doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Lengthening forcing cones....good or bad?

Many competition shooters of skeet, trap and sporting clays have forcing cones lengthened in their competition guns in an effort to improve patterning and decrease perceived recoil. Personally, I have always stayed away from this with my guns because I believe it harms value, but more importantly I feel it may reduce bridge pressure, thus allowing some gases to escape around the wad, thusly reducing a guns ability to 'shoot hard'. In pigeon shooting, the guns that have lengthened forcing cones seem to be 'feather blowers' and don't seem to kill as well as guns with tight forcing cones. I have no scientific evidence to base this on, just empirical observation. Does anyone know of any scientific evidence which proves the theory that lengthening forcing cones is a BAD idea? or, conversely a GOOD idea?

Lots of debate on this one. Here are a few articles to peruse:

RW article 1

RW article 2

If you're concerned with pressure in the sense of keeping it to a minimum (for older guns), Sherman Bell's tests showed that lengthened cones do usually result in some pressure reduction (few hundred psi) when shooting 2 3/4" shells in 2 1/2" chambers.

Lengthening of forcing cones along with overbore will give very uniform patterns. My Kolar SC has no discernible chamber and the patterns are the most uniform I have ever seen.
Conversely, felt recoil is subjective and there is no scientific evidence that supports the claims.
Removing metal from an engineering perspective on an item designed for specific pressures is not something that i would do or recommend. Many believe that the attributes of lengthening a chamber or forcing cone are worth the effort but I don't believe anyone can supply scientific evidence that it accomplishes any quantifiable change to be worth while and the safety considerations far out weigh any possible gains.
In short, I leave my field guns alone and purchase Target guns with overbore barrels and long forcing cones.-Dick

My pattern testing about 20 yrs ago confirms to me what Dick said. Patterns are better with long cones. The longer, smoother the transition, the better the pattern got in my tests. I tested three cone lengths. A 4" long cone was the longest I tested and it produced consistantly the best patterns.

PS, I would not modify a vintage gun with long cones. The improvement is not worth the devaluation or the cost.

For a serious competitor any mod that "seems", he "believes", or he "feels" enhances performance is a good idea. Whether it's been proven is secondary to what it contributes to the supreme confidence that is so helpful to winning.

FWIW, a theory is just a theory. There may be evidence to support it, but if it hasn't been proven and widely accepted as fact, it's still a theory. Seems intuitive that any scientifically proven improvements to shotgun barrel configuration would be embraced my the makers and users and quickly become SOP. There is ample reading to suggest those barrel mods are an improvement. Most of it is written by people wishing to sell you those mods. You'll have to dig harder to find evidence they don't work. You can't prove a negative...absence of evidence is not evidence of absence. In short, it's not scientific evidence, but acceptance in the public realm that will convince people (or not) of their worth. Browning has been at the forefront of providing competitors with what they thought they needed but, more important, what they wanted. It surely didn't hurt their sales temporarily to increase bore diameters from .729 to .745, lengthen forcing cones and port the muzzles.

Somehow, the 500 yr old maker, Beretta, didn't get the memo. They reluctantly enlarged the bore from .721 to a whopping .733 and called it the "optima bore." Otherwise, they seem to have ridden out the fashion wave for the last 20 years as I've never seen a factory ported Beretta O/U. Meanwhile, many shooters now consider ported barrels to be an absolute deal breaker on a used gun.

I "believe" longer cones than those of 80 years ago are useful for alleviating some of the very slight concern I have for shooting modern factory shells with plastic wads in my Foxes. Anyway, I "feel" it can't hurt and 3 of my Foxes that shoot thousands of modern target loads per year have lengthened cones. Two of my Foxes are bird guns and part of the appeal is shooting and hunting only with factory paper shells loaded with fiber wads in the 1950's. They have the original short cones.

If I were shooting loads with fiber wads in competition I would not want lengthened forcing cones. Gough Thomas Garwood contended that the long forcing cones sometimes allowed gas to escape around the (fiber) wad and weld the shot together.

I wouldn't worry about lengthened forcing cones if I were shooting modern plastic wads with shotcups.

Best,

Mike

Ever seen a pair of forcing "steps"? Sharp, abrupt halt of the chamber area, typically on older guns, likely intended for use with roll crimped, paper rounds.

I've had one set of those worked on. Both barrels were choked full and full, and the choke was let out as well. I probably wouldn't do it to a more modern gun, but, the old girl throws very uniform hunting patterns today, versus the dense, splotchy patterns previous. It works well with either plastic wads or fiber wads, from my limited testing.


Best,
Ted

Beretta did get the memo. I have a Brit market 682 "Sporting" that has factory screw-ins and ports. I got it NIB so I'm pretty sure the factory did the ports. I don't recall that Perazzi did any ports but they are into bigger bores and have had long cones prolly before anyone noticed. That "shoot harder" crap is always fun to hear. What a yuk!

As to the forcing cones - The initial pressure impulse has to be lower and resultant shot deformation lower with longer cones. Is it lower enough to make a difference? How long is long enough? there were "chamberless" guns a century ago. If that is so great why do we still have forcing cones and 12ga bores? I dunno. But I do know that Julius Del George had a Pigeon factory engraved M12 that flat kicked like a MFer until he noticed that it had no visible cone at all. So he had that taken care of and guess what - his $200 purchase instantly increased several fold.

However opening the cones in old gun has a dangerous potential - the barrel thickness may be inadequate to tolerate that bigger ID that the long cone creates. If it gets sent for re-proof it could easily come back in a couple pieces.

Like most of the BS that floats on this and other gun sites, empirical evidence is non-existent for forcing cones, big bores, ports, and a multitude of other "topics of interest". Those are all things that, to my shame, I have participated in with past guns. Abstinence, just like the Repugnicans say, is the best policy and one that I presently endorse.
For guns anyway.

Dr.WtS

I was asked this question some years ago when they became the "in thing" in the UK. I listened to both sides of the argument,I spoke to shooters and to the Proof house who had carried out some unofficial tests and came to a simple conclusion. I dont care what any one say's but at �35 a time I'd do them all day .