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Posted: 10/14/2013 5:35:07 AM EST
My barrel is mil spec (except for the 16” length) with a twist rate of 1/7.
I have tried many different type of ammo and the most accurate has been the Hornady 55 grain vmax with average groups of around 1.5 MOA at 100 yards (below picture).

Overall I’m getting better results with 50 (AE Varmint tip) to 55 grain bullets, and XM193 is more accurate than the heavier green tip.

The Colt brand 5.56 77 SMK ammo gave me a very disappointing 3moa group at 100 yards.

What are your thoughts on this?


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Link Posted: 10/14/2013 5:47:05 AM EST
Have you tried any match ammo?
Link Posted: 10/14/2013 5:57:48 AM EST
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Originally Posted By dj_taboo:
Have you tried any match ammo?
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"The Colt brand 5.56 77 SMK" is match ammo at $1/round. Groups were a deceiving 3MOA.
Link Posted: 10/14/2013 5:59:29 AM EST
Not necessarily surprising. I find it a bit tiring when people insist that 1-9 barrels are only good for lighter bullets and you need a 1-7 for heavier bullets. As you have found out, you never really know how your barrel will shoot with various weights until you actually try them. Usually, a 1-7 twist will work better with heavier bullets - except when it doesn't.

Link Posted: 10/14/2013 6:06:12 AM EST
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Originally Posted By kevin1:


"The Colt brand 5.56 77 SMK" is match ammo at $1/round. Groups were a deceiving 3MOA.
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Originally Posted By kevin1:
Originally Posted By dj_taboo:
Have you tried any match ammo?


"The Colt brand 5.56 77 SMK" is match ammo at $1/round. Groups were a deceiving 3MOA.


That sucks! Thats the Black Hills loaded MK262 "clone" stuff too (I think)
Link Posted: 10/14/2013 6:27:23 AM EST
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Originally Posted By slowkota1:


That sucks! Thats the Black Hills loaded MK262 "clone" stuff too (I think)
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Originally Posted By slowkota1:
Originally Posted By kevin1:
Originally Posted By dj_taboo:
Have you tried any match ammo?


"The Colt brand 5.56 77 SMK" is match ammo at $1/round. Groups were a deceiving 3MOA.


That sucks! Thats the Black Hills loaded MK262 "clone" stuff too (I think)

I know the whole twist debate and I'm not going to comment on it but have you actually checked your barrel twist rate? Not just what is stamped on it or what you "thought" you purchased. It is not unheard of that the perceived twist ratio was wrong.
Link Posted: 10/14/2013 6:30:48 AM EST
It happens. I have a 1-7 twist 18" White Oak barrel that shoots best with a 36 grain Barnes Varmint Grenade, as long as I back them down from max a few tenths.
Link Posted: 10/14/2013 6:35:19 AM EST
Sometimes you find ammo that does not shoot well in your rifle. My M1a loves Federal Gold match 168gr but not so much 175gr or my Winchester Model 70 likes both but does measurably better with the 175gr.

Part of shooting some barrels the harmonics, crown, and chamber love one load but the next not so much. This is why you search to find the load for your rifle.
Link Posted: 10/14/2013 6:54:01 AM EST
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Originally Posted By Espos1111:

I know the whole twist debate and I'm not going to comment on it but have you actually checked your barrel twist rate? Not just what is stamped on it or what you "thought" you purchased. It is not unheard of that the perceived twist ratio was wrong.
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Originally Posted By Espos1111:
Originally Posted By slowkota1:
Originally Posted By kevin1:
Originally Posted By dj_taboo:
Have you tried any match ammo?


"The Colt brand 5.56 77 SMK" is match ammo at $1/round. Groups were a deceiving 3MOA.


That sucks! Thats the Black Hills loaded MK262 "clone" stuff too (I think)

I know the whole twist debate and I'm not going to comment on it but have you actually checked your barrel twist rate? Not just what is stamped on it or what you "thought" you purchased. It is not unheard of that the perceived twist ratio was wrong.


Purchased the rifle new. It's a Colt 6920 with 1/7 stamped on the barrel (as well as the other usual marking). Do you really think I need to actually measure the twist rate myself?
Link Posted: 10/14/2013 6:55:54 AM EST
People need to stop spreading the myth that 1:7 barrels can't shoot light bullets. My Colt match hbar with a 1:7 shoots 40 gr v match like a champ.
Link Posted: 10/14/2013 7:32:52 AM EST
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Originally Posted By kevin1:


"The Colt brand 5.56 77 SMK" is match ammo at $1/round. Groups were a deceiving 3MOA.
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Originally Posted By kevin1:
Originally Posted By dj_taboo:
Have you tried any match ammo?


"The Colt brand 5.56 77 SMK" is match ammo at $1/round. Groups were a deceiving 3MOA.


You tried one brand of match ammo. All that your results tell me is that your rifle doesn't like that specific type of ammo. Go back to your LGS and pick up at least half a dozen different kinds of match ammo, of varying weights. Test again and report back. One box of one type of expensive ammo tells us nothing of value, other than you shouldn't get more of that ammo.
Link Posted: 10/14/2013 9:01:59 AM EST
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Originally Posted By johnfz6:
Not necessarily surprising. I find it a bit tiring when people insist that 1-9 barrels are only good for lighter bullets and you need a 1-7 for heavier bullets. As you have found out, you never really know how your barrel will shoot with various weights until you actually try them. Usually, a 1-7 twist will work better with heavier bullets - except when it doesn't.

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Originally Posted By johnfz6:
Not necessarily surprising. I find it a bit tiring when people insist that 1-9 barrels are only good for lighter bullets and you need a 1-7 for heavier bullets. As you have found out, you never really know how your barrel will shoot with various weights until you actually try them. Usually, a 1-7 twist will work better with heavier bullets - except when it doesn't.


Originally Posted By Will816:
People need to stop spreading the myth that 1:7 barrels can't shoot light bullets. My Colt match hbar with a 1:7 shoots 40 gr v match like a champ.


Yes! It is a breath of fresh air to hear people say this. You never know what your barrel will like until you actually run different loads through it. I think the "chart" is an excellent tool, but the barrel twist debate is not a rule, it is a suggestion. I used to work behind the counter, and I had customers who refused to believe that a 1:7 twist 5.56mm barrel will shoot anything lighter than 75 grains. It is definitely exhausting to hear that myth over and over. 55gr shoots well enough for me.
Link Posted: 10/14/2013 9:05:45 AM EST
[Last Edit: 10/14/2013 9:06:59 AM EST by urbanredneck]
Sounds like you are using all factory ammo. Get you self a reloading press. Sound like you need to play with powder charge and OAL to get it fine tuned.

I think you will be surprised. I shot my varminter with 75 gr Fed gold Match and was disappointed. Then I picked up some 68 and 75 gr pills and did some reloads, group size went from an inch to touching....

You have to find the barrels sweet spot.
Link Posted: 10/14/2013 9:08:51 AM EST
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Originally Posted By urbanredneck:
Sounds like you are using all factory ammo. Get you self a reloading press. Sound like you need to play with powder charge and OAL to get it fine tuned.

I think you will be surprised. I shot my varminter with 75 gr Fed gold Match and was disappointed. Then I picked up some 68 and 75 gr pills and did some reloads, group size went from an inch to touching....

You have to find the barrels sweet spot.
View Quote


Amazing what happens when you know exactly your round is loaded to FPS wise, true bullet weight vs what is stamped on box, and type of powder etc etc can make all the difference.
Link Posted: 10/14/2013 9:28:26 AM EST
My BCM 1:7 loves Silver Bear 62gr. Weird huh?
Link Posted: 10/14/2013 12:12:52 PM EST
I've yet to have a 1/7 that didn't LOVE black hills blue 52's.


But really it comes down to what others have said and it's my mantra:




every barrel is prejudiced. You just have to find what yours likes. 1 wouldn't say that 1 heavier load tested makes it a general rule. You might want to try some 75's in a different brand. Hornday, Black hills. 68's 69's. Etc etc. You may still find that your barrel favors the lighter bullets though. It would be a little odd, but after shooting enough, I would not find it hard to believe that it could happen. Because:
every barrel is prejudiced.
Link Posted: 10/14/2013 12:25:51 PM EST
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Originally Posted By urbanredneck:
Sounds like you are using all factory ammo. Get you self a reloading press. Sound like you need to play with powder charge and OAL to get it fine tuned.

I think you will be surprised. I shot my varminter with 75 gr Fed gold Match and was disappointed. Then I picked up some 68 and 75 gr pills and did some reloads, group size went from an inch to touching....

You have to find the barrels sweet spot.
View Quote


I do reload for my long range bolt action gun. Not only it’s cheaper, but I get much better accuracy.
But honestly, I wasn’t planning in reloading for my AR15. The rifle is a standard M4 carbine length with mil spec barrel that isn’t free floated. It already shoots 1.5moa at 100 yards with ammo it likes and I don’t think a load development will make this a 0.5moa gun. Not to mention that the ammo cost is cheaper…..finally good luck in fining some Varget powder…


Link Posted: 10/14/2013 1:19:20 PM EST
[Last Edit: 10/14/2013 1:24:48 PM EST by Rooster-Cogburn]
Edited...I need to read OP more carefully.

That does seem strange. However, bullet weight is only part of the equation. I'm pretty sure that if you hand loaded the larger projectiles to suit that rifle, they would be more accurate.

The effect of twist rate is way overrated.
Link Posted: 10/14/2013 1:25:10 PM EST
I think those are 5 round groups.
Link Posted: 10/14/2013 1:43:37 PM EST
My 1:10 .308 likes i68's better then 175's. So that's what I shoot.

Try some 69's.
Link Posted: 10/15/2013 7:21:38 AM EST
[Last Edit: 10/15/2013 7:22:50 AM EST by urbanredneck]
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Originally Posted By kevin1:


I do reload for my long range bolt action gun. Not only it’s cheaper, but I get much better accuracy.
But honestly, I wasn’t planning in reloading for my AR15. The rifle is a standard M4 carbine length with mil spec barrel that isn’t free floated. It already shoots 1.5moa at 100 yards with ammo it likes and I don’t think a load development will make this a 0.5moa gun. Not to mention that the ammo cost is cheaper…..finally good luck in fining some Varget powder…


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Originally Posted By kevin1:
Originally Posted By urbanredneck:
Sounds like you are using all factory ammo. Get you self a reloading press. Sound like you need to play with powder charge and OAL to get it fine tuned.

I think you will be surprised. I shot my varminter with 75 gr Fed gold Match and was disappointed. Then I picked up some 68 and 75 gr pills and did some reloads, group size went from an inch to touching....

You have to find the barrels sweet spot.


I do reload for my long range bolt action gun. Not only it’s cheaper, but I get much better accuracy.
But honestly, I wasn’t planning in reloading for my AR15. The rifle is a standard M4 carbine length with mil spec barrel that isn’t free floated. It already shoots 1.5moa at 100 yards with ammo it likes and I don’t think a load development will make this a 0.5moa gun. Not to mention that the ammo cost is cheaper…..finally good luck in fining some Varget powder…





I bet you might be surprised... And if you aren't going to try then you won't know. You might decide that you want to take it out deer hunting some time. Try AA2230 if you can't find Varget.
Link Posted: 10/15/2013 9:19:12 AM EST
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Originally Posted By Will816:
People need to stop spreading the myth that 1:7 barrels can't shoot light bullets. My Colt match hbar with a 1:7 shoots 40 gr v match like a champ.
View Quote


I think one of the origins of the myth stems from some older thinly jacketed varmint bullet designs that would rip apart when shot out of a 1-7 barrel. They were designed back in the days when 1-12 twist was commonly found in bolt action varmint rifles. I first read of the issue in a reloading manual about 12 years ago, and at that time they suggested backing off on the velocity when reloading. The change in velocity can also affect group sizes. Ammo has improved since then.
Link Posted: 10/15/2013 9:38:18 AM EST
OP per my post eariler. You just stated that you had a " mil spec barrel (besides it being 16" ) ". I was not assuming that you had a Colt as you gave no other info about your AR. So, no, you wouldn't have to check the twist ratio.

I also have a 1/7 that loves Hornady 52gr Match, likes 68gr and is just so-so with anything heavier. I reload so maybe I haven't found the sweet spot for those heavy pills yet.
I don't recall reading how many rounds you put down range with that barrel but from my experience barrels require a break in period before they really shine. Sometimes a few dozen, sometimes a few hundred.
I'm not saying that your AR should or shouldn't like light or heavy bullets. I'm just saying that it just may take some more time and different rounds.
Link Posted: 10/15/2013 10:22:37 AM EST
Take it out to 400 yards with a scope and see how they do.

1:7 should shoot 50gr just fine. It should also be able to handle 80gr. Bullet weight isn't going to play into accuracy within 100yds using factory loaded ammo. This isn't surprising.

I'm not convinced your sample size is large enough though. Correlation does not equal causation. You also threw a round with an entirely different CG with the green tip in there.
Link Posted: 10/15/2013 12:06:25 PM EST
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Originally Posted By kevin1:


I do reload for my long range bolt action gun. Not only it’s cheaper, but I get much better accuracy.
But honestly, I wasn’t planning in reloading for my AR15. The rifle is a standard M4 carbine length with mil spec barrel that isn’t free floated. It already shoots 1.5moa at 100 yards with ammo it likes and I don’t think a load development will make this a 0.5moa gun. Not to mention that the ammo cost is cheaper…..finally good luck in fining some Varget powder…


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Originally Posted By kevin1:
Originally Posted By urbanredneck:
Sounds like you are using all factory ammo. Get you self a reloading press. Sound like you need to play with powder charge and OAL to get it fine tuned.

I think you will be surprised. I shot my varminter with 75 gr Fed gold Match and was disappointed. Then I picked up some 68 and 75 gr pills and did some reloads, group size went from an inch to touching....

You have to find the barrels sweet spot.


I do reload for my long range bolt action gun. Not only it’s cheaper, but I get much better accuracy.
But honestly, I wasn’t planning in reloading for my AR15. The rifle is a standard M4 carbine length with mil spec barrel that isn’t free floated. It already shoots 1.5moa at 100 yards with ammo it likes and I don’t think a load development will make this a 0.5moa gun. Not to mention that the ammo cost is cheaper…..finally good luck in fining some Varget powder…



so what was the intent of this post ?
Link Posted: 10/15/2013 12:13:55 PM EST
My DD 10.3" 1:7 barrel loves the 55 grain FMJ from PMC. Cheap and tight groups for me.
Link Posted: 10/15/2013 12:18:53 PM EST
So your gun shoots cheap ammo great and expensive ammo poorly. DAMN IT that is horrible luck. Thank god I don't have that problem.
Link Posted: 10/17/2013 11:05:19 AM EST
[Last Edit: 10/17/2013 11:05:48 AM EST by kevin1]
I have put around 1000 round through the rifle. So the barrel is broken in (and the accuracy is better now).
For heavy bullets, I have used Prvi Partizan Match Ammunition 223 Remington 69 Grain HPBT (it’s called match but the price was pretty cheap), M855 62 grain and only used one brand of true heavy match load (3 boxes of Colt 77 SMK). I didn’t have good results with any.
I do agree that based on this, I can’t conclude that my barrel doesn’t like heavy bullets. I only tried one brand of true match ammo.

I’ll try to get my hands on some Fiocchi 69 and 77 SMK and see how it goes. I’ll let you know (If this post isn’t archived by the time I’m done )
Link Posted: 10/18/2013 9:27:58 AM EST
Repeat after me: Black Hills Black Hills Black Hills.



Sierra makes the 69's and 77's. Hornady makes the 68's and 75's. 52's bthp also.

Hornady has some good loaded ammo too. Match ammo.


There's so many choices out there. But so much harder to find nowadays.
Link Posted: 10/18/2013 12:33:52 PM EST
Lighter bullets, especially the ballistic tipped ones, have always shot very well for me at 100 yards.

When you stretch past that, the ability of the heavier rounds to buck the wind and their better b/c will give you better groups.
Link Posted: 10/18/2013 12:58:54 PM EST
I've yet to have a rifle that didn't like the 55gr Vmax, and all mine are 1-7 except for one 1-8.


I don't think I've ever heard of someone having a bad result with them, factory loads or hand loads.
Link Posted: 10/18/2013 1:18:11 PM EST
I reload for all 3 of my 1-7" rifles. Using 77g w/cannelure, I get very good accuracy at 200m.
Link Posted: 10/26/2013 5:11:22 PM EST
I tried Fiocchi 77 SMK and Federal 69 SMK.
69 SMK were just Ok,
Fiocchi 77 SMK…. Sub MOA!!!

So my rifle loves 77 SMK, it’s just the colt brand that it doesn’t like. The Colt brand is 5.56 and Fiocchi is 223. Can this be a factor?

I was so impressed with the results, that I started the below post.
http://www.ar15.com/forums/t_3_118/626316_.html&page=1
Link Posted: 10/26/2013 7:23:16 PM EST
[Last Edit: 10/26/2013 7:23:38 PM EST by JJREA]
Could be. Sometimes lower pressure and lower velocity helps accuracy. Less violent I guess. But you might find another 5.56 load that it likes. Because they're just picky. It's just not something you can get around. Some less than others though, of course. I think that's what's kind of neat about it all. You take your standard M4gery and they all look the same. But the fact is, they're not. In small subtle ways. Kind of like people I guess.
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