I have a SR-15 that I've got about 3000 rounds thru, Last month the bolt started closing after it was retained on the bolt catch. After the last round its retained back but a slight bumb or jolt and it slams forward. This happens with or with out a mag. It seems like such a simple problem but I dont see the cause! Any suggestions.

I'm not Joe Expert, but when I was having a similar problem, it was suggested that I check the bolt stop for free movement. Mine would move, but it would bind, so a friend took out the bolt stop, and honed the sides lightly. From then on it moved freely, allowing the mag follower to push the bolt stop to the fully engaged position. Good luck.

I'd agree totally if this was a new or nearly new gun; but he's saying that it's been used quite a bit, and just recently started acting up.  So let me add the possibility that some sort of crap has gotten into the slot that the holdopen body rides in, and is causing the hang ups.

Either way, whether ir's a burr on the holdopen piece itself, or some junk in the slot, it is almost certainly the holdopen not fully rising to engage the front of the bolt.  The only other possibility is that the mag springs have weakened to the point where they're not pushing the follower up firmly enough to fully engage the holdopen arm.

With the action open, work the holdopen up and down with your fingers.  If you feel friction, then it's a burr or some crap in the slot.  If it moves up and down freely, try a brand new mag, or replace the follower and spring in an old mag.  If niether solution fixes the problem, get back to us for further consultation[:D]

Shamayim: Good points. I have a question for you. Last range outing I had the bolt close after the last shot on different mags, but never on the same mag twice in a row. Any ideas?

Mags are Colt 9 rd., 20 rd. GI, and New Style 10 rd. BM.

Thanks

Thanks for the info, Later today (if i got time) I look at the bolt catch a little harder and try clean around it a little better. I'll let you know the results. Thanks again

Well I tried to clean out behind the catch with action blaster then oiled it up- Still have the same problem. It looks like it is sitting as high on the bolt as my other AR's, But it's letting the bolt go? Does the tension of the buffer spring help hold it in place when it's retracted ? How long should the buffer spring be on an SR-15 M4 ?
Thanks

Try and engage the bolt catch manually, if it engages and holds the bolt then it is probably the spring in the mag that doesn't have enough power to engage the bolt catch. I had this problem when replacing the bolt catch to a different model ( Tachtical catch )

Had the same thing happen on my Oly.  Cause was a chip off the corner of the bolt locking lug that catches the bolt stop fence.

Hoppy