Penetration Difference With Bore?


İs there Penetration difference between 18.3, 18.4, 18.5, 18.6 etc. Bore diameter shotguns.




Penetration depends on pellet speed, size and, to some extent, hardness, To the extend that bore diameter affects pellet speed, bore diameter will affect penetration, all else remaining the same.

There are two schools of thought on whether backboring or overboring affects velocity. If you listen to the manufacturers, you will hear that overboring lowers friction of the shotload and wad in the barrel and this increases velocity. They also argue that recoil is reduced with larger bores, but if Newton has anything to say about it, when velocity goes up, so does calculated recoil.

Obviously, if you overbore too much, the shot wad won’t seal properly and everything goes to pot. On a cold day, I tested an .800″ bore Baker barrel which did just that with a certain shell.

The other camp holds that a larger bore diameter lowers velocity because it increases volume and this lowers pressure and hence lowers velocity. Lower velocity does lower recoil.

The only way to know for sure whether a change in bore diameter will change velocity is to measure the velocity of a certain gun with a certain shell. Then backbore the gun to a new barrel diameter and remeasure with the same shell. I’ve not personally done that, so I have no facts to back up my opinion.

I do know from personal experimentation that tightening a choke will increase velocity. It works the same way a garden hose works. The pressure in the water pipe doesn’t change, but when the nozzle of the hose is full open to a wide spray, the water doesn’t go very far. Then the nozzle is tightened down, the water comes out faster (though still with the same basic water pressure) and the water squirts further. Works the same way with a shotshell. I’ve seen differences as high as 50 ft/sec going from Cylinder bore to Full choke.

But that’s an aside and not what you asked. I don’t absolutely know the answer to your question, but I lean towards larger bores lowering velocity due to lowering pressure, not increasing it due to lowered friction. But take your pick.

Perhaps one of our knowledgeable readers will clear up my waivering with some hard facts.

Best regards,
Bruce Buck
Shotgun Report’s Technoid

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August 2015 RELOAD!

August 2015 RELOAD!

Published by the Connecticut Travelers Sporting Clays Association

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Dear Bruce,

I have been chronographing some reloads trying to duplicate some factory velocities. In my past experience chronographing pistols & rifles, we always placed chrono screens @ least 10 ft from the muzzle to avoid muzzle blast. My results were a little less than that published. Now I am aware of all the variables involved with factory testing and it would be difficult to duplicate exactness. I read somewhere recently where chrono testing was done 3 ft from the muzzle. This seems to awful close to the muzzle even for a shotgun. Please enlighten me as to how the factory does it and how I should do it?



Dear Carl,

The US standard for chronographing is three feet from the muzzle, but it is also to the center of the mass of the shot cloud. “Home” chronographs, like yours and mine, measure the lead pellet. The difference really isn’t that much so you shouldn’t lose sleep over it the way I do. I’ve been slow to move the chronograph further out as I am concerned that a flyer might hit it. I’m sure that your aim is better.

I was concerned about muzzle blast on my ProChrono’s front plastic LED readout, so I stuck a thicker piece of plastic over it. Worked fine. My chronograph is quite sensitive to ambient light and light angle, at least that is what I think the problem is when I sometimes don’t get consistent readings. It could be muzzle blast. Moving the chronograph further out (and holding tighter) is worth the experiment.

Do remember to accurately measure the distance from your muzzle to the center between your chronograph screens to get consistent results. The difference could be a couple of feet per second. That really matters, right?

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)

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Curing A Light Muzzle

Dear Techness,

I recently bought a 28 ga 30″ browning ultra xs sporting. So far so good. However, I would like to add some additional barrel weight for a smoother swing when skeet shooting. Any ideas or products you recommend would be appreciated.



Dear Tom,

Nice gun! You are indeed a lucky dog. You can pick up a slight bit of extra weight by using Briley extended chokes. They won’t add much, but it will be right at the front where it does the most good. If you call Briley up, they will tell you how much weight the extended chokes will add. They will also give you an exact choke diameter if you ask for it.

Next, I would try holding your hand a bit further forward on the forend. While that does limit your swing arc a bit, it should provide a noticeable increase in apparent forend weight. It’s worth a try and doesn’t cost anything.

I have seen some clamp-on weights advertised in Shotgun Sports or similar, but I believe they were only for 12 gauge barrels and meant to equal the weight of tubes. One of the problems with any clamp-on weight is that it adds the weight all in one place. 10 ounces of weight added on one glob in the center of the barrel does NOT produce the same feel as 10 ounces of metal added all along the barrel. The balance point will be the same, but the moment of inertia will not be.

You can always add lead using lead wheel weight tape. Check your local auto supply store. Just stick on where you want to. It stays really well, but looks nasty. I once loaded a bunch of it on the barrels of an FN O/U under the forend. It didn’t do much. The weight added under the forend is only half way up the barrel and doesn’t change the feel of the gun too much unless you use a ton. You can’t get a ton in there. It helped, but not a lot.

You can also get a weight forward shift if you pull some weight from the stock by drilling out some wood. Unfortunately, if you shoot your American-style skeet gun up, you won’t notice it much. If you shoot gun down, it may help a bit. It’s probably not worth the effort on a clays gun, but is a common practice in fine balancing a good game gun.

Bottom line: I don’t think that there is really a neat answer. That’s why I sold my 30″ 28 gauge Browning. I had the same problem with a slightly too light barrel that you do. I sure wish I hadn’t sold it though. Some guns you should just learn to live with. That long 28 is one of them.

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)

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More On Choke Percentages

Hi Bruce.

I’m happy to report I’m over my tight wad stage, spent the money and had my gun properly serviced and the wedge replaced. I know my gun loves me all the more for it too. After all, what sort of technoid could I ever hope to be if I was to be dictated to by my wallet.

OK, you know you wanted it now that you have stuck you’re neck out and all.

I also happen to like the number 7. It’s very pleasant, minds it’s own business and can be found associating with other mutually beneficial numbers as in .729, 7 1/2’s etc. and 77% sounds equally harmonious.

You’ve mentioned or alluded to it many times before, so we know you have the opinion that “most people under choke for the clay target games”. But in all seriousness, and with the utmost respect, what do you base this view on?

Firstly, what chokes do you suppose are the average or norm for most users and in which games? On what evidence? Secondly, most trap shooters I know compete with fixed choke guns, so are the manufacturers therefore producing substandard equipment? (Apart from the obvious flaws.)

Is this view based on derivatives of mathematical models and technoidal wisdom only, or in combination with your own extensive and illustrious “real world” competitive experience?

Are we really just talking about sporting variants here where choke choice and choke changing is more widely practised? In answering many of your novitiate reader’s questions as to a gun’s suitability to a given application, you usually reply that observation of the champion’s choice of gun in their preferred discipline is often the best guide. ie look around at all the 391’s in use and in the winners circle, ipso facto it’s a pretty good sporting clays gun, get one, you’ll be a legend in no time. Shouldn’t this anecdotal modelling method also hold true for choke choice v’s results? “Fred Smackem won the Turkey Cup using skeet and 1/4 and we all know how good a shot he is, therefore I’m going to use skeet and 1/4.”

This would have to be as good a guide as any wouldn’t it? If the points are on the board, surely the kill and a win rather than the amount of smoke drawn from the crumbling clay is what’s more important. I’ll take a chip any day over soot or nothing because your pattern went whistling past in a fist.

What chokes do the regular winners in your neck of the woods use? We all know some of the world’s best FITASC shooters have produced exceptional results, ie: Smoker Smith, using very open fixed choke guns. Surely that’s justification enough to open up and have at ’em?

Or, does that lead us to the real solution? You need to become a good shot and learn where to put the pellets rather than be overly concerned with how many get there? The blending of art with science.

So, are most people underchoked to see soot from 95% of their targets, or underchoked to win a shoot?

Having said all that, due in part to your earlier dissertations on the matter, I personally pretty much shoot 1/2 and 3/4 for most stuff in sporting these days after having shot 1/4 and 1/2 for years. Stronger breaks do instill a certain amount of confidence in what you’re doing, which once again plays just as important a role in successful shooting as the pure science of it all.

I’m really just nit-picking and hoping for a better justification of your opinion other than what sounds like “the numbers said so”. They’re better than tea leaves granted but neither actually wins you a shoot in the real world, not even a fifth : )


Dear Peter,

You like the number 7? Do you know why number 6 fears number 7? Because 7 8 9. Gotcha! (Thank you, Sesame Street.)

It’s always tough to discuss chokes, especially for sporting. The reason is that sporting shots vary so widely that there is no reliable data base on a particular shot. That’s why I like to use trap and skeet as the best comparisons. These have ample databases with millions of iterations for the same distance and angle of shot.

As I state (and magnificently defend, I might add) in another bit of Technoid drivel recently or about to be posted, you are generally best off with about a 77% or bit more pattern in the 30″ circle AT THE DISTANCE at which you take the target. I won’t go into all the logic yet again, but I base my observations on the far more informed observations of Winchester ballistican Ed Lowry and SR’s own ballistic math wiz Warren Johnson. That 77% depends somewhat on the size of shot, hence pellet count, but it’s a pretty good general rule.

So, what choke produces 77% patterns of the correct sized pellet for your distance at your distance? It obviously depends on the distance. If it’s 23 yard handicap ATA trap where the average bird is taken at about 40 yards, then you are talking Full choke. If It is skeet, shot at 21 yards with #9s, you are talking Skeet choke (Surprise!). In between is, well, in between.

It gets even muddier in that the 77% figure is based on a full edge on bird. Any turning exposes more target area and thus permits a more open choke. But it’s also interesting (see referred to Technoid column) that, while you often lose effective pattern diameter by opening the choke, you less often lose it by tightening the choke. In many instances, the killing circle of a 77% pattern does not decrease when it goes all the way up to 90+%. Depends on pellet count in the load. Instead of fixating on 77%, I might be best just saying 70~90%, but it doesn’t sound as neat.

In a trap situation, I see many of the best ATA trap shooters (our “Down the Line”) using Full choke for everything, including 16 yard where the bird is taken at about 32 yards. They obviously don’t feel that they are handicapping themselves or these money shooters wouldn’t use that choke. Their patterns at that distance from Full choked guns have to be 90+%.

Smoker Smith really shouldn’t be associated with open chokes. He often said that he used them, but there’s more to it. First of all, how do you think he got the name “Smoker”? I can guarantee you that it wasn’t with open chokes. If he went to open chokes later in his career, you can’t prove it by me. When he came over to the US to shoot some years ago, he told everyone that he used “almost no choke” and “just a bit more” in his Miroku or Classic Double (I seem to remember). He also said he used #8s for everything. He loved to fish. One day he was invited fishing and left his gun with a pal of mine. My pal is a curious type and miked Schmoker’s bores. I forget what the exact numbers were, but he had a bunch of choke. Definitely not “almost no choke and a little bit more”. Apparently Smoker knew the advantage of smoke in a number of ways.

I also hear that Digweed, uses heavily choked guns. 1/2 and 3/4 come to mind. I suppose I could call Perazzi up to find out. Doesn’t he also carry an even more heavily choked 3/4 and 1/1 longer second barrel? Does or did anyway.

I know that Andy Duffy in the US won our Nationals one year using .015 Light Mod for the entire shoot. His gun had some barrel work and probably shot more like a pure Modified though. Front end constriction doesn’t tell the whole story all the time.

Most people feel that solid fixed chokes are more efficient than screw chokes because they allow more gradual tapers in the tighter chokes. All fixed chokes, unless they are extended like the FABARM “In/Out” chokes, are the same length. Fixed chokes tend to be shorter in the open chokes and much longer, up to 6″ or 7″ in the tight chokes. The theory is that length provides a smoother transition where a lot of constriction is called for. Screw chokes also usually (except the excellent Teagues) have a disruptive “skirt relief”, often up to .020″ or more. This can’t help patterns and bumps the shot about. When I want the best pattern possible, I stick with solid fixed chokes too.

Is it always right to copy the gun and choke that the winners use? Dunno, but many people think so. That’s why people who win are given guns by sponsors, while you and I (well, me at least) have to buy our own. I don’t believe that it is wise to slavishly copy what each month’s top gun is shooting, but it is smart to keep an eye on trends. Having the correct shotgun and choke may account for as much a 5% or 10% of your score. When you are at the top, every little bit matters. When you are a weekend hacker, it probably doesn’t matter all that much. Since none of us admit to being hackers, and all of us are potential World Champions, there is always a line to buy the gun that the winners use. And the manufacturers know that.

As to open chokes vs tight chokes, that also depends on your skill level. Do you shoot in a way that a larger, but unreliable, pattern is better than a smaller, reliable one? The Pros come very close to centering a high percentage of their birds. They want it to break every time they do their job. The weekender misses a far higher percentage of his birds. He may be willing to trade more holes in his pattern for a more forgiving fringe and more chances at a lucky hit.

The nice thing about shooting is that Cylinder Bore and #9s will break a 50~60 yard sporting clays target. I’ve done it occasionally and seen my betters do it fairly consistently. Does that mean Cyl/#9s is the best choke for that bird? Not hardly. But it works just often enough so that some idiot will tout it as the be all and end all of choke shot combinations suitable for every possible shot. And people will believe him because it works occasionally. That’s how that stuff gets started. If you made registered sport out of shooting 60 yard crossers only, after a million billion rounds had been shot at that bird, the averages would show that XFull and all the #7-1/2s the law allows would be the way to go.

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)

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Does Your Shotgun Fit?

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Converting A Trap Gun Into A Sporter Gun

Dear Technoid,

I own a fairly new Browning O/U B425 Trap with 3/4 and full fixed chokes. As it’s usage is more or less restricted to shooting trap, I wonder whether this gun could be modified/converted in order to be able to shoot (in addition to trap), Skeet as well as sporting clays (gun down disciplines).

The alterations I have in mind are:-

1. To fit Briley chokes.

2. To add on an adjustable comb to the existing stock. I am not sure whether the stock on my gun is hollow and also whether it is possible to modify a trap stock. On the other hand, would it be better to fit a new stock with an adjustable comb?

3. To lengthen the forcing cones. There is a theory that by lengthening the forcing cones, (a) felt recoil can be reduced substantially, and (b) pattern quality can be improved.

Is this correct? I would imagine that the makers would have designed the barrels to achieve optimum performance. I am rather confused, therefore please clarify.

Thank you,

Best regards,

Dear Charles,

You have an ideal gun for trap, skeet and sporting clays. Since your gun came with fixed chokes, it has lighter barrels than Brownings screw choke guns so it handles better. Screw chokes are an easy conversion and Briley does a marvelous job. It will cost you around US$365 and will include your choice of 5 chokes. You can order more at an additional price. You might consider ordering Sk, Sk (two skeets), IC, Mod and Full. That will certainly get you started.

Many of the very best sporting clays guns are simply converted trap guns. The Miroku 38s and 3800s and the Perazzi sporters from England are just tricked out trap models.

You really shouldn’t have to replace your stock. As to having an adjustable comb done, that’s up to you. I shoot trap stocked guns on ALL my clay target games. I have high cheek bones, so a trap stock isn’t all that high for me. I see a figure 8 with the middle bead just under the front bead. I’ve found that this sight picture is absolutely perfect for skeet and works for me at sporting. I’ve gotten used to covering my birds at trap with this slightly lower sight picture. I also shoot a lot of wobble, so I am used to covering those low birds.

I would suggest that you get the gun screw choked and try it out on skeet and sporting. Actually, even with your tight chokes, you can experiment at skeet and sporting before you get it screw choked. The tight chokes will give you a very good feedback on where your gun is impacting. Then you’ll know if you need an adjustable stock. If your gun does shoot high for you, you may find that you can just cut your existing stock down a bit as a compromise. Take off a little at a time. You may find that you can keep it high enough for trap and yet have it perfect for sporting. It depends as much on your trap shooting technique as anything else.

One downside to the adjustable stocks is that the mechanism often adds some weight to the rear of the gun. You may or may not want this depending on how you like your guns balanced. Find out from the stockmaker how much weight will be added first. He may be able to remove an equivalent amount of wood to keep the balance the same. A stock maker shouldn’t have any trouble fitting an adjustable comb to your trap stock. Make sure to ask what provisions the mechanism has for not coming loose. Some adjustable stocks insist on adjusting just when you don’t want it.

The jury is still out on lengthened forcing cones. Beretta always had medium length cones and has just gone to super long cones in their Optima Bore guns. It may just be a marketing ploy, or they may have done their homework. They aren’t saying. Browning has always had short cones and doesn’t seem to want to budge. Stan Baker felt that cones lengthened to 1-1/2″ ~2″ are ideal and that you don’t need more than that. Seminole, Ballistics, Briley and the rest all push super long 5″ (1-1/4 degree or thereabouts) cones. That’s how they make their money.

I have not seen any proven, written, statistical pattern before and after work on any improvement from lengthened cones. I have had the work done on several Belgian Brownings and haven’t been able to detect the slightest difference in recoil or pattern. Others of my friends claim that they can feel a difference in recoil. There’s an argument that long cones kick less because they lower velocity a bit. I never put a chrono on a gun before and after, so I don’t know if that is true. In theory, the longer cones should help the shot transition, but I think that his is most seen on very large pellet sizes used for hunting. For a goose gun, I would look into longer cones. For target-sized shot, I think that the benefits of coning are like the benefits of porting. It works in theory, but the big question is whether it works enough to notice in the real world. Since your Browning bore isn’t chromed, you really don’t have too much to lose if you want to experiment. Ask Briley what they think and why they think it. Get specific test results. I’d love to hear what they say.

One downside to long cones that no one (except me) discusses is that chance that they will produce “bloopers”. A pal of mine lengthened the cones on a Belgian Browning to 5″ or so. He found that in cold weather and when using promotional loads, he got some off-sounding shells. The wad was failing to properly seal in the cone area. This did not occur in warm weather or with higher quality shells. I’ve tested two Berettas with the Optima Bore barrels and long cones. I had no problems, but there is that potential. A modest lengthening of the cones to 1-1/2″ or so would be a safe compromise.

Best regards,

Bruce Buck
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)

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