What bullets for 1-9 twist AR?
- Thread starter Grassman
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Al Thompson
Moderator Emeritus
You appear to have a very, very unique, one of a kind rifle there.
You appear to have a very, very unique, one of a kind rifle there.
just your regular bushmaster 18" freefloated chrome lined bull heavy barrel
pre ban that i have never seen again for sale or anyone else with one like it
Al Thompson
Moderator Emeritus
Just so I have it right - your Bushmaster is putting both 75 and 55 grain bullets to the same POI at 400 yards? What sort of groups are you getting?
And you have a 1/9 twist barrel produced prior to 1994?
And you have a 1/9 twist barrel produced prior to 1994?
BullfrogKen
Moderator Emeritus
Many people used 69gr bullets in a 9 twist AR for High Power competition and did just fine. Some still do, but not many. I have heard limited anecdotes where a few rifles shot 75s and 77s out of a 9 twist just fine out to Mid-range (600 yard line). Others, not so well. Best advice I've been told is buy a small quantity and see if your rifle likes them.
I just picked up a 9 twist .223 Model 70 for competition. I bought some 77s just to experiment with. I'll let you know how they do.
So, I guess that whole "this is my rifle. There are many like it but this one is mine," doesn't really apply to you?
Huh. Maybe on a 2 foot steel plate it is.
See, when I'm out on the range for a match the guys there talk about how they had to make a slight dope change when they change components from 69 grs to 77 grs at 300 yards for the rapids. And with the shortages and stock-outs of the past few years, High Power competitors have learned to be very flexible and not as rigid about our components.
Upside is we get dope on a wider range of bullets and learn how slight changes in weight affect the impact downrange.
Now I'm wondering when Sierra introduced that 69 grain bullet . . .
I just picked up a 9 twist .223 Model 70 for competition. I bought some 77s just to experiment with. I'll let you know how they do.
j.kramer said:
So, I guess that whole "this is my rifle. There are many like it but this one is mine," doesn't really apply to you?
j.kramer said:
Huh. Maybe on a 2 foot steel plate it is.
See, when I'm out on the range for a match the guys there talk about how they had to make a slight dope change when they change components from 69 grs to 77 grs at 300 yards for the rapids. And with the shortages and stock-outs of the past few years, High Power competitors have learned to be very flexible and not as rigid about our components.
Upside is we get dope on a wider range of bullets and learn how slight changes in weight affect the impact downrange.
Al Thompson said:
Now I'm wondering when Sierra introduced that 69 grain bullet . . .
You have to be very specific when talking about what will stabilize. It isn't really the bullet weight, but rather the length that matters. For example, the Hornady 75gn AMax thanks to a different ogive shape and the inclusion of the polymer tip, is a great deal longer than the HPBT design of the same weight. Likewise, 70gn Barnes TSX bullets contain no lead and as a result are very long for their weight.
As far as the Hornady 75gn offerings go, the AMax is not going to stabilize in a 1:9 barrel under the best of circumstances. It's simply too long. The HPBT *might* stabilize if the velocity and density altitude are high enough. Here at 4,000 ft they do just fine. At sea level on a cool day, they might be fine with a hot load and abysmal with a more moderate load or they might just be abysmal.
The 77gn offerings from Nosler and Sierra are a little to long for the 1:9 in most cases.
As far as the Hornady 75gn offerings go, the AMax is not going to stabilize in a 1:9 barrel under the best of circumstances. It's simply too long. The HPBT *might* stabilize if the velocity and density altitude are high enough. Here at 4,000 ft they do just fine. At sea level on a cool day, they might be fine with a hot load and abysmal with a more moderate load or they might just be abysmal.
The 77gn offerings from Nosler and Sierra are a little to long for the 1:9 in most cases.
BullfrogKen
Moderator Emeritus
Spot on!
The bullet profile must also be factored in, just as described.
The bullet profile must also be factored in, just as described.
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