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A-Max is a VLD design. Those have to have 1 in 8" or quicker to stabilize. They're also long enough that they can't be loaded to mag length.
Hornady 75 BTH is a different bullet. Those too prefer quicker twists, but if you have a "quickish" 1 in 9", they can work. These can be laoded to mag length, as can the 75 Nosler BTHP, the 77 grain Sierra and the 73 grain Berger. But as soon as you get into any VLD design, they are designed for slowfire competition, and are single loaded to ensure bullet ahs minimal jump to lands. Often these OALs run around 2.450"
DMR brings up something that makes me think that this is an example of a document crafted around a specific seller's item and not from someone that knows what they are doing to acquire the best fitting item.
"The U.S. Department of State, INL Section, U.S. Embassy Bogota, Colombia , has a requirement for the purchase of a six hundred (600) M4A1 type assault rifles, to be donated to the government of Colombia for INL program purposes."
"Rifling: 1 turn in 9 (22.8 cm) R.H. twist, 6 grooves and lands (this is an absolute requirement, no other twist rate is acceptable), weight not to exceed 6.5 lbs, mode of operation semi auto and 3 shot burst. "
Within the military an M4A1 is differentiated from an M4 by being equipped with a full-auto trigger group, whereas the M4s are equipped with the crappy A2 burst mechanism. M4A1s feature a 1:7 twist rifling, there have never been any M4A1s with 1:9 barrels. The twist rate printed on the barrel is irrelevant. If they had a need for the rifle to shoot a particular bullet/cartridge, that should have been part of the document, as in, "Must achieve under 6" groups at 300 yards with M193 from a machine rest". It's the performance that is supposed to matter, not the method. This implies to me that the author of the document does not know what an M4A1 really is, and is being fed twisted information by the vendor or a supporter of the vendor.
There are some very angry dudes that can tell you what happens when you write a document with the intention of getting something that everybody thinks is great, and they don't show up to compete for the contract and you get something you really didn't want because the wrong language was used in the requirements.
Last edited by Failure2Stop; 06-19-09 at 09:50.
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