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Benelli M4 Tacstar mag extension problem


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I'm new to the forum. I recently ( a couple of months ago) got my Benelli M4.


My brother-in-law was nice enough to give me a Tacstar mag extension tube +2 for the Benelli M4. He's a dealer.


I installed it. I was easy to install. I followed the simple instructions to the letter. I believe I installed it correctly.


However, I noticed I can only get +1 in the tube, i.e., 6 in the tube (2 3/4 inch shells).


Has this been discussed before? Am I missing something simple? It looks like the 7th shell only has about 1/8 inch or so left to go, but try as I might I cannot push it in there. The shell follower hits a stop at the end of the tube and won't go any further, so unless I do not screw it down all the way, I can't get 7 shells in there.


Thanks for any help.

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In terms of the spring, I put in the one that came with the tacstar. Doesn't matter, because I tried loading shells with the end cap off and the spring out (I won't do that again, it's hard to get them out with no spring!!). The follower (whatever you call the piece that pushes the shells out of the tube) hits the end of the mag extension too early, so limits the number of shells you can put it.


Type of shells I tried, were Winchester game loads, 2 3/4 inches.


I don't think there is a limiter plug, but I don't know. My gun is just basically stock out of the box. Does it come stock with a limiter plug?? I shined a light in there, but I'm not sure what to look for. I saw limiter plug installation instructions in the manual, but I don't have anything that looks like that in the gun.

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when I get home tonight, I will try a different brand of shells. I think I have a box of Remingston somewhere, and I know I have Federal 00 buck in my Mossberg.


I will post a picture. Another thread someone posted the same problem, but no resolution to the problem.


I have a feeling it is the way the extension tube was made. Other than this issue, it seems to fit pretty solid. Finish doesn't match the mag tube, but is the same as the original limiter cap (black).


I think the OEM spring will be too short to reliably feed the last couple of rounds into the carrier, but I will try it.

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I figured as much, because as far as I could tell, it has nothing to do with the spring, but more with the construction of the extension tube. I also know I'm not retarded and I did put it on correctly.


Weird, because the packaging claims +2.


Well, as long as it works. I have not fired it yet.

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Guest cleefurd

IF the extension reaches the barrel's front band, and nut can be screwed on, then the extension CAN'T limit the # of rds. Try that same Tacstar extension with all OEM internals, and consider the following;






Very common anomoly. Variances in "true" loaded length vary and thus effect capacity. Examples;

  • Federal Field and Target factory loads 2.28" (avg length)
  • Winchester Universals 2.27" (avg length)
  • Remington sluggers 2.35" (avg length)

Taking the longer of the two (Federal) multiplied times 7 = 15.96"

7 Remington Sluggers at approx 2.35" multiplied times 7 = 16.45"....


...A difference of approx .49" (1/2"). These results are averages and results may vary, but do represent real world experiences as we have noted. Clearly a 1/2" excess can cause the 7th round to fall short of fitting. Some Benelli literature states that the M1014 is a 6+1 capacity due to these variances, when in fact it WILL hold 7 rds of most field/target type shells.


The capacity is NOT dictated not by the tube, but by the cumilative length from the receivers shell stop forward to the rear/internal face of the barrel retaining nut, where the mag tube's spring retainer is held from popping out when fully loaded. (You'll note the nut position is dictated by the barrel bands distance from the receiver, which we have no control over) Now subtract the space required by the follower, spring retainer, and spring, and you should be able to fit 7 rds of 2-3/4" field/target type ammo from many manufacturers... but not all.

Edited by cleefurd
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Full length tube you mean?





Your math is reasonable, but there is one thing you are probably not aware of that is not math related. I alluded to it in the earlier posts. There is a ridge on the inside of this tube that stops the follower. If that ridge has been placed more proximal than it should be, you will never get the last round in. That is a manufacturing issue that is out of our control. I can see the ridge. I unscrewed the end cap and took the spring out. I put the shells in, and I saw the follower stopped at the ridge. Spring doesn't matter.


Anyway, I will still try some different shells tonight and see what happens. I have a couple of different boxes of stuff.


I also noticed that the very last shell out of the tube does not always fully eject into the carrier. That is probably a spring issue. I might need to replace the spring.


I might need to buy that factory extension.


I also need a good tri or quad rail system. I can get a free handle from my brother-in-law. I just need a good foreend stock replacement with rails. Anyone recommend one? Surefire?


Check this one out:



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The site won't let me upload pics for some reason. It says I have already uploaded the maximum of 1 files. I didn't load any files. I'm working on a Mac with Firefox, maybe there is some capability. I will try tomorrow from work PC.


Anyway, I tried three different brands of shells, Winchester, Federal, and Remington. All only load 6 in the tube with the mag extension. And, it's not even close. I said before there was 1/8 left, but actually it looks like that veries from 1/4 to maybe 1/2 inch.


There is a ridge in the mag extension that holds back the follower, and it seems the ridge is placed to close to the receiver to allow an extra two shells. Others seem to have the same problem. Funny thing is, the packaging clearly states "Benelli M4 7-shot".


I learned a new thing, how to float a shell in the carrier, from these forums. Yes, if you float a shell, it's 7. Maybe that is what they meant.


Another piece of good advice was to use the OEM spring. I noticed cycling the shells through, that with the TacStar spring (which is considerably shorter), the last round out of the tube would not completely load into the carrier every so often. So, I put in the OEM spring. No problems. Last round shoots out right into the carrier. Floating the shell seems to cycle fine- by hand anyway, still have not tried firing this.


So, it looks like if I want 7 rounds, I have to either buy that factory extension tube off Gunbroker for $180, or get a full length tube.


I do have a heat gun. I will try this one I have and see how it functions with live fire. I got it for free afterall.


Thanks for the help.

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