Sighting in 450 bushmaster

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Re: Sighting in 450 bushmaster

Postby pauleberly » Mon Jul 31, 2017 7:11 pm

dantheman wrote:Use the Hornady ballistic calculator as someone has previously suggested. I usually sight in for the longest shot that I could have within the capabilities of my rifle.

My 358 Win BLR is sighted to about 150 yds.
270 WSM is sighted in at 250 yds .
7x57 Mauser is sighted in at 200 yds.

I've made 50 yard shots with all of them. I think a 100 yard zero with a 450 Bushmaster will be a piece of cake in the deep woods.

Dan


That does make sense, but at the same time usually 90% of all my shots in the woods are going to be closer to 50 yards or less. I was afraid if I sighted the gun into a 100 yard range, I would have to compensate some , which is what I was trying to avoid. However, it almost seems at a 50 yard sight in or 100 yards, the point of impact is gong to be an inch or less, which would give me more room to open up if the opportunity ever did arrive.

Most of the hunting I had done before, I just knew at 125 yards I was zerod in. I had to raise up for 150 and aim a little lower for 100 or less. I kind of want to eliminate that "guessing" factor if thats what you are wanting to call it.
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Re: Sighting in 450 bushmaster

Postby Texas Sheepdawg » Mon Jul 31, 2017 8:32 pm

pauleberly wrote:
Texas Sheepdawg wrote:You also have to keep in mind the rifle twist of each individual rifle. The heavier bullets do better with the faster twists. But this also increases PSI, so you really need to be mindful of who's shooting what loads in what rifles. I've already noticed that my 230 grain FMJs loaded for my AR are screaming out of my single action and bolt action rifles that have the 1:16 twist rate. And they are showing some considerable pressure signs. Think on this. A 230 grain FMJ at 2700+ feet per second. That's not just meeting the TKO factor of the 375 H&H..... that's screaming insanely past it. And the pressure signs were equally frightening. So always consider the twist rates and factor in the faster twist rate is going to raise pressures.


I have a factory 450 bushmaster upper with a 16 inch barrel. What is the twist rate?

Faster twist means the bullet accelerates out of the gun faster, causing a greater velocity? Wouldn't you want a fairly high twist rate then?

And when you mention the TKO factor, that is the potential killing factor that a bullet has upon an animal correct?

And when you mention 230grain bullet at 2700+ fps, that is at the muzzle correct? I am assuming (but do not know) that muzzle velocity and the velocity at lets say 75 yards is much different. If we are killing animals at 75 yards, wouldn't we want the bullet to be traveling at a faster velocity at 75 yards to have more energy when it collides with said animal for more foot pounds of energy?


Lots of good questions. If your upper is a factory "Bushmaster" upper, it's 1:24 twist.

The faster the twist rate, (1:16 is faster than 1:24), means how many 360° revolutions the bullet rotates on its axis AS it is traveling and leaving the barrel. The slower rates are sometimes not fast enough to stabilize a heavier projectile on its axis. The faster twist rates tend to spin the heavier bullets faster so as to make them more stable and therefore more accurate in flight. However, twist rates also cause pressure changes, as it takes more pressure in the faster twists. The higher pressure ALSO means that there could possibly be a marked increase in velocities. But this may or may NOT be a good thing.

As for TKO, google Taylor Knock Out Value Formula.
Once you learn to use it, compare your favorite most used cartridges to the 450 Bushmaster.
Learn more HERE. https://en.m.wikipedia.org/wiki/Taylor_KO_Factor
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Re: Sighting in 450 bushmaster

Postby dantheman » Mon Jul 31, 2017 9:30 pm

pauleberly wrote:
dantheman wrote:Use the Hornady ballistic calculator as someone has previously suggested. I usually sight in for the longest shot that I could have within the capabilities of my rifle.

My 358 Win BLR is sighted to about 150 yds.
270 WSM is sighted in at 250 yds .
7x57 Mauser is sighted in at 200 yds.

I've made 50 yard shots with all of them. I think a 100 yard zero with a 450 Bushmaster will be a piece of cake in the deep woods.

Dan


That does make sense, but at the same time usually 90% of all my shots in the woods are going to be closer to 50 yards or less. I was afraid if I sighted the gun into a 100 yard range, I would have to compensate some , which is what I was trying to avoid. However, it almost seems at a 50 yard sight in or 100 yards, the point of impact is gong to be an inch or less, which would give me more room to open up if the opportunity ever did arrive.

Most of the hunting I had done before, I just knew at 125 yards I was zerod in. I had to raise up for 150 and aim a little lower for 100 or less. I kind of want to eliminate that "guessing" factor if thats what you are wanting to call it.


Eliminating the guessing factor is exactly what I've done for my rifles. 90% of the shots with my 358 Win are 50 yds or less. I have shot deer at 120 yds with it just once. I was right on. I started to look at shooting a pie plate instead of a half dollar (pick any coin) when hunting deer. By having a longer zero, I'm in that pie plate from muzzle to slightly beyond my zero. I still want very tight groups at the range, but by accepting an 10" or so kill zone makes hitting the deer easier for me.

Dan
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Re: Sighting in 450 bushmaster

Postby Al in Mi » Tue Aug 01, 2017 4:35 am

[/quote]

Eliminating the guessing factor is exactly what I've done for my rifles. 90% of the shots with my 358 Win are 50 yds or less. I have shot deer at 120 yds with it just once. I was right on. I started to look at shooting a pie plate instead of a half dollar (pick any coin) when hunting deer. By having a longer zero, I'm in that pie plate from muzzle to slightly beyond my zero. I still want very tight groups at the range, but by accepting an 10" or so kill zone makes hitting the deer easier for me.

Dan[/quote]

I do the same paper plate target with the gf and kids before season, put it at various yards let them fire one shot, mark and move it around, shoot again etc. It builds a lot more confidence for them plus you'd be surprised at their groups after 5 shots.
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Re: Sighting in 450 bushmaster

Postby pauleberly » Tue Aug 01, 2017 2:04 pm

Texas Sheepdawg wrote:
pauleberly wrote:
Texas Sheepdawg wrote:You also have to keep in mind the rifle twist of each individual rifle. The heavier bullets do better with the faster twists. But this also increases PSI, so you really need to be mindful of who's shooting what loads in what rifles. I've already noticed that my 230 grain FMJs loaded for my AR are screaming out of my single action and bolt action rifles that have the 1:16 twist rate. And they are showing some considerable pressure signs. Think on this. A 230 grain FMJ at 2700+ feet per second. That's not just meeting the TKO factor of the 375 H&H..... that's screaming insanely past it. And the pressure signs were equally frightening. So always consider the twist rates and factor in the faster twist rate is going to raise pressures.


I have a factory 450 bushmaster upper with a 16 inch barrel. What is the twist rate?

Faster twist means the bullet accelerates out of the gun faster, causing a greater velocity? Wouldn't you want a fairly high twist rate then?

And when you mention the TKO factor, that is the potential killing factor that a bullet has upon an animal correct?

And when you mention 230grain bullet at 2700+ fps, that is at the muzzle correct? I am assuming (but do not know) that muzzle velocity and the velocity at lets say 75 yards is much different. If we are killing animals at 75 yards, wouldn't we want the bullet to be traveling at a faster velocity at 75 yards to have more energy when it collides with said animal for more foot pounds of energy?


Lots of good questions. If your upper is a factory "Bushmaster" upper, it's 1:24 twist.

The faster the twist rate, (1:16 is faster than 1:24), means how many 360° revolutions the bullet rotates on its axis AS it is traveling and leaving the barrel. The slower rates are sometimes not fast enough to stabilize a heavier projectile on its axis. The faster twist rates tend to spin the heavier bullets faster so as to make them more stable and therefore more accurate in flight. However, twist rates also cause pressure changes, as it takes more pressure in the faster twists. The higher pressure ALSO means that there could possibly be a marked increase in velocities. But this may or may NOT be a good thing.

As for TKO, google Taylor Knock Out Value Formula.
Once you learn to use it, compare your favorite most used cartridges to the 450 Bushmaster.
Learn more HERE. https://en.m.wikipedia.org/wiki/Taylor_KO_Factor


So the 1/16 twist barrel, the bullet will do a full rotation 16 times before it exits the barrel. The only reason for increased pressure being bad is because if the barrel is not up to snuff, it could cause damage or even blow up?

Now how does all this direct relate to muzzle velocity vs velocity at point of impact.

3000fps out of a muzzle sounds impressive, but at 200 yards if its only 800fps that is not as good as a bullet with a 2600fps muzzle and 1200fps at 200 correct.

FPS and the Mass of the bullet equals the total kinetic energy hitting the animal, which is what you want
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Re: Sighting in 450 bushmaster

Postby pauleberly » Tue Aug 01, 2017 2:06 pm

dantheman wrote:
pauleberly wrote:
dantheman wrote:Use the Hornady ballistic calculator as someone has previously suggested. I usually sight in for the longest shot that I could have within the capabilities of my rifle.

My 358 Win BLR is sighted to about 150 yds.
270 WSM is sighted in at 250 yds .
7x57 Mauser is sighted in at 200 yds.

I've made 50 yard shots with all of them. I think a 100 yard zero with a 450 Bushmaster will be a piece of cake in the deep woods.

Dan


That does make sense, but at the same time usually 90% of all my shots in the woods are going to be closer to 50 yards or less. I was afraid if I sighted the gun into a 100 yard range, I would have to compensate some , which is what I was trying to avoid. However, it almost seems at a 50 yard sight in or 100 yards, the point of impact is gong to be an inch or less, which would give me more room to open up if the opportunity ever did arrive.

Most of the hunting I had done before, I just knew at 125 yards I was zerod in. I had to raise up for 150 and aim a little lower for 100 or less. I kind of want to eliminate that "guessing" factor if thats what you are wanting to call it.


Eliminating the guessing factor is exactly what I've done for my rifles. 90% of the shots with my 358 Win are 50 yds or less. I have shot deer at 120 yds with it just once. I was right on. I started to look at shooting a pie plate instead of a half dollar (pick any coin) when hunting deer. By having a longer zero, I'm in that pie plate from muzzle to slightly beyond my zero. I still want very tight groups at the range, but by accepting an 10" or so kill zone makes hitting the deer easier for me.

Dan


That was what I was going for. I want to know if I hold on a heart shot at 50-125 yards, as long as I am holding dead center that bullet is still going to hit the heart. I also picked this round because where I am at in the mountains, when a deer runs, its either 80 degrees up hill, or 80 degrees down hill. I really do not like dragging a deer on either one of those. So when I hit it, I want it down, and dead right then and there
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Re: Sighting in 450 bushmaster

Postby plant_one » Wed Aug 02, 2017 1:05 am

[quote="pauleberly"}

So the 1/16 twist barrel, the bullet will do a full rotation 16 times before it exits the barrel. [/quote]

no. you've got it backwards.

it means it makes one full rotation every 16" of barrel it travels through.
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Re: Sighting in 450 bushmaster

Postby Texas Sheepdawg » Wed Aug 02, 2017 5:56 am

plant_one wrote:[quote="pauleberly"}

So the 1/16 twist barrel, the bullet will do a full rotation 16 times before it exits the barrel.


no. you've got it backwards.

it means it makes one full rotation every 16" of barrel it travels through.[/quote]


Thank you. I was about to say the same thing.
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Re: Sighting in 450 bushmaster

Postby pauleberly » Wed Aug 02, 2017 3:57 pm

So my 16 inch barrel with a 1-24 twist rate, does not make a full spin in the barrel before the bullet exits?

How do it get enough spin to be able to stabilize in the air?
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Re: Sighting in 450 bushmaster

Postby Bmt85 » Wed Aug 02, 2017 4:50 pm

Play with a twist rate calculator, you will see there's a few variables that determine if a bullet will stabilize. Your main factors are bullet length, weight, twist rate, and velocity.
With that said there are a lot of examples where a bullet won't make a full rotation before leaving the barrel, pistol calibers come to mind.

Also one more note, having a faster twist rate (say 1:16 instead of 1:24) will usually add pressure for the same load. There's a lot more involved in that, such as number of lands and grooves, dimensions of lands, and type of rifling, but usually it adds pressure. Now with more pressure you usually get more velocity for the same load, but if you end up over pressure, things can turn bad a lot quicker with the faster twist. Tex proved that earlier in the thread.
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