Benelli M4 magazine problems

[vanfunk]

Hi Everyone! I bought a Benelli M4 about a month ago, and it has been positively excellent. I’ve enjoyed its balance, accuracy, recoil control, 100% reliability, and general high quality so far. Last week I decided to order a +2 extension for the 5 round tubular magazine from RX in Canada. The extension came in a couple of days ago and the fit and finish are perfect (yes, I am in the process of maintaining r922 compliance with the requisite number of US parts). Reportedly, Benelli uses the same magazine spring for the 5 and 7 round tubes so I stuck with the original spring. After re-assembly, I proceeded to load 7 rounds of Winchester 00 Buck into the magazine without issue (the last round barely seem to fit, but fit it did). I took it to the range today and fired off those 7 rounds, after “ghost loading” it with a round in the chamber and one on the carrier. Everything worked flawlessly. I put the shotgun away at that point as I had limited time and I needed to sight in a new optic on a rifle. After I got home, I decided to return the M4 to “cruiser ready” status and attempted to load another 7 rounds into the magazine. 6 loaded smoothly but the 7th wouldn’t budge, with 1/4” of high brass ass sticking out into the receiver. I unloaded the gun and proceeded to break it down. Everything was in order and assembled correctly, so I tried again. No go. WTH? So now I am wondering how something can work once but not again? I know that there is some variation between 2.75” shells but these are all the same. 6 +2 (ghosted) is still a formidable arrangement but I’d still like to get that 7th round in there. If it’s a matter of the spring “breaking in,” then why did it work once and not again? Something fishy seems to be going on. I did re-install the spring keeper at the end of the +2 extension but it’s out as far as it can go and still stay in place. Any thoughts on what’s going on here?

Thanks!

 

[KivPanther]

It's probably binding on the split between extension and standard tube or something similar. I had one of those extension tubes before I bought a US-made one-piece titanium magazine tube (wish I could remember the company), and that problem vanished instantly once I made the swap.

 

[vanfunk]

Thanks KivPanther! I thought of that too initially and I put a thin patch around a cleaning rod and pushed it up and down over the union between the magazine tube and magazine extension. Totally smooth! In fact it was pretty much impossible to feel any transition at all, so I don’t think that’s it. What I am noticing as I continue to research this is that there is a great deal of variability with OAL between 2.75” shells, even among the same brand/load. Fiocchi shells, both buck and slugs, fit in the tube with no problem. Winchester/Olin military 00 buck, no problem. I now have it broken in enough so that Winchester Super-X 00 buck will fit all 7 rounds again, just barely. Federal slugs, buck (both 00 and #4) are six only and come up 1/4” short of chambering 7 rounds. I have a Shell Tactical follower and Wolff Spring coming on Wednesday, with together should buy me that 1/4” I need for the Federal shells. I’d really like the Benelli to be able to hold 7 rounds of Federal 2.75” “magnum” 12 pellet 00 buck, which is my preferred load. It’s an absolutely devastating round.

 

[KivPanther]

That’s interesting. I don’t think I’ve had issues with any particular brand of shells loading leas than 7 in the tube. Your extension may be a hair short? Dunno, but glad you’ve got it sorted!

 

[vanfunk]

Hi all:

Update for those interested… based on online feedback, I began to investigate the role of the magazine spring as it relates to capacity in magazine tubes. Many suggested a new Wolff spring as spec’d by Carrier Comp (makers of an excellent titanium magazine tube as well) so I decided to order two from them. They lost my first order but made up for it quickly by shipping fast on the second order and throwing in an extra spring; no harm no foul. I got the springs yesterday and installed one this morning before heading to the range. Amazingly and excitedly, all seven rounds loaded without issue. i tried four different loads and all fed and cycled just fine. I would highly reccomend their springs for an M4!