I have an opportunity to acquire a quantity of 75 grain A-max bullets. Do you think they will stabilize in my 9" twist Remington? The charts I've seen indicate that they might be borderline.
Thanks,
Sherlok
Thanks,
Sherlok
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- 75 grain amax in 9 twist
Re: 75 grain A-Max in 9" twist
No one can say for sure. You have to try to find out.
No one can say for sure. You have to try to find out.
Re: 75 grain A-Max in 9" twist
They should, works in my rifle, but USMCj is right.
They should, works in my rifle, but USMCj is right.
Re: 75 grain A-Max in 9" twist
OK, I'll give em a whirl.
Thanks guys,
Sherlok
OK, I'll give em a whirl.
Thanks guys,
Sherlok
Re: 75 grain A-Max in 9" twist
If they do, I have some I will trade you. Mine did not shoot as good as I like.
If they do, I have some I will trade you. Mine did not shoot as good as I like.
Re: 75 grain A-Max in 9" twist
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sherlok</div><div class="ubbcode-body">OK, I'll give em a whirl.
Thanks guys,
Sherlok </div></div>
If you do test them make sure you do it at the longest range you plan on shooting. Just because a bullet is stable at 100yds doesn't mean it will be at 600.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sherlok</div><div class="ubbcode-body">OK, I'll give em a whirl.
Thanks guys,
Sherlok </div></div>
If you do test them make sure you do it at the longest range you plan on shooting. Just because a bullet is stable at 100yds doesn't mean it will be at 600.
Re: 75 grain A-Max in 9" twist
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Falar</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sherlok</div><div class="ubbcode-body">OK, I'll give em a whirl.
Thanks guys,
Sherlok </div></div>
If you do test them make sure you do it at the longest range you plan on shooting. Just because a bullet is stable at 100yds doesn't mean it will be at 600. </div></div>
Really? Can you explain that?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Falar</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sherlok</div><div class="ubbcode-body">OK, I'll give em a whirl.
Thanks guys,
Sherlok </div></div>
If you do test them make sure you do it at the longest range you plan on shooting. Just because a bullet is stable at 100yds doesn't mean it will be at 600. </div></div>
Really? Can you explain that?
Re: 75 grain A-Max in 9" twist
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Falar</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sherlok</div><div class="ubbcode-body">OK, I'll give em a whirl.
Thanks guys,
Sherlok </div></div>
If you do test them make sure you do it at the longest range you plan on shooting. Just because a bullet is stable at 100yds doesn't mean it will be at 600. </div></div>
Really? Can you explain that? </div></div>
As velocity decreases so will RPMs. If your barrel was able to barely generate enough RPMs (which are determined by velocity and rate of twist) to stabilize them initially (say 50-100yds) then as velocity decreases then its chances of staying stable will decrease. The subject of 75/77gr bullets in 1:9 barrels comes up alot on the AR forums. I tried searching but couldn't come with it, but a user on M4carbine.net and arfcom named Molon has posted up some charts that illustrate relative stability in regards to twist rate, velocity, and RPM. I'm not an expert in this field, I learned about it from his posts.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Falar</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sherlok</div><div class="ubbcode-body">OK, I'll give em a whirl.
Thanks guys,
Sherlok </div></div>
If you do test them make sure you do it at the longest range you plan on shooting. Just because a bullet is stable at 100yds doesn't mean it will be at 600. </div></div>
Really? Can you explain that? </div></div>
As velocity decreases so will RPMs. If your barrel was able to barely generate enough RPMs (which are determined by velocity and rate of twist) to stabilize them initially (say 50-100yds) then as velocity decreases then its chances of staying stable will decrease. The subject of 75/77gr bullets in 1:9 barrels comes up alot on the AR forums. I tried searching but couldn't come with it, but a user on M4carbine.net and arfcom named Molon has posted up some charts that illustrate relative stability in regards to twist rate, velocity, and RPM. I'm not an expert in this field, I learned about it from his posts.
Re: 75 grain A-Max in 9" twist
Ok. Good answer, but totally wrong.
When a bullet emerges from the bore, it is at maximum velocity both in forward flight and rotation. The spin rate of the bullet is a function of the muzzle velocity and twist rate; for purposes of illustration, lets take a bullet in a 1:12(*) twist going at 3000 FPS. Its spin rate is 3000 RPS (revolutions per second.)
The reason a bullet needs to spin is to keep it point on during its flight, using the gyroscopic effect. Without this, the air resistance the bullet encounters would try to destabilize it and make it tumble, because the bullet is not a sphere. Longer, more aerodynamic bullets are more unstable and require a faster spin to stabilize. Of course, the faster the bullet goes, the greater the air resistance and thus the greater the tendency to tumble so a faster spin rate is required for that.
Now, as the bullet we talked about emerges from the barrel, it is going forward at 3000 FPS and spinning around its axis a 3000 revolutions per second. That is the fastest it will ever go as the air resistance is now acting upon it at full strength and slowing it down in its forward motion. However, there is really nothing to slow down its rotation, so it continues to spin at 3000 RPS. But as its forward velocity drops rapidly (and that's where the BC of the bullet comes in) the tendency for the bullet to tumble also drops. Since the spin rate remains the same but the bullets is slowing down, the bullet becomes more stable as time (distance) grows.
Provided there is no event to cause the bullet to tumble, such as going transonic for certain bullets, it is safe to say that if a bullet is statically stable at the muzzle, it will be staticaly stable throughout its entire flight. (Please don't bother with the shooting from the side of a cliff or a mountain, or an aircraft.)
(*) Fixed typo pointed out by FCS below.
Ok. Good answer, but totally wrong.
When a bullet emerges from the bore, it is at maximum velocity both in forward flight and rotation. The spin rate of the bullet is a function of the muzzle velocity and twist rate; for purposes of illustration, lets take a bullet in a 1:12(*) twist going at 3000 FPS. Its spin rate is 3000 RPS (revolutions per second.)
The reason a bullet needs to spin is to keep it point on during its flight, using the gyroscopic effect. Without this, the air resistance the bullet encounters would try to destabilize it and make it tumble, because the bullet is not a sphere. Longer, more aerodynamic bullets are more unstable and require a faster spin to stabilize. Of course, the faster the bullet goes, the greater the air resistance and thus the greater the tendency to tumble so a faster spin rate is required for that.
Now, as the bullet we talked about emerges from the barrel, it is going forward at 3000 FPS and spinning around its axis a 3000 revolutions per second. That is the fastest it will ever go as the air resistance is now acting upon it at full strength and slowing it down in its forward motion. However, there is really nothing to slow down its rotation, so it continues to spin at 3000 RPS. But as its forward velocity drops rapidly (and that's where the BC of the bullet comes in) the tendency for the bullet to tumble also drops. Since the spin rate remains the same but the bullets is slowing down, the bullet becomes more stable as time (distance) grows.
Provided there is no event to cause the bullet to tumble, such as going transonic for certain bullets, it is safe to say that if a bullet is statically stable at the muzzle, it will be staticaly stable throughout its entire flight. (Please don't bother with the shooting from the side of a cliff or a mountain, or an aircraft.)
(*) Fixed typo pointed out by FCS below.
Re: 75 grain A-Max in 9" twist
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body">... lets take a bullet in a 1:10 twist going at 3000 FPS. Its spin rate is 3000 RPS (revolutions per second.)...
</div></div>
Really? Would you explain that?
I'd expect it to be closer to 3600 RPS.
Never hurts to check your rifle/ammo at longest distance possible. Seen too many loads that shot great at short distance give it up at longer ranges.
I'd not test a 223, 9 twist barrel with 75 A-max at 100 and call it good for going to 600 or further.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body">... lets take a bullet in a 1:10 twist going at 3000 FPS. Its spin rate is 3000 RPS (revolutions per second.)...
</div></div>
Really? Would you explain that?
I'd expect it to be closer to 3600 RPS.
Never hurts to check your rifle/ammo at longest distance possible. Seen too many loads that shot great at short distance give it up at longer ranges.
I'd not test a 223, 9 twist barrel with 75 A-max at 100 and call it good for going to 600 or further.
Re: 75 grain A-Max in 9" twist
Here is the kind of chart I was referring to, I guess I was reading them wrong as I assumed the bullet RPM would decrease as velocity fell of.
Here is the kind of chart I was referring to, I guess I was reading them wrong as I assumed the bullet RPM would decrease as velocity fell of.
Re: 75 grain A-Max in 9" twist
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: FCS</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body">... lets take a bullet in a 1:10 twist going at 3000 FPS. Its spin rate is 3000 RPS (revolutions per second.)...
</div></div>
Really? Would you explain that?
I'd expect it to be closer to 3600 RPS.
Never hurts to check your rifle/ammo at longest distance possible. Seen too many loads that shot great at short distance give it up at longer ranges.
I'd not test a 223, 9 twist barrel with 75 A-max at 100 and call it good for going to 600 or further. </div></div>
You would expect 3600RPS, but I made a typo, as I meant a twist rate of 1:12. That's what happens when you write too fast.
I absolutely agree about testing the ammo at the longest range possible; I shoot to 1000 yards. However, my point is that a bullet that is stable at the muzzle will not become unstable further down range (discounting the transonic event.)
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: FCS</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body">... lets take a bullet in a 1:10 twist going at 3000 FPS. Its spin rate is 3000 RPS (revolutions per second.)...
</div></div>
Really? Would you explain that?
I'd expect it to be closer to 3600 RPS.
Never hurts to check your rifle/ammo at longest distance possible. Seen too many loads that shot great at short distance give it up at longer ranges.
I'd not test a 223, 9 twist barrel with 75 A-max at 100 and call it good for going to 600 or further. </div></div>
You would expect 3600RPS, but I made a typo, as I meant a twist rate of 1:12. That's what happens when you write too fast.
I absolutely agree about testing the ammo at the longest range possible; I shoot to 1000 yards. However, my point is that a bullet that is stable at the muzzle will not become unstable further down range (discounting the transonic event.)
Re: 75 grain A-Max in 9" twist
Mine shoots them well, but they need to be pushed hard. Great out to 600yrds.
YMMV- Rob
Mine shoots them well, but they need to be pushed hard. Great out to 600yrds.
YMMV- Rob
Re: 75 grain A-Max in 9" twist
I guess we'll just have to agree to disagree. All things being same but barrel twist I've watched a barrel swapped on range and smaller groups shot at distance (1K).
Same bullet, same velocity, different twist rate. Faster twist barrel held better vertical/overall group size.
Group of us shooting 308s, 10 twist, 11.25 twist, and a 12 twist. Basically all running about the same velocity but the 10 twist held better vertical the further out we went.
Empirical data indicates that being on edge of enough twist rate hurts you more as range increases.
YMMV and worth what you paid for it.
I guess we'll just have to agree to disagree. All things being same but barrel twist I've watched a barrel swapped on range and smaller groups shot at distance (1K).
Same bullet, same velocity, different twist rate. Faster twist barrel held better vertical/overall group size.
Group of us shooting 308s, 10 twist, 11.25 twist, and a 12 twist. Basically all running about the same velocity but the 10 twist held better vertical the further out we went.
Empirical data indicates that being on edge of enough twist rate hurts you more as range increases.
YMMV and worth what you paid for it.
Re: 75 grain A-Max in 9" twist
Bullet spin is in a state of Perpetual motion?I'm sure it starts degrading as soon as it leaves the muzzle.How much,how fast is the question.
Steve
Bullet spin is in a state of Perpetual motion?I'm sure it starts degrading as soon as it leaves the muzzle.How much,how fast is the question.
Steve
Re: 75 grain A-Max in 9" twist
.
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Re: 75 grain A-Max in 9" twist
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: FCS</div><div class="ubbcode-body">I guess we'll just have to agree to disagree. All things being same but barrel twist I've watched a barrel swapped on range and smaller groups shot at distance (1K).
Same bullet, same velocity, different twist rate. Faster twist barrel held better vertical/overall group size.
Group of us shooting 308s, 10 twist, 11.25 twist, and a 12 twist. Basically all running about the same velocity but the 10 twist held better vertical the further out we went.
Empirical data indicates that being on edge of enough twist rate hurts you more as range increases.
YMMV and worth what you paid for it.
</div></div>
Actually, we do not disagree at all. What I said is if the bullet is statically stable at the muzzle it will be stable throughout the flight. You just said the same thing by stating that you got smaller group sizes at 1k with a faster twist. If the bullet shot from the slower twist had been unstable, it would never have shown up on the target at 1000 yards. And I would think that swapping a barrel might have introduced any number of variables beyond the twist rate difference.
What you are saying is that some bullets go better with specific twist rates. What a shock. Of course they do.
You can also go the other way and spin the bullets so much that you induce a dynamic instability in the bullet and then watch the group size increase. This is more rare now with the quality of bullets that are manufactured.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: FCS</div><div class="ubbcode-body">I guess we'll just have to agree to disagree. All things being same but barrel twist I've watched a barrel swapped on range and smaller groups shot at distance (1K).
Same bullet, same velocity, different twist rate. Faster twist barrel held better vertical/overall group size.
Group of us shooting 308s, 10 twist, 11.25 twist, and a 12 twist. Basically all running about the same velocity but the 10 twist held better vertical the further out we went.
Empirical data indicates that being on edge of enough twist rate hurts you more as range increases.
YMMV and worth what you paid for it.
</div></div>
Actually, we do not disagree at all. What I said is if the bullet is statically stable at the muzzle it will be stable throughout the flight. You just said the same thing by stating that you got smaller group sizes at 1k with a faster twist. If the bullet shot from the slower twist had been unstable, it would never have shown up on the target at 1000 yards. And I would think that swapping a barrel might have introduced any number of variables beyond the twist rate difference.
What you are saying is that some bullets go better with specific twist rates. What a shock. Of course they do.
You can also go the other way and spin the bullets so much that you induce a dynamic instability in the bullet and then watch the group size increase. This is more rare now with the quality of bullets that are manufactured.
Re: 75 grain A-Max in 9" twist
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: steve123</div><div class="ubbcode-body">Bullet spin is in a state of Perpetual motion?I'm sure it starts degrading as soon as it leaves the muzzle.How much,how fast is the question.
Steve </div></div>
I'm sure, but what is the force acting upon it to slow the spin down? Remember Newton's first law.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: steve123</div><div class="ubbcode-body">Bullet spin is in a state of Perpetual motion?I'm sure it starts degrading as soon as it leaves the muzzle.How much,how fast is the question.
Steve </div></div>
I'm sure, but what is the force acting upon it to slow the spin down? Remember Newton's first law.
Re: 75 grain A-Max in 9" twist
Guys,
I gotta rock 1/9 20" 223 barrel. It shoot the BH 75 grainers well nd the 77's are good to. I took the 75's to range. Sighted in at 100 yards. Looked up the drop and shot at 650 yards.First round hit. Ask Texgal about SOTA's "bb gun".
SOTA
Guys,
I gotta rock 1/9 20" 223 barrel. It shoot the BH 75 grainers well nd the 77's are good to. I took the 75's to range. Sighted in at 100 yards. Looked up the drop and shot at 650 yards.First round hit. Ask Texgal about SOTA's "bb gun".
SOTA
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