Why doesn't shotgun porting reduce muzzle rise?

S

Super-Dave

New member
Over all everyone on this site seems to agree that porting a shotgun barrel does nothing for the muzzle rise and is just a gimmick.

My question is how come it does not work? It works for pistols and rifles and the theory seems sound enough that it should work on shotguns as well.


How come it does not work?
 
It does reduce muzzle rise a little. It does not work as well as with handguns and rifles because the gas pressure is much lower.
 
Ports or muzzle brakes work by taking the propellent gasses out of the recoil equation by redirecting them up or backwards.

With high power rifles, the powder gasses are a significant percentage of the total stuff that comes out of the barrel. In the more extreme varmint calibers that approach 4000 fps, the gunpowder actually begins to outweigh the bullet, by directing these gasses backward, they can nearly cancel the reaction caused by accelerating the bullet. It may even be possible to overcancel and cause the gun to recoil forward.

With shotgun loads, you are accelerating about 500 or so grains of shot using only 18 to 25 grains of powder so a muzzle brake on a shotgun has much less effect than it does on a rifle.
Ditto with rifles that shoot heavy bullets at shotgun velocities like the .45-70, the bullet so outweighs the powder charge that eliminating the powder gasses' recoil contribution only makes a small difference.
 
Vent ports (compensator) at the top of the barrel do very little to reduce muzzle lift. There is not enough "retro-jet" thrust.

Whereas a muzzle brake has a chamber with a flat wall that the propellant gases directly impinge. The impingement thrust "pulls" the the gun forward, reducing recoil and muzzle lift. After striking the flat surface(s) the gases can vent in any direction, sideways or upwards. Venting upward does not assist in reducing muzzle lift.
 
With proper porting gases are vented up and rearward. It does reduce slightly muzzle lift in a shotgun. If someone tells you different they don't know simple physics.
 
works for me.

I've made several modifications to my 32 in. Hi rib Citori trap gun, it's used mainly for bunker trap and live bird shoots.

I ported the under barrel, just before the screw in chokes, (8 .060" holes .375" O/C) and noted about the same recoil reduction as lengthening the forcing cones provided, a side benefit was the total stop of muzzle rise with 1 OZ. loads.

Really helped my doubles scores and greatly reduced the fatigue factor across the board.
 
I disagree - I think porting makes a big difference / and it works very well. I think it reduces muzzle jump at least 25 - 50 %.

All 5 of my target guns in 12ga and 20ga are ported / even my semi-auto Benelli's are ported in both 12 and 20ga - and its a big improvement in muzzle jump vs some of my older O/U's that don't have the porting. My O/U's are all Brownings / and the ports are angled / but I don't think that's the issue.
 
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I know adding some weight to the front will reduce muzzle climb. With some more weight on the other end for balance , then felt recoil is reduced to where you will feel the difference.

Check out different types of shotguns .Some types weigh more than others.....less felt recoil.
trap...................wt.
skeet.................wt.
target................wt.
hunting...............wt.
home defence......wt.
 
Super-Dave, I beg to differ with your initial premise, there is no consensus on barrel porting at this forum. At best, several of us have agreed to disagree. IMHO, porting is not a gimmick, it's applied physics.

Here's a [SIZE=+1]+ 1[/SIZE] to BigJimP's response.

Go out and shoot 1000 pairs of comp 12-ga doubles without ports and then do again with a ported gun. Then you'll have an intimate understanding of muzzle rise. Porting may not turn a B-class shooter into an overnight Double-A; but, it let's you get on the second target a little quicker.

Another AA Skeet shooter wanted to know why I was able to shoot my doubles quicker than he could. The quicker you can shoot your second shot in doubles, the more time you have to adjust, if something goes wrong, before the target goes out of bounds. He knew I been taking special effort with my doubles and wanted to know if would share some of what I'd learned. We took a Skeet field for the afternoon for some practice. I followed the basics my mentor had passed on to me: Take the first target at the same spot you'll be be breaking the second one and minimize your gun movement. Hold out as far a possible before calling for the first target. See the lead with the first target, shoot, keep your face on the gun while you watch the first target break, acquire the second target, see the lead, shoot and follow thru. There's less than a second between shots. The part about keeping your head on the stock and seeing the first target break before you make your move on the second one is very important and takes less that 1/10-second. I shared everything I could with my buddy and he was shooting respectable pairs by the end of the day. I thought he'd be satisfied with his progress. He'd adapted well to the new timing and revised hold and break points, but he was unhappy because he wasn't faster. What I didn't point out at the time: He was shooting a K-80 with un-ported barrels and I was using a P-Mirage with ported barrels.
 
Well, of course porting is effective in a shotgun. The effect is just not as dramatic as it is with high powered rifles.

The gasses that push the bullet out of the barrel weigh exactly as much as the gunpowder that generated these gasses. A 12 gauge one ounce (437.5 grains) of shot propelled by 18 grains of Red Dot means that only 18 grains of gasses are available to redirect backwards to cancel the recoil.

Compare that to a .300 Weatherby Magnum loaded with a 115 grain bullet propelled by 90 grains of powder. The powder nearly weighs as much as the bullet and you can almost make the gun recoil-less. Just be sure to wear earplugs!!
 
I have two 18" barrels for my Remington 870, both are factory barrels modified by Hans Vang (Vang Comp). Both have had their forcing cones back bored. One has vent ports along the top of the barrel, the other doesn't. There is no difference in muzzle lift between the barrel with the compensator vent ports and the barrel without.
 
I actually think it does. The thing is, it's hard to notice. While your gun (usually 12 gauge) is going bang, I am gonna blink. I am also so busy looking for my second target and bringing the gun toward the target that I really don't notice what the muzzle is doing.
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.
 
For muzzle rise, NOT to be confused with recoil reduction, porting MIGT have some minor value. I see NO value in porting the top barrel, a la Browning, as there is no third shot to acquire.

I have the utmost respect for Zippy and Jim, but I really don't place much value in porting - even for targets. If you THINK it works, then it works, whether true or not. The few studies and high-speed photography I have seen do not, IMO, show a discernible adjustment in muzzle rise.

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.............

Again, if YOU think it works, go for it. If I find a gun I want that has it, I will not NOT buy it because of the porting, but I will never spend extra $$$$ to have it done..
 
oneounceload said:
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………….
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My P-MX(SC)3 came with factory "Tula'' port/choke system -- a very nice little shooter, and the flat sides provide a canvas for the engraver's art. The heavier P-Mirage and Mirage based ones came without factory ported barrels.

It should be noted that my friend, oneounceload, and I have had been on opposite sides of the muzzle rise debate from the get go. However, we do agree that: porting does reduce recoil and the recoil reduction is a greater factor in porting that any reduction of muzzle rise.
 
I see NO value in porting the top barrel, a la Browning, as there is no third shot to acquire.
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There may be a sporting clays station somewhere where you might elect to shoot the top barrel first.
 
Porting both barrels on an o/u is usually done to give the option to shoot either barrel first. Some folks would rather just shoot the other barrel than change chokes on a clays course.
 
And yet the porting on the top barrel is not the same as the one on the bottom barrel. I shoot sporting every week - I do not change chokes, but, as required, I may change which barrel. Since I only shoot light target loads in these guns, muzzle rise is minimal at best.

Seems funny to me that field guns typically do not come with porting, yet the guns are lighter, you're usually shooting heavier loads - which would mean more muzzle rise. If there was ever an argument for porting, it would be there.

But that's OK, these discussions are mild and kinda fun.

And sorry, Zippy, I'll give you a smidgen on porting for muzzle rise, but I won't give you anything about it reducing recoil - Heavy gun plus light load in a properly fitted gun makes that happen!....;)
 
A few years ago I experimented with a Beretta 390 and two barrels, one was ported while the other wasn't. In blind tests between the two I could not tell a difference in either recoil or muzzle rise. They seemed exactly the same to me.
 
Depending on where the ports are located from the muzzle (for example, a distance ranging between 3.5" - 7"), with a shotshell that achieves 1200 fps muzzle velocity, the vent port "retro-jet nozzles" are "thrusting" for a period of time between 250-500 MICROseconds (1/4000th - 1/8000th second).

Increased muzzle velocity decreases "thrust" time.

Decreased distance between the vent ports and the muzzle also decreases "thrust" time.

Food for thought.
 
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