Am I missing something? The 1 in 9 stabilizes the widest range of bullets. The only reason for the 1 in 7 was to stabilize the long tracer.......it was a NATO thing. The 55 gr groups like poo in the 1 in 7 and the military had fits in the first Gulf War trying to get the right ammo for the right guns. The 1 in 12 doesn't stabilize the 62 gr. In my opinion the 1 in 9 is the best choice. I think if the military had a do over all those A2's and later rifles would have been 1 in 9.
1/9 is good enough for anything over 16". but make a SBR out of a 1/9 twist barrel and you start to suffer in velocity and accuracy. Although 1/9 twist on a 16" barrel is just fine for most home defense/ sporting guys who use the 55gr stuff, I'd rather have a 1/7 twist rate that could chew threw 77+gr ammo like butter.
My otjher question is why arent they putting chrome lining in the barrel?!?! so they are basically giving you a cheaper barrel than you can get on an $800 AR!
77 gr is robbing Peter to save Paul kinda thing trying to get more thump for the bang in a small caliber round. The neat thing about the ACR is we won't have to rob anyone, we can go with the 6.8. Now with the chrome barrel issue, I would have to assume that are trying to go the cheaper route for the civilian guns. I certainly hope they are not going to submit a non chromed barrel and chamber to the military and I damn sure hope the military demands one..........they tried that shortcut in the 60's with the first m16 which cost people their lives.
I believe the finish they are using on the barrels is similar to nitriding...and is actually supposed to be similar or better than chrome lining with regards to durability and corrosion protection. LWRC has been doing this process to their barrels as well.
1/7" twist barrels will shoot down to 55 grain just fine although not completely ideal...but will also shoot the 75 & 77 grain ammo much better than 1/9". The trend in ammo selection has been towards the heavier bullets for the last several years because they provide better fragmentation at slower velocities. This means that they will kill stuff better at longer ranges with both long and short barrels. As was stated above, mixing a short 1/9" twist barrels with expensive suppressors is a bad idea.
1/9" is perfectly fine for range shooting, plinking, and varmint hunting...but you're not going to find a knowledgeable operator that would ever choose 1/9" over 1/7" for a serious use carbine.
My rant is not wether they will ever have a 1/7" barrel offered or not, I know they will, I mean it uses a standard M4 barrel for crying out loud. I was actually complaining that it will not be offered with one out the box, at least from what I know and its still priced quite high. I know it wont be hard to come across after market stuff to add later such as barrels , just stick a standard M4 barrel with a nut extention or an adaptor and your done. But can you clarify this for us: you are saying it will be offered straight out the box with an option to have a 1/7" ?? If thats the case I'll apologize and take my mis-informed happy butt outa here..lol.
Yeah, OTO, I think you have it right. 1 in 7" barrels will be available in time ( maybe May-June
That's what BM tells me).
And you are correct that the ACR's released in March ( the first batch) will only be available with the 1 in 9 twist barrel.
I hope we look back at these posts in the 4th qtr 2010 and laugh at all these issues.
I'm going to talk to BM next week to get more info on their shipping schedule. They told me that a few of them traveled from Maine to the N. Texas production line and the ACR's should be moving out the door at a pretty good clip in the next couple months.
With any luck , I'll have at least some of my orders of ACR's by mid-March and am looking forward to doing a range report on the 1 in 9 barrels. I will set aside one ACR as a demo gun for my range.
Actually it comes down to this. The civilian markets are flooded with 1/9 because that is the ideal twist for 55 and smaller grain rounds which is what the majority of the civilian market use. Sure some 62/64 grain rounds are used as well, but the bulk is still 55gr.
The military use 62/64gr and up to 77gr ammo. These heavier rounds require a faster twist rate to stabilize them. Of course you probably already know this.
So, if you are a manufacturer and you are marketing to the civilian and LE markets, then 1/9 is the ideal.