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Aurelio Corso
PostPosted: Mon Jan 17, 2022 2:46 pm  Reply with quote



Joined: 08 May 2018
Posts: 110

I am thinking about getting another 16 sxs .My pattern at 20 yards is about 3” to the left so about how much cast off would I need?.........thanks
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John Singer
PostPosted: Mon Jan 17, 2022 5:20 pm  Reply with quote



Joined: 03 Sep 2014
Posts: 372
Location: Rochester, MN

You need enough cast to center your dominant eye over the rib.

Here is a good resource on the topic.

https://www.theyorkshiregent.com/shooting/gun-fitting-guide-fit-shotgun/

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Builder
PostPosted: Tue Jan 18, 2022 6:00 am  Reply with quote



Joined: 21 Mar 2013
Posts: 98
Location: Northern New Jersey

Recommended distance is 16 yards for patterning since the math works more easily. I would guess that would change 3" to 2 1/2". For every inch it is off at 16 yards you need to move your eye 1/16". Since your eye sits about 1/3 the way down the stock you need to move the butt end 3 times as much. So 2 1/2 times one sixteenth is 5/32 times 3 equals 15/32 or approximately 1/2". You need to move the butt 1/2" to the right or cast off. I hope that makes sense to you.

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Aurelio Corso
PostPosted: Tue Jan 18, 2022 7:12 am  Reply with quote



Joined: 08 May 2018
Posts: 110

Thanks ,that’s the info I was looking for. I see a lot of used guns with 1/8 to 3/16 cast off.
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MSM2019
PostPosted: Tue Jan 18, 2022 8:14 am  Reply with quote



Joined: 04 Mar 2019
Posts: 1247
Location: Central ND

I am not looking for an argument. I just want to help the OP.

1/2" of cast at the heel is a LOT. I have never seen that much cast put in a shotgun. Maybe some where out there, but none that I have seen.

I am going to take a quick guess and say about 1/8" to maybe 3/16" at the heel and maybe a tiny bit more at the toe, for what you need to get the pattern back to center. That is in addition to whatever amount of cast is already in your stock dimensions.

I require quite a bit of cast and at the heel of my shotguns (professionally fit) is between 1/4" and 5/16" at the heel, depending on the shotgun.

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Builder
PostPosted: Tue Jan 18, 2022 10:24 am  Reply with quote



Joined: 21 Mar 2013
Posts: 98
Location: Northern New Jersey

Thank you for the way you handled that. Think of a teeter totter. Think of where you eye is on the stock. Then think of how much your eye has moved if you bend the butt 1/8". You can draw your own conclusions.

Patterning your gun is the only way to know if it shoots where you want it to. One of the reasons (not the only one) some guns "shoot better" for you and some do not is what you have experienced. You can shoot that gun (the one that is 3" off) OK but when you adjust the stock you will shoot higher scores. Few people take the time and effort to do this right.

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MaximumSmoke
PostPosted: Tue Jan 18, 2022 10:47 am  Reply with quote
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OK guys, here's the math of cast requirements: It is a simple problem of similar triangles if you remember from your geometry classes. Your eye is the rear "sight", or alignment point/device. If your eye aligns the bead or muzzle with a target at 16 yards, and the point of impact is off by 1 inch, then your eye, which is assumed to be 1 yard behind the bead is off line by 1/16 inch. You can go ahead and draw these triangles if it helps you see the problem.

That sound OK? -- Similar triangles -- same shape and proportions, one is just 16 times longer than the other. Got it? The average double with 28 inch barrels is about 45 inches long. Yes, it varies. Lets call that 1.2 yards. That's approximately the distance from the barrel bead to your shoulder. That similar triangle will have an offset of about 1.25 x 1/16th inch for that 1 inch of point-of-impact (POI) deviation. That's 0.079"

Now Aurelio (great name -- The Golden One) you say you're off by 3 inches at 20 yards. 16 = .8 x 20. Therefore at 16 yards you would be off 3 x .8 = 2.4 inches.

Using the .079" cast per inch of horizontal POI deviation times 2.4 inches gives a cast reqirement of .189 inches or about 3/16 inch. -- MSM2019's quick guess is on the money.

The old traditional assumption was and still is 1/16" change in eye position to effect a 1 inch change in POI at 16 yards. Most people take that all the way back to the butt end of the stock, and the error is still small. If the barrel (the distance from the bead to the shooter's eye) is extremely short or long some compensation will likely be required, but for typical barrel lengths from 26" to 30" (66 cm to 76 cm) on break action guns, the 1/16" per 1" POI at 16 yards gets you pretty close. The precision and consistency of which most shooters can position the shooting eye during the mount probably causes the slight differences in actual gun geometry to be of little to no consequence.

Then there is "static" fit and "dynamic" fit. Static is typified by the geometry exercise above, and observations of eye alignment. The static method is simple and usually gets the shooter in the ballpark. Sometimes it's all that's needed. But the proof is in the putting, and that's dynamic fit, which can only be done by having the shooter mount and shoot the gun.

When I fit a gun, there are some other factors besides pure and simple "cast". The gun butt must fit in the "pocket" of your shoulder for a comfortable and repeatable mount. If you get extreme with cast, it can move the butt to an uncomfortable spot on your shoulder. If that happens, comb offset will be required to keep the butt of the stock in that comfortable shoulder "pocket" - i.e. to move the eye over without moving the butt end of the stock. You can see how there really is a practical limit to stock bending as a way to move move the shooter's eye sideways. Needless to say, comb heights or "drops" must be changed to compensate for vertical POI deviations. There will also be practical limits to how much bending can be done for vertical POI adjustments before you start to run into shoulder position problems -- and pitch problems, but that can be adjusted separately -- get out the saw.

Then there is comb angle. As an example, for my skeet gun, which I need to be comfortable as well as repeatable since I shoot it a lot, I not only offset my comb for side-to-side POI adjustment (actually very little in my case), I angle the comb away from my face so that recoil tends to move it away. That eliminates face slap. If you look at the stock of a typical English double, you will see a comb that tapers in width from wide at the butt to very narrow at the nose of the comb. That actually is "comb angle" at work! Narrow combs can hurt if the gun is not fit to avoid flipping up, though. That must be cured with proper "pitch". Big fat American combs can cause folks with wider faces to have horizontal POI problems. Often, reshaping the comb can cure problems at which some folks unnecessarily throw the "cast" solution.

Then there is "twist", or "toe-out", as MSM2019 has pointed out. This is another comfort issue, but it also is very necessary in some folks of heavy shoulder or chest build to avoid "canting" the gun. Length of pull (LOP) is the least important gunfit factor. Drop at comb and at heel are the most important factors. Getting "pitch" right (avoids flip and other comfort issues) is much more important than getting LOP right within any more than a half inch. A further note on LOP is that it becomes co-mingled and confused with "hand fit" in pistol grip stocks.

It's all about how a person's body is shaped or built. For instance, women in general have longer necks, narrower shoulders and chest features different than men. They tend to need less drop, less cast, and considerable toe-out. Each person is an individual. I'm ordinary in build and, at 68", not tall. I find it amazing that I shoot standard US stock designs such as found on Winchesters and Remingtons and the like, just fine, even though they are not really "right" fits. I guess these dimensions came from a sort of "average" for some time long ago. If you're going to mass-produce guns, you've got to do that. They did pretty well. And the point? -- A practiced shooter can adjust his technique to fit a gun. Sometimes that is the best thing to do. It is economical. A lot of fitting depends on the shooter's objectives.

Cheers!
Tony


Last edited by MaximumSmoke on Tue Jan 18, 2022 3:11 pm; edited 3 times in total
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Builder
PostPosted: Tue Jan 18, 2022 12:38 pm  Reply with quote



Joined: 21 Mar 2013
Posts: 98
Location: Northern New Jersey

Very in depth discussion. Thank you.

I would point out that the small triangle measures very close to 36". That is the distance from bead to eye. The big triangle is target to eye. Therefore the 1 to 16 ratio is pretty accurate. You need to move the eye 1/16" for each inch you are off. To move the eye location you must move the butt. The eye is 2/3rds the way down the stock so you must move the butt more to compensate.

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MSM2019
PostPosted: Tue Jan 18, 2022 1:19 pm  Reply with quote



Joined: 04 Mar 2019
Posts: 1247
Location: Central ND

I found this article and maybe this will help. It does explain where cast is measured from.

https://www.shootinguk.co.uk/answers/line-up-cast-to-check-gun-fit-110302

When I measured both shotguns that I had professionally fit, the measurement at the heel is 1/4" of cast off on my 1100 and possibly a light 5/16" on my Beretta 686 Onyx. The 1100 was re-inletted the Beretta stock was bent.

At 16 yards I typically shoot a shotgun with no cast in the stock about 6" to 7" to the left. Right handed shooter here.

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Pine Creek/Dave
PostPosted: Tue Jan 18, 2022 2:03 pm  Reply with quote



Joined: 17 Mar 2017
Posts: 2220
Location: Endless Mountains of Pa

AC,

The best way to handle this is to have the gun professionally fit to your shooting needs, especially if you own a good double gun. Max Smoke has give you a lot of good info, what this comes down to is every person is different and doing it right takes a professional. Lots of sportsman try to do their own gun fitting, most times it does not turn out very well.

all the best,

Pine Creek/Dave
L.C. Smith Man

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Aurelio Corso
PostPosted: Tue Jan 18, 2022 2:21 pm  Reply with quote



Joined: 08 May 2018
Posts: 110

Dave if there was someone near me and I was considering a new gun I would definitely take your advice cause you always have steered me in the right direction.I am really hung up on old hammer guns right now and sounds like 3/16 cast off is what I will be looking at.Hope you got out this fall and shot a lot of grouse.
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Pine Creek/Dave
PostPosted: Tue Jan 18, 2022 5:54 pm  Reply with quote



Joined: 17 Mar 2017
Posts: 2220
Location: Endless Mountains of Pa

AC,

Look around for somebody professional to accomplish what you need done, don't mess up a good gun.

Got out the better part of Grouse season, Swampy and a few others visited, real tough Grouse hunting this season, bird numbers way down and the Woodcock flight passed thru after the season ended.

all the best,

Pine Creek/Dave
L.C. Smith Man

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MaximumSmoke
PostPosted: Wed Jan 19, 2022 4:19 pm  Reply with quote
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Builder, et al,

I have been thinking about your 3X cast to make 1X face movement statement, and I believe you are much more correct than I. My amateur state and my hide-bound adherence to traditional writings and statements clouded my reasoning. It appears Aurelio Corso does need a half inch or so of cast at the butt if the offsetting of the eye is done purely by lateral bending of the stock, and the stock is bent only in the forward area of the grip. A half inch is a lot -- enough to cause concern about a shoulder fit problem. If there was such a problem, and there might or might not be in this case, I think I'd use comb offset and taper as much as possible, to lessen the amount of stock bend.

Though it appears I shoot better with a gun having about 1/4 inch cast off, and my two AyA's are cast about like that, I've never had a double bent just for me, and I've never bent a stock nor do I have the equipment to do so. Can a stock be bent to get the right position at the face and still keep the butt in the comfort zone -- by using a sort of S-bend for instance?? I don't know.

Anyway, thanks for your insight, Builder.

Cheers,
Tony
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Builder
PostPosted: Thu Jan 20, 2022 6:40 am  Reply with quote



Joined: 21 Mar 2013
Posts: 98
Location: Northern New Jersey

First, let me say I am not a gunsmith. I do have some experience with wood. You can see it in my handle, Builder.

I have bent a lot of SxS stocks. I like to shoot a different gun each time I shoot sporting clays. I have a lot of older SxS and to shoot well they all have to fit me. Half of them have to be bent to fit. Because of that I built a bending device. Some have to be bent up because they have a lot of drop. Not all bend especially American Walnut. 90 percent do bend. They bend at the wrist with heat and pressure. I don't think you can bend the thicker areas to bring the stock back to parallel as you ask. Breaking a stock is an expensive mistake. You either need a new stock or you can repair it. Glue melts when exposed to heat so once a stock has been repaired with glue you cannot heat it which means you cannot bend it. I will not buy a gun with a stock repair for that reason.

You have to remove or at least turn the trigger guard sideways while bending. Sometimes you have to adjust it to fit if it is a big bend. From my experience, if you bend it with the trigger guard left in place the stock will slowly go back to its original shape.

I recently purchased a Manufrance Robust 16g. for hunting. I patterned it and found it to be 7 or 8 inches to the left. I bent it but it was stubborn and I got it to 4" left. Looking at the stock I realized the comb was very fat. Out came the belt sander. I matched both sides but I now had to refinish the stock. That is something I enjoy however it is a lot more effort then bending. I enjoyed shooting Pheasants with it in South Dakota this past October.

I have bent several guns to 3/4" cast off. It is not a problem for it to fit the shoulder pocket. If you are willing to refinish a stock it would look better to do a combo of bending and wood removal as you suggest.

If you look around, there are several methods to bend a stock. I chose to build a device with scrap wood left over from a house I was building. There are simpler methods if you look around the internet for ideas. There were a couple I recall on doublegunshop. Not sure if you can find it with a search though.

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Riflemeister
PostPosted: Thu Jan 20, 2022 9:08 am  Reply with quote
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My experience with stock bending pretty much reflects the info posted by Builder in his informative post. Pictured below is my stock bending jig.








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