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9/22/2017 12:11:25 AM
Posted: 8/16/2005 7:34:22 PM EDT
I have been trying to decide on a new colt purchase in September, cant decide
between the 6721 or 6920,only differance that makes it a touch choice is the
barrel twist 1/7 or 1/9.
I mostly shot 55gr or 62gr max..
some advice on this would be great...
Link Posted: 8/16/2005 7:39:45 PM EDT
If thats all your gonna shoot 1/9 will do.In my experience my 1/9 Bushy will shoot 75 grain fine.I got a 1/7 just to have something different and also will shoot any weight ammo with good results.The 1/7 was made to accomodate the longer tracer round to begin with but both twist rates will serve you well.
Link Posted: 8/16/2005 7:43:32 PM EDT
bushy says you can shoot up to 75 grain with little degradation in accuracy in a 1/9.
Link Posted: 8/16/2005 7:46:21 PM EDT
If you are shooting 55 and 62 mostly then I'd 1/9, reason throat erosion.
Link Posted: 8/16/2005 7:48:44 PM EDT
"Can Shoot" and "Can Shoot Real Well" are two different worlds when it comes to twist...for 55-69grs the 1:9 would be great..but for 69grs and up?...1:7 is far better...as I witnessed and understand.
Link Posted: 8/16/2005 8:54:54 PM EDT
Out of those rifles I would go with the 6920 for the simple reason it is the M4 and I prefer the M4 over the Hbar. As for which twist rate will better serve you, most likely the 1/9" if you plan on sticking to the 55-62gr. I have a Bushy 1/9" and usually only shoot 55gr but I have gone as high as 69gr w/ great results. I do plan on trying a box of 75gr just to see what happens though.
Link Posted: 8/16/2005 8:59:26 PM EDT
Throat erosion has nothing to do with twist and everything to do with heat and how fast you shoot wich will cause the heat.
Link Posted: 8/16/2005 9:11:05 PM EDT
h
Link Posted: 8/16/2005 9:18:47 PM EDT
get the 1-9

Link Posted: 8/16/2005 9:20:13 PM EDT
you have greater/more options for ammunition using 1/7 twist than 1/9, although 1/9 will suit you for average use. If you ever want to get into the heavier type ammo (ie 75gr) it would be recommended that you go with 1/7.
Link Posted: 8/16/2005 9:22:11 PM EDT
It feels good to be back here after a few years
Link Posted: 8/16/2005 9:37:27 PM EDT

Originally Posted By niceguymr:
you have greater/more options for ammunition using 1/7 twist than 1/9, although 1/9 will suit you for average use. If you ever want to get into the heavier type ammo (ie 75gr) it would be recommended that you go with 1/7.



That is not true. The 1/7 will do well with the mid to heavy loads as well as some lighter loads where the 1/9 will do equally well with the lighter to middle weight as well as some heavier loads. 1/9 is widely thought of as the most practical twist rate for the non LEO/military shooter. They both offer pretty much just as much flexibility as one another just at the other end of the spectrum. Like he said he shoots 55gr to 62gr max. So he doesn't need the 1/7".
Link Posted: 8/16/2005 9:38:09 PM EDT

Originally Posted By rg7620:
It feels good to be back here after a few years



welcome back!
Link Posted: 8/17/2005 10:52:01 AM EDT
I dunno I disagree, if you shoot 55 more then 1/9 if you shoot 62 gr then 1/7 may be slightly better
Link Posted: 8/17/2005 11:13:29 AM EDT
A lot of people tell me that a 1/7 twist is more accurate then a 1/9, is this ture?
Link Posted: 8/17/2005 11:24:52 AM EDT

Originally Posted By thisisagenericname:
A lot of people tell me that a 1/7 twist is more accurate then a 1/9, is this ture?



depends on the ammo you shoot
Link Posted: 8/17/2005 11:59:35 AM EDT
1 X 7 is #4 on the list just ahead of #5, M4 ramps. What list, you say.

The list of the most over rated items in the world.

1. Chris Craft boats
2. Harley Davidson motorcycles
3. Teenage pussy
4. 1 x 7 twist
5. M4 ramps

Link Posted: 8/17/2005 12:22:10 PM EDT
Unless you have some compelling reason to want to shoot 45gr varmint bullets out of your M4gery, get the 1/7.

It'll do anything the 1/9 does with 55 and 62 gr bullets, and you can use 75's and 77's with no worries as well.
Link Posted: 8/17/2005 1:08:35 PM EDT
both
Link Posted: 8/17/2005 1:50:23 PM EDT
Link Posted: 8/17/2005 2:01:28 PM EDT

Originally Posted By dsg2003gt:
bushy says you can shoot up to 75 grain with little degradation in accuracy in a 1/9.



Bushy also says M16 bolt carriers are illegal in AR15s. Bushy is often full of shit.
Link Posted: 8/17/2005 2:03:16 PM EDT

Originally Posted By Firelotus:
I dunno I disagree, if you shoot 55 more then 1/9 if you shoot 62 gr then 1/7 may be slightly better



Why M855 was specifically designed to be shot in a 1/9. Why would you make such a claim?
Link Posted: 8/17/2005 2:24:26 PM EDT
just to add my 2 cents- Keep in mind that many bolt guns in 223 have a 1-12 to 1-14 twist. I personally think 1-7 is overkill. If I wanted to shoot expensive 75grn and up bullets, I would get a 6.5 Grendel or 6.8 SPC.
Link Posted: 8/17/2005 2:33:35 PM EDT

Originally Posted By Parrandero:
1 X 7 is #4 on the list just ahead of #5, M4 ramps. What list, you say.

The list of the most over rated items in the world.

1. Chris Craft boats
2. Harley Davidson motorcycles
3. Teenage pussy
4. 1 x 7 twist
5. M4 ramps




#1 is Christ Craft boats? Did you forget about Colt Firearms?
Link Posted: 8/17/2005 2:38:52 PM EDT
this topic again?

1/7 will allow you to shot a wider range of ammo
Link Posted: 8/17/2005 2:40:32 PM EDT
why not 1:8?
Link Posted: 8/17/2005 2:42:26 PM EDT
BOTH SHOULD BE BANNED!!!
Link Posted: 8/17/2005 2:53:10 PM EDT

Originally Posted By Parrandero:
1 X 7 is #4 on the list just ahead of #5, M4 ramps. What list, you say.

The list of the most over rated items in the world.

1. Chris Craft boats
2. Harley Davidson motorcycles
3. Teenage pussy
4. 1 x 7 twist
5. M4 ramps




How about combining your last three.

3. Teenage Pussy-self explanatory

+

4. 1/7 twist - because more twist is always a good thing.

+

5. M4 ramps- cures pesky "feeding" problems.

=

Something you could mount your Aimpoint on.
Link Posted: 8/17/2005 3:21:29 PM EDT

Originally Posted By Creeper:
If you are shooting 55 and 62 mostly then I'd 1/9, reason throat erosion.



Throat erosion is not a function of barrel twist rate. It is a function of how much powder load and bore diameter.
Link Posted: 8/17/2005 3:30:07 PM EDT
Yes, 55 and 62 in either 1/9 or 1/7 reason: Ass erosion- from getting reamed from the price of heavy OTMs ect.
Link Posted: 8/17/2005 5:27:37 PM EDT

Originally Posted By luckypunk:
Yes, 55 and 62 in either 1/9 or 1/7 reason: Ass erosion- from getting reamed from the price of heavy OTMs ect.



Roll your own.
Link Posted: 8/17/2005 5:38:33 PM EDT
I own and use both twists and love them both. My range/training ammo is 55/62 grains, and I can't perceive any difference in accuracy with either twist. With decent ammo both twists are far more accurate than I am.

If I had to choose one I'd probably go with 1/7, simply because I know that my defensive ammo of choice (75gr TAP) will work with it. 75gr will probably work in a 1/9, but it will most certainly work in a 1/7. Both my Rock River and Colt 1/9 barrels seem to shoot 75gr ammo fine, but I have a 1/9 barrel of unknown origin that doesn't group worth a damn with it-though it's great with 55 and 62gr of any flavor.

That being said, there are other more important choices to consider in an AR than barrel twist-at least to me anyway. I'd rather have a well built AR in 1/9 than a shoddily built AR in 1/7.
Link Posted: 8/17/2005 5:46:29 PM EDT
For your choices, go with 1:9. If you plan on going heavier, go with the 1:7. The 1:7 might have a little bit more resale value if you ever decide to sell it.
Link Posted: 8/17/2005 6:21:58 PM EDT
This past Sunday I tried out my 1/7 LMT at 100 yards and was able to get a 4x1.5 inch group consistantly with 77 grain Fed match. With my old BM M4 with a 1/9, I could only do around 8x4 inches on my groups with 62 grain Fed match. If I had a scope, I could do better I'm sure.
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