AL 390 Modifications

Dear Technoid,

I took your advice and bought the AL390 sporter. I like it. I want to spend more money on it. What tubes would you recommend… Briley, Seminole, Rhino, Ballistic Specialties etc.? Have you had experience with any (or all) of these. Do you suggest porting, back boring, lengthening the forcing cone etc.? I am also interested in changing the butt pad. I shoot trap with this gun and was wondering if a cheek pad would be of any benefit. In general I am looking for some common sense modifications.

Thanks for your sage advice.


Dear Fred,

Well- if you are just mad to spend more money on your 390, there are certainly enough ways to do it. Personally, if I were bound and determined to toss more money into a 390, I would buy a second one and leave them both pretty much stock once I got them to fit me. The 390s are extraordinarily reliable as gas guns go, but it never hurts to have a “complete” set of spare parts. That way, no matter what breaks, you have the part.

45,000 rounds ago, I bought two Beretta 303s. The backup is still in the box in the safe, but I have cannibalized the occasional part from time to time. When the new part comes in the mail from Rich Cole, it goes into the backup gun so that stays completely new and unfired.

If you just have to spend more money on your gun and don’t want to buy a second gun, then I would suggest that you invest the money on lessons with the best instructor you can find. To me, a series of good shooting lessons- say one every one or two two months with plenty of practice in between- is far more valuable than turning some Hoenig lathe loose on you barrels.

Are you getting the idea that I am not so enthusiastic about aftermarket machine shop modifications to the 390? Am I communicating the fact that I think that most of them are a complete and total waste of time and money?

OK, if you still insist on modifying your 390, here’s the list. Remember, one thing though. You are going to void any warranty you might have with Beretta (considering their service, it is of dubious value) and you are making the assumption that a machine shop with limited capital and computer resources can redesign a gun better than a multi million dollar International company with rooms full of professional gun designers and computer jocks.

So, if you must- here are the ankle-deep Technoidal opinions on the various modifications:

Trigger job: Allan Timney in Cerritos, CA (562-865-0181) is THE man for Beretta auto triggers. His trigger job is about $65 and is actually worth it. He replaces parts. He doesn’t just stone the sear. You end up with a decent pull in the 3.5# area and virtually no over travel and creep. Beretta triggers look simple, but they are trickier to work on than they seem. Anyone can make them light, but removing the creep is the hard part. Timney does it right and I highly recommend him.

After-market chokes: Save your money. You DID mike and pattern the chokes that came with your gun, didn’t you? If your chokes mike out pretty close to the standard numbers, they will perform pretty much in the standard way with the usual selection of shells. Beretta is much better about getting its choke IDs on or about the standard industry numbers than Browning is. Yes, a custom Ballistics or Seminole choke will be dead on the numbers (.010″ for IC, .020″ for Mod, etc. Those have become industry standard, though no number will absolutely guarantee you a certain pattern). Your factory Beretta chokes may be a bit off one way or the other. It is sort of the luck of the draw. Briley over the counter after market chokes are pretty good if you have a .722″ bore, but they vary a bit too. Frankly, a few thou either way isn’t going to change your pattern anyway that you can measure.

I did a test comparing a Beretta flush seated Mod choke of exactly .020″ constriction against a Briley 2X extended choke of exactly .020″ and a Briley flush seated over the counter choke of exactly .020″. They all patterned the same with Remington STS #8s. True, the Beretta factory chokes leak a little more gas at the skirt and carbon up faster than the Brileys, but the pattern difference was non existent IF the diameters were the same. The extended portion of the choke made no difference in the pattern. I did think that the Briley chokes were a bit better machined and more of them (but not all) were smoother on the inside.

Here is something that people tend to forget: A 60% pattern is a 60% pattern is a 60% pattern. It doesn’t matter if it came out of a Purdey or a Mossberg. If you read the works of Lowrey, Brindel, Thomas, Johnson, Giblin or any of the other respected professional ballisticians, you will know that patterns are Gaussian in nature and follow the rules of the bell shaped curve. Once you achieve a 60% (or whatever) by whatever combination of shell and constriction, your pattern is the same as any other 60% pattern. If a Ballistics choke is tuned to throw a 60% pattern with a certain shell, it is not better or worse than a 60% pattern thrown with your factory Beretta choke. Either choke requires doing the homework and patterning to find out how they perform with your specific shells. No matter what choke you get, you have to test it. Naturally, the custom houses will give you exactly what you want first time out, but a little experimentation with the factory chokes can produce patterns that are just as good. Bottom line: if your factory Beretta chokes give you the range of patterns you want, there is absolutely no point in getting other chokes. Save your money.

Backboring, cones and porting: If you owned a machine shop, you would quickly realize that you make money by removing metal. The more metal you can remove, the more money you can make. Therefore you would stay awake at nights to think of new ways to remove metal from guns to “improve” them. Some of these guys have become very innovative in removing metal and should be applauded for their imagination.

Porting: Yes, it works. No, it doesn’t work enough to matter. At least that is my considered opinion (and worth exactly what you are paying for it). That’s it in a nutshell. It does NOT reduce recoil to a measurable amount. (Show me the patent performance studies, please) Yes, muzzle brakes definitely work on high powered rifles, pistols and tank cannon, but you are dealing with far higher gas pressures and thicker deflection surfaces. As to reducing muzzle jump, same thing. Using standard target loads, I just don’t feel that there is enough gas pressure at a shotgun muzzle to cause vectored gas to make a noticeable difference in a real shooting situation (as opposed to a free standing gun with no normal forend retention). Seminole’s “Sun Porting” makes the most sense as it is the only one that goes straight up through the rib, but I still don’t think that there is enough gas pressure to matter. Also, what do you do with the lower barrel? It is usually shot first and is the one that really needs the muzzle jump reduced. You can’t drill holes straight up for that one. Any gas vectoring to the side has its doubtful initial efficiency very much reduced.

Backboring: Japanese Brownings do it and claim that it does all sorts of wonderful things. Beretta doesn’t do it and their guns generally have bores in the .722″ area- quite a bit tighter than the .729″ nominal 12 gauge standard. Does Browning know something that Beretta doesn’t? Is it just marketing hype? Krieghoff has always had larger bores (.735″) but the equally prestigious Perazzi and Belgian Browning have stuck with standard bores. Show me the proof that backboring makes an improvement that you can measure. The SAAMI recoil formula doesn’t care about bore size. If backboring can actually “improve” a pattern, that means that one 60% pattern can be better than another, which flies in the face of proven mathematical Gaussian science.

One thing that we know for sure about backboring: If it is “factory” backboring (Japanese Brownings) it will make the barrels heavier if wall thickness is maintained. If it is aftermarket backboring, it will make the barrels lighter. If you want to take weight out of the barrels, backboring is a great way to do it as long as you leave enough wall thickness. I have balanced several guns to my liking by having them backbored and have been pleased with the results. I didn’t do it to improve the patterns. In fact, aftermarket backboring necessitates redoing the chokes- which can be a pain in the neck. Backboring a 30″ O/U .010″ will pull about 2.75 ounces out of the barrels. That is a very noticeable weight change, so be careful. It is easy to over do. Read on.

Many people have found that the 390 is fairly light up front to begin with. Backboring a 30″ 390 bbl from the usual .722″ to .740″ will pull 2.49 ounces from that single barrel. You may well find that this makes the barrel far too light. I can’t tell you how many people have sent their Beretta autos to the shop for backboring and gotten back barrels that felt too light. You can usually spot them. They are the guys who have had to screw on one of those Graco mercury recoil reducers onto the forend nut to add weight back to get the gun to swing right.

Also, backboring will remove the chrome lining on your Beretta bbl. I have always felt (as does Beretta) that the chrome plating of the bbl kept leading down and improved rust resistance. Backboring sacrifices that to some extent, though if the barrel is properly polished it should be OK. One thing’s for sure. A heavy backbore job will definitely necessitate new screw chokes and the expense that entails.

Forcing cones: Do you know how long your Beretta 390 cones are as they come from the factory? Did you know that Beretta offers some of the longest cones in the industry as standard? Well known gunsmith and writer, Stan Baker says that his tests with progressively lengthening forcing cones showed no additional improvement after about 1.5″ to 1.75″. Beretta is very close to that as they come. Does everyone think that long cones are a good idea? Not hardly. The Japanese Brownings (who espouse porting and “backboring”) have SHORT cones. Browning doesn’t think that they do anything worthwhile. Naturally, if you choose to lengthen the already long cones on your Beretta 390 even further, you will be cutting through the chrome plating in just the area where lead build up is most severe and where you want the chrome the most.

I have had the cones on some of my Belgian FNs lengthened and it does seem to me that recoil might possibly be slightly reduced as I perceive it. I couldn’t swear to it, but there might be a slight, almost imperceptible, reduction. Since the Beretta 390 already comes with pretty long cones, I don’t think that it would matter the slightest on that gun.

Having said all this- that I don’t really like backboring, porting or long cones, I do have to be fair. We did a blind test swapping my stock 30″ 303 bbl back and forth with a fully modified 30″ Ballistics 303 bbl which had been backbored, ported, ported chokes and coned. We swapped the two barrels back and forth on my gun to keep everything else constant. Four experienced Beretta gas gun shooters tried the gun with both bbls. The Ballistics bbl was definitely, positively slightly lower in recoil. It wasn’t dramatic, but it was noticeable to each of the shooters. The reduction could be due to the barrel modifications or it might be all or partly attributed to the alteration of the gas port diameters which gas gun barrel modification requires. This changes bolt speed and may affect recoil sensation. It can also change the parts breakage rate and most of the shops found out early on. At any rate, the Ballistics barrel was slightly softer to shoot.

Still, the owner of the Ballistics barrel sold it and went back to a standard 303 bbl. So much weight had been taken out of the barrel by the modifications that the gun was too light up front for him to shoot well. Go figure.

Remember, all of the above is strictly my opinion based on the shooting and testing I have done. I would be more than happy to change my opinion in an instant if someone would just give me proof. Until then, I remain an unreconstructed Luddite.

That’s it. Boots off. Beer open.

Best regards,

Bruce Buck
Shotgun Report’s Technoid
(Often in error, never in doubt.)

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1 Response to AL 390 Modifications

  1. Andy Wilson says:

    A very comprehensive reply and I agree with all of it having owned and altered a number of guns.
    I have recently bought a Benelli, it will stay stock, it shoots where I look and has been 100% reliable. It does suffer from dirty chokes by leaking up from the skirt as you describe and that is the only item I might consider changing to either Briley or Teague.


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