Bores, Triggers And Barrels

Dear Technoid,

I have three questions that are unrelated.

A: What is the standard accepted 12 gauge bore diameter? My research has found both .725 and .730.

B: Do you have a preferred trigger pull weight on your sporting clays guns?

C: Would it be helpful to have a longer barrel than my 28″ Beretta 390 for what seems to be a trend towards longer distance competition targets thrown over the past few years? Or would the shooter’s size be more of a factor in choosing barrel length? Thanks again for your experienced knowledge.


Dear F.B.,

Unrelated questions? That’s OK. The Technoid can multi-task!

1) Twelve gauge bore diameter: The definitional 12 bore barrel measures .729″ because if one pound of lead were divided into twelve equal parts, each part would make a ball of .729″ in diameter. That is how all the gauges are measured, except .410 bore which was designed to measure .410″ like any pistol or rifle caliber.

That said, I have seen 12 gauge bore diameters from .715″ to .800″. They will all fire a 12 gauge shell as long as one will fit into the chamber. The 12 gauge chamber is .800″ and that is kept fairly standard.

Generally, more or less, sort of, the current industry standard for mass produced 12 gauge bores is .725″, but Beretta is consistently around .723″, Krieghoff is .735″ more often than not and “factory backboring” has also altered the picture. There really isn’t a standard any more.

2) Trigger pull weight: I prefer a pull weight of 4.5# to 5#. This is a bit heavier than most people like, but it works best for me. I miss a lot of targets when I start to “milk” a light trigger. I shoot best when I hold my guns tight and pull hard. It is not a pretty sight, but it is effective for me. Many shooters ride and miss the bird due to the inability to decide when to pull the trigger. A good hard crisp pull goes a long way towards solving that. A very wise man once told me “It takes guts to pull the trigger.” Indecision costs more misses than aggressive commitment.

Many people like their O/Us to have a lighter first trigger and heavier second so that recoil will not cause them to double pull. I like them both the same as I often shoot my top barrel first on certain combinations. On my gas gun (a Beretta 303) I have a trigger reworked by Allan Timney. Although he does an excellent job, very few semi-auto triggers will equal an O/U trigger in crispness when set to a light pull. Heavier triggers seem to feel crisper than lighter ones and so the 4.5# pull on my 303 makes the trigger seem crisper than it really is.

3) Barrel length: The most popular O/U barrel length for sporting clays by far is 30″. You read about the hot shots using 32″, but the average guy out there usually picks a 30″ and is well served by it. The problem is that most of the factory screw choked O/Us are too barrel heavy in 32″. The shooting pro will go to the trouble and expense of lightening them up. The weekend warrior will shoot them as is. In an O/U 30″ is a wise choice.

The gas gun is an entirely different matter. Remember that the semi-auto has an extra 3.5″ of receiver when compared to the O/U. That means that your most excellent 28″ Beretta 390 has the same sighting plane length as a 31.5″ O/U. This is one of the attractions to the gas gun- you can have a long single sighting plane with lighter muzzle balance than most O/Us.

As sporting clays has matured in this country, shots have indeed become longer. Advanced sporting courses are hopefully no longer “skeet in the woods”. The whole idea about longer barrels is that they help you more on the long birds than they hurt you on the short ones. That is the bottom line.

28″ or 30″ on the Beretta 390? It depends. Partly it depends on your stature and build, partly on the weight of the barrels. I am a large man but found the original A-390 30″ sporting clays guns too muzzle heavy. I preferred the original A-390 in 28″ due to the barrel weight. That said, I shoot a 30″ Beretta 303 because that gun is a bit lighter up front than the A-390 and handles very nicely indeed. My opinion is shared by others as you will note if you try to find a 30″ 303 target gun on the used market.

So, bottom line is that either the 28″ or 30″ gas gun barrel is fine. It really depends more on the weight of the particular version that you have. If the 30″ barrel is light, go for it, but don’t lose sleep over it if you stick with the 28″. It is more important to keep the gun lively than it is to have those extra two inches.

Bruce Buck
Shotgun Report’s Technoid


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