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Underlug hole elongation...

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Not being sarcastic here at all. I just need to understand this better. How can the stock move when pinned thru an elongated hole when the tang is bolted/screwed into the stock? The breech plug/tang is threaded into the barrel. What am I missing? Thanks in advance.
The tang screw locks the breech of the gun to the stock. As the stock swells and shrinks over time that 36” to 40”+ of stock in front of the breech and under and around the barrel needs to be allowed to move. The steel barrel is not going to move. The slots allow the stock forearm (and the pins held in the stock) to move.

Question for you. Guessing you live in a house and have over time noticed doors sticking, walls cracking, screws or nails popping and woodwork separating for example. What do you think causes that to happen?
 
The tang screw locks the breech of the gun to the stock. As the stock swells and shrinks over time that 36” to 40”+ of stock in front of the breech and under and around the barrel needs to be allowed to move. The steel barrel is not going to move. The slots allow the stock forearm (and the pins held in the stock) to move.

Question for you. Guessing you live in a house and have over time noticed doors sticking, walls cracking, screws or nails popping and woodwork separating for example. What do you think causes that to happen?
SDSmlf has it exactly correct, many moons ago (Indian lingo) I lived in a house with no air conditioning and the hot humid summers would cause wood to swell over a few months, doors would stick etc. when winter hit the furnace would remove all the humidity, after a few months the wood would shrink again.

For the newbies, this does not happen rapidly.
 
SDSmlf has it exactly correct, many moons ago (Indian lingo) I lived in a house with no air conditioning and the hot humid summers would cause wood to swell over a few months, doors would stick etc. when winter hit the furnace would remove all the humidity, after a few months the wood would shrink again.

For the newbies, this does not happen rapidly.

Or if you don’t shoot in the rain, you may never notice it.

the only gun i use in the rain or damp conditions is a 1766 charleville and an 1816 musket.
 
Or if you don’t shoot in the rain, you may never notice it.
Or never go outside or travel anywhere with your gun. Per the weather channel, current relative humidity in my little corner of North Carolina is 30%. Others times of the year it can be above 90% for days. Ever go on hunting trip? One of the first things suggested when you get to your destination is to make sure your gun’s zero hasn’t changed. Or do you hope you may never notice it?
 
Or never go outside or travel anywhere with your gun. Per the weather channel, current relative humidity in my little corner of North Carolina is 30%. Others times of the year it can be above 90% for days. Ever go on hunting trip? One of the first things suggested when you get to your destination is to make sure your gun’s zero hasn’t changed. Or do you hope you may never notice it?


Yes, and yes, and I’ve never noticed anything.

I have been caught in poor weather, i just choose not to take my good stuff out if I already know before hand the weather is poor.

I will say that I also do not own any rifles with cross grained wood, such as curly maple. I prefer straight grained walnut, English and American. I also inlet the lugs with more space, mine are not overly tight.

And i live in the very damp weather.
 
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I have read in Shumway’s books that some old guns he examined with no slots in their tenons had fore-stocks pulled apart by up to an 1/8”. There must have been a lot of recoil and pressures from the barrel back in the day? Or maybe the stock wood expanded and contracted over time?

I’ve disassembled original guns 250-300 years old, i have original barrels and guns in my collection, none of their underlugs are slotted to prevent the gun from breaking, they’re just drilled. The lugs are cut through the rammer channels.

Bear in mind these are military guns mostly, But I’ve just never seen it before, on any originals, that i’ve viewed or have in my collection. I’m sure they’re are some specimens out there that exist. Original guns I’ve been given the opportunity to view had the lugs tight too. This fact has also been brought up by some very notable gun builders on this site, search it out if you need to.

The only thing i can say i do that might be different is i inlet my under lugs with more space forward and aft in the forestock, i also cut them through to the rammer channel, they’re visible if you remove the rammer.
 
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Back in the 1970's , barrel harmonics tests were done by someone writing an article in Muzzle Blasts Magazine. It was determined , that a tightly held in place longrifle gunbarrel was affected by changes in the barrel's original sight in work. One of the determinations was , that when fired barrels stretch , and rebound back longitudinally. If this isn't consistent shot to shot , inaccuracy can result. dunno?
 
Not being sarcastic here at all. I just need to understand this better. How can the stock move when pinned thru a elongated hole when the tang is bolted/screwed into the stock? The breech plug/tang is threaded into the barrel. What am I missing? Thanks in advance.
There's plenty of wood forward of the tang bolt that can contract and expand.
 
Not being sarcastic here at all. I just need to understand this better. How can the stock move when pinned thru a elongated hole when the tang is bolted/screwed into the stock? The breech plug/tang is threaded into the barrel. What am I missing? Thanks in advance.
The slight swelling of the stock due to humidity is what does it.
Ohio Rusty ><>
 
Not being sarcastic here at all. I just need to understand this better. How can the stock move when pinned thru an elongated hole when the tang is bolted/screwed into the stock? The breech plug/tang is threaded into the barrel. What am I missing? Thanks in advance.
Wood moves with a cross grain more so than with length. Moisture, Temperature etc can affect this. It in its self generally isn’t a big issue.
The elongation is suggested for recoil purposes. Supposed to allow a little less shock to the stock and prevent potential cracking and the likes.
At least those are the theories .
 
A 40 inch barrel will grow/shrink in length .0252 inches over a 100 degree F change. which covers most hunting scenarios. Rate of expansion/shrinkage change per degree per inch in most steels is .0000063/inch/degree F.
 
A 40 inch barrel will grow/shrink in length .0252 inches over a 100 degree F change. which covers most hunting scenarios. Rate of expansion/shrinkage change per degree per inch in most steels is .0000063/inch/degree F.
And the expansion/shrinkage change per degree F and relative humidity percent change for maple and walnut per inch would be…..?
 
Each chunk of wood will be different I'm sure, especially those with a lot of figure, however wood just doesn't expand/contract over its length to any degree. Unlike metals which have well known thermal expansion numbers that are "written in stone" wood is a living thing even when it is dead. It is well known wood expands/contracts significantly across the grain, however my experience indicates it expands/shrinks very little in length. I have a 155 year old random length t&g maple floor in my kitchen, nailed not glued. Some boards are 16 feet long and some are only a foot long, the rest anywhere in between. The boards are all 2-1/2" wide. Some are straight plain grain, some are quite nicely figured, a few even have some burl in them. Winter brings us 30% humidity and floor temps around 60, summer brings us 90% humidity and floor temps some days around 90. The floor gets mopped from time to time and gets water spilled on it near the sink now and again. I never ever see the end joints open up at all anywhere, but I do see the width of the boards, as narrow as they are, widen in summer and become narrower in winter. So I doubt our stocks are changing length any appreciable degree under normal operating/storage conditions we ourselves could survive in. And unless they are soaked in water when the canoe tips over and the rifle is found on the bottom a couple days later I'd wager it isn't a problem. Wood properly finished even with that extreme water exposure likely wouldn't saturate the wood.
I do know the rifle barrel from zero degrees to 200 degrees changes length .050" or more (which could happen in the same day during a range event) and if you don't have room enough on either side of the pins the barrel will bow up and down with temperature change when the pins come in contact with the lugs.
 
Absolutely not. I go through thousands of stocks each year and can assure you movement can be significant. I would suggest at least one pin diameter fore and aft of the pin. Listen to professionals and highly respected top builders. Why I keep preaching I sometimes wonder…
But if you listen to a couple of know it all experts on here they say the METAL moves, not the wood. Ha ha.
 
But if you listen to a couple of know it all experts on here they say the METAL moves, not the wood. Ha ha.
Well, metal expands and contracts with temperature, so I suppose you might say it "moves", though I really don't think it's a factor in this application. Totally different scenario if you happen to be flying an SR-71. ;)
 
Not being sarcastic here at all. I just need to understand this better. How can the stock move when pinned thru a elongated hole when the tang is bolted/screwed into the stock? The breech plug/tang is threaded into the barrel. What am I missing? Thanks in advance.
IMHO, The forestock can expand or contract, lengthwise, with humidity, just as long barrels can expand and contract with temperature. Higher ambient moisture increases the potential for the forestock to swell, lengthwise, as well as in all other dimensions. Un-slotted underlugs can also put pressure on the barrel, as the forestock lengthens, or contracts, affecting accuracy, as mentioned above. Slotted underlugs, simply prevent binding of the forestock and barrel in changing damp and dry conditions.
 
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