Balancing Act


Technoid:

I have a Beretta 390 that has been backbored (.735), ported and had the forcing cone lengthened. Also added a kick-eez recoil pad.

Given that the above procedures can reduce the wt (except adding the kick-eez), and shift the balance point slightly rearward, I’m considering adding a mercury recoil suppressor (C&H magazine cap model wt. 8oz).

What is you opinion on these recoil suppressors? Also, where is the ideal balance point on a shotgun?

Thanks and Regards,

Jay

Dear Jay,

The ideal balance point on the gun is what you want it to be. One of the nice things about the gas guns is that it is easy to add weight to the front as well as the back, something you have a harder time doing with an O/U.

One of the reasons that I am not a big fan of backboring the 390 is that it often makes an already light barrel too light. Backboring from .722″ to .735″ pulls 1.7 oz. That’s a lot. Then the shooter has to add a forend weight to attempt to rebalance the gun. Adding weight in one place at the forend nut never quite feels the same as adding weight all along the length of the barrel. It is a question of moment of inertia.

Still, backboring the 390 seems to be one of the favorite hobbies out there, so who am I to push my opinions in the face of the machine shops who make a ton of money selling backboring and then selling forend weights.

I personally don’t like the mercury weights on the front of the gun. The mercury “sloshes” slightly and I find it disconcerting, especially up front where there is a lot of gun movement. I have never really noticed that the mercury recoil reducers did a better job of reducing recoil than the same amount of inert lead in the same place. If you just want to add a couple of ounces back, the old solid steel forend nuts from the original Beretta A-390 will substitute for the current alloy one of the AL-390. Rich Cole should have them. Call him at 207-833-5027. If you want more solid weight to screw on the front, I believe that Briley (tel: 800-331-5718) makes one. When you call, please tell them that you were referred by http://www.ShotgunReport.

As an aside, adding weight to a gun will reduce recoil more or less, sort of, in a 1:1 ratio. If you add 5% of a gun’s weight, you will reduce free recoil by 5%. It isn’t linear, but it is in the ball park. Reducing shell load or velocity is more or less 2:1. If you lower the payload from 1-1/8 oz to 1 oz (11%), you will reduce recoil of the typical 8# gun by 19%, about 2:1.

One final thought, adding weight to the front and back of a gun is a LOT different than distributing the weight all through out the gun. It all has to do with moment of inertia. Consider a broom stick with a brick at each end. It will balance in the middle, but it will be difficult to start and stop it when swinging it. Now grind up those bricks and glue the brick dust all along the broom stick evenly. The stick will still weigh the same and balance in the same middle spot, but it will swing much, much differently and be easier to start and stop when swinging. Just a thought to remind everyone that balance point doesn’t tell the whole story.

Best regards,

Bruce Buck
The Technoid at <www.ShotgunReport.com>
(Often in error, never in doubt.)

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