Is there actually any downrange advantage for very heavy for caliber bullets?

[justinp61]

Having been invited to shoot 600 yards with some friends I've done some digging on bullets for my 1-9 twist 260. This rifle was built to shoot 120 grain and lighter bullets for deer and coyotes.

I ordered Sierra 123gr Match Kings after playing with Hornady's ballistic calculator. I compared them with a couple 130 grain offerings. Using 2950fps for the 123's and 2850fps for the 130's the only place the 130's looked better was wind drift and it wasn't much 19.6-22.1" for the 130's and 22.8-23.4" for the 123's depending on who's bullet I checked.

Just for fun I ran the same calculator for a 140gr bullet with a .646 BC compared to the 123's .510 BC. I used 2650fps for the 140's velocity and 2950fps for the 123's velocity. The 123 dropped 11" less at 600 yards and 30.5" less at 1000 yards than the 140. Using a 10mph 90° wind the 140 drifted 2.7" less at 600 and 10.2 less at 1000 yards than the 123.

Are these calculators close to real world results?

 

[RockyMtnMT]

Having been invited to shoot 600 yards with some friends I've done some digging on bullets for my 1-9 twist 260. This rifle was built to shoot 120 grain and lighter bullets for deer and coyotes.

I ordered Sierra 123gr Match Kings after playing with Hornady's ballistic calculator. I compared them with a couple 130 grain offerings. Using 2950fps for the 123's and 2850fps for the 130's the only place the 130's looked better was wind drift and it wasn't much 19.6-22.1" for the 130's and 22.8-23.4" for the 123's depending on who's bullet I checked.

Just for fun I ran the same calculator for a 140gr bullet with a .646 BC compared to the 123's .510 BC. I used 2650fps for the 140's velocity and 2950fps for the 123's velocity. The 123 dropped 11" less at 600 yards and 30.5" less at 1000 yards than the 140. Using a 10mph 90° wind the 140 drifted 2.7" less at 600 and 10.2 less at 1000 yards than the 123.

Are these calculators close to real world results?

It would be very interesting to shoot them at the same time and see what actually happens on target. I think the drop data will be pretty close.

 

[hawlejr]

As @Bghunter338 noted, mine in 1:7" ...

Smart to go for 1:7 for those long bullets. I think the standard rifle mfgrs. are missing an opportunity to sell more rifles by offering some faster barrel twists. I have a 30-378 Weatherby which only comes with a 1:10" twist. It won't stabilize the 200 gr Barnes LRX, so I've had to drop back to 190 gr GMX. Pity, because that powder reservoir could drive longer bullets really fast! The Swedes knew something when they standardized a 1:7.5" twist on their 6.5 Mausers. Of course, that was for the long 160 gr round nosers, but it shows some forethought. Take care, and shoot straight!

 

[tim_w]

Especially with these high bc mono turned bullets as the density is significantly reduced. To get a 1:7 in 6.5mm you basically have to order as almost no one stocks them. I am ordering one from Bartlein for a pack gun in 6.5 Max (SAUM -Imp). But I am fine if needs to be a mono bullet only setup with fast twist and high vel as the only cup/core I would be using is the 156 Berger otherwise Badlands, Hammers, CEB etc.

It's amazing where we have gotten to with these heavy for cal low drag bullets. I recall when 10 twist was fast for a 30 cal now we need a 1:8 if it's got the case vol. 1:9 for a 338 if not faster. 1:7 for 6.5 & 7mm. I think we have reached the upper limits without a change in technology either in propulsion and or material density.

 

[RockyMtnMT]

With our bullets we have not found the line of too much twist. I'm sure there is a point but as far as I'm concerned more stability is better. The only down side I have seen to fast twist is in big cartridges running heavy bullets causing the rifle to torque more.

 

[Phil Rizzo]

With our bullets we have not found the line of too much twist. I'm sure there is a point but as far as I'm concerned more stability is better. The only down side I have seen to fast twist is in big cartridges running heavy bullets causing the rifle to torque more.

Need some training wheels? Outriggers?

 

[MagnumManiac]

With our bullets we have not found the line of too much twist. I'm sure there is a point but as far as I'm concerned more stability is better. The only down side I have seen to fast twist is in big cartridges running heavy bullets causing the rifle to torque more.

Yes, torque is huge when you start running heavy bullets fast.
First noticed this running 260g Accubonds in my 375 Weatherby (un-braked). Then with the 300-416 Rigby Improved 9" twist with 230's, then the 338-416 Rigby Improved 9" twist with 300g/323g and the most is 375-416 Rigby Improved 8.5" twist running 400g+ bullets.
Without the 4 port brake I would think the rifle would twist to the left leg of the bi-pod fairly easily, but I'm not willing to fire it un-braked to see. You feel it twist in your hands if you shoot standing, which is not ideal.

Cheers.