I’m new to changing choke tubes having just bought a Beretta 391. I always had fixed choked guns before. I remember recently you had a post regarding a change in point of impact depending on how tight the choke tube was in. The manual doesn’t give any info in this regard. Just how much can/should you crank on a choke tube. Are there choke tube torque wrenches available?
I’d like to deal with this one before I cause further confusion. Your question is an excellent one and, as is usual in cases like this, stems from me not being quite as crystal clear as I ought to be. I’ve always preferred to work behind a smoke screen, but sometimes I go too far.
I believe that when I referred to the tightness of a choke tube affecting point of impact, I was referring to the indexing of specially made eccentric choke tubes. This is a custom choke situation and is not applicable to normal guns. Here’s what happens: Every now and then a gun’s barrel(s) don’t shoot where you want them to. Commonly this is with an O/U that doesn’t shoot both barrels to the same place, but it can also occur with a single barrel gun that doesn’t print where the owner wants it to when he has a certain rib picture. To cure this, it is possible to have eccentric choke tubes custom made for the gun if the gun was originally built with choke tubes. This is involved, but Briley (Briley Manufacturing, 1230 Lumpkin, Houston, TX 77043, tel: 800-331-5718, http://www.briley.com) can get it done for you. An eccentric choke tube will alter the point of impact of that barrel to where you want it.
Eccentric choke tubes have a couple of drawbacks. They are relatively expensive. They work only in the barrel they were designed to work in. And they have to be properly indexed when being inserted. Obviously, if they aren’t put in with the same pressure and torque each time, they won’t line up right and they will not change the point of impact as they are supposed to. My guess is that this is what your question of changing point of impact and tightening choke tubes is all about.
The above situation is the exception. With standard choke tubes and normally functioning barrels, how tight you snug in your choke tubes will have nothing to do with your point of impact. Don’t worry about it. If the choke tube was bored true and the barrel was made and threaded correctly (as it is in most cases), how hard you seat your choke tube has no effect on your point of impact.
BUT—- Here’s my chance to talk about how hard you should snug in your choke tubes. Soapbox, please. I STRONGLY recommend that my SR readers use a wrench to seat their choke tubes. I tighten my chokes snugly with a wrench. Not forza bruta hogged-down snug, but I definitely want to feel a little resistance. I use a wrench because I don’t like my chokes coming loose when I shoot. I occasionally use extended chokes and found that when I simply finger-tightened them, there was a greater chance that they would start to loosen up and start to unscrew while I was shooting.
It’s important that your chokes remain solidly in place when you shoot. If they start to come loose, carbon bearing gasses force their way underneath the choke threads. This does two things. It makes a mess that you have to clean out eventually. It also deposits carbon between the choke and the barrel threads. If you fail to clean this off, sooner or later you can deposit enough carbon to actually raise the skirt of a choke tube into the bore. This may take a while and many choke changes, but it has happened. The original Perazzi MT-6 screw chokes had this problem. Once the rear skirt of that choke gets pushed up into the bore to any significant degree, just as sure as the Lord made little green apples, you’re gonna shoot that choke out.
That’s why I snug all my chokes down with a wrench. It’s just a little ounce of prevention and a touch of peace of mind. I won’t say that finger-tightening won’t work. It does for many people. But it’s an extra chance and forces you to always be checking the choke to see if it has come loose. Stick it in properly with a wrench and you should be in fine shape until you decide to change the choke or remove them when you clean the barrels.
As to the exact amount of torque to be applied, I don’t know. I use about as much pressure as I do to put the metal top back on a bottle of chili sauce. I use a nice twist until it is well seated, but nothing extravagant. My wife just barely puts screw tops on.. When I grab the jar out of the fridge and shake it, it occasionally comes off with predictable results. She refuses to use a wrench on the chili sauce cap, but I’m working on it.
I’ve always used the Royal Wrench. I think that they are the best by far. They work like an old-fashioned bottle stopper. You push them in, align the teeth in the choke notches, and push the lever down so it’s at right angles to the barrel. Now you can spin the choke on or off with one finger. I’ve found it far faster and more convenient than using my fingers only on extended chokes. And, most importantly, it puts the choke in securely.
So that’s it on snugging chokes down and changing point of impact. More than you ever wanted to know, but then again I get paid by the word. Yeah, right…
The Technoid writing for Shotgun Report, LLC
(Often in error. Never in doubt.)