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Old January 26, 2010, 08:08 PM   #26
zippy13
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Once again, a porting question has evoked many opinions, questions, and comments. I'll try to respond to some that have been directed my way.

PJR
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zippy13
Come on, now, let's play fair... a Beretta 390 is not the gun for your test. Let's start with something that has some significant recoil. The B-390 starts out as one of the lowest recoiling stick guns around, and you wonder why you couldn't detect the difference with a ported barrel. The difference is going to be very subtle in that gun.
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zippy13
IMHO, porting is not a gimmick, it's applied physics.
Zippy, these two posts by you are contradictory. If it's applied physics than the physics should apply equally regardless of the gun.
The physics of a one ounce load versus a 1-1/8 load are noticeable in a 390. If the porting difference is so "subtle" that I couldn't notice it then why bother having the work done.
Your totally correct, the laws of physics apply equally to all guns. I was implying that since your B-390 is already a soft shooter any reduction in recoil/lift for a given load will be much less noticeable in a B-390 than a harder kicking stick gun.

I don't recalling saying that porting reduces recoil/lift on the level of changing between 1-oz and 1 1/8-oz loads. Why bother to have the work done it the effect is so subtle you don't notice it? As I said earlier, "Perhaps you might not be aware of the difference; but, at the end of the year your average may be a little higher with the ported barrel." Many comp shooters are willing to bear the expense of modifications that improve their scores. You may or may not be in this camp and porting may or may not increase your scores even if you're unaware of the slight differences while you're shooting.

oneounceload
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It seems funny that P guns, Zippy's favorite, do not come with porting, yet they are THE choices for some of the fastest shotgun games known - bunker and pigeons………….
I recall my first time at a bunker, the only thing I had without fixed Skeet chokes was my B-682x trap combo that has been ported. When I put it in the in bunker's rack, the ref commented, "That's okay for practice, but you can't shoot it matches." I gave him a questioning gesture, and he went on to explain, ported barrels weren't allowed in the international events because they gave the shooter an unfair advantage. 1-oz, perhaps, it they weren't allowed in international events, that's why you don't see too many factory ported P-guns. I was lead to believe, the effectiveness of the Tula-style ported guns led to the prohibition.

BigJimP
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But recoil reduction isn't a factor in "porting" in my opinion / just muzzle rise... In my opinion, there is no significant reduction in recoil from "porting".
lambertsteeth
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I actually think it does. The thing is, it's hard to notice… If my guns didn't already have this feature, I wouldn't spend my money to have it done.
I've shot my Benellis (ported) with the ports taped up. I noticed a very small difference. It was minimal.

I absolutely agree that porting does not reduce recoil.
Thus far, I've avoided the physics of the aspect of the question; but, now, I gotta bring in it a little. Those new to shooting may not realize that recoil is based upon the Newtonian physics of action and equal and opposite reaction. Everything that comes out of the muzzle (shot, wadding, gas and powder ash (assuming a complete burn) contributes to the total energy package. How the gun reacts (free recoil) to the energy is simple mechanics and can be expressed in terms of masses, velocities and forces. How the gun's recoil is resisted by your body is much more complicated because so many variables are introduced; but, the experience is known as perceived recoil, or kick. The feeling of kick is your body's reaction the the maximum unit stress (force/area) applied at a given instant in time.

There are only two ways to reduce kick:
1. Change the way the body reacts to the gun's recoil (buffer the reaction an/or increase the contact area. This is why a good fitting stock in important to reducing kick.)
2. Reduce the gun's free recoil (make it heavier and/or reduce the energy).

If you reduce the energy going out the front of the gun, you'll reduce the Newtonian reaction (lower recoil and less kick). Venting (redirecting) some of that energy (in the form of pressurized gasses)c before it is allowed to exit the muzzle, by porting the barrel, will reduce the recoil. Just because you don't like it, or the reduction isn't significant, doesn't mean that it doesn't happen.

Okay, now we know why porting reduces kick. Next up, what causes barrel hop, or muzzle rise? It's the Newtonian result of the recoiling barrel's eccentricity to the reaction's centroid. Traditional gun design has the barrel above (eccentric to) the center of the resistance to recoil. This "offset" in action and the opposite reaction is a force pair known as a couple and it generates and rotation about an axis perpendicular to the plane containing them. You may not have studied mechanics, but you're familiar with the smack in the face in addition to the shoulder reaction.

Assault weapon designers found a simple solution - just minimize the eccentricity and hop is minimized, too. This results in a gun that stays on target during auto fire, but looks like a broom stick. While adding the ergonomic necessities. The mass should be distributed evenly above and below the centerline. A low mass detached grip and hollow straight stock with elevated sights are an answer. Because of physics, modern assault weapons appear similar. But, we're taking about shotguns, not designing assault weapons. When selecting a shotgun, try to get one that is a "flat" as possible. Ideally, the bore should line up with the center of the butt plate. Most likely you won't find a shotgun like that; but, given the choice, shy away from the taller gun designs. This one reason you'll see trap guns with very high sighting ribs, they are trying to get the barrel as low as possible to reduce the eccentricity. One reason BigJimP likes those high stocked Brownings, they have less hop.

Let's say you've reduced your loads, minimized the eccentricity and ported your barrels but, your gun still hops. Consider directed porting, or the jet effect. There's more than one way to port a barrel. One of my P-gun's factory Tula system has side vents that resemble sharks gills. They vent the gasses left and right, and any reduction in hop is purely because of reduced recoil. My other guns have locally done directed porting. These have a series of holes along the upper portion of the barrel. These ports are supposed to vent the gasses in such a manner as to provide a jet effect. The force of the jets acts to resist the couple's rotational force. When lambertsteeth says that he can tape over ports to simulate an un-ported barrel, it makes me wonder why the jet action doesn't quickly destroy the tape. I question the jet action with the lower pressures typically associated with shotguns.

Let's assume directed porting and their jets work great, they are still venting energy from the system. So, there's no way they can resist hop without reducing recoil. What we see in handguns and rifles that works at higher pressures, that I've not seen in shotguns, is a system that involves an angled thrust block muzzle device that directs the gasses upward. I still say: porting does reduce recoil and the recoil reduction is a greater factor in porting that any reduction of muzzle rise. If I was to do it again, I probably opt for the old Tula vents over the directed porting. You can draw your own conclusions.
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Old January 26, 2010, 08:41 PM   #27
oneounceload
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Zippy - lots of thought and information in that retort. Some I agree with, some I don't.

As to your two ways to reduce - IMO, only one actually decreases ACTUAL recoil - heavy gun plus light load. No argument about proper gun fit - but that affects felt, not actual, recoil. Just like a gas-operated gun, felt/perceived recoil can be offset by gas guns, proper fit, etc. However, the basic physics equation has nothing to do with that. Most shotgun loads' burns are complete in the first 14" or so of the barrel, thus the recoil and reactions are accomplished in that time frame - which is before any barrel porting comes into play. As I mentioned earlier, porting may have some effect on muzzle rise (depending on the load, weight of the gun, etc...), but as far as actual recoil goes, that has already happened by the time the ejecta leaves the barrel - which allows top shooters to shoot very rapidly (a la Tom Knapp).

The main thing is this - as with changing chokes - if a person believes it works, then it works, because the mental game is 90% of this anyway. I have watched folks shoot 1400fps loads and others shoot 1100fps loads.....and scores are about the same - same with loadings; some go for 1-1/8, others 7/8......whatever YOU believe works for you, then that is what will work for you, regardless of internet opinions or Newton.

Porting aside, it is interesting that when certain disciplines reduced allowable loads to 7/8, scores went up - porting had nothing to do with it.

Zippy, my friend, I guess we'll agree to disagree on this one......
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Old January 26, 2010, 09:46 PM   #28
zippy13
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Originally Posted by oneounceload
whatever YOU believe works for you, then that is what will work for you, regardless of internet opinions or Newton.
1-oz, my friend, here's a ditto for that. Anyone who's been in the shooting sports, to any serious degree, will agree: The overwhelming majority of the game is between your ears.

A few years after he'd won the World shoot, I watched Alan Clark work his way thru a field of other 100-straight shooters to win a sudden death shoot-off. At each station, as they got on line to shoot their pair, Al went thru some weird looking finger motions with his hand at his side. It looked like he was trying to flick off a snot ball. Hall of Fame shooter Brian Holt was next to me along the spectators' fence. I nodded my head towards Al and made a flicking motion for Brian to see. His response was that it was Al's way of clearing his head. Al's hand motion was a symbolic wadding up of his list of bad thoughts and throwing it away.
Ya gotta go with what works for you.
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Old January 27, 2010, 12:14 PM   #29
BigJimP
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A honorable discussion - with some disagreement - among Gentlemen...nicely done guys.
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Old January 27, 2010, 08:51 PM   #30
oneounceload
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BigJim - your comments are always welcome as usual.

IMO, too many folks rely on gadgets and gizmos thinking they help their scores. Whether they actually do or not, it is irrelavent, because the mental aspect is 90% or better of the game.

Example - one of the guys I shoot with truly believes on one station at our favorite sporting course that he NEEDS to shoot a thread and skeet combo in order to hit the targets. He runs the station with that combo; but then, so do I using a IC and M combo. BUT, for HIM, with his mental picture, he felt he NEEDED to do that. If it works, then it works................if that means an extra target, so be it..........
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