The Accurate Reloading Forums
Lock open last round

This topic can be found at:
https://forums.accuratereloading.com/eve/forums/a/tpc/f/132105729/m/6051091262

13 October 2020, 22:19
sputster
Lock open last round
I have been using 30rd Magpul MOE M2 and M3 magazines in my S&W M&P 15 as well as DDM4V7 carbines for several years. They have always locked in and fed cartridges well, but lately have started to not lock the bolt open after the last shot, especially the older M2s. I don't have this problem with 20rd and 10rd Magpuls, but they don't see as much range time. Would it be time to replace magazine springs?


sputster
14 October 2020, 06:08
p dog shooter
I would clean them first along with the rifle
14 October 2020, 18:19
tsturm
quote:
Originally posted by sputster:
I have been using 30rd Magpul MOE M2 and M3 magazines in my S&W M&P 15 as well as DDM4V7 carbines for several years. They have always locked in and fed cartridges well, but lately have started to not lock the bolt open after the last shot, especially the older M2s. I don't have this problem with 20rd and 10rd Magpuls, but they don't see as much range time. Would it be time to replace magazine springs?


Change the follower? the plastic tab that hits the bolt catch will wear over time. Pull them apart & compare with a follower that works and cleaning wont hurt tu2 tu2


15 October 2020, 06:26
Bobster
I recently saw one in the shop with the same issue. In that case there was a clearance problem with the bolt latch/stop and the receiver frame. The mag tab couldn't push it up far enough to catch the bolt. I had to spot with Dykem and relieve the area.

Examine the bolt/lock interface with the action open and bolt locked back. If there is plenty of overlap the issue is likely the mag follower or spring as stated.

quote:
Originally posted by sputster:
I have been using 30rd Magpul MOE M2 and M3 magazines in my S&W M&P 15 as well as DDM4V7 carbines for several years. They have always locked in and fed cartridges well, but lately have started to not lock the bolt open after the last shot, especially the older M2s. I don't have this problem with 20rd and 10rd Magpuls, but they don't see as much range time. Would it be time to replace magazine springs?

16 October 2020, 15:46
Samuel_Hoggson
They've occasionally failed, even new. K2 seems more susceptible than the 16s. Oddly, never had an Orlite fail, even when the feed lips were cracked.

No USGI alloy mag - regardless how old - ever failed to engage the catch for us. No matter how dirty they got at shoots from cases of Russian steel-case.
22 October 2020, 00:21
sputster
I have been cleaning them and the rifles regularly, but will check out the points mentioned.

Thanks


sputster
13 November 2020, 18:43
tsturm
How did it turn out?

tu2


27 November 2021, 02:47
sputster
I should have replied earlier, sorry about that. In the short run I just switched to using Magpul MOE M3 magazines and the problems stopped. As the older magazines do have a lot of cycles through them I have looked at replacing the magazine springs. Have cleaned and inspected the followers as described above.


sputster