Why butt plates are hollow?

[thirdslow411]

So I want to add a crescent shape butt plate to a gun. I'm posting this to this group because the shape I'm looking at would probably be modified from a 'golden era' shape. (TOTW calls it that)
Question: why do some plates have a hollow area that touches only the edges of the wood- a stepped sort of shape to the plate? I'm assuming it is to lighten the metal part itself. Does that hollow area act as buffer/ cushion?? I'm wondering if it's not all ml replicas. Is it modern repo only type plates? How about like a Winchester crescent, is that hollow also? PS I'm not asking for advice on a Winchester... wondering if it is chronologically still in later guns also.
I'm interested in discussion not just,"buy a buttplate and make it fit."

 

[bubba.50]

Pure speculation on my part but, two thoughts come to mind. One is, hollow is lighter. The other is, every two or three plates & you've saved enough metal to make another.

 

[necchi]

why do some plates have a hollow area that touches only the edges of the wood-

Basically,, it makes it easier to inlet to the wood and finished surface, allowing for the installer to do minor filing if necessary.(but he shouldn't have to file the plate much, only inlet it to the wood)
I find butt plate install and finish to be the biggest PITA for a beginner in-leter,,

 

[Obi-Wan Cannoli]

This is sheer speculation on my part, but I wonder if the shape also makes it more conducive to casting?

 

[Phil Coffins]

The hollow uses less metal and is lighter. The first step in doing a good inlet is to file the edges flat and square and file the finial shape to the part. Iron butt plates were often made by forging the top and back parts then braising or riveting them together. That would be more difficult to do as a solid. All this has no effect as a buffer or absorbing recoil. All the old guns and most new ones are still made that way. The only exception I can think of is a shuzen rifle, the heavy hooked butt plate are solid.

 

[Zonie]

This is sheer speculation on my part, but I wonder if the shape also makes it more conducive to casting?

I think this, and the idea of weight reduction are the main reasons for the hollowed out area.

Castings are less likely to have flaws in them if the thickness of the material is fairly uniform.

They are also less fussy about the location of the casting gates and risers.
The gate is the area where the liquid metal is poured into the mold. The riser is an outlet for the metal after it has filled the cavity.

For instance, if a thinner area is the area where the gate is located and it's feeding a thick area of the casting, the thin area will chill before the thick area does. This keeps metal from flowing from the gate into the thicker areas so as they shrink while cooling the casting will develop porosity or voids.

 

[Elnathan]

I know you are mostly thinking of cast plates, but if you are swaging out a brass buttplate or forging one, the slight radius in the plate virtually guarantees a hollow spot in the center. It is kind of the way the buttplate wants to be, if that makes sense.

 

[thirdslow411]

LOL Zonie- Porosity, one of the rare words that even the dumbest person in the room understands when they hear it used; I haven't seen it used since I was making foundry forms in the '90's. Thanks for the chuckle. :applause:
PS I hadn't even thought of the buttplate as a casting... you are probably most correct in gating and flow comment.

 

[Stophel]

Well, the "hollow" of the buttplate tang is to be filled with wood. It should be inlet so that it is completely supported under there (at least, well enough). The vertical butt surface can be inlet as well, so that wood fills the buttplate "cavity", and some people do. I generally only worry about the area of the lower screw to the toe. The buttplate can support itself above the screw quite fine, even though it is "hollow" in there.

You might be able to get away with sawing out a notch for the narrow tang of a stiff, investment cast steel buttplate, but try that with a wide, dead soft brass buttplate, and as you tighten the screw, watch, as it squeezes the buttplate down and springs the sides out. :wink:

If the buttplate were cast with flat surfaces underneath, it would weigh about 6 pounds. :td: