Barrel Modifications…

Few things are closer to the heart of the Technoid than projects which have the potential to really mess up a good gun. To be truly worthwhile, a gun project has to have risk. Anyone can alter their gun when there is a guaranteed outcome, but where is the thrill, where is the rush, that comes with dancing right on the razor’s edge? (Sorry, Somerset.) Having said that, you will notice that the Technoid always manages to inflict his projects on the Editor’s guns. The Technoid feels that the thrill of courting risk is not diminished in the slightest by having that risk assumed by someone else. In that vein, the Technoid will now address potential barrel modifications to your gun, not his.

There are four basic barrel modifications: 1) chokes, 2) porting, 3) forcing cones and 4) backboring. Since you asked, here is what the Technoid thinks of all four- Yes, No, Yes, Maybe.

1) Chokes: You should have screw chokes. You can probably survive with fixed chokes of IC (.010″) and Mod (.020″), but there is no need to. Most modern guns come with screw chokes. Every machine shop with a thread cutter makes after market chokes, so there are plenty of different lengths, weights, colors and constrictions to choose from if you do not like the factory versions. If your gun does not have screw chokes, consider having Briley install a set. Briley’s thin wall choke tube sets are excellent and are now installed as an original equipment option on Holland and Hollands. The job costs about $350 and includes five chokes. Installing chokes is a low risk modification and very much worth while.

Most factory screw chokes added muzzle weight. This is because the factories did it, shall we say, inexpensively. They simply bulged the barrel at the muzzle, threaded it and popped in a big, fat, heavy choke. In addition to saving production costs, this method was strong. Unfortunately, it was also heavy because the weight of the screw chokes was added to the original weight of the barrel. Recently Beretta, Perazzi and some Rugers have gone to lighter chokes in non-bulged barrels. A set of standard after market extended chokes for the popular Citori weighs about two ounces- a tremendous amount of weight to add right on the end of the barrel. To get around added muzzle weight many of the best British shooters buy fixed choke guns (Mirokou 3800s and 38s currently) and then get them screw choked. Aftermarket choke installations only replace metal which has been removed and keep the muzzle weight on those 32″ barrels manageable. If you have a gun with factory screw chokes, take them out and test the balance of your gun. This is the way that your gun was originally designed to feel.

2) Porting: A few new guns, notably a large part of the Japanese Browning Citori series and many of the Berettas, now come with barrel porting standard. There are also a dozen aftermarket companies that perform this modification. Does it actually work? Probably a little, but equally probably, not enough to matter. It definitely does not work as well as it does in the high gas pressure environments of rifle and pistol. Stroboscopic photography seems to show that porting does indeed slightly reduce muzzle jump when the gun is unrestrained. The heavier the shell, the better it works. Whether the reduction in muzzle jump will be noticeable to the shooter is another question, especially if the shooter uses light loads.

In the 1970s the Technoid conducted a blind comparison (some say that all of the Technoid’s comparisons are blind) of Magnaported barrels vs standard barrels on a Remington 1100 and could detect absolutely no difference. Then again, it is hard to tell with gas guns. His later tests on two identical Browning Citori GTI O/Us, one factory ported and one not, also showed no discernable difference. We are talking about muzzle jump here. No one has ever substantiated any claim that porting has reduced rearward recoil, although several of the machine shops claim it. Be aware that many types of porting increase muzzle blast to obnoxious levels, but other port hole shapes do not seem to.

So, do you port? If you are a pigeon shooter, shoot max loads, are already deaf and are not concerned with the resale value of your gun, you might give it a try. For sporting, if you habitually have a weak forehand grip or choose to shoot a zero pitch stock to reduce face slap, there might be some slight benefit. Other than that, skip it. If the gun comes ported from the factory, it probably does not hurt anything, so there is no point in filling the holes back up.

3) Forcing Cones: We refer here to lengthening the taper where the chamber and the barrels meet, not where the barrels and the choke meet. Technically, they are both forcing cones. Some modern shotgun come with long cones, some do not. The softest shooting (but most log- like) O/U ever made, the Krieghof K80, has long cones. However, it is interesting to note that most of their high end Ulm pigeon guns have short cones. Most current production Berettas come with fairly long cones. Japanese Brownings do not, although they come backbored and ported. Obviously, there is no universality of opinion here either. Well, you don’t have to worry about what the manufacturers say, listen to the Technoid. Grind ‘em out!

Lengthened forcing cones are the one barrel modification which the Technoid has found to unfailingly reduce perceived recoil and slightly improve pattern. John McDougall, in the Australian magazine Guns & Game, wrote that his tests have shown a consistent 10% pattern tightening when cones are lengthened. This is attributed to less shot deformation.

Long cones appear to take a touch of the peak off of the recoil. The area under the recoil curve remains the same (Newton still has to be accommodated and apples still fall to the ground), but the slope of the curve seems to change and the recoil is drawn out a bit. This is the “shove vs punch” comparison which makes semi-automatics seem so soft shooting.

It is vital that the lengthened cones be properly polished as any roughness in this area will pick up a lot of plastic from the wads. Tom Roster claims that the maximum beneficial cone length is 1 3/4″ and that longer cones do not improve things. This may be so, but the Technoid has observed that extra long 4″ to 6″ cones as done by The Shotgun Shop and Seminole seem to be able to take an absolutely mirror polish. The shorter cones with their sharper angle may be more difficult to polish correctly and never seem to buff up as well.

Rumor has it that fiber wads do not perform well in guns with long cones due to gas blowby. This is baloney. The Technoid’s checkered past included shooting tens of thousands of 3 1/2 dram Federal T123 fiber wad International Skeet loads through Belgian B-25s with lengthened cones and there was never a problem. Modern plastic wads present no difficulty whatsoever and appear to be able to properly obturate in a sewer pipe. Long forcing cones should cost you $50 to $150 and are worth it.

4) Backboring: The nominal interior diameter of a 12 gauge shotgun barrel is .729″, but your barrel could measure anything from .720″ to .800″ and still handle a 12 gauge shell. Anything bigger than .729″ is technically overbore or backbored. Stan Baker, the late Seattle gunsmith, claims to have coined the term “backbore” in order to avoid the less attractive connotation of “overbore”. They mean the same thing.

The Technoid, in one of his denser moments, had some guns backbored in an attempt to reduce recoil. It did not work and should not have come as a surprise. If you look at the formula for free recoil, bore size is not one of the components. From a purely subjective (not mathematical) point of view, it also failed to lower the recoil sensation the way that elongating the cones did. Don’t know why.

In theory, backboring decreases friction and provides a larger wad base for the powder gases to push upon. Both of these should increase velocity and they may to a slight extent. Stan Baker claimed that his extreme and maximum .800″ Big Bore barrels added 50 fps. Even so, normal shell to shell factory variation is 30 fps, so the most extreme backboring does not really affect velocity for all practical purposes.

Very often when people have guns backbored, they also run the cones out and may also have the gun ported. When everything is done at once it is impossible to tell if one particular change had a measurable effect. Subjective recoil reduction caused by elongated cones is often attributed to backboring or porting.

Instead of decreasing recoil, aftermarket backboring actually increases it because the weight of the gun is reduced by the amount of metal removed and ejecta velocity may be increased slightly. Gun weight and ejecta velocity are important components of the recoil formula.

There is a big difference between “aftermarket” backboring and “factory” backbored new guns. The factory backbored barrels are actually a little heavier because wall thickness is maintained while barrel diameter is increased. There is more metal. If you want an example of road hugging weight brought on by factory “backboring”, try to swing a new Browning 425 Ultra with 32″ barrels.

Large bores may help slightly when using extremely heavy hunting loads, but there is no proven meaningful change in velocity or recoil with standard target loads. The aforementioned Australian tests found that backboring neither meaningfully increased velocity nor consistently improved patterns. Sorry folks, factory “backboring” is just another marketing ploy to go along with barrel porting.

Does aftermarket (not factory) backboring have any benefit at all? You can bet your Junior Technoid magic slide rule ring that it does. While aftermarket backboring may not reduce recoil or improve patterns, it sure reduces weight. If the barrels on your gun feel too heavy and unresponsive, you may be able to put them on a diet. Most standard barrels have a wall thickness of around .040″. This is a lot of meat and might be substantially reduced. On a standard 30″ set of barrels, backboring .010″ will reduce barrel weight by 2.77 ounces. A .020 backbore will take off a monumental 5.58 ounces. A change of 3 ounces is a lot, so go easy. Check first with your gunsmith. He will know what is safe. Be aware, however, that aftermarket backboring will void any factory warrantee. Briley charges about $150 per tube for backboring.

Good news/bad news. Backboring works well to reduce the weight of solid choke barrels. Unfortunately, solid choked barrels are usually pretty well balanced and seldom need it. It is the factory screw choke barrels that are usually too loady up front, especially the 32″ jobs. A backbore of 3 to 4 ounces could transform these guns from pigs to peacocks. That is the good news. The bad news is that Briley does not want to hear about backboring a gun with factory screw chokes. Now you know how Tantalus felt when the Greek gods kept the water and grapes just out of reach. The problem is that enlargement of the bore may cause the skirt of the unaltered choke tube to intrude into the bore itself. This would cause the choke to be added to the ejecta on the first shot! Bad move.

Though Briley will not touch your screw choked Beretta or 425, Ken Eyster and several other custom gunsmiths may still be willing to backbore a screw choked gun. Whatever you do, make sure your backboring is done by a pro . There you go Junior Technoids. You now have four separate and efficient ways to ruin a perfectly good set of barrels. Remember the Technoid’s motto: “The factory never does it right. It is up to us.”

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One Response to Barrel Modifications…

  1. potlicker says:

    If, IMHO, if you were trying to make a move from Master Class to Elite Master (being able to compete with the pros.) you might do well to have the above work done. I’ve had all of it done and it does help (shooting 1 1/8 oz. loads @ 1300fps.)and porting will reduce muzzle jump going to the 2nd. bird on a true pair. After market chokes (Muller) are light and perform well. Backboring out to .740 does help with tightening the patterns if that’s what you want.

    The only gunsmith’s that I would have do the above work would be Wilkinson, Allor or Eyster with Wilkinson the preferred on OU guns and Allor on autos.

    All the above said, I would not do it again and instead spend the $$ on a good instructor. As Digweed would say “there you have it.”

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