The Missing Measurement in Gun Specification

   09.28.14

The Missing Measurement in Gun Specification

My first three rifles, an SKS, A Mini14 and an AR15A2, had fixed stocks. I gave little thought to my preferred length because there was little I could do about the stock dimensions. Later, as I tried telescoping stocks, I discovered that I almost always used them fully collapsed. For years, I thought that it meant a preference for short length of pull (distance from buttstock to trigger).

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Recently, I watched the diminutive Tatiana Whitlock, a nationally recognized firearms trainer, shoot her AR15 with the stock fully extended. She said it gave better recoil control, the statement I was able to confirm for myself after following her directions. Was my impression of preferring shorter stocks an error?

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IWI Tavor, like most bullpup rifles, has a fairly long length of pull. It’s also slightly heavier than an AR15 of the same barrel length, yet it is easier to aim steadily unsupported and can be controlled with one hand easily. This has to do more with the point of balance than with the sheer weight or length of pull.

In most loaded AR15s, the balance is somewhere between the front of the magazine well and the delta ring, depending on the particulars of the barrel length and weight. That’s 17.5″ to 18″ from the buttplate. In a Tavor, the balance is at the top of the folded rear sight (with 16.5″ barrel) or at the base of the rear sight (with 18″ barrel). Both points are behind the pistol grip, 10.5″ to 11″ from the buttplate. Addition of an optical sight and a forend light moved the Tavor balance right over the supporting hand, while doing the same on an AR15 doesn’t change the balance much. The sight over the receiver is usually heavier than the forend light, but the light has greater leverage. For comparison, the center of balance for HK G3 or PTR91 is a full 18.5″ from the buttplate, and although it’s not much heavier than the Tavor or a 20″ AR in total, the .308 is considered far harder to handle.

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Custom Tavor in 300Blackout chambering, set up with an Aimpoint, a 7.62 YHM sound suppressor, and a weapon light.

This balance consideration, more than the overall length, may be behind the increasing popularity of bullpups. They are just easier to hold steady. Even when a suppressor is added to the muzzle and a light inserted into the forend, the balance moves a bit to the front, but not nearly as drastically as it would in a conventional rifle. An M1A with the same size suppressor would handle like a brick tied to a two-by-four!

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Perhaps gun makers could start adding the “distance to balance point from the stock” to the other specifications. That information would go a long way towards predicting how a firearm would handle.

 

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