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Posted: 11/28/2006 8:47:19 PM EDT
| Anybody use them? Will they rotate? Are they rock solid? |
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Virtually all of our competition uppers are built with PRI forends. They are very light and strong. You can have rails at the standard 3-6-9-12 positions, leave them clean, or put rails only where you need them. They use a 3-piece mounting system, barrel nut, tube and locking collar, so they stay in position and the tube can be removed for cleaning if needed. (With a low profile gasblock, otherwise the front sight will have to move too.) This is the forend used on the MK12 Mod0 SPR, and it is still an Army favorite. A few competition uppers with PRI forends... 
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Studs are easy to install virtually anywhere there isn't already a hole. The carbon fiber is very strong. Not easy to drill, a carbide drill bit is best but for a few holes a HS steel bit is fine. The back side of the hole will tend to splinter if not supported, but the tube will be fine. Another option that I use from time to time is to drill and tap into the alloy tube that the carbon fiber is mounted into. Then you can just thread a stud into the tapped hole iwth a little loctite. Mounting a front sight on a top rail works fine. The tubes are very rigid. A plus is that the top rails are adjustable so they can be fine-tuned after the tube is mounted to get the front sight perfectly true to the rear sight for windage. |
| They seem to be less ventilated than some of the other options. Am I just mistaken or is this true? I'm guessing that I might just be mistaken, otherwise you (MSTN) would not use them on most of match uppers you produce. Just curious; I've always been drawn to them for some reason. |
Thanks, 96Ag |
When we started using PRI tubes for our comp stuff, I had them do a different hole pattern for us. It has three rows of holes on the upper half of the tube, two short rows forward on the lower half. Also several sets of small holes for mounting rails (in the typical spots). As to heat, the carbon fiber heats up more slowly than aluminum, but cools more slowly as well. The short answer, there is no forend that won't get hot. Fact is, if you set one out in the sun here in August on a sunny day, it will be too hot to pick up barehanded in 15 minutes without firing a single round. Carbon fiber or aluminum, both suck up radiant heat well. ( the reason we don't put holes on the bottom is that heat pours out of them when you are shooting ). In practice, we use carbon fiber for competition builds because it is strong, light, and versatile. Most shooters have no need for rails and employ a shooting style that focuses on lightly cradling the forend with the support hand. Set up correctly, this makes for very fast pairs on paper targets while moving as you won't oversteer the gun. Heatwise, the forends typically don't even get warm for 10-15 minutes once you start shooting. In 3-gun, this means you are done with a stage and your gun is re-bagged before it gets warm. Then it sits for an hour or more until you shoot again. So heat is not really an issue for hand comfort, even with the light barrel contours used on comp guns. with a more typical barrel contour, it takes longer to heat them up. Also, you can use various grip tape products to cover the carbon fiber. This gives gripping texture for hot, sweaty days and it also acts as a further contact heat barrier, and doesn't affect convection cooling through the vent holes. |
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