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January 26, 2010, 08:08 PM | #26 | ||||||
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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 Quote:
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 Quote:
BigJimP Quote:
Quote:
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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January 26, 2010, 08:41 PM | #27 |
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Join Date: April 18, 2008
Location: N. Central Florida
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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...... |
January 26, 2010, 09:46 PM | #28 | |
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Join Date: August 23, 2008
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Quote:
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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January 27, 2010, 12:14 PM | #29 |
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A honorable discussion - with some disagreement - among Gentlemen...nicely done guys.
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January 27, 2010, 08:51 PM | #30 |
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Join Date: April 18, 2008
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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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