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[firstflabn]

I've tried to ask the question before, but never got anything resembling an answer: where is the contemporaneous Ordnance report, study, or any kind of legitimate attempt at an engineering analysis of the supposed pin weakness? Lacking that, what is the earliest document of any sort making the claim? Please, no personal anecdotes (unless you were an Ord officer before 1943).

Making the assumption that pin location met well understood edge distance requirements, it's just not plausible that it could actually weaken the stock. Simplifying further, drilling a 3/16" diameter hole through the stock recoil lug cross member would reduce the cross section (and hence its resistance to shear) by less than three percent. So, even if air had the same structural attributes as brass, the loss of strength would be barely noticeable.

Failure occurs first at the recoil lug (assuming proper installation of in spec components). According to Hathcer's calcs, recoil force is 3700 lbs. Shear resistance of black walnut is about 1350 psi. The front cross member is close to 1/2" x 1", so adding areas of the left and right surfaces yields a total area of about 1 sq. in. Thus, the front cross member is only capable of resisting 1350 lbs. by itself. This is a bit under 40% of the applied load - meaning that the system relies mostly upon friction from the clamping force applied by the recoil bolts. By these calcs, the crossmember would probably fail at the first rifle shot if no clamping force was applied. And that is likely the cause of most stock failures - loose recoil bolts. The other possible factor is observation bias - the expected result is noticed, but the unexpected result is ignored. This effect even sometimes occurs in groups with a basis in science - many emergency room doctors and nurses believe the full moon increases violent crimes and thus, ER visits. The data doesn't support the conclusion (it's not even close), but once a myth is established, it's extremely difficult to overcome.

If the data exists to support the claim that pinned stocks are weaker, it ought to be easy to find.

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[John Beard]

I've tried to ask the question before, but never got anything resembling an answer: where is the contemporaneous Ordnance report, study, or any kind of legitimate attempt at an engineering analysis of the supposed pin weakness? Lacking that, what is the earliest document of any sort making the claim? Please, no personal anecdotes (unless you were an Ord officer before 1943).

Making the assumption that pin location met well understood edge distance requirements, it's just not plausible that it could actually weaken the stock. Simplifying further, drilling a 3/16" diameter hole through the stock recoil lug cross member would reduce the cross section (and hence its resistance to shear) by less than three percent. So, even if air had the same structural attributes as brass, the loss of strength would be barely noticeable.

Failure occurs first at the recoil lug (assuming proper installation of in spec components). According to Hathcer's calcs, recoil force is 3700 lbs. Shear resistance of black walnut is about 1350 psi. The front cross member is close to 1/2" x 1", so adding areas of the left and right surfaces yields a total area of about 1 sq. in. Thus, the front cross member is only capable of resisting 1350 lbs. by itself. This is a bit under 40% of the applied load - meaning that the system relies mostly upon friction from the clamping force applied by the recoil bolts. By these calcs, the crossmember would probably fail at the first rifle shot if no clamping force was applied. And that is likely the cause of most stock failures - loose recoil bolts. The other possible factor is observation bias - the expected result is noticed, but the unexpected result is ignored. This effect even sometimes occurs in groups with a basis in science - many emergency room doctors and nurses believe the full moon increases violent crimes and thus, ER visits. The data doesn't support the conclusion (it's not even close), but once a myth is established, it's extremely difficult to overcome.

If the data exists to support the claim that pinned stocks are weaker, it ought to be easy to find.

Permit me to respond to your posting. I may have the document/report that you inquire about, but I have not yet indexed it.

Having examined and analyzed a very large number of cracked stocks at the CMP, I can state that your analysis is faulty. Recoil from the receiver is absorbed by the stock in three locations: (1) behind the recoil lug, (2) behind the magazine well, and (3) behind the receiver rear tang. The stock can crack in any and all of these three locations.

The most dominant area for recoil absorption is behind the magazine well. Cracking in this area appeared very early and resulted in addition of the first stock bolt circa 1907. It wasn't until 1917 that cracking behind the recoil lug became serious enough to necessitate installation of a second stock bolt. Army Ordnance eventually increased the routing behind the receiver rear tang and eliminated cracking in that location. Recoil absorption capacity behind the receiver rear tang was minimal anyway.

Unlike spiral pins, stock bolts cinch the wood together from the sides and increase the wood shear strength. Spiral pins have little or no cinching effect and, therefore, do not increase shear strength. Pin-reinforced stocks, therefore, are far more prone to cracking.

Spiral pins were originally believed to be adequate for stock reinforcement and were approved for production in mid-1942 as a cost-reduction measure. Experience, however, demonstrated that the pins compromised stock reinforcement and resulted in increased cracking. The Army, therefore, directed that Remington and Smith-Corona revert back to crossbolts in late 1943 even though the crossbolts would increase production cost. In a move to control costs, the front and rear crossbolts were standardized to a single length instead of the previous two different lengths.

Hope this helps.

J.B.

[pondcreekfarm]

JB: Thank you for the information. It seems that I have a nice rifle that I should not shoot for fear of cracking the original stock. Should I get a replacement stock so I can shoot it and keep the original undamaged or should I just not shoot it at all? I have plenty of rifles, so it is not like I will not kill a deer this year without it. I do enjoy shooting it none the less.

[John Beard]

JB: Thank you for the information. It seems that I have a nice rifle that I should not shoot for fear of cracking the original stock. Should I get a replacement stock so I can shoot it and keep the original undamaged or should I just not shoot it at all? I have plenty of rifles, so it is not like I will not kill a deer this year without it. I do enjoy shooting it none the less.

Whether you choose to shoot your rifle is a personal decision. I can understand your attachment to the rifle and desire to shoot it. Under the circumstances, I would recommend that you shoot it as is with the original stock. If, however, you find yourself desiring to shoot it regularly and often, I recommend that you acquire an arsenal-overhauled rifle for that purpose so as to preserve your original rifle.

Hope this helps. Good Luck!

J.B.