Machining a featureless stock - Opinions?

[TerraHawk]

Without any precise legal definition, I have been using the "placement of web between the thumb and index finger" as well as "protrudes conspicuously beneath the action of the weapon".

Here are two modified pictures of the Thorsden and my stock showing just the piece that interfaces with the Lower. I personally think the Thorsden looks like a revolver grip.

The Thorsden starting tangent angle is shallower than mine but the finish angle is steeper.

I want to be squeaky clean because my wife will have one of these on her AR. Does anybody know a legal entity where I could submit my design?


Finally, if anyone is willing to measure the length of your stock when deployed for shooting from the back of the lower (where the buffer tube screws in) to the end of the stock, I am interested in seeing how much variation there is.

Cheers

At some point the "pistol grip" turns into a "rifle grip". OP is getting pretty close to the Thorsden stock configuration with his newest iteration and the Thorsden stock is legally NOT a pistol grip. Don't know where the dividing line is but its around there somewhere...

T

[strongpoint]

At some point the "pistol grip" turns into a "rifle grip". OP is getting pretty close to the Thorsden stock configuration with his newest iteration and the Thorsden stock is legally NOT a pistol grip. Don't know where the dividing line is but its around there somewhere...

Please share a citation for the bolded. Or the definition of "rifle grip" anywhere in state law or regulation. Or some evidence that supports even the mere existence, in a legal sense, of a "dividing line" or the "some point" you refer to.

Without any precise legal definition, I have been using the "placement of web between the thumb and index finger" as well as "protrudes conspicuously beneath the action of the weapon".

The "protrudes conspicuously" phrase is part of the label, not the definition. As such, it's got no real legal weight. The reasonably precise "placement of web" definition of the phrase at 11 CCR 5469 is what you really need to be worried about.

Here are two modified pictures of the Thorsden and my stock showing just the piece that interfaces with the Lower. I personally think the Thorsden looks like a revolver grip.

The Thorsden starting tangent angle is shallower than mine but the finish angle is steeper.

Can you point out the part of 11 CCR 5469 that specifies an angle at which compliant turns into noncompliant?

Does anybody know a legal entity where I could submit my design?

There isn't one. CalDOJ doesn't make such determinations, leaving the state's 58 district attorneys free to bring cases to court as they deem appropriate.

[J Huan]

Not qualified to be offering legal opinion, but that particular topology is what is known in the field of higher mathematics as a "thumbhole stock."

Regarding the impact force on plastic causing you to cringe, polymer gunstocks are typically made from glass filled nylon. That's one of the strongest engineered materials available, and more than strong enough to handle the force of recoil, especially when you consider that the force of recoil is countered by the the shooter's shoulder. There is no part of the human shoulder which is strong enough to bust a thick chunk of glass filled nylon.

apparently, OP isn't much of an engineer. maybe an imagineer.

[Ardbeg]

Doesn't look bad. Is it comfortable to shoot?

Mike

[mntbighker]

It is a beautiful thumbhole stock. I love the look. But what I think is needed is an improved version of the hammerhead.

Or an improved version of the Headbutt.

[timdps]

Please share a citation for the bolded. Or the definition of "rifle grip" anywhere in state law or regulation. Or some evidence that supports even the mere existence, in a legal sense, of a "dividing line" or the "some point" you refer to.

I was under the impression that the Hammerhead and Thorsden had both been declared non-pistol grips by a CA DOJ expert in a court case. I was wrong and it was the Hammerhead, Monsterman Grip, and California Rifles' U-15 buttstock.

I see from other posts that you think the Thorsden could meet the definition of a pistol grip, although I have not seen where you stated why this is. I'm guessing that it is the location of the thumb/first finger web when the hand is in firing position?

T

[TerraHawk]

Or maybe I have two degrees in Mechanical Engineering and 30 years of experience

Regardless of what substrate material you use to make a composite, if the "resin" part is capable of plastic flow, it will eventually deform at the surface if the applied stress exceeds its yield strength. With only a single cap screw to attach the stock, you cannot transmit the firing induced torque through the cap screw. It must be transferred through both the cap screw and a contact area between the plastic and aluminum lower. If you use a nice Nylon, yield strength is ~6000 psi. Other less expensive plastics can be as low as 1000 psi. For comparison, 6061-T6 aluminum has a yield strength of 35,000 to 39,000 psi.

If all of the AR-15 lowers were practically identical then you could design your plastic interface to maximize the contact area and minimize the contact stress. I have personally measured variations of 0.05" in the external dimensions of lowers made by different vendors. If the contact point you were counting on to take your load is 0.05" away, something else will have to stand in.

I am not disparaging the Thordsen stock. For myself, my wife and my friends, I am taking the easy way out at the cost of some additional weight. If, that is, I can convince myself that what I am doing is clearly legal.

apparently, OP isn't much of an engineer. maybe an imagineer.

[Exile Machine]

It is a beautiful thumbhole stock. I love the look. But what I think is needed is an improved version of the hammerhead.

Or an improved version of the Headbutt.

Hey, wait a minute, what is this, pick on Exile Machine day? First the youtube guy, then this. To avoid threadjacking this thread, we'll respond over here:

http://www.calguns.net/calgunforum/showpost.php?p=19405962&postcount=185

[strongpoint]

I was under the impression that the Hammerhead and Thorsden had both been declared non-pistol grips by a CA DOJ expert in a court case. I was wrong and it was the Hammerhead, Monsterman Grip, and California Rifles' U-15 buttstock.

The Haack & Haack case wrapped up in early November 2010. The FRS-15 was released in late November 2012.

I see from other posts that you think the Thorsden could meet the definition of a pistol grip, although I have not seen where you stated why this is. I'm guessing that it is the location of the thumb/first finger web when the hand is in firing position?

That definition is the only thing in California statute, regulation or case law that directly addresses what legally constitutes a pistol grip ... so, yeah.

Note that the Hammerhead, MonsterMan, and U-15 don't qualify as pistol grips under that definition.

[Cokebottle]

Would be helpful to get a legal opinion. From what I've understood is that the thumbhole stock is also held to the pistol grip definition in terms of positioning of the hand.

Which that one is also not compliant, even without the buffer tube attached.
The web of the thumb still wraps below the top of the trigger.

The Thorsdon rides higher than that, pushing the web of the thumb above the bottom of the receiver.

[timdps]

For myself, my wife and my friends, I am taking the easy way out at the cost of some additional weight. If, that is, I can convince myself that what I am doing is clearly legal.

The web placement location appears to be the critical factor in this. Perhaps you could use the Hammerhead or U15 as your concept starting point instead of the Thorsden, since these have been determined to legally "squeeky clean".

By moving the rear intersection point of the stock and receiver up a bit higher, you should be able to make sure the web is where it is supposed to be. Also leave a sixteenth of an inch of web in the two holes so there can be no possibility of a "thumbhole stock". As it is, any hole that someone could put a digit in, even a child is going to render it a thumbhole stock.

T

[Blisstar]

It is a beautiful thumbhole stock. I love the look. But what I think is needed is an improved version of the hammerhead.

Sorry just catching up the new lame laws. Are there concerns that the Hammerhead is no longer compliant for a featureless?

[Cokebottle]

Sorry just catching up the new lame laws. Are there concerns that the Hammerhead is no longer compliant for a featureless?

No concerns that I've seen... it's just a bit "clunky"
It is the definition of pure function and could use a bit more refining in the appearance category.

[Blisstar]

No concerns that I've seen... it's just a bit "clunky"
It is the definition of pure function and could use a bit more refining in the appearance category.

Awesome. Thank you for the clarification.