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E.T.
May 20, 2009, 02:36 PM
I’ve got some issues with my (recently purchased) 28 year old 9 mm Benelli B-76...

First I encountered FTI’s which I dealt with by tensioning the main spring (set screw and lock screw are built-in). This proved to solve the FTI problem but however added some more resistance to have the hammer re-cocked by the slide upon each shot fired.

But now I’m facing several FTF’s, i.e. the slide does not fully return into battery and clearly lacks the (recoil spring) power to properly and smoothly feed a fresh cartridge into the chamber. This mostly happens with a magazine fully loaded (8 cartridges) and the FTF’s tend to decrease with the decreasing number of cartridges in the magazine.

I did some research on the internet and found that - due to the sharp angle of the magazine - Benelli pistols have a tendency for FTF. Note that I only use Winchester 115 gr. FMJ ammo (HP not allowed for civilians here in Europe).

When examining the working of the pistol I found that upon recoil of the slide, the breech block has to push down the top cartridge in the magazine a little bit. I removed the magazine and checked (by hand) the force required to push down the top cartridge of a fully loaded magazine. Much to my surprise the mechanical resistance proved to be huge! As a matter of fact one can not fully load the clip without manually pushing down the follower by means of the two protruding “follower ears” in the lateral magazine slots. This means that - upon recoil - already a large amount of the recoil power is absorbed by the upper cartridge in the magazine. Also the increased resistance to re-cock the hammer must be added. I was even more surprised when I discovered that the force required to slip the top cartridge out of the magazine also is very substantial!

When returning into battery the slide/breech block, again, has to overcome an increased resistance of the now cocked hammer. Hence the recoil spring hasn’t enough power left to overcome the (substantial) resistance of the top cartridge in the magazine.

This gives me 2 problems to solve:

how to increase the recoil spring force
how to decrease the cartridge resistance when stacked in the clip.

I tried to solve the first issue by installing a new recoil spring. According to Wolff’s website the factory standard is 10 lb. while 12 and 14 lb. springs are also available. I ordered all three of them and went to work. First setback was that apparently my gun features the original (early) recoil spring assembly design with shorter and wider recoil spring. The Wolff springs are meant for the second (widely used) design. To make a long story short, I shortened the 14 lb. spring by 12 % to fit the assembly. According to my calculations this spring should have generated about 26 lb. counter acting force with the slide fully retracted. However I could only measure about 11.6 lb. (????) with a slide travel of about 1.85”, which of course did not solve my problem.

As for the second problem I’m thinking about shortening the magazine spring to reduce the spring power, maybe combined with using LRN bullets to reduce friction forces.


Any suggestions ?? :confused: Although I got 2 other guns (a Walther P5 and a Walther P99) I love this Benelli because it’s a real tack driver and it has superb ergonomics. So I would very much like to continue shooting this gun. Thanks on beforehand.

Crapulence
May 20, 2009, 07:59 PM
I am pretty ignorant about the fine details of gunsmithing so take what I say with a grain of salt. Do you have a second magazine for this gun and if so does it let the rounds ride as high? My non qualified guess is that the lips on the magazine are worn or bent and it is now allowing the brass to run too high.

James K
May 21, 2009, 01:52 AM
I have had no problems with my Benelli, but I do have a thought. Before spending a lot of time on parts and/or labor, try another brand of ammo. US made standard 9mm ammo has always been notorious for being lightly loaded and just might not have enough power to reliably operate that pistol, which takes a bit stiffer initial kick than a standard locked breech pistol like the Glock.

A little appreciated fact is that auto pistol slide return depends on a lot of the energy of recoil being returned to the forward movement (in other words, the slide "bounces" off the frame). So it may not suffice to just increase spring tension as that would cushion the slide even more.

Jim

E.T.
May 21, 2009, 10:08 AM
I guess you've got a very strong point regarding the ammo. I've been shooting Sellier & Bellot 115 gr. FMJ without any problem and thinking back, it's been since changing over to Winchester ammo that I had the FTF's.

As for the magazines, I've got 2 of them and they both are in very good condition. I fully agree that a lot of FTF problems are due to damaged, bent or worn magazine lips but this is not the case here.

Allright, I'll switch back to S&B ammo (dammit ! I just bought 1,000 rounds of Winchester...:D) Fortunately I can shoot the Winchesters with my Walthers.

Thanks for the advice :cool:

schmeky
May 21, 2009, 04:38 PM
New recoil springs are still available for the B-76. Do a search, I'm going off memory here, but it was, Bob's Guns Shop, Arkansas.

The B-76 is ammo sensitive and was not designed for anything but SAAMI spec FMJ ammo. I've had 3, still have 1, and a bunch of mags.