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Posted: 2/21/2007 10:19:46 AM EDT
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What is the longest barrel you can have before you see a drop off in velocity? Specifically 62 grn rounds, but if there's info about the heavier stuff I'll take that too. I'm assuming 24", since we see that in varmit rigs.... |
After a certain point (however ridiculously long) the gas will stop forcefully expanding and friction will slow the bullet. At least I think. They didn't go over firearms related topics in physics too much 
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Of course. If the bullet is slowing due to friction, then its velocity at X+1 will be slower than at X. For centerfire rifle cartridges, the distance at which this happens is "rediculously long." |
Longer than anything commercially made, for sure. |
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I know that .22lr gets the fastest velocity out of an 18" barrel, anything longer or shorter reduces velocity. Remember a .22lr is a straight wall cartridge, not a bottle neck cartridge. IIRC the .308 was around 9' before it would slow down because of barrel length. You are giving me some expensive thoughts, I would have to buy a flat bed trailor or a roof rack to haul a 10' rifle to the range LOL. |
Nice.  Glad I could instigate some pondering. Okay, how about this: I'm guessing there's a point of an optimum velocity, what is the point where the returns begin to diminish to a point where they are statistically insignifigent? What was the reason 20" was decided on as the barrel length of the M16? Was it arbitrary? Was it due to handling characteristics? The M14 was 24", why was the M16 a shortened length? I guess the reason for this is to figure out what is the most effective length for a long range 5.56 rifle. I've got 140-ish magazines for 5.56, 100 of them for SHTF. Got to thinking, EBR is great for CQB, but we all know the best use for a weapon for patriotic activities is at extended range. Due to the previously stated reason, I want to know the most effective barrel length of a 5.56 rifle intended for long range use in a tactical environment, which has common parts and can actually swap recievers with a CQB upper/companion rifle. I'm excited to see your opinions, and remember different scenarios: Use from a defended position, plenty of ammo and supplies, and no intent/ability to move. Use while on the move, if you had to abandon your position, or make your way to a better one? |
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556 is not a good cartridge for long-range anything. It can make do, but it's not good. It's up to you to decide when the hassle of carrying around a 24" barrel outweigh the extra 100 or whatever fps you get from a 20". Palma guys shoot 30" 308's. Most field-practical magnums are 26-27". |
A bit off topic...but..... 100 mags for a SHTF contingency? It is not plausable scenario. |
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