The Mystery of the Beretta 391 Series Shotguns
When it comes to gas-operated semi-auto shotguns, few lines of shotguns have distinguished themselves more than the 300 series Beretta self-loaders over the years. It was the Beretta 302 / 303 that provided relief for Browning after the poor sales of their B-2000 autos (though the 20 gauge 2000 shotgun was and is a fine autoloader, as far as Im concerned). Along with the Browning B-80 and Beretta A303 we saw the action that obsoleted the Remington 1100, the proliferation of the Mobil screw chokes, still one of the most popular factory screw chokes ever introduced (fixed and std. Invector in the B-80), and the popularity of buttstocks user adjustable for drop in the form of shims.
And now, the mystery begins. Whats wrong with an A303, anyway? Was the 390 an improvement, or an advance to the rear? Is the 391 better than either, or worse than both? Now that the 390 is back in the form of the Beretta 3901, is that better than a 391, and if sowhy? There is no easy answer; thats a good thing for mysteries, of course.
The problem in large measure revolves around shooting style considerations, load variations, and the use of steel and other no-tox shotshells. Fundamental to gas auto operation is pressure past the barrel ports. MAP has little to do with it, as peak pressure occurs inside the shot shell hull itself, not downstream across the gas ports. Peak pressure has nothing to do with recoil, and professional ballisticians can tell you that three, four, or even five thousand psi variance can be created with just the change of shotshell primer.
This complicates shotgun design, as today the traditional notion of 3/4 ounce 28 gauge, 7/8 oz. 20, and 1-1/8 ounce 12 gauge standard loads has been altered. Apparently no standard load satisfies segments of shooters today: we want to shoot 28 gauge loads out of our 12 gauges because of our eternal terror of recoil, or we want to shoot 10 gauge loads out of that same 12 gauge as well all know it take hundreds of pellets to kill a turkey, not just one. Or so we would like to believe. Marketing departments have screwed up common sense, or at least taken great liberties with it. A three inch shell must be a magnum - - - even though a 27 gram 3 inch shell is involved in the evolution of the current 391 shell carrier. If all this sounds confusing, it is only because it is.
Ive owned dozens of A303s, B-80s, 390s, and 391s. Lets start with what is wrong with the 302 / B-80 / 303 platformthe answer being not a thing. It is, in my view, the simplest and best field gun action of all of them. The B-80 / 303 scatterguns are easy to clean, and very easy to work with. Changing from 1-1/8 ounce loads to heavy three inch shells is a momentary task, with a quick and easy barrel change. As long as we have some clue about what we want to shoot, there are no issues. The problem is, of course, is that many of us are decisionally challenged about that.
The 303-esque action is non-compensating. The more gas flow through the ports, the higher the bolt speed. The faster we drive the bolt, the more stress it takes to the point where the 1-1/2 ounce baby magnum loads can peen the back of the receiver. Too lazy or too cheap to change a barrel, we still search for the ultimate crescent wrench of shotgunswith no adjustments. It doesnt exist, of course, but that doesnt stop us from trying.
So, enter the evolutionally A390, the gas action that does compensate for more or less gas across the barrel ports with a secondary bleed. A simple addition of a flange and spring in front of the barrel gas piston housing does the trick. A gassy shell has the excess gas bled off around the flange, and now we have more flexibility with the same barrel. Optimal bolt speed can be further dialed in with switching out secondary gas bleed spring of different strengths. Cole Gunsmithing offers theseand they work well. The stiffest springs allow no secondary gas venting at all, so those wanting 20 gauge payload reliability (7/8 oz.) can quickly find it. A softer spring with very quick collapse allows the use of heavier, gassier shells without excessive bolt speed as well. A bit more complex, no better than a 303 when used within design parameters, but more versatility which is what we say we prefer. The A390 was and is an excellent design in form and functionso, you might think that would be that. Well, it wasnt, at least with the introduction of the 391 series.
The 391 has its gas springs and system attached to the barrel. The why considering the increased complexity, tooling costs, engineering costs, and other R & D expenses associated with the 391 gives cause to wonder what was so badly broken with the 390 that needed fixing, or what the great commercial appeal of the 391 was supposed to be to deserve this new treatment. A mystery, indeed. Is the 391 any better at all than what it replaced? Is it better than the new 390, the 3901?
The answer is not as easy as you might think. If all shooters were clever enough to shoot 1-1/8 oz. 1200 fps lead loads, or anything reasonably close, then there would be little basis to believe that the 390 / 3901 (much less the 391) is anything but a needlessly more complicated variation for variations sake inferior improvement to the 303. I have a personal B-80 12 gauge with over 100,000 rounds through it with no major parts replacement in all this use. The final version of the 300 series, the A304, is lamentably not available that I know of in the United States in any quantity.
Apparently, thats not good enough for many prospective buyers. Many of us feel we need 3 inch shell capability, even though many thousands of three inch chambered Berettas have never seen a three inch shell in their lives, and likely will not. It is part of the human condition to want things that we never use, it seems.
For those that wanted, or think they wanted more versatility without changing barrels, the A390 was a great success. I still own two semi-hump alloy receiver A390ST Gold Mallards; with the addition of the secondary gas bleed spring and flange beneath the fore end nut, we have a tunable action without drilling out ports or changing barrels. Again, you might think that was that. Well, apparently the few extra parts that give the 390 its versatility are the source of perceived problems. Shooters dont like to clean their guns, and more often than you might think lose the couple of extra parts that make the 390 a 390the gun fails to cycle without the secondary spring flange and the owners manual was never read, and is now nowhere to be found. Comparatively few shooters tune their bolt speed and resultant ejection distance, or replace their stock springs as regular maintenance. So, we get jammers as the 390 doesnt work well with missing parts, and if neglected long enough, excessive bolt speed can peen the back of the receiver. At long last, we enter the reason for the 391.
The 391 has its gas system spring attached to the barrel. As there is no loose spring, shooters have a rougher time losing it. Shooters that fail to maintain their 391s can go a very long time, as the addition of a plastic recoil buffer at the back of the receiver inhibits peening due to excessive bolt speed with a worn recoil spring. The initial recoil buffers were problematic, though, a situation that has been long ago resolved. The recoil buffer is what Beretta calls a sacrificial part. This is common engineer speak for a part that wears and requires periodic replacementthats all. The sacrificial bit just means that it is more desirable to replace a part that you plan to replace as opposed to a part you do not, in this case a battered receiver.
Berettas recent addition of a toothed or serrated 391 gas piston that lets the gun function about twice as long without cleaning. For those who wont service a semi-auto until it fails to cycle, the 391 is far more tolerant of neglect and abuse. It still does not make the 391 a better or more desirable field gun in my view.
There is more, though. The 391 has a very complicated (or sophisticated, as you wish) fore end nut full of parts. It defines the term contraption to some. Yet, there is a reason for it. The fore end nut when tightened down fully (or excessively) on a 303 or 390, cranked down like you would the fore arm nut on an A-5 captures the 303 / 390 barrel. Beretta discovered that with extremely high-volume competitive shooting, the captured barrel when heated to burn your fingers through the wood levels also exhibited a change in point of impact. The nut captures the barrel, but the barrel grows and lengthens when super-heatedand the resultant sway-back horse look of the slightly, temporarily deformed barrel while not readily perceptible to the naked eye may yield a POI change. The 391s floating, springed forearm nut accommodates barrel lengthening due to temperature change with no point of impact shifts. Perhaps the crazy Italians were not so crazy after all?
Well, that is Berettas assertion, anyway, without any supporting details. This mysterious point of impact shift is nothing Ive witnessed, nor is it plausible as to having any practical implications one way or another. If indeed barrel heating was contorting your barrel like a piece of a piece of spaghetti due to the for arm nut pressure, the more clever competitive shooters would loosen the forearm nut a couple of clicks rather than calling for this nasty little seven part nut (more parts than the 303s entire gas system). Its Berettas story, though, and they are sticking to it or stuck with it as the case may be.
Moving on, we have the notion of 391 Bent Carrier Syndrome resulting in jamming that is solved be replacing the flat 391 carrier with a bent, better 390 shell carrier. This is a mystery as well. There is a reason for the 391 style carrier, having its roots in light payload (27 gram) three inch shells favored by some European competitive shooters. A long shell with a long wad with a lead payload at the crimp end of it is an unbalanced, nose-heavy shell. This new (foreign to most American shooters, as foreign things tend to be) load can be problematic in the 390so the 391 bent carrier was introduced to take care of that isolated issue as well. It created its own set of mysteries as well.
The very early 391s used 390 carriers, exhibiting the unbalanced shell difficulty just noted. So, the Generation One 391 flat carrier was introduced. Problem was, the tooling was badand the die that formed the Genertaion One carrier sometimes deflected the next shell to be loaded to the right, resulting in a failure to feedthe very thing the 391 carrier was designed to address. Bad tooling, warped carriers (that had nothing to do with the design, but the manufacture) gave the 391 carrier a bad name in some circles that still persists, or is at least gossiped about. Well, finally, the 391 Generation Two carrier with new tooling was introduced, and that is what is prevalent today still a 391 flat carrier, but made as originally intended with appropriate tooling. The two guys in New Mexico that shoot 3 inch, 27 gram shells will be delighted, of course.
While the 391 is more of a pain to clean, it is far more tolerant of going a very long time with no attention at all. Thats the trade off against the 390; harder to clean but needs it less. It is more complicated, but harder to lose integral parts.
As a field gun, my preference remains for the 303 / 304 series. Again, I wish the 304 was commonly available in the U.S. Both the 303/304 and the 390 could be updated with the spinning gas piston it seems without drama to the benefit of both models.
So, that is the resolution of the 391 mysteries, at least for now. Beretta of course adds their own special brand of mystery by naming their A391 Xtrema2 a 391, even though it is an entirely different rotating bolt O ringed piston gas action not a part of the 303 / 390 / 391 lineage at all, but a new action offered to accommodate 3-1/2 in. loads more than anything else.
So, after all this (more than most normal people care to know) the consumer is left with choices. For most shooters, the 391 is of no great tangible benefit over the 390 and the 303 that preceded it, in fact the made or assembled in the US 3901 Series is the 390 brought back, and is a more affordable shotgun than the 391 with no less field utility.
As to the eternal mystery of what is better, only the individual can decide that. There is, of course, no better just more better for the individual application. For me, there is nothing better than a 303just different, but hardly better. Target shooters may well opt for the 391, value shooters for the 3901 (390). I hope this explains some of the differences, if not completely all of the mysteries. Why I just penned over two thousand words on Beretta 300 series gas autos is a mystery to everyone, including myself.
Copyright 2008 by Randy Wakeman. All Rights Reserved.