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Posted: 8/29/2004 3:23:34 PM EDT
[#1]
I can't speak to the comparison of 1/9 to 1/7, but I can say that I chose 1/7 because I like having the option of shooting heavier bullets. In the search for the more effective round, we are trending toward heavier bullets and those heavier bullets will filter down to the civvy market. IMHO, 1/9 just doesn't give enough stabilization for these heavier rounds.
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Posted: 8/29/2004 3:33:26 PM EDT
[#2]
IIRC, the reason given in the Bushmaster catalog for the 1/9 twist rate was that the faster twist barrels (1/7) showed increased wear for the same number of rounds, especially with lighter, faster bullets.
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Posted: 8/29/2004 3:38:35 PM EDT
[#3]
Marketing 
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Posted: 8/29/2004 3:42:29 PM EDT
[#4]
1x9 is plenty of twist for everything up to 69 gr in the real world, and covers about 99% of what most people will shoot. It has been the defacto standard, one size fits all, for many years.
The 1x7 is actually overkill for the 62 gr M855. It was used as it stabilized the tracer round in arctic conditions. Next time you fire tracers in Alaska during January, you can thank your lucky stars that the NATO and our military has shown such wisdom. Barrels with 1x7 twist are manufactured for military use, to meet mil spec. 1x8, 1x8.5 twists are offered, usually, in heavy target barrels for use with bullets in the 69-77 gr range. |
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Posted: 8/29/2004 3:46:59 PM EDT
[#5]
My take on the subject:
www.ar15.com/forums/topic.html?b=3&f=12&t=197439 |
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Posted: 8/29/2004 3:47:44 PM EDT
[#6]
Good point, but if you want to shoot the 75, 77, or 100 gr loads coming down the pike, then 1/9 won't cut it. As the search for a more effective round continues, the bullets are gonna get heavier. |
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Posted: 8/29/2004 3:51:01 PM EDT
[#7]
Oh GREAT, someone who actually shoots comes along and blows the whole theory out of the water. 
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Posted: 8/29/2004 4:08:02 PM EDT
[#8]
No...he only showed that one load worked for his barrel. It was hardly scientific. The problem is that heavier loads may or may not work with 1/9. I don't like leaving things to chance. |
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Posted: 8/29/2004 4:19:53 PM EDT
[#9]
I still use 1:12 almost exclusively.
I'm a 55 gr. person. and 1:12 is great for 55gr. and for my .22 LR upper ;) |
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Posted: 8/29/2004 4:20:01 PM EDT
[#10]
Your not telling me anything. I'm fully converted to 1/7 barrels now, except for one. SPR - 1/7 18" RECCE - 1/7 16" A4gery - 1/7 20" M4gery - 1/7 14.5" Middy - 1/7 16" - if giffman ever gets the group buy together Commando 1/7 11.5"/5.5" - gotta have that 5.5" FH so I can play with a "SBR" legally SAM-R - 1/8 20" - just to be different But, I can take a 1/9 upper to the same place he shot his and see how it does. Mine will be a lowly Bushmaster barrel, not some high-filuting Lijla barrel. I could use some of my 77gr SMK loads, similiar to what bigbore used also. Oh, it won't be scientific, as a matter of fact, I'll bet it would be pretty ugly, but I'm willing to take one for the team. ETA: If I can work it out on Wed, I'll put this rifle back together with the 1/9 barrel and shoot it at 600yds. It was disassembled for installation of the 1/7 barrel, but it can wait. That way the rifles used in bigbore's test and mine will be pretty similiar. 
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Posted: 8/29/2004 5:48:56 PM EDT
[#11]
Yes but that is my point: Why market a 1/9 if it is no improvement over a 1/7 (which you are already tooled up for with a gubment contract anyway)? I mean, all manufacturers went to that as a default twist and I never really heard a bunch of "WOW! IT'S A 1/9 TWIST! BUY YOURS TODAY!" It's just the way it is. 77 gr. Blackhills is mucho expensive and I don't handload. I don't know that it will ever get prevalent enough to be cheap in the next 5 years. All this magic death ray business about 75 gr.+ sounds like the same stuff heard about 9mm silver tips, etc. back in the 80's. If the 55 gr. and 62 gr. didn't drop goblins then I think we'd have heard alot more about it in the last 40 years.
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Posted: 8/29/2004 5:51:42 PM EDT
[#12]
Anymore searching and we are going to a new caliber, such as 6.8.
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Posted: 8/29/2004 5:56:41 PM EDT
[#13]
We are hearing more about it now that we are involved in real conflicts hence the coming of the 75, 77, and 100 gr bullets. The goal is to extend the fragmentation range of the weapon and 1/9 limits your options. |
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Posted: 8/29/2004 6:00:03 PM EDT
[#14]
First, it sounds like you won't have a real need for a 1/7 barrel, so don't get one, stick with the 1/9, you won't be disappointed. Never mind you have both. Second, the heavier weight bullets are effective at longer ranges than the standard 55gr and 62 gr loads. There seems to be a small push in the military ranks for a more effective load at longer range and the 77gr stuff seems to be fitting their needs. It is relatively common knowledge that a heavier bullet will be more lethal, up to certain limits. I load 77gr loads and shoot them from a variety of configurations. It makes my shooting experiences interesting and challenging. Third, with a 1/7 barrel you can shoot 99% of the loads that are readily available accurately, so what do you lose going to a 1/7 vs. the standard marketed 1/9. IMO, very little. Wouldn't be surprised if you saw the 1/9 barrel phased out in the future, but with the abundant supply of surplus 55gr and 62gr ammo, it isn't likely to be too soon. As always, YMMV. |
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Posted: 8/29/2004 6:01:25 PM EDT
[#15]
Ding - Ding - Ding..................................we have a winner! 
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Posted: 8/29/2004 6:02:46 PM EDT
[#16]
Bradd_D,
Look for this this a few years down the road, but you are going to see two different types of issue ammo for the miltary. One for close range, and one for distance. At least that is the projected goal. |
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Posted: 8/29/2004 6:16:26 PM EDT
[#17]
If that's the case, I hope we don't have another war like WWII. The battlefield changed constantly and trying to issue two kinds of ammo would have been a logistical nightmare. |
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Posted: 8/29/2004 6:40:51 PM EDT
[#18]
Oh my, then it's time to change calibers then. Let's think about that for a minute. However, most battlefield deaths do not result from small arms or rifle fire. I'd venture to say that now it is less than small arms deaths in WW2, which were something like less than 10% (someone correct me if I'm wrong). If you have to start jacking about with loadings, twist, and different loadings and twists for close range and long range, then there is a fundamental weakness in the round. And btw, I love the 5.56, probably more so than the 7.62. But I shoot things that don't shoot back............
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Posted: 8/29/2004 6:42:55 PM EDT
[#19]
thanks for the well thought out and patient reply Mongo.
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Posted: 8/29/2004 7:00:57 PM EDT
[#20]
The only thing i can see with that would be to issue Mk 262 ammo en masse. Out of a 20" M16 barrel, that round should reliably perform out to at least 225 yards, which is more than adequate from a practical standpoint. The only thing that would be needed would be 6.8mm SPC or even just stick with 7.62 for that purpose, which we are doing right now anyway, for ranges past that and issuing that to DMs and snipers only. I can't see issuing troops two different types of ammo to each person for one weapon for diffferent distances or issuing two long arms for each person. That would be a nightmare. The only way this could be done would be to have one of those "smart weapons" that everyone keeps talking about that can switch from different types of ammo at the push of a button or a flick of the switch. However, i think that is a decade or two off. In the short term, the smart thing would be to issue Mk262, keep the M16 or issue the M8 with a 18" or 20" barrel, and issue heavier calibers to longe range shooters while we wait for the invention of the phaser.
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Posted: 8/29/2004 9:05:00 PM EDT
[#21]
My defensive rifles are all loaded with 75Gn- 77Gn OTM ammo. that's why i use the 1:7
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Posted: 8/30/2004 12:46:46 AM EDT
[#22]
The change to 1:9 was made 15 years ago, because this was the optimal twist rate for the ammo that most people were shooting then (and what most people are STILL shooting): 55-62gr ammo.
The use of heavy match bullets to get increased terminal ballistic performance is only about 5 years old, and has only been widely understood for a couple of years (I'd like to think the Ammo Oracle had a little to do with that...). But, even with this knowledge, MOST people will STILL only ever use 55gr and 62gr ammo, because it's readily available and much cheaper than quality, NATO-pressure 75-77gr ammo. Thus, even today, 1:9 best meets the needs of the vast majority of AR owners. Now, if you ARE one of the small minority of people who both understand the usefulness of the heavy OTM loadings AND are willing to actually pay to buy and use it, then you obviously want to make sure you choose 1:7 barrels. I'm a member of this little subset of AR owners myself. -Troy |
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Posted: 9/1/2004 12:51:02 AM EDT
[#23]
I dont know about all the info from the higher learned than I......
the reason I have a 1/9 barrel, is #1: my old Colt with a 1/7 didnt shoot 40 grain TAP worth a poop... #2: I really liked my new rifle, so I bought it, and it happened to have a 1/9 HBAR....... the 1/7 barrel gave me about 8MOA with 40g TAP, the 1/9 with the same ammo is around 2MOA...mind you this is with my decrepid eyes and iron sights.... Pilk |
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