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CJW

Benelli M2 Hammer Following Bolt Forward

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I just swapped my M2 parts into a Roth XB3G receiver. The action parts are the same as I've been using for quite a while—bolt, trigger assembly, and recoil spring are all the same.

 

Dry fire function testing had no issues. In live fire today, however, this issue cropped up, where the gun would fire, eject, and cycle, but the hammer ended up against the bolt, rather than cocked...therefore dead trigger.

 

It happened a couple of times in about fifty rounds of bird (1145fps), not at all in about a dozen slugs (Fiocci 1300fps), and pretty much every time on 6 or 8 rounds of buck (Fiocci 00 low recoil).

 

These are all the same ammo types I've used in the past without problems.

 

Can anybody tell me what can cause this problem? Since the gun was cycling, the bolt was definitely traveling far enough to cock the hammer, and the bolt locked open on empty with all ammo types.

 

Thanks for your help!

 

Sent from my HTC U12+ using Tapatalk

 

 

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Is it the same recoil spring you pulled out of the factory receiver or did you put in a new recoil spring when you put it together?  I've never had this happen in the shotgun, but had it happen a lot when I was testing PCC triggers

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There is a bind or drag on your shell release tab. If you took your trigger group  apart make sure the hammer pin's flanged head is on the side the shell release tab is on. If you didn't there is a tight spot or burr in the new receiver in this area.

Edited by kurtm

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Halo09, I re-used the old recoil spring in the new recoil system.

 

Kurt, by hammer pin, do you mean the hollow bushing that holds the hammer, lifter, and cartridge drop lever in place and that contains the trigger group pin?  I did put that back in correctly with the flange on the side of the cartridge drop.

 

I did take the trigger group apart to put the guts into an A&S trigger housing.  Could there be clearance issues with the new trigger housing?

 

Thanks!

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On 2/15/2019 at 1:14 PM, CJW said:

Halo09, I re-used the old recoil spring in the new recoil system.

 

Kurt, by hammer pin, do you mean the hollow bushing that holds the hammer, lifter, and cartridge drop lever in place and that contains the trigger group pin?  I did put that back in correctly with the flange on the side of the cartridge drop.

 

I did take the trigger group apart to put the guts into an A&S trigger housing.  Could there be clearance issues with the new trigger housing?

 

Thanks!

Any variation in the tolerance of the trigger pin and hammer pin locations could cause the sear to release early or the disconnector to not hold.

 

Take the trigger group out of the gun. Pull the trigger while restraining the hammer so the hammer goes forward. Now hold the trigger back and manually recock the hammer. Does the disconnector hold the hammer cocked as long as you keep the trigger pulled back? Slowly release the trigger and let it move forward. When the disconnector lets go of the hammer does the sear catch the hammer in the cocked position, or does the hammer go forward as in firing?

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On 2/16/2019 at 9:04 PM, GunCat said:

 

Take the trigger group out of the gun. Pull the trigger while restraining the hammer so the hammer goes forward. Now [...]

 

I did that after the problem surfaced during the first test firing.  The hammer caught both with the trigger pinned back as well as fully forward, and the hammer did move off the disconnector to the sear as I let the trigger forward.  I will pull it and try again, though, as it's possible there is just enough play in there for something to go wrong; I shot a match yesterday and had the hammer slip forward about once or twice per stage shooting both bird and slugs.

 

Buckshot turned out to be a totally different hot mess; it just wouldn't cycle at all, even though I've used this load before and the gun was freshly cleaned and lubed.  It was, however, really cold (sub-freezing), and as I can only recall warm weather matches where I've shot buck before, it's quite possible I've never tried running them at such low temps before.

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Ok, so we now have more than just a new receiver. I'm going to go out on a limb and guess you got a T.T.I. spring kit in that new trigger housing? What other changes have been made? Don't be bashful, list them all😁. It is real hard to help if we don't know what we are "looking" at.

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Sorry I haven't posted in a while; got sidetracked and haven't had time to troubleshoot...  I do appreciate everyone's input!

 

Okay, here's the exact situation.  Old trigger guts moved to an A&S housing, and Briley trigger shoe added to the trigger.  All other trigger group parts (all springs, etc.) are the same as before—no TTI springs. :)  As I said earlier, with the trigger group removed, I am unable to produce conditions where the hammer slips between the sear and the disconnector.

 

I went to the range today and took the trigger group out of another M2 for comparison.  Everything ran fine with the second trigger group, so I think I have definitively ruled out any problem with the receiver or the recoil system.  I visually compared the bearing surfaces on my group and the second group and didn't see any obvious differences, though of course they could be slight enough not to be visible with the naked eye.

 

With my trigger group, I got hammer follow on pretty much every single round of Fiocchi Low Recoil 00BK, and also one time in about 50 birdshot (Federal 1150fps Top Gun).  Also, it was 80 degrees today, so cold weather was definitely not a factor...  I fired about a dozen rounds of Fiocchi JM slugs and didn't produce a hammer follow.

 

When shooting, I tried all the following:  (1) Pinning the trigger back; (2) shooting as fast as possible; (3) aggressively shouldering/leaning in to the gun; and (4) shooting as loosely mounted as possible (including firing one round of buck with the gun completely off my shoulder and just held in my hands).  The buckshot produced hammer follow in all of those conditions.  The birdshot hiccup came on the 6th shot of a mag dump, shouldered but not particularly aggressively.

 

My next step would be to put all the parts back into the original housing, of course, to see if I can isolate it down to the A&S, but I have to find time to get back to the range and try that.

 

Any other suggestions?

 

 

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