doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Will this work...Manson gauge modification

Like all good alcoholics, my desire to find rock bottom is a necessity. I have been thinking about drilling a hole in the ball of my manson gauge, tapping and then inserting a screw such that the tip will align with the gauge tip. Im thinking that will allow me to measure the rock bottom 9f a pit inside the bore. Thoughts?

Pits are not always straight. If the pit takes a turn to one side before it bottoms out you will only be measuring to the bend, not the entire pit. Pits are a b----- to measure and need to be removed if possible, but do not forget some pits are just benign, some like a cancer and some are hopeless. It is worse with twist or Damascus barrels. The pit will follow the pathway of least resistance and may spread into the layers of metal at different rates and different depths. Each pit needs to be evaluated on its own merits and it is still an educated guess in many cases.

I don't normally do this, but...Are there any visible examples of the kind of thing you mention? Using your example, I suppose it is also possible that a rust pit the size of a pin prick might turn in to an unseen grand canyon inside the barrel walls. That would be impossible to see unless you were trying to xray all of your barrels, and even then you might not be able to see it. It is the sort of post I would expect to read on Shotgun World.

Your opinion leads me to think that perhaps a slingshot would be my best bet, as even modern guns have catastrophic failures. At any rate, allowing for the fear of termite tunnel rust pits should remove any and all vintage guns from your consideration.

The screw you are speaking of putting on you Manson gauge is the same type of setup that the Hosford gauge uses. It will not tell you everything by way of pitting depth, but will allow the gauge to show more than the standard Manson setup does.

Slingshots are very dangerous when the elastic breaks and smacks back into your hand. That is why I went to guns.

Pits occur a lot like cavities in teeth. A small surface defect starts, material below the surface can be lost. Never a straight line like a drilled hole. Sometimes you get a cone shape defect which is larger than the pinpoint on the surface sometimes it is wider at the top than at the bottom. With the pinpoint at the top defect the surface gets very weak and then fails to expose a larger than expected pit. I have seen pits that were smaller at the deepest part and some which were larger. Rust will follow the pathway of least resistance so in internal defect or difference in metal will change the shape of the defect. I have seen a set of twist barrels with a defect that was between two layers and was at an angle to the bore. Pits can be weird like that.

So given that you screw will give you more information use it as another tool to evaluate the pit. Just take it with a grain of salt. Metal defects like pits are more about location than depth sometimes. A ported barrel, which is just a pit that was through and through is safe at 28" but not one I want to risk closer to my hand or face.

I guess we would use a soft screw to avoid scratching the bore.

Would a brass screw be safe to use, and maybe polish the point a bit?