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Posted: 3/3/2006 8:28:02 PM EDT
I hate to whine, but! Bushmaster probably paid a few lawyers large to get to use the "M4" moniker. So why don't they offer the M4geries in 1/7 twist.? I am a middle of the bell curve guy, so what I want is what everyone wants. We all want the 1/7 in the carbines, and with the M4 feed chutes all matched up by the way. They just sold a raft full of the 1/7 rigs through Ed Sr.'s SEBR program. We all want to be able to sling that 77+gr long bullet stuff down range with tack driving accuracy. I would like to try some even heavier tungsten stuff. I think Bushy is about the only major not offering 1/7 now. What is the problem?
Link Posted: 3/3/2006 8:42:07 PM EDT
+1
I think they offer 1/7 as an option, but I am not for sure. You would need to call and ask.
Link Posted: 3/3/2006 8:45:56 PM EDT
They don't make many runs of them each year.

But they do make them. Call and ask them.

I put a 14.5 in 1:7 with perm Phantom on my rifle after the 94AW ban sunset.
Link Posted: 3/3/2006 8:47:14 PM EDT
[Last Edit: 3/3/2006 8:49:12 PM EDT by safetyhit]
Some think the 1/9 twist is a better overall rate than the 1/7. They say it is better for the majority of rounds (55gr-67gr), where the 1/7 is better for heavier rounds. I understand the folks at Bushmaster think the same way, but I can't say for sure.
Link Posted: 3/3/2006 8:52:11 PM EDT
they do offer the m4 profile bbl. in 1x7



check with gds_enterprise, he has them in stock for a fair good price.
Link Posted: 3/3/2006 9:02:26 PM EDT
Bushmaster does make 1/7 twist in both the 20" govt profile, and m4 profile (14.5" and 16"). They are just as readily available in the EE as any other Bushmaster barrel.
Link Posted: 3/3/2006 9:03:35 PM EDT
[Last Edit: 3/3/2006 9:06:16 PM EDT by Another-Bill]
For almost all civilian uses where a M4 style rifle is used a 1/9 is better.
For Service Rifle competition where 77 grain and up is shot out to 600 yards my Kreiger has a 1/7.75
which still is not 1/7 but it is for heavy bullets at long ranges.
The 1/7 is to stablize heavy tracer rounds.

Bill
Link Posted: 3/3/2006 9:07:45 PM EDT

Originally Posted By uglygun:
They don't make many runs of them each year.

But they do make them. Call and ask them.

I put a 14.5 in 1:7 with perm Phantom on my rifle after the 94AW ban sunset.



+1
You can get a 1/7 Bushmaster.
This may require patience, though.
Link Posted: 3/3/2006 9:52:00 PM EDT
The 3-4 times I have ordered 1/7 twist barrels, both M16A2 and M4, from BFI, they have always shipped them the next day.
Link Posted: 3/4/2006 4:23:25 AM EDT
I emailed them..if they have them on hand from an over run your set...if not they told me I would have to order 100 for them to make a run of barrels in 1/7 twist.It depnds on what they have on hand if they have none they will not do just 1 barrel.
Link Posted: 3/4/2006 9:30:56 AM EDT
Hummm thats funny I talked to bushmaster on the phone and they said no to 1/7 barrels no reason just that you can get a 1/7 govt. profile barrel but that's it anyone else actual obtain a 1/7 from BM that is not Govt profile?
Link Posted: 3/4/2006 10:05:16 AM EDT

Originally Posted By Another-Bill:
For almost all civilian uses where a M4 style rifle is used a 1/9 is better.



What will 1:9 do that 1:7 won't?
Link Posted: 3/4/2006 10:08:46 AM EDT
The 05 Bushmaster SEBR has an M4 barrel with a 1/7 twist.

You did buy one, right?
Link Posted: 3/4/2006 10:20:54 AM EDT

Originally Posted By KA3B:
The 05 Bushmaster SEBR has an M4 barrel with a 1/7 twist.

You did buy one, right?



I did .

NATO 5.56mm 1/7
Link Posted: 3/4/2006 5:41:05 PM EDT
Thanks for all the inputs and suggestions. I notice that the Colt 6920's NIB are going for around $1300 in the EE section. The Bushmaster Catalog MSRP for their M4gery is $1,200+ with 1/9 and ? feed ramps, so I guess that settles it for me.
Link Posted: 3/4/2006 5:45:02 PM EDT

Originally Posted By CCW:
Thanks for all the inputs and suggestions. I notice that the Colt 6920's NIB are going for around $1300 in the EE section. The Bushmaster Catalog MSRP for their M4gery is $1,200+ with 1/9 and ? feed ramps, so I guess that settles it for me.



I don't think that Bushmaster has M4-style extended feed ramps,
if that is what you are referring to.
Link Posted: 3/4/2006 5:51:58 PM EDT

What will 1:9 do that 1:7 won't?



It will handel the lighter 55grs better. What is the most popular FMJ round around? 55grain.
Let me pose a question to you; how many tracer rounds do you shoot?
I don't shoot any and if I did accuracy would not be the top concern as it would be mostly for fun.
On the other hand, 1/9 will preform better with what we generally shoot up to about 69grs.
The 1/7 was designed for tracer rounds, if you don't shoot tracers then the 1/7 is a moot point unless looking like GI Joe is important.

Bill

P.S. My 6520 has a 1/7 as did all of my previous Colts. No big deal.
Link Posted: 3/4/2006 6:58:55 PM EDT
I have a 14.5" M4 and an 11.5" Bushmaster barrels, both are 1/7 twist.
Link Posted: 3/4/2006 7:19:45 PM EDT
Some people say that the 1/9 twist is better than the 1/7 especially with the shorter barrel AR's. Some say that the 1/7 twist over stabilizes the 55 and 62 grain rounds so that they are not has effective as far as stopping power goes. Don't know if that is true, but that is one of the arguments against the 1/7 twist.
Link Posted: 3/4/2006 7:21:28 PM EDT
I have a 1/7 twist bushmaster M4 barrel. I got it last year from PK Firearms (check equipment exchange, they rock).

I could have got it directly from Bushmaster, but after speaking with one of their staff the only 1/7 barrels they had immediatly available came with the stock front sight post, which I did not want.

Link Posted: 3/4/2006 7:35:04 PM EDT

Originally Posted By Another-Bill:

What will 1:9 do that 1:7 won't?



It will handel the lighter 55grs better. What is the most popular FMJ round around? 55grain.
Let me pose a question to you; how many tracer rounds do you shoot?
I don't shoot any and if I did accuracy would not be the top concern as it would be mostly for fun.
On the other hand, 1/9 will preform better with what we generally shoot up to about 69grs.
The 1/7 was designed for tracer rounds, if you don't shoot tracers then the 1/7 is a moot point unless looking like GI Joe is important.

Bill

P.S. My 6520 has a 1/7 as did all of my previous Colts. No big deal.



It was a trick question. The 1:9 will shoot bullets below 55gr better and 1:7 will shoot bullets above 69gr better. From 55gr to 69gr they are more or less the same.
Link Posted: 3/4/2006 7:58:03 PM EDT

Originally Posted By Mdripley:
Hummm thats funny I talked to bushmaster on the phone and they said no to 1/7 barrels no reason just that you can get a 1/7 govt. profile barrel but that's it anyone else actual obtain a 1/7 from BM that is not Govt profile?


I have some 16" 1/7 HBARs, but that was part of special run.
Link Posted: 3/4/2006 8:30:39 PM EDT
[Last Edit: 3/4/2006 8:34:42 PM EDT by Lon_Moer]
As previously stated, BM does make 1/7s, and I do have one of their 14.5 1/7 M4's w/4-port Phantom.
I also have two of CMMG's 1/7 barrels, a 14.5" M4 w/5-port Phantom and a 14.7" LW w/A2. The CMMG barrels have all features.
Link Posted: 3/5/2006 7:48:32 PM EDT

Originally Posted By Lon_Moer:
As previously stated, BM does make 1/7s, and I do have one of their 14.5 1/7 M4's w/4-port Phantom.



Did you read "pun" and "mdripley"? Did you read the Bushy 2006 catalog? It seems the Bushy twist is going to be 1/9 with few to no exceptions. Nothing wrong with making a marketing decision and sticking with it.

Read "Barrel Twist. Is this true?", if you want a good dose of twist misinfo.

I think it is the DaVinci Code. Take 2006. Add the integers = 8. Add one to 8 = 9. There you have it.
Link Posted: 3/5/2006 8:39:46 PM EDT

Originally Posted By CCW:
Thanks for all the inputs and suggestions. I notice that the Colt 6920's NIB are going for around $1300 in the EE section. The Bushmaster Catalog MSRP for their M4gery is $1,200+ with 1/9 and ? feed ramps, so I guess that settles it for me.



Can't go by MSRP. 6920's typically sell at a street price of $1100-$1200 or so while the Bushy patrolman sells for around $800 now. As said earlier Bushy does offer 1/7" but as a special order item. You could always buy a Bushy lower in the EE and get a 1/7 upper from Bushy or maybe even from a vendor and still undercut the 6920 by hundreds. CMMG is also a great option.
Link Posted: 3/5/2006 10:35:39 PM EDT

Originally Posted By KA3B:
The 05 Bushmaster SEBR has an M4 barrel with a 1/7 twist.

You did buy one, right?



Yes I did.
Link Posted: 3/5/2006 10:49:02 PM EDT
[Last Edit: 3/5/2006 10:51:32 PM EDT by STG77]

Originally Posted By Another-Bill:

What will 1:9 do that 1:7 won't?



It will handel the lighter 55grs better. What is the most popular FMJ round around? 55grain.
Let me pose a question to you; how many tracer rounds do you shoot?
I don't shoot any and if I did accuracy would not be the top concern as it would be mostly for fun.
On the other hand, 1/9 will preform better with what we generally shoot up to about 69grs.
The 1/7 was designed for tracer rounds, if you don't shoot tracers then the 1/7 is a moot point unless looking like GI Joe is important.

Bill

P.S. My 6520 has a 1/7 as did all of my previous Colts. No big deal.




Can you actually tell an accuracy difference shooting 55 grain ammo out of a 1/7 and 1/9? I seriously doubt it. I sure can't.

1/9 may certainly be better for ammo UNDER 55gr, but who shoots that stuff in their AR anyway?

1/9 is pointless in an AR unless it is a dedicated varmint rig.
Link Posted: 3/5/2006 11:01:06 PM EDT
Link Posted: 3/6/2006 3:41:55 AM EDT

Originally Posted By RR:
Some people say that the 1/9 twist is better than the 1/7 especially with the shorter barrel AR's. Some say that the 1/7 twist over stabilizes the 55 and 62 grain rounds so that they are not has effective as far as stopping power goes. Don't know if that is true, but that is one of the arguments against the 1/7 twist.



Absoloutely, positively NOT true at ALL. Not even a hint of truth. Total urban legend.
Link Posted: 3/6/2006 5:27:27 AM EDT
[Last Edit: 3/6/2006 6:24:51 AM EDT by Yojimbo]

Originally Posted By Another-Bill:

What will 1:9 do that 1:7 won't?



It will handel the lighter 55grs better. What is the most popular FMJ round around? 55grain.
Let me pose a question to you; how many tracer rounds do you shoot?
I don't shoot any and if I did accuracy would not be the top concern as it would be mostly for fun.
On the other hand, 1/9 will preform better with what we generally shoot up to about 69grs.
The 1/7 was designed for tracer rounds, if you don't shoot tracers then the 1/7 is a moot point unless looking like GI Joe is important.

Bill

P.S. My 6520 has a 1/7 as did all of my previous Colts. No big deal.



I guess both my 1/7 carbines are broken because they both shoot 45gr-62gr ammo just as accurately as the 1/9 barrel.

The only thing you may have issues with are very thin jacketed lightweight ammo. So if you select your ammo properly you wont have any issues. Heck IIRC, our very own brouhaha has shot 40gr ammo out of his 1/7 barrels!

BTW, I don't shoot tracer rounds but I like to shoot 75gr and 77gr ammo does that count?

Also, how does a 1/7 barrel look differently than a 1/9 barrel? Will the guy with 1/9 barreled M4gery look less like GI Joe than the guy with the 1/7 barreled M4gery?
Link Posted: 3/6/2006 6:10:22 AM EDT

Originally Posted By Bradd_D:
It was a trick question. The 1:9 will shoot bullets below 55gr better and 1:7 will shoot bullets above 69gr better. From 55gr to 69gr they are more or less the same.



I think it's more like; The1/9 will shoot bullets up to 69g better, and the 1/7 will shoot bullets above 69g better. There is plenty of documentation that supports the fact that the 1/7 is too fast, and is not optimal for 55 g bullets.
Link Posted: 3/6/2006 6:20:11 AM EDT

There is plenty of documentation that supports the fact that the 1/7 is too fast, and is not optimal for 55 g bullets.



Are you serious? Where is this documentation? I have been shooting 45-55 grain bullets out of my 1/7 twist barrels for years with no accuracy penalty, as have many fellow shooters. I've never seen any evidence to support that variances in accuracy are due to the rate of twist, and not other factors. Certainly all the anecdotal evidence available on this site and other gunboards supports my experience as well. If I can be pointed towards some more scientific evidence to the contrary I'd sure like to reead it, though.

I don't feel that there are any penalties, and only advantages, to running a 1/7 twist in an AR.

Brewer
Link Posted: 3/6/2006 6:34:25 AM EDT
[Last Edit: 3/6/2006 6:34:53 AM EDT by Yojimbo]

Originally Posted By BrianNH:

Originally Posted By Bradd_D:
It was a trick question. The 1:9 will shoot bullets below 55gr better and 1:7 will shoot bullets above 69gr better. From 55gr to 69gr they are more or less the same.



I think it's more like; The1/9 will shoot bullets up to 69g better, and the 1/7 will shoot bullets above 69g better. There is plenty of documentation that supports the fact that the 1/7 is too fast, and is not optimal for 55 g bullets.



I agree that the 1/7 may not be optimal for 55gr ammo but most of us are talking about shooting mil-spec 5.56 out of a battle grade chrome lined barrel! Even with lighter match ammo I can't tell the difference between 1/9 and 1/7.

I won't deny that differences between the 1/9 and 1/7 twist are there but the effects of over spinning the lighter bullets in 1/7 barrels are so negligible that 99% of the people will never notice it...
Link Posted: 3/6/2006 6:41:11 AM EDT
[Last Edit: 3/6/2006 6:48:32 AM EDT by metroplex]

Originally Posted By Bradd_D:

Originally Posted By Another-Bill:
For almost all civilian uses where a M4 style rifle is used a 1/9 is better.



What will 1:9 do that 1:7 won't?



It will also supposedly last longer

I shoot mainly 55/62 gr and not 69gr or higher. 1/9 for me.
1/9 twist on 20" or longer barrels are reported by Bushmaster to stabilize up to 75 gr bullets.
Link Posted: 3/6/2006 6:47:48 AM EDT
[Last Edit: 3/6/2006 6:50:32 AM EDT by Yojimbo]

Originally Posted By metroplex:

Originally Posted By Bradd_D:

Originally Posted By Another-Bill:
For almost all civilian uses where a M4 style rifle is used a 1/9 is better.



What will 1:9 do that 1:7 won't?



It will also typically last longer.



Not by much, I asked Gunzilla about this and he mentioned that the 1/9 may last about 500-1000 rounds longer.

Again the difference is so small that 99% of the users will not notice...

In fact Gunzilla mentions it again in the thread linked below.

www.jobrelatedstuff.com/forums/topic.html?b=3&f=118&t=270950
Link Posted: 3/6/2006 6:49:46 AM EDT

Originally Posted By Yojimbo:

Originally Posted By metroplex:

Originally Posted By Bradd_D:

Originally Posted By Another-Bill:
For almost all civilian uses where a M4 style rifle is used a 1/9 is better.



What will 1:9 do that 1:7 won't?



It will also typically last longer.



Not by much, I asked Gunzilla about this and he mentioned that the 1/9 may last about 500-1000 rounds longer.

Again the difference is so small that 99% of the users will not notice...



I'm not against using 1/7 but most of the time I have found that the 1/7 barrels to be out of stock or slightly more expensive than the 1/9 barrels when I was sourcing parts for an AR build.
Link Posted: 3/6/2006 6:52:48 AM EDT
[Last Edit: 3/6/2006 6:53:33 AM EDT by Yojimbo]
Metroplex,

No problem, I know what you're saying.

Sorry if I came on too strong it's just that I've heard so much BS about the 1/7 twist that I can't help putting in my 2 cents...
Link Posted: 3/6/2006 6:52:50 AM EDT

Originally Posted By Brewer:

There is plenty of documentation that supports the fact that the 1/7 is too fast, and is not optimal for 55 g bullets.



Are you serious? Where is this documentation? I have been shooting 45-55 grain bullets out of my 1/7 twist barrels for years with no accuracy penalty, as have many fellow shooters. I've never seen any evidence to support that variances in accuracy are due to the rate of twist, and not other factors. Certainly all the anecdotal evidence available on this site and other gunboards supports my experience as well. If I can be pointed towards some more scientific evidence to the contrary I'd sure like to reead it, though.

I don't feel that there are any penalties, and only advantages, to running a 1/7 twist in an AR.

Brewer



Just because you have been shooting 45g bullets out of your 1/7 twist for years doesn't mean that it's the optimal twist for your bullets. I'm not saying it's bad, or there is a huge penalty as far as accuracy or barrel life, but talk to any reputable barrel maker regarding caliber and optimal rate of twist and then get back to me.

Link Posted: 3/6/2006 7:20:37 AM EDT


i have (2) 14.5" M4 barrels, and (1) 11.5" H-bar both Bushmaster, both 1/7 twist.

scrounge around and you'll find 'em.


Link Posted: 3/6/2006 8:15:45 AM EDT
[Last Edit: 3/6/2006 8:20:31 AM EDT by Another-Bill]

1/9 is pointless in an AR unless it is a dedicated varmint rig.



Is "pointless" too strong?


I won't deny that differences between the 1/9 and 1/7 twist are there but the effects of over spinning the lighter bullets in 1/7 barrels are so negligible that 99% of the people will never notice it...


Yojimbo, I agree, there is VERY little difference, which really was my point. A 1/9 is fine for what we do. I have a kreiger 1/7.75 on my DCM service rifle and it shoots the Wincherster 45gr JHP's damn good at 100 yrads, which some would say it shouldn't. I have no idea where they go south but I doubt they would hold up at 600 yards. I have shot Colts from 1988 until 2000 when I bought a 1/9 Bushy. I shot 55 grs and had no problems. So I do believe that a 1/9 will stabilize a 77 gr as well as the 1/7 stabilizes the 45 grs. My point is only that the 1/9 will do most anything you want to do. If you really want an absolute tack driver like the Camp Perry boys do at 600 yards, then Kreiger will sell you a 1/7.75 and RR, Armalite etc will sell you a 1/8. Which points out that the military went with the 1/7 solely for the tracers. I you gotta have a 1/7 to be "mil spec" what ever that is, then go for it, personally I would not worry about it. If I some how get into the military they will give me a 1/7 rifle to shoot, but at my age, that would be scarry.

Bill
Link Posted: 3/6/2006 9:35:25 AM EDT
[Last Edit: 3/6/2006 12:07:41 PM EDT by Yojimbo]

Originally Posted By Another-Bill:

1/9 is pointless in an AR unless it is a dedicated varmint rig.



Is "pointless" too strong?


I won't deny that differences between the 1/9 and 1/7 twist are there but the effects of over spinning the lighter bullets in 1/7 barrels are so negligible that 99% of the people will never notice it...


Yojimbo, I agree, there is VERY little difference, which really was my point. A 1/9 is fine for what we do. I have a kreiger 1/7.75 on my DCM service rifle and it shoots the Wincherster 45gr JHP's damn good at 100 yrads, which some would say it shouldn't. I have no idea where they go south but I doubt they would hold up at 600 yards. I have shot Colts from 1988 until 2000 when I bought a 1/9 Bushy. I shot 55 grs and had no problems. So I do believe that a 1/9 will stabilize a 77 gr as well as the 1/7 stabilizes the 45 grs. My point is only that the 1/9 will do most anything you want to do. If you really want an absolute tack driver like the Camp Perry boys do at 600 yards, then Kreiger will sell you a 1/7.75 and RR, Armalite etc will sell you a 1/8. Which points out that the military went with the 1/7 solely for the tracers. I you gotta have a 1/7 to be "mil spec" what ever that is, then go for it, personally I would not worry about it. If I some how get into the military they will give me a 1/7 rifle to shoot, but at my age, that would be scarry.

Bill



Bill,

While tracers were one reason the 1/7 twist was chosen there were other reasons including leaving more options for down the road. Check out the thread I linked above where Coldblue who was actually involved in the M16a2 design spells out the reasons they went with a 1/7 twist.

Also the original poster was asking about chrome lined battle grade barrels not match barrels. It's true that some 1/9 will be able to accurately shoot 75-77gr ammo but there will also be quite few that can't.

It seems that the match barrels and longer(16"+) 1/9 twist barrels have a much better chance of shooting the heavier/longer bullets well as compared to the chrome lined barrels. Some will some won't you won't know until you try.

My 1/9 shot patterns with 77gr ammo at 100 yards.

The bottom line is it really depends on how you will be using your AR. If you want the option to shoot heavier/longer bullets and want to be 100% sure they will shoot as accurately as you can then get a 1/7 and skip the guesswork with the 1/9.

If you already have an 1/9 barrel give it try it might work well and then it might not either way you have nothing to loose by trying.

IMHO, these days the 1/7 is the best general purpose twist because it will still let you accurately shoot the lighter 45gr-55gr less expensive ammo all the way to the heavier/longer "best of class" ammo like 75gr 5.56 TAP and MK262 Mod 1, etc...

Link Posted: 3/6/2006 11:25:28 AM EDT

Originally Posted By BrianNH:

Originally Posted By Bradd_D:
It was a trick question. The 1:9 will shoot bullets below 55gr better and 1:7 will shoot bullets above 69gr better. From 55gr to 69gr they are more or less the same.



I think it's more like; The1/9 will shoot bullets up to 69g better, and the 1/7 will shoot bullets above 69g better. There is plenty of documentation that supports the fact that the 1/7 is too fast, and is not optimal for 55 g bullets.


Have you read the Ammo Oracle?
Link Posted: 3/6/2006 11:28:05 AM EDT
Yojimbo

I see your point. I figure my 1/9 Bushy is for IPSC and I shoot 55's or 62's and that is about it.
If I shoot heavy bullets then I will shoot my Kreiger tubed CMP, and them I have an old LNIB 6520 that is a 1/7 but I usually don't shoot it. I have another upper that I will barrel and put a lower on and I really have looked at the Sabre Defense products, they look nice, but of course I don't need it.

Bill
Link Posted: 3/6/2006 1:36:08 PM EDT

Originally Posted By Lon_Moer:

Originally Posted By BrianNH:

Originally Posted By Bradd_D:
It was a trick question. The 1:9 will shoot bullets below 55gr better and 1:7 will shoot bullets above 69gr better. From 55gr to 69gr they are more or less the same.



I think it's more like; The1/9 will shoot bullets up to 69g better, and the 1/7 will shoot bullets above 69g better. There is plenty of documentation that supports the fact that the 1/7 is too fast, and is not optimal for 55 g bullets.


Have you read the Ammo Oracle?



Have I read it?, or has Bradd_D read it? Better yet, have you read it? Heres a few excerpts;

Q. What twist rate do I want for my rifle?

Probably 1:9, but it depends on what kind of bullets you intend to shoot.

The majority of shooters, though, typically shoot bullets of 50 to 69 grains in weight (note that the 62gr SS-109/M855 bullet is as long as a 71 grain lead core bullet) and should select 1:9 twist barrels. At typical .223 velocities, a 1:9 twist will stabilize bullet lengths equivalent to lead-core bullets of 40 to 73 grains in weight.

1:7 twist rifles are slightly less accurate with lighter bullets and will often blow apart the thin jackets of lightweight varmint bullets. The 1:7 twist is used by the military to stabilize the super-long L-110/M856 tracer bullet out to 800 yards, but unless your plans include shooting a significant amount of M856, the 1:9 twist rate is better suited for general use.

Link Posted: 3/6/2006 1:57:37 PM EDT

Originally Posted By BrianNH:

Originally Posted By Lon_Moer:

Originally Posted By BrianNH:

Originally Posted By Bradd_D:
It was a trick question. The 1:9 will shoot bullets below 55gr better and 1:7 will shoot bullets above 69gr better. From 55gr to 69gr they are more or less the same.



I think it's more like; The1/9 will shoot bullets up to 69g better, and the 1/7 will shoot bullets above 69g better. There is plenty of documentation that supports the fact that the 1/7 is too fast, and is not optimal for 55 g bullets.


Have you read the Ammo Oracle?



Have I read it?, or has Bradd_D read it? Better yet, have you read it? Heres a few excerpts;

Q. What twist rate do I want for my rifle?

Probably 1:9, but it depends on what kind of bullets you intend to shoot.

The majority of shooters, though, typically shoot bullets of 50 to 69 grains in weight (note that the 62gr SS-109/M855 bullet is as long as a 71 grain lead core bullet) and should select 1:9 twist barrels. At typical .223 velocities, a 1:9 twist will stabilize bullet lengths equivalent to lead-core bullets of 40 to 73 grains in weight.

1:7 twist rifles are slightly less accurate with lighter bullets and will often blow apart the thin jackets of lightweight varmint bullets. The 1:7 twist is used by the military to stabilize the super-long L-110/M856 tracer bullet out to 800 yards, but unless your plans include shooting a significant amount of M856, the 1:9 twist rate is better suited for general use.




Like I said earlier, 1:7 will do everything a 1:9 will do (as evidenced by posters in this thread), but it also gives you the option of keeping up with the current trend toward heavier 5.56 rounds. You have noticed that trend haven't you or are you too busy rereading the two year old Ammo Oracle? When you can provide proof that 1:7 is less accurate or more barrel damaging than 1:9 in a chrome-lined M4 carbine I will pay heed. Until then, I'm heading to the range...
Link Posted: 3/6/2006 2:03:02 PM EDT
I'm not a follower of trends. I just shoot whatever's safe and cheap. Mk 262 / 77 gr match stuff is great if you really need it. I certainly can't afford to plink 1000+ rd of BH in a range session.
Link Posted: 3/6/2006 2:31:32 PM EDT

Originally Posted By metroplex:
I'm not a follower of trends.



I am if it makes my carbine more effective or lethal. The bottom line is that either twist will work for the shooting most of us do. If you're shooting varmint loads, you're probably going to go with 1:12 or 1:14 so that argument is moot. The realistic range for 1:9 is 55-69 and the realistic range for 1:7 is 55-77. Not a helluva lot of difference. Choose your rifle configuration and manufacturer and know that whichever twist they choose to sell you will service most if not all your needs just fine.
Link Posted: 3/6/2006 4:35:08 PM EDT
I agree. However I am not planning to use my rifles or carbines defensively out to 800m. I'd be surprised if I would even need anything past 200 yd.

I shoot 50/50 55gr/62gr, nothing lighter or heavier (too pricey). I'm sure most of the plinkers are in the same category: buy lots and lots and lots of Wolf/cheap plinking ammo to make their weapons go bang at the range. I wouldn't mind keeping a box of 75gr or 77gr ammo handy, and I have heard that 77gr will shoot FINE out of a 1/9 twist barrel out to 100yd, past 100yd is anyone's bet.
Link Posted: 3/10/2006 10:27:10 PM EDT
[Last Edit: 3/10/2006 10:27:55 PM EDT by ErinMT]
OK, so out to 300m, which is what most 14.5-16" barrels are used for, the 1/7 will fire everything from M855 to the 77 grain Mark 12 designed ammo with accuracy good enough to get a COM hit on a human being?

And the 1/9 is good for use with M855 and the lighter loads that are good for varmit hunting and prevention of over penetration that many LEOs are concerned with?


Do I have this right?
Link Posted: 3/10/2006 11:20:08 PM EDT
Because most users really don't care...
Link Posted: 3/13/2006 2:30:31 PM EDT

Originally Posted By ErinMT:
OK, so out to 300m, which is what most 14.5-16" barrels are used for, the 1/7 will fire everything from M855 to the 77 grain Mark 12 designed ammo with accuracy good enough to get a COM hit on a human being?

And the 1/9 is good for use with M855 and the lighter loads that are good for varmit hunting and prevention of over penetration that many LEOs are concerned with?


Do I have this right?



Bushmaster stated that their 20" and longer 1/9 twist barrels will stabilize up to 75 gr bullets.
The sub-20" barrels in 1/9 twist form will stabilize up to 69 gr bullets from what I recall.

Use that and draw your own conclusions.
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