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Posted: 9/8/2009 1:01:37 PM EDT
| I get the value of a free floated barrel in a precision distance gun, but how important is it really for a 14.5-16" barrel for CQB to 300-400 yds? I ask because I am about to get a new rail and trying to decide which way to go. |
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Not sure what you mean by "CQB to 300-400 yards"? I think test shave shown that a 16" barrel on an AR15 can be just as accurate as a 24" barrel, although you will have a difference in velocity. In any case, free floating is never a bad thing, and in most cases the free float version of a quad rail is only a little bit more expensive than a 2-piece, so why not? *Edit- I've often felt that the barrel nut used in many free float rails (YHM, for example) is better than the stock half-moon notch barrel nut used on a standard AR15. It is a heckuva lot easier to torque, anyway. (without breaking the teeth and marring something) |
| Seems to me that getting all outside influence off the barrel is a good thing. People say 300 or 400 hundred yards like its a stones throw. 1 degree off at 400 yards would result in around 7" (according to my unscientific methods), easily enough to get off target. Getting the stress of a sling, bipod, VFG, and even just you gripping the handguard- getting that stress off the barrel is important even if you are just looking for hits on target, and not tiny groups. The theory is pretty simple- all of these forces are variables in your accuracy. You might have the sling a little tighter from one shot to the next, if you are using a bipod, you mind lean a little differently from one shot to the next, and these tiny influences add up to inconsistencies in the stress on the barrel. Remove as many variables as possible to attain consistent POI. I want to know that ultimately, I am responsible for the accuracy of the weapon. |
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1 degree off at 400 yards would result in around 7" (according to my unscientific methods), easily enough to get off target.
Yep, but it's actually much worse than this. Moving a rifle barrel just 1/60th of a degree (that's a "minute of angle" or MOA) causes a 1-inch shift in the point of impact at 100 yards. Therefore, you only need to deflect your barrel relative to your sights by 7 x 100 / 300 = 2.3 MOA or about 1/30th of a degree to change your point of impact by 7 inches at 300 yards. If you were to deflect your barrel by a full degree when trying to hit a target 300 yards away, you'd be off by 60 x 3 = 180 inches, or about 15 feet. It always amazes me how such tiny movements in a rifle barrel relative to your sights can shift your point of impact. If you plan to shoot your rifle under varying conditions with different types of support at the front (for example, different hand positions or using a sling or bipod), it's not hard to see how tiny barrel deflections can translation into differing points of impact down range. A free float rail helps to eliminate these variables. |
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