Ambi bolt catch not grabbing on right hand side

[DocMorbius]

I am a newbie on the forum and have a newbie question.

I have an M&P 10 and when pulling the charging handle back I can only catch (hold) the bolt carrier using the left hand bolt catch. The right side does not grab it. I've seen other posts that are similar but I did not see a solution.

Again it seems like it is just short of being able to catch it.

I thought I would ask the experts. Any foxes out there?

Thanks

 

[DocMorbius]

Slight correction!

It should be...any FIXES out there?

Thanks!

 

[sgtsandman]

Take a look in your lower. the right catch has two fingers that mesh over a raised part on the left one so they both operate at the same time. Is the right sitting correctly over the left?

If so, you might need to send it to S&W for them to look at it and replace whatever is machined incorrectly. It could be the catch lever or the lower.

 

[Rjin316]

Hmm...kinda sounds like my problem....just curious, how many bolt lugs does your left side catch hold onto? I just heard back from s&w the other day and they are replacing my rifle. See my thread "bolt closing automatically".

The right side ambi bolt catch latches onto the left side bolt catch so they can work in unison. Whats weird with your problem is that the right side catch should move up in unison with your left side, which its not.

Try this....on your right side bolt catch, with the charging handle pulled back, try either pushing in the catch with a paperclip or pulling back on the paddle release. If that gives you enough angle to catch your bolt, your problem may be the hinge section on your lower receiver (hinge is too close to the receiver) on the right side, or where the both sides connect is off somehow and it's positioning the right side catch in a way that it starts out already depressed in. Either problem will still require you to send the rifle back to s&w.

With mine, both bolt catches werent giving me the proper angle. Due to the left side hinge (where bolt catch rotates on) not being far out enough to give proper angle, it was affecting the right side as well. My left side was bottoming out on the receiver before it could give enough angle. The reason i also asked how many bolt lugs is your catch holding onto is because since mine didnt have enough angle, it was only barely holding onto the edge of 1 bolt lug. This caused my bolt to close automatically with any jarring or hard reloads when the bolt is locked back to the rear. Again, s&w confirmed this and is sending me another rifle due to the hinge being part of the lower receiver. Read my "see-saw theory" on my "bolt closing automatically" thread as to why the height of the hinge is important.

So again, try pulling back the padde release or pressing the catch with a paperclip and see if that gives you enough angle to catch the bolt. If so, what is happening is your finger is hitting the receiver before the bolt catch is depressed all the way. Another way to confirm is to press the left side catch all the way and check if your right side catch is recessing into the receiver.

Like sgtsandman said, its either the right side catch itself not aligned properly to the left side catch or the lower receiver (ie. Hinge not tall enough). Either way, you gotta send it back.

 

[DocMorbius]

Hmm...kinda sounds like my problem....just curious, how many bolt lugs does your left side catch hold onto? I just heard back from s&w the other day and they are replacing my rifle. See my thread "bolt closing automatically".

The right side ambi bolt catch latches onto the left side bolt catch so they can work in unison. Whats weird with your problem is that the right side catch should move up in unison with your left side, which its not.

Try this....on your right side bolt catch, with the charging handle pulled back, try either pushing in the catch with a paperclip or pulling back on the paddle release. If that gives you enough angle to catch your bolt, your problem may be the hinge section on your lower receiver (hinge is too close to the receiver) on the right side, or where the both sides connect is off somehow and it's positioning the right side catch in a way that it starts out already depressed in. Either problem will still require you to send the rifle back to s&w.

With mine, both bolt catches werent giving me the proper angle. Due to the left side hinge (where bolt catch rotates on) not being far out enough to give proper angle, it was affecting the right side as well. My left side was bottoming out on the receiver before it could give enough angle. The reason i also asked how many bolt lugs is your catch holding onto is because since mine didnt have enough angle, it was only barely holding onto the edge of 1 bolt lug. This caused my bolt to close automatically with any jarring or hard reloads when the bolt is locked back to the rear. Again, s&w confirmed this and is sending me another rifle due to the hinge being part of the lower receiver. Read my "see-saw theory" on my "bolt closing automatically" thread as to why the height of the hinge is important.

So again, try pulling back the padde release or pressing the catch with a paperclip and see if that gives you enough angle to catch the bolt. If so, what is happening is your finger is hitting the receiver before the bolt catch is depressed all the way. Another way to confirm is to press the left side catch all the way and check if your right side catch is recessing into the receiver.

Like sgtsandman said, its either the right side catch itself not aligned properly to the left side catch or the lower receiver (ie. Hinge not tall enough). Either way, you gotta send it back.

It seems like you may have at least partially the same issue (or is very similar). Both sides move in unison, but when pressing on the right catch, it does not pivot high enough to release the bolt. The difference is pretty small, maybe a 1/8th of an inch space on the right side fork as it pivots into the area where the bolt travels. The left side has sufficient travel when you press on it. It seems like there is too much play on that 'fork' that pivots the right side upward.

 

[Rjin316]

Just to make sure we're on the same page, by 'fork' you mean the area where both bolt catches latch onto each other? The 2 'fingers' on the right side latching onto the 1 raised bump on the left side? If so, you're saying that there is a lot of play where they both connect? When you press in the catch on the right side, is there enough play where the right side catch is already depressed somewhat before it starts bringing the left side up?

Also, just curious, how many bolt lugs is your bolt catch holding onto when using the left side catch?

 

[DocMorbius]

There does seem to be excessive play in the mechanism for the right side button.

There are buttons on both sides. The right hand side, the one that sticks out slightly over the trigger, ends in two fingers that are on either side of a little rod. When pushing the right hand side button, the lever action pushes the rod up and engages the bolt catch. Again there seems to be excessive play (about 1/8th of an inch difference) in the mechanism. The left hand side moves directly up and engages the bolt catch when pushed.

I am catching two lugs on the bolt when it engages from the left side. Again, the right hand side button does not engage the catch.

 

[Rjin316]

It sounds like those 'fingers' are off spec and too far apart, thus giving you way too much play. I dont remember mine having that much play if any. Well guess you gotta make the phone call to s&w. I think you should still send it in, unless they're willing to send you just the right side bolt catch thru warranty. Most likely not though, as they'll just send you a shipping label to send it in and let the engineers deal with it.

Good luck bro...keep us posted

 

[DocMorbius]

Update:
I did call S&W and yes they wanted to send me the shipping label.

A major piece of info that I neglected to mention...I had recently been attempting to replace the trigger mechanism with one with a lighter pull. (sorry!)

After checking this forum and other places, I had tried a CMC trigger and it did not fit without modification. I then decided on a Timney trigger. This seemed to fit perfectly, once the ambi bolt catch was removed and replaced.

First thing I checked was to make sure that I did not screw up the part or modify the fit. It looked Ok. However, sometimes you can see something right in front of you and miss the obvious.

It turns out that the right catch was depressing...but not quite enough. The new trigger was blocking about 1/8th of an inch of travel on the catch.

My choice was to replace the trigger again (probably with the highly recommended Geissele trigger) or drill a hole into the side of the trigger housing.

The Geissele trigger seemed intimidating since it was not a single drop-in unit. I ended up carefully and slowly drilling the hole, filing out the edges and installing it.

This solved my problem. The catch works without any issues and the trigger is a smooth 4lb pull.

Looking back, starting the Geissele trigger may have solved the issue from Day 1.

Thanks to everyone for their advice on this issue.