so what exactly is OCB board, I know what OSB is but this bullet proof OCB board sounds like it would be cheaper than ceramic stand alone plates.
SF troops using hollow point TAP ammo?
WOW, lot of info going around in this thread.
OSB board, you are probably correct. It's particle board, there are basically 2 kinds that my local hardware sells. One is referred to as plywood, the other is OSB. This comes from my own experience. There is an LGS / gunsmith in Flemingsburg KY, Sheps Gun World I believe, he constructed a target wall outside of his shop with sand sandwhiched between 2 pieces of 3/4" OSB board. I asked him about it (not even realizing its efficiency), and he explained that specific sizes of OSB board would stop any rifle round that is smaller than a .338, and slower than a 7mm Mag. I really can't give the exact dimensions, ballistics and information from the top of my head, but there has never been any apparent damage to the back of his target (of course it's a little more robust than a 1" piece of OSB - he added the sand to make the wall foolproof, it's quite overbuilt), and he got the information from somewhere, so I'm assuming that anybody could search and find it if they wanted - or take $50 to the hardware store and buy a couple pieces and test it yourself.
As for the SF troops using TAP ammo, they shoot what they can get their hands on. I can't speak to where they got it, or how easy it is for them to procure, but I do know that many SF troops fielding SBRs got their hands on a couple rounds that aren't army issue. As for the hollow point, keep in mind that the hollow point on a 5.56 round is not there for expansion, it's there for balance to stabilize the bullets in flight - but an added effect is that the bullets are heavier in the rear and when it hits a target it has even more of a tendency to yaw than even standard 5.56 (which is one of the factors in fragmentation). An added note, the ballistics of 5.56 is tricky, and different guns and ammo combinations get wildly different performance at close ranges because the bullet is NOT stabilized at first. You can get some nasty effects (and unpredictable wound channels) shooting at close range because the bullets strike at a high angle of attack.
Back to the SF Troops: the ballistics of 5.56 in shorter barrels has been a major point of contention for a while, and I've discussed it at length several times with lots of people, especially on forums. I knew that others shared the information regarding 75gr TAP being preferred by special forces, but I didn't think I could find any references. I did a quick search, and ended up finding a reference though, you can read
this article in the shooting times about MK 262 mod 1, the quote is toward the bottom of the article:
I spoke with a good friend with multiple combat tours in both Iraq and Afghanistan. His experiences as both a Special Forces sniper team leader and assaulter offered a unique perspective on ammo performance. As a sniper, MK 262 was his preferred round (when he was not using 7.62x51mm NATO), and he said simply, “It’s the best, most accurate round the Army has ever issued.” When carrying the shorter SBR, he ranked Hornady’s 75-grain TAP as the most lethal, followed by MK 318 and with MK 262 riding herd at third. Anything was better than M855 in a CQB environment.
“All 5.56 rounds suck out of SBRs, but MK 262 is way better than M855,” he said. “The only time M855 shines is when you are shooting through intermediate barriers like car doors.”
I will add that the other school of thought is using ultra light rounds to get higher velocities, rounds that are specifically designed to retain their terminal effects at even lower velocities - when it comes to that school of thought, the favorite is the 50gr Barnes TSX. Out of a 10.3" barrel the 50gr barnes will still be traveling at over 2,800fps at 15 yds (faster than M855 would be traveling right at the end of the barrel), and it is designed so that it will fragment at supposedly 1900fps. The problem is that the 50gr bullet limits range, is not as accurate or stable, and it hasn't been proven that the advertised ballistic properties are accurate. It also wouldn't have as high of a BC, and would likely fall short on kinetic energy, not to mention barrier penetration (like windshields and such, not walls). Barnes TSX drops petals when it travels through auto glass, and in some cases results in compromised expansion.
The military also now has the M855 A1 EPR, which has proven to be superior to classic M855, and offers much better performance in SBRs. It also has better penetration of metals, and more kinetic energy due to component makeup. I don't know a whole lot about it, but it might be something to look in to.
