When the Bushmaster Dissipator model came out, it instantly became popular with a segment of rifle buyers. The long forend covered the rifle-length gas tube mated to a carbine-length barrel, giving a longer sight radius than typical of 16-inch carbines of the time. Compared to the typical M4gery (below), Dissipator provided four more inches of sight radius.
We get the same picture with 45ACP carbines, a long forend on the AlphaWolf PPC versus the older BAZ45.
After all, the price of the longer rails is the additional weight and increasingly front-heavy balance. The reasons are several, besides the classic “more forend space helps use the weapon in a melee or a bayonet fight.”
The benefits of longer forends begin with bipod placement. The closer to the end of the barrel, the easier it is to make minute, precise adjustments to the aim.
On the opposite end of the spectrum, for short entry guns, longer forend means the ability to mount weapon light where its beam doesn’t get occluded by the barrel. On the rifle below, the front of the light is even with the muzzle.
The same long forend permits better control during rapid fire, either by an overhand grip or with a vertical foregrip. An overhand grip with a short forend would have exposed the thumb to a hot gas block.
The challenge of making a rifle balance well despite the forend length is real. Some makers, like Midwest Industries, have skeletonized the forend and removed Picatinny rails.
Others, like Taccom, used carbon fiber tubes.
Brigand Arms wove carbon fiber mesh rigidly enough to support sights and bipods. Their method adds almost no weight and also promotes efficient ventilation of the barrel and the gas tube. Moreover, this material dampens vibrations, and so may be used for direct support on a hard surface with a minimal shift in the point of impact.
In sum, while short forends help to maintain a nimble, quickly pointable carbine, they also limit the degree of control and the placement of accessories. Several technical solutions to the balance issue exist and should be used.
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