Varmint Stock Diagram

M

mturner

Member
I have a question concerning the NBRSA varmint stock diagram. While there is no mistaking that you drop down 4" below the bore centerline by inserting a cleaning rod and bore guide to mark point "A". My concern is point "B". Mark the barrel 18" in front of the bolt face. Lets say you put a wrap of masking tape. The thing is this. It does not say that the height of point "B" is the bore centerline, and furthermore, the diagram shows the line from the butt of the stock intersecting point "B" on the underneath side of the barrel, not at the bore centerline. This would put point "B" down from the bore centerline by .530" based on the HV barrel taper. This would allow the bottom of the butt to have a slower taper than if the intersection was at the bore centerline. If I were to build a stock based on the drawing, and someone said the taper was too slow based on point "B" being a bore centerline measurement, it seems to me that it could be protested according to the drawing. I do realize that point "A" being based on 4" down from bore centerline could not be protested. Before anyone jumps to any conclusions, please understand that I do understand how to read a blueprint. Maybe a better explanation of this drawing lies elsewhere with a better description or better drawing.

Just to let you know, my CAD drawing shows the two angles to be 5.45 degree to the bottom of the barrel versus 6.27 degrees to the bore centerline. So it makes less than 1 degree difference, but I just want slower angle, and I don't want anyone to tell me it's not legal after I've done it. What it really comes down to is the drawing is either right or wrong. That's all I need to know.

Michael

BR Stock.jpg
 
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I agree there is a discrepancy, but logic would say since the drop is taken from bore centerline, so should the angle.

What is missing is the measurement to the butt end of the stock, from somewhere. If I'm not mistaken, the IBS used to have that dimension, but the current rule book on line is missing the stock diagram. This stock dimension to the butt end, will also dictate the angle of the stock.
 
Truth is, we rely on the custom stock manufacturers to make a stock that complies with the rules as laid out in our Rule Book. A gunsmith has to get reall creative to install the barreled action to render these stocks illegal.

If you make your own stock, then it is your responsibility to insure it is in compliance.

I have never been to a match where these dimensions were checked. The only thing I have ever seen checked was weight of the rifle and the width of the forearm, because these can be checked easily and quickly and are exact figures, not open for interpretation.
 
I do agree that they probably meant for the front measurement to be the bore centerline. But at the same time, nothing says that it has to be. The drawing not only shows the bottom of the barrel, but sometimes when a mistake is made, it needs to be grandfathered in. There are a lot of people in this game that make their own stocks, and if anyone has spent the time to make one according to the diagram, do we go back and tell them that it isn't legal? This is why people need to be more careful to get things right. I realize we all make mistakes, but do we go back and make each person correct their stocks? There is nothing wrong with leaving the drawing the way it is. It has been taken for face value by someone by now. If we change the drawing, do we make people adhere to it from that day forward? We are talking about less than 1 degree. A tolerance needs to be specified. We have a 1/2 ounce if i remember right on the weight. Not trying to make trouble, just trying to avoid trouble.

Wayne, I agree that the measurement to the but end of the stock is missing. The thing is this. Changing the length of pull by an inch or two has little change on the angle. Dropping the point "B" to the bottom of the barrel changes the angle way more, but still less than one degree. If the drawing stays the way it is, then I would use it as it is. The drawing in it's current state is fair to all. Changing it might be unfair to some.

I wish they have just said something like minimum angle is 5 degrees. Lets say a kid has a stock with an 10" pull, and a Marsh action. Then from the 18" number to the butt could be as much as 6" less. That means his stock angle has to be steeper that someone with a longer bolt and length of pull.

Michael
 
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jackie schmidt said:
I have never been to a match where these dimensions were checked. The only thing I have ever seen checked was weight of the rifle and the width of the forearm, because these can be checked easily and quickly and are exact figures, not open for interpretation.
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Actually the stock width is open to interpretation. In the rule book it says "The stock should have a flat or convex forearm not more than 3 inches wide". It does not say that stock width shall be a maximum of 3.000" wide. All other dimensions are given as X.000". This suggests to me that when the rule was written, most stocks were made of wood and subject to swelling. Therefore the stock width should be measured with a measuring tape and the other components measured with calipers. Or, there should be a so many thousands over allowance if measured by calipers. Similar to to .5 oz over allowance in weight. I suggest using 3.049 as that measurement would still be rounded down to 3 inches.
 
Lawrence W. said:
Actually the stock width is open to interpretation. In the rule book it says "The stock should have a flat or convex forearm not more than 3 inches wide". It does not say that stock width shall be a maximum of 3.000" wide. All other dimensions are given as X.000". This suggests to me that when the rule was written, most stocks were made of wood and subject to swelling. Therefore the stock width should be measured with a measuring tape and the other components measured with calipers. Or, there should be a so many thousands over allowance if measured by calipers. Similar to to .5 oz over allowance in weight. I suggest using 3.049 as that measurement would still be rounded down to 3 inches.
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There should be tolerances on all of this. Just like the speed limit of 70, is really 75. :)
 
i disagree with anyone that has to "assume" instead of reading english as printed.
i agree with std blueprint tolerances 3 inches is not 3.000 as pointed out.

one should not need a lawyer to read english.
 
At the extremes, a rifle that has a smaller barrel diameter 18" in front of the bolt face, an action that is close coupled from bolt face to trigger (where the LOP measurement starts) and a short LOP will be required to have a greater toe angle than one with a barrel of the maximum allowed diameter 18" in front of the bolt face, installed on an action that is relatively long from bolt face to trigger, in a stock that has a long LOP. Because of this built in variability, I suggest that no matter how well intended those that came up with it were....it is a badly written rule. I suggest that all existing stocks that meet the existing rule, as measured in the prescribed manner, be grandfathered in, and a new rule that simply gives the allowable toe angle in reference to the barrel CL be adopted in the interest of clarity. Of course this will never happen. Has anyone ever seen a stock toe angle challenged at a match and measured?
 
I'm not sure changing the print addresses the real problem with this rule...that being feasible enforceability. I would suggest doing away with the rule altogether. 3 inches wide seems sufficient and doesn't discourage experimentation....but that's just me.
 
here 's a novel idea lets remove all the uninforceable rules and keep it simple . how about a 13.5 # rifle and 3" fore end as u.b.r. does . I find it amusing the rule BOOKS state both organizations are for the advancement of rifle accuracy but should read advancement under our rules.
 
LIKE POLITICIANS WHAT THEY SAY AND WHAT THEY DO ARE VERY DIFFERENT.

limit rifle accuracy, not promote......

way too many rules for "promoting" accuracy.

you do not believe me ?
how many classes? ( real classes requiring a true different rifle)
how many organizations ?
how many shooters ? how many matches ?
and you basically shoot TWO cartridges.
6ppc and 30 br

IMHO,
you shoot for the enjoyment, not a search for
true rifle accuracy.
 
Francis,
My question was to the larger audience. It was not meant to say that stocks had never been measured, but that to my knowledge (admittedly quite limited in this area) that such measuring is uncommon. Have plans for the stock measuring jig been published? Do you believe that the allowable stock angle should vary with action length, LOP and barrel diameter ?
 
For reasons more numerous than I want to take the time to explain, most forms of competition that involve the use of equipment have rules relating to that equipment. This does not mean that those participating in those sports are not striving for excellence. It means that they recognize the need for uniformity of conditions under which that performance is measured. No one is prevented from experimenting by any competition rule, but rather competitors have agreed by their participation on the conditions under which they are to compete. If one wants to compete with no rules, all that is required is to find at least one other person of like mind. Surely sanctioning bodies do not own competition, they just facilitate and organize it. If a person does not like a given set of rules, he is free to put on his own matches under whatever conditions the participants can agree upon.
 
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Face Value

Boyd Allen said:
At the extremes, a rifle that has a smaller barrel diameter 18" in front of the bolt face, an action that is close coupled from bolt face to trigger (where the LOP measurement starts) and a short LOP will be required to have a greater toe angle than one with a barrel of the maximum allowed diameter 18" in front of the bolt face, installed on an action that is relatively long from bolt face to trigger, in a stock that has a long LOP. Because of this built in variability, I suggest that no matter how well intended those that came up with it were....it is a badly written rule. I suggest that all existing stocks that meet the existing rule, as measured in the prescribed manner, be grandfathered in, and a new rule that simply gives the allowable toe angle in reference to the barrel CL be adopted in the interest of clarity. Of course this will never happen. Has anyone ever seen a stock toe angle challenged at a match and measured?
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Boyd,

From what I'm seeing in the responses is that I might as well just take the diagram at face value, and don't worry about what they might have meant. If I go to the bottom of the barrel, I will have an angle of .8 degrees less than if I go to the bore centerline. The stock would more than likely never be checked, and if for some reason it ever was, I could simply say that it matches the diagram.

At the beginning I felt like I might have opened a can of worms, but for the most part people are saying "don't worry about it, and just follow the diagram for what it says, not for what we think they meant to say".

One thing that may not be clear to some is this. The bottom of the butt does not have to be 4" below bore centerline. This measurement is simply to determine the minimum angle. Once the minimum angle is determined. Let's say 6 degrees. That angle can be offset up or down to make the butt the desired height.

Michael
 
mturner said:
One thing that may not be clear to some is this. The bottom of the butt does not have to be 4" below bore centerline. This measurement is simply to determine the minimum angle. Once the minimum angle is determined. Let's say 6 degrees. That angle can be offset up or down to make the butt the desired height.
Michael
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I know you are asking about NBRSA rules, but IBS states that the toe must be no higher than a line that is 4" below the bore at 13.25" length of pull. With this rule, if you put the trigger right at your shoulder (zero length of pull) with an XP-100-like extension in reverse, the toe could be much higher and the angle more level with the bore.

FWIW, IBS defines the front point for defining the angle to be 18 forward of the bolt face and on the centerline of the bore. So if you build a stock just barely meeting the NBRSA drawing, it will be illegal for IBS.

I agree with the proposed KISS rules - 3" forearm and a weight limit. ... But then there are the rests. If these were the only rules, then it would be open to rail-style rests.
 
mks said:
I know you are asking about NBRSA rules, but IBS states that the toe must be no higher than a line that is 4" below the bore at 13.25" length of pull. With this rule, if you put the trigger right at your shoulder (zero length of pull) with an XP-100-like extension in reverse, the toe could be much higher and the angle more level with the bore.

FWIW, IBS defines the front point for defining the angle to be 18 forward of the bolt face and on the centerline of the bore. So if you build a stock just barely meeting the NBRSA drawing, it will be illegal for IBS.

I agree with the proposed KISS rules - 3" forearm and a weight limit. ... But then there are the rests. If these were the only rules, then it would be open to rail-style rests.
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easy enough to fix must be shot off rest with sand bags, ain't that hard:rolleyes:
 
I researched this a lot back when I was laying out new stock designs. First, to Mr. Turner, there is no dimension that references the bottom of the barrel. All critical dimensions are to the bore centerline. A sketch supports the legal description, not re-defines it. Second, the "flaw" in the NBRSA dimension specification is that it describes a legal stock with what appears to be a triangle, but fails to specifically define either 2 legs and an angle, or two angles and leg... either of which would give a definitive max/min design. Instead, one leg is partially described with the 18" from the bolt face wording. This means that the measurement from the bolt face back to the butt of the stock is variable. It also means that a stock built to absolute minimum specifications with one action might not be legal with another action (a longer action would result in a too-shallow angle on the butt stock). Also note that there is no description of the angle of the forearm. There is some room for manufacturers to differentiate their products by playing with the angles and lengths. I experimented with some designs that attempted to minimize the difference between forestock and butt stock by bedding the action at tilted down so as to flatten the overall profile while still maintaining the 4" distance at the butt.

Rod
 
About 10 or 12 years ago George Kelbly, Sr. designed a jig to test this rule. I volunteered to have my BAT B/Scoville measured. He said that my rifle "passed" but it was close. I don't know if he pursued any further action with his invention, but maybe he or Jim could update us with this. Good shooting...James
 
CubCouper said:
I researched this a lot back when I was laying out new stock designs. First, to Mr. Turner, there is no dimension that references the bottom of the barrel. All critical dimensions are to the bore centerline. A sketch supports the legal description, not re-defines it. Second, the "flaw" in the NBRSA dimension specification is that it describes a legal stock with what appears to be a triangle, but fails to specifically define either 2 legs and an angle, or two angles and leg... either of which would give a definitive max/min design. Instead, one leg is partially described with the 18" from the bolt face wording. This means that the measurement from the bolt face back to the butt of the stock is variable. It also means that a stock built to absolute minimum specifications with one action might not be legal with another action (a longer action would result in a too-shallow angle on the butt stock). Also note that there is no description of the angle of the forearm. There is some room for manufacturers to differentiate their products by playing with the angles and lengths. I experimented with some designs that attempted to minimize the difference between forestock and butt stock by bedding the action at tilted down so as to flatten the overall profile while still maintaining the 4" distance at the butt.

Rod
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Rod,

While there is no dimension referencing the bottom of the barrel, the line drawn does actually hit the bottom of the barrel, and stops. It does not continue to the bore centerline intersection to form a closed triangle. Nothing refers to a closed triangle in the diagram at all. The bore centerline measurement is only mentioned as a means to establish the distance to drop down the butt of the stock. The diagram also does not say that the bottom edge of the stock has to be 4" down. Just have to use a 4" drop to establish the bottom point of the angle. So, I'm not disagreeing with you, I'm just asking where the legal description is located? Shouldn't the legal description be in the "Rule" book if we are to adhere to it? I also agree with you concerning the floating dimensions. Length of pull, and action length will cause a stock to be legal with one action or pull length, but not with another. Why didn't they just make the angle about 5 or 6 degrees minimum, and then if it was contested, the jig would have the minimum angle machined on it. Now I realize I can copy the drawing realizing that it means something other than what it says, and get away with it, but I just prefer for rules to say what they mean, and mean what they say.

Michael
 
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