Improving the 308 Win performance

[nralifer]

The semi-retired benchrest gunsmith who did initial testing with the cartridge gave me some pointers on how to handle the 80K pressure with the 700.

Let me know either by PM or posting the results you get. A gun that can safely handle those pressures can potentially replace the 300 Norma, 300 WM and 300PRC as sniper cartridges in a 308Win sized rifle by not only making the rifle lighter, but also greatly simplifying logistics if the Fury cartridge was applied to the .308 caliber.

 

[bamban]

Let me know either by PM or posting the results you get. A gun that can safely handle those pressures can potentially replace the 300 Norma, 300 WM and 300PRC as sniper cartridges in a 308Win sized rifle by not only making the rifle lighter, but also greatly simplifying logistics if the Fury cartridge was applied to the .308 caliber.

What is the ideal twist for your 175 BD2? I will order a barrel, and chamber it using my FTR reamer with 0.168 freebore. If I can get good precision with the .308 Fury, then we shall see how accurate I can shoot it under hunting field shooting positions, and conditions. Field shooting positions for me would be, sling prone, forward hand over a roll bag, tripod prone, tripod sitting, tripod standing. First and foremost system had to be precise enough for hunting mid to long range. Mid being inside 600.

I ran the Berger Juggernauts in my double lugged heavy barreled, heavily modified 14 type at 2650 fps. At 1000 yards prone matches they ran the same wind (actual, not ballistics program tabletop exercise) as the Berger 168 Hybrids coming out at 2800. The statement I said about 175 BD2s might be the best compromise was based on my experience shooting at 1000 yards with a NM 14.

I figure in a bolt gun and Fury case, the 175 BD2s should shoot inside either one of the Bergers in the same wind. I haven't shot sling and irons at 1000 since 2012, but I have access to a KD range to test 308 Fury and get actual terminal velocity using Shotmarker. If you trust the system accuracy. Initial test will be at 500 to ascertain mid range terminal velocity, precision and drop, then proceed to 1000 when the KD range becomes available.

 

[Chad Erickson]

I have been using for years the 150 BD and BD2 bullets with MVs of 2920 from a 20"barrel and 3050 from a 24" barrel using Leverevolution which outperforms most 3006 loads. Have killed African Plains Game and a large Alaskan Coastal Black Bear all with single shot DRT kills. The attachment is a JBM trajectory calculation of our 175 gr BD2 bullet propelled from a 24" barrel which I think is entirely achievable for the 308 Win at 4500 ft elevation, which is not an unusual elevation to hunt Elk. The higher you go the better. At 900 yds that bullet still has 1300 ft# of energy snd is traveling at 1836 fps which is at least 100 fps more than is required to get it to expand. What makes this possible, and it is the point of the thread, is using a bullet with a high enough BC that will expand reliably at 1700 fps impact. That has already been done by a friend of mine using our 195 gr bullet with a higher BC from a 300WM at 1225 yds.

I enjoyed your analysis of the .308's energy vs velocity.

Every time one analyzes any .30 caliber ballistics, as you superbly did here, an amazing phenomena appears: The maximum yardage at which the 1800 ft/sec minimum requirement for expansion is reached, it matches the maximum yardage at which the 1300 ft/lb minimum requirement for elk is reached. If you go to a larger caliber, surplus energy is wasted, and if you go to a smaller caliber, surplus velocity is wasted. This phenomena of efficiency probably explains why our military doggedly held to the .30 caliber for its weapons for 70 years, whereas most all of Europe and Japan had gone to the .264. However, in the .264 caliber the same performance can be accomplished with 20% less recoil, even though some of the velocity is lost in the analisis.

And the .264 is about the lowest limit for good performance. Go to .243 or .223 and you just get a mouth full of feathers. Take the 6mm Creedmoor, where for the first 300 yards you have too high of a destructive velocity and after 380 yards there is not enough energy left to penetrate an elk.

Going the other direction, the yardage at which the .338 Win. Magnum's velocity hits the critical 1800 ft/sec, is less than the yardage for the 7mm Remington Magnum, with 45% more recoil. All the surplus energy and recoil of the .338 is wasted.

Comparing the .338 Win. Mag. to the 6.8 Western, with its "large for caliber" bullets, the 6.8 Western nearly matches the .338's 1800ft/sec threshold, with 62% less recoil.

Yes, I know these are "just numbers". However, with "numbers" we can design and build ten or twenty new rigs for comparison, with little cost or time. And to say that these are just numbers is to dismiss the Engineering profession that has designed our vast array of structures, before they were built.

 

[nralifer]

What is the ideal twist for your 175 BD2? I will order a barrel, and chamber it using my FTR reamer with 0.168 freebore. If I can get good precision with the .308 Fury, then we shall see how accurate I can shoot it under hunting field shooting positions, and conditions. Field shooting positions for me would be, sling prone, forward hand over a roll bag, tripod prone, tripod sitting, tripod standing. First and foremost system had to be precise enough for hunting mid to long range. Mid being inside 600.

I ran the Berger Juggernauts in my double lugged heavy barreled, heavily modified 14 type at 2650 fps. At 1000 yards prone matches they ran the same wind (actual, not ballistics program tabletop exercise) as the Berger 168 Hybrids coming out at 2800. The statement I said about 175 BD2s might be the best compromise was based on my experience shooting at 1000 yards with a NM 14.

I figure in a bolt gun and Fury case, the 175 BD2s should shoot inside either one of the Bergers in the same wind. I haven't shot sling and irons at 1000 since 2012, but I have access to a KD range to test 308 Fury and get actual terminal velocity using Shotmarker. If you trust the system accuracy. Initial test will be at 500 to ascertain mid range terminal velocity, precision and drop, then proceed to 1000 when the KD range becomes available.

They work well using a 1:10 twist.

 

[JAYgs8163]

@nralifer, I'm putting a new barrel on my 308 bolt gun and plan on testing with the 150 BD. Any suggestions on the chamber and still be able to stay within the short action BDL mag length requirements?

 

[bamban]

@nralifer, I'm putting a new barrel on my 308 and plan on testing with the 150 BD. Any suggestions on the chamber and still be able to stay within the short action BDL mag length requirements?

Not @nralifer, let me take a shot at it. You have plenty of choices; Obermeyer, Bisley, 1995 Palma, 2011 Palma or stick with what your gunsmith suggests based on your requirements.

When I shot the 14s a lot, the rapid fire ammo have to fit in the magasine, I came up with my own reamer that also works for 600 and LR slow fire prone, single loading by rules, we load them long. Mine were 2.93, where the short range ammo are at 2.80.

 

[JAYgs8163]

Thanks, I appreciate the info. I'd like to hear what @nralifer is running in his bolt gun as well.

 

[nralifer]

@nralifer, I'm putting a new barrel on my 308 bolt gun and plan on testing with the 150 BD. Any suggestions on the chamber and still be able to stay within the short action BDL mag length requirements?

What is the longest COAL you could use snd still feed from your magazine? I would go for a chamber that allowed a free bore that would allow a clearance of about 0.0004"/side and is about 0.150" long depending on the allowable COAL of your magazine, the shorter the allowable COAL the shorter the free bore. The principle here is tight clearance of the bullet through the free bore maintains good alignment with the rifling and less dependence on a short jump to be sure the bullet engages the rifling straight. Barrel brands such as Douglas, Bartlein, Benchmark, McGowan and Preferred shoot our bullets well. Clean burning powder is a must.

 

[JAYgs8163]

Now in stock in containers of 100. Good stuff and it goes quick! 100 boxes in there now. My new PBB 10 twist should be here in a few days.

.308 Winchester SRP (Small Rifle Primer) | Alpha Munitions

– OCD-Optimized Case Design with Optimized Case Head Technology -Primer pockets sized for small rifle primers -100 count boxes ship in custom Alpha Munitions plastic cases with perforated bi-layer foam...

alphamunitions.com

 

[bamban]

@nralifer , have you had the time to ascertain the water capacity difference between the fireformed Lapua SRP and Remington SRP?

 

[DoneNOut]

What's the advantage of the small rifle primer? Availability?

 

[JAYgs8163]

What's the advantage of the small rifle primer? Availability?

The case head is harder and in most cases can handle higher pressure loads without primer pocket deformation. I run SRP in my 6CM, 6.5CM, some 308 and in my 6.5x47 Lapua. Some loads I use magnum primers and others not.

 

[DoneNOut]

The case head is harder and in most cases can handle higher pressure loads without primer pocket deformation. I run SRP in my 6CM, 6.5CM, some 308 and in my 6.5x47 Lapua. Some loads I use magnum primers and others not.

Well no kidding. I should try them. Use faster burning powders I take it?

 

[JAYgs8163]

Think about it. Smaller pocket in the same size case head. More material in the head results in primer pockets lasting longer in MOST cases. I run magnum primers on some of the above mentioned cartridges.