt part...http://www.specializedarmament.com/a...catch-9mm-smg/
https://www.ar15.com/forums/ar-15/Pr...0--/66-479984/
Sure worth a try... http://www.primaryarms.com/cmmg-ar-9...rifles-90ca572
And.. a real Colt part...http://www.specializedarmament.com/a...catch-9mm-smg/
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I tried cutting the spring earlier, and there was no change at all in its behavior. I’m now completely lost as to why this is happening. I’m 99% sure I have checked every single possible part that interacts in any way with the bolt catch, and nothing affects it. I wouldn’t be nearly as frustrated if this lower hadn’t worked fine in the past, but I’m all the more lost because this is a problem that developed over time and didn’t show from the start. I guess I’ll either try getting another bolt catch with a longer arm, or just say f it and get the San Tan lower I’ve been wanting anyway. I’ve also considered modding my ASC mag with 2 rails in front of the follower to keep it pushed fully rear without decreasing my max OAL, but that would be hard to do in a way that would last a while, and really isn’t an ideal solution to the problem.
If it is moving freely and you have replaced the spring then the next thing I would check is the tension on the magazine catch. i would adjust the magazine catch a turn or two each way to confirm that the magazine is locking into the lower receiver correctly. I would also try a different bolt carrier as sometimes they will drag against the bolt catch as well. If all else fails you may have to send it to a smith and have him check it or call the lower receiver maker and quiz them.
I’m having the same issue. Tried multiple bolt catches (4 in total) and it only malfunctions with colt 20rd mags. Pmags work fine. Super frustratingas this is a MK12 mod 1 clone and I want the colt mags to work. Plus I don’t like having a gun not be able to function with any mag I throw at it. Not sure if the lower is out of spec or what just yet
