.308 BC versus weight

Benonymous · November 27, 2007, 10:55 PM

I'm setting up a new rifle for long range shooting. It's a Steyr Tactical Elite that I'm topping off with a Nightforce NXS in 8-32x56. I have another target rifle in 6.5x55 that I handload for. I use a Sierra Match King bullet in 140Gn. That gives me a BC of around .52 or so. I'd like to start off in the ballpark with the .308 but I find myself spoiled for choice in the bullet area. Just looking at the Sierra catalog I can get anything from 100Gn to 240 and the 240 has a BC up around .71. i also notice a Palma bullet there at 155Gn but the BC on that one is closer to the 6.5x55.

My main question here is, should I go with the highest BC and get the 240Gn bullet or will the weight cause more problems with drop and outweigh the advantage of the high BC.?

Thanks in advance for any advice.

4EVERM-14 · November 28, 2007, 08:24 AM

My LR experience showed the 308 marginal for driving bullets heavier than 190 grains. My best results came with the 168 MK at 600yds. 175's beyond that. I think a medium bullet weight [168-180] at the highest reasonable velocity would be a place to start. IIRC the 175 was designed for the .308 at LR.
The Marines,back in the M14 days, shot 168's loaded to something like Mach 18 plus for their LR guns. It shot accurately but they also only fired new cases one time and trashed them afterwards. Plus they had armorors to put the guns back together.

Jim Watson · November 28, 2007, 08:46 AM

The 175 SMK is a good place to start.

I have also bought a supply of Lapua Scenar 155s. They have a higher BC than the Sierra Palma; about the same as 175 SMK, and can be driven at higher velocity. Accurate, too.

Benonymous · November 28, 2007, 06:00 PM

Thanks for the replies David and Jim. After I posted my question I went looking for some data on the BC versus weight relationship and found this

http://www.exteriorballistics.com/ebexplained/index.cfm

After reading this and getting your feedback I see that the relationship is really between BC and velocity. There's no use having a high BC projectile if it's travelling too slowly. You'd get a rainbow trajectory. I think the medium to medium-heavy bullets you've suggested would be the best compromise. I'll get either the 175 or 168 depending on availability.

Thanks again

Ben.

Jim Watson · November 28, 2007, 07:02 PM

Depends on what you call "long range."
The 168 SMK is NOT suitable for 1000 yards; a .308 won't keep it supersonic that far and it gets weird when it goes transsonic. Some ranges won't even allow them.

And try some 142 gr SMKs in your 6.5. Two grains doesn't do much for SD but they worked over the shape and its BC is .595. I see a lot of those in the F-open 6.5x284s.

sigfreak · November 28, 2007, 07:11 PM

i to am setting up a long range .308 for the first time.my last long range rifle was a hot rod.i shot 168grn. 7mm bergers(.65 BC) @ about 3100fps with a 7SAUM.awesome 1000yd. gun.for my new rifle i started with a remington 700r5 milspecSS. with a little custom work.i haven't started working a load for it yet but was thinking about trying the 155 lapua's.they have higher BC's than most 175's(excluding bergers)and shoot roughly 200fps. faster.can some .308 expert out there talk me out of this on why a 175 may be better or would the 155's be OK for 300-1000 yards.

Jim Watson · November 28, 2007, 07:46 PM

See Post #3. When my present stock of 175 SMK runs out, I have 500 155 Scenars ready to go, load data, chronograph readings, sight settings, and all, already worked out. Just load, zero, and shoot.

sigfreak · November 28, 2007, 09:50 PM

hey,jim.keep us posted when you start running your lapuas.curious to hear how they did.i know at a local f class match a couple years ago a guy i know was trying some 155 berger vld in the match.it was only a 500 yard match,but he shot it clean.23 X's,county his 3 sighters.he had'nt shot the load at 1000 yet,but i was impressed with the 500yd results.

Zak Smith · November 28, 2007, 11:24 PM

I've shot thousands of the 155gr Lapua bullets in 308. Good bullet. You should be able to fire them at 2850-2950 fps from a 24-26" barrel.

Benonymous · November 29, 2007, 07:50 AM

Thanks for all the information guys. Very useful.. I'm not sure how I'd go getting Lapua bullets locally but I'll give my local shop a try.

Cheers!

Ben.

Jim Watson · November 29, 2007, 08:27 AM

Same way you get anything these days... phone or computer. No local store can stock everything, certainly not a bullet they can't pronounce.

I got mine from Powder Valley.
http://www.powdervalleyinc.com/

sigfreak · November 29, 2007, 10:15 PM

damn it jim,i wish i'd seen your post earlier.i just order some bullets from midway,155 lapuas and 125 nosler b-tips because they were one of the few places that had both in stock.now you come along and turn us on to this place.about 8 dollars cheaper than what i just paid from midway.oh well,i know were i'm getting them next time,thanks for the link.

Ken O · November 29, 2007, 11:10 PM

I order a lot from Powder Valley, (and Midway also). What really makes PV cheaper is the shipping. They use the flat rate shipping boxes, I recently bought a couple thousand 230 gr .45acp bullets and they got them in one box so the shipping was about $9.

I shoot the SMK 155s for Palma matches, I plan to try the Lapua and Burgers next year. For the 6.5 I use the 142 SMK, they work real well at 1000 yards.

November 27, 2007, 10:55 PM	#1
Benonymous Senior Member Join Date: January 6, 2005 Location: NSW Australia Posts: 254	.308 BC versus weight I'm setting up a new rifle for long range shooting. It's a Steyr Tactical Elite that I'm topping off with a Nightforce NXS in 8-32x56. I have another target rifle in 6.5x55 that I handload for. I use a Sierra Match King bullet in 140Gn. That gives me a BC of around .52 or so. I'd like to start off in the ballpark with the .308 but I find myself spoiled for choice in the bullet area. Just looking at the Sierra catalog I can get anything from 100Gn to 240 and the 240 has a BC up around .71. i also notice a Palma bullet there at 155Gn but the BC on that one is closer to the 6.5x55. My main question here is, should I go with the highest BC and get the 240Gn bullet or will the weight cause more problems with drop and outweigh the advantage of the high BC.? Thanks in advance for any advice.

November 28, 2007, 08:24 AM	#2
4EVERM-14 Senior Member Join Date: November 12, 2006 Location: Pennsy Posts: 720	My LR experience showed the 308 marginal for driving bullets heavier than 190 grains. My best results came with the 168 MK at 600yds. 175's beyond that. I think a medium bullet weight [168-180] at the highest reasonable velocity would be a place to start. IIRC the 175 was designed for the .308 at LR. The Marines,back in the M14 days, shot 168's loaded to something like Mach 18 plus for their LR guns. It shot accurately but they also only fired new cases one time and trashed them afterwards. Plus they had armorors to put the guns back together. __________________ David NRA Benefactor Member Distinguished Rifleman #731 Presidents 100

November 28, 2007, 06:00 PM	#4
Benonymous Senior Member Join Date: January 6, 2005 Location: NSW Australia Posts: 254	Thanks Thanks for the replies David and Jim. After I posted my question I went looking for some data on the BC versus weight relationship and found this http://www.exteriorballistics.com/ebexplained/index.cfm After reading this and getting your feedback I see that the relationship is really between BC and velocity. There's no use having a high BC projectile if it's travelling too slowly. You'd get a rainbow trajectory. I think the medium to medium-heavy bullets you've suggested would be the best compromise. I'll get either the 175 or 168 depending on availability. Thanks again Ben.

November 28, 2007, 07:11 PM	#6
sigfreak Member Join Date: June 15, 2007 Posts: 53	.308 i to am setting up a long range .308 for the first time.my last long range rifle was a hot rod.i shot 168grn. 7mm bergers(.65 BC) @ about 3100fps with a 7SAUM.awesome 1000yd. gun.for my new rifle i started with a remington 700r5 milspecSS. with a little custom work.i haven't started working a load for it yet but was thinking about trying the 155 lapua's.they have higher BC's than most 175's(excluding bergers)and shoot roughly 200fps. faster.can some .308 expert out there talk me out of this on why a 175 may be better or would the 155's be OK for 300-1000 yards.

November 28, 2007, 11:24 PM	#9
Zak Smith Senior Member Join Date: December 12, 1999 Location: Fort Collins, Colorado, USA Posts: 2,682	I've shot thousands of the 155gr Lapua bullets in 308. Good bullet. You should be able to fire them at 2850-2950 fps from a 24-26" barrel. __________________ Zak Smith . DEMIGOD LLC . THUNDER BEAST ARMS CORP . COLORADO MULTI-GUN *My PM inbox full? Send e-mail instead.*

November 28, 2007, 08:46 AM	#3
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,541	The 175 SMK is a good place to start. I have also bought a supply of Lapua Scenar 155s. They have a higher BC than the Sierra Palma; about the same as 175 SMK, and can be driven at higher velocity. Accurate, too.

November 28, 2007, 07:02 PM	#5
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,541	Depends on what you call "long range." The 168 SMK is NOT suitable for 1000 yards; a .308 won't keep it supersonic that far and it gets weird when it goes transsonic. Some ranges won't even allow them. And try some 142 gr SMKs in your 6.5. Two grains doesn't do much for SD but they worked over the shape and its BC is .595. I see a lot of those in the F-open 6.5x284s.

November 28, 2007, 07:46 PM	#7
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,541	See Post #3. When my present stock of 175 SMK runs out, I have 500 155 Scenars ready to go, load data, chronograph readings, sight settings, and all, already worked out. Just load, zero, and shoot.

November 28, 2007, 09:50 PM	#8
sigfreak Member Join Date: June 15, 2007 Posts: 53	hey,jim.keep us posted when you start running your lapuas.curious to hear how they did.i know at a local f class match a couple years ago a guy i know was trying some 155 berger vld in the match.it was only a 500 yard match,but he shot it clean.23 X's,county his 3 sighters.he had'nt shot the load at 1000 yet,but i was impressed with the 500yd results.

November 29, 2007, 07:50 AM	#10
Benonymous Senior Member Join Date: January 6, 2005 Location: NSW Australia Posts: 254	Good feedback Thanks for all the information guys. Very useful.. I'm not sure how I'd go getting Lapua bullets locally but I'll give my local shop a try. Cheers! Ben.

November 29, 2007, 08:27 AM	#11
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,541	Same way you get anything these days... phone or computer. No local store can stock everything, certainly not a bullet they can't pronounce. I got mine from Powder Valley. http://www.powdervalleyinc.com/

November 29, 2007, 10:15 PM	#12
sigfreak Member Join Date: June 15, 2007 Posts: 53	damn it jim,i wish i'd seen your post earlier.i just order some bullets from midway,155 lapuas and 125 nosler b-tips because they were one of the few places that had both in stock.now you come along and turn us on to this place.about 8 dollars cheaper than what i just paid from midway.oh well,i know were i'm getting them next time,thanks for the link.

November 29, 2007, 11:10 PM	#13
Ken O Senior Member Join Date: November 2, 2005 Location: Half way between Grayling and Cadillac, Michigan Posts: 353	I order a lot from Powder Valley, (and Midway also). What really makes PV cheaper is the shipping. They use the flat rate shipping boxes, I recently bought a couple thousand 230 gr .45acp bullets and they got them in one box so the shipping was about $9. I shoot the SMK 155s for Palma matches, I plan to try the Lapua and Burgers next year. For the 6.5 I use the 142 SMK, they work real well at 1000 yards.