doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Back-boring tubes to lighten them?

I realize that the law of diminishing returns applies here as well, but assuming it can be done with a good margin of safety...how much of a weight savings can one expect on a set of 28-inch 20-bore tubes? Also, on a mod/full choked gun, by opening the chokes significantly (to like...skeet1 and light mod?) what sort of weight savings could one expect? Anybody care to speculate?

Lloyd,
you left out the key info as to how much you would like to open the bores. Here is an online calculator that may help.

http://servicesteel.com/weight-per-foot-of-steel-tube/

In one of the Sherman Bell articles, didn't they hog out a pair of LC Smith barrels and shave something like 9 ounces off of them?

Cool calculator Steve, thank you for that! I guess I'd need to confirm what the units of measurement were to use it? (Thousandths and ounces?) I do know from working with English guns that the constant honing of pits over many decades and owners can produce some frightfully light tubes. I certainly don't want to go that far. This is also an older American 20, so the pressures involved would make me need a substantial margin to be comfortable. I am also considering lengthening the forcing cones (which might already happen by back-boring it in the first place?). I'll be working with a very competent and safe 'smith (Terry Nicholson) so I'd expect that he'll keep me honest.

Dan, I must have missed that article. Nine ounces off of even a 3 1/2 lb set of tubes is pretty substantial. Like what? 20%? Sounds like a good way to make #3 barrels on a Fox weigh more like #4s.

20 gauge = .53 oz per foot of tube when ID is increased by .010"
Therefore maybe @2oz on a pair of 28" barrels/ .010"increase.

Some few ounces, for practical purposes. If you want a lighter gun, this is not a very productive place to start. If you are intending to move the balance closer to the trigger and/or lower swing efforts, you may get some results. Note that the muzzle is the farthest point from the muzzle, so metal removed in the muzzle zone will have much more effect on balance and swing effort than will weight removed near the balance point. Calculating the weight removed is not mathmatically difficult, but it can be very complex. If you want to run some examples, post back and do the math for you.

DDA

Rocketman: Thank you. I need to get the gun in hand first and then mic the barrels to see what I have to work with. Once I have a sense of what is reasonably possible, I may be talking to you. Weight and balance are both goals here and it would be nice to know how I might want to approach them instead of.... just blindly removing material. This should be an interesting project.

According to the summary of "finding out for myself Part VIII", they removed over 1/2 pound from a pair of LC Smith barrels

http://www.shotgunworld.com/bbs/viewtopic.php?f=13&t=259371&start=40

I also have a hammer gun that was significantly lightened by honing from 12 gauge to 10 gauge dimensions while retaining ample wall thickness. Don't know what the original weighed, but it must have been a similar weight reduction to the LC Smith described above.

I guess I don't understand the quest to achieve the lowest possible weight in a shotgun. A seven pound gun is not heavy. That to me is about where they should be.

A 6 lb. 12 ga. can be a delight, especially when you are doing more walking than shooting. But I've noticed that if you carry and shoot a 9 1/2 lb. gun for awhile, when you switch to a 7 lb. gun, it will seem light as a feather and swing like a wand.

Lloyd, you mention that your proposed lightening project is an old American 20 ga. gun. I have two Ithaca Flues 20 ga., and a 16 ga. Flues that I bought as parts guns. All three have barrels that are ruptured in the forearm region. I have no idea what caused the ruptures, but the barrels are typically pretty thin in that area on a Flues. I doubt any of these had ever been honed, and none had pitting. You might do better to just keep shopping until you find something safe that was originally built as a light upland game gun.