So just how capable is a 26" barrelled,magazine fed .308 out to 1000yds?

[Laurie]

Very informative post.Where would I get a copy of Bryan Litz' book???

 

Gazzar,

 

here!

 

Midway UK

 

You used to be able to get it direct from Bryan Litz's website, but it just refers you to retailers now. It's still worth looking at this website though

 

Applied Ballistics LLC

 

Laurie

[brown dog]

 

Midway UK

 

 

f-f-f-f-fifty seven quid !!! :blink:

[Redfox]

Interesting stuff and reminds me of an article on the border barrels site by Geoff Kolbe on the subject, it vanished but has now re-appeared with an explanation, here http://www.border-barrels.com/articles/art1.htm

In playing with the 300WM I found as stated by many that it performed far better at distance with the 185gr and 220gr bullets at fair velocities than the 167 gr launched at super velocities which went poor over 8ooyds. I remember that we were taught that a rule of thumb for mach was 1100fps at sea level but of course it is only that and not precise.

Keep it coming Lads.

Redfox

[Laurie]

f-f-f-f-fifty seven quid !!! :blink:

 

 

 

Considering the US price is $39.95 and there is no VAT on books, methinks MidwayUK is taking the proverbial Michael!

 

Unfortunately, Amazon.co.uk and Amazon.com quote similar prices, but Sinclair International has it at the author's original price of $39.95, so if you know anybody putting a Sinclair order together, that's the place to get it.

 

Prospect Books is a good source for books on military weapons, ammo and sporting rifles, but Mike there doesn't list it on his website. It might be worthwhile fro anybody trying to get a copy to contact him. The website is

 

Prospect Books

[MarinePMI]

Considering the US price is $39.95 and there is no VAT on books, methinks MidwayUK is taking the proverbial Michael!

 

Unfortunately, Amazon.co.uk and Amazon.com quote similar prices, but Sinclair International has it at the author's original price of $39.95, so if you know anybody putting a Sinclair order together, that's the place to get it.

 

Prospect Books is a good source for books on military weapons, ammo and sporting rifles, but Mike there doesn't list it on his website. It might be worthwhile fro anybody trying to get a copy to contact him. The website is

 

Prospect Books

 

 

Laurie,

 

In one of your previous posts, you mention the tubulence from the bullet transitioning through the speed of sound being a factor. You post also alluded to it being around 1080 (or a hundred fps before that). I was wondering what your thoughts were on the effect on the bullet as it passes through the transonic barrier the first time (since 1080fps would be the second one, right?). Just curious...

 

Everyone talks of the last one, as it does have the most effect, but I'd be curious what your thoughts were when it passed through the one that's around, what, 2160fps? I'm thinking it's negligible due to the velocity, but I'm sure there's some, and often wonder if this is what gives that erratic accuracy at closer ranges (i.e. what perople refer to as "the bulet not going to sleep yet"). Your thoughts?

[Laurie]

Laurie,

 

In one of your previous posts, you mention the tubulence from the bullet transitioning through the speed of sound being a factor. You post also alluded to it being around 1080 (or a hundred fps before that). I was wondering what your thoughts were on the effect on the bullet as it passes through the transonic barrier the first time (since 1080fps would be the second one, right?). Just curious...

 

Everyone talks of the last one, as it does have the most effect, but I'd be curious what your thoughts were when it passed through the one that's around, what, 2160fps? I'm thinking it's negligible due to the velocity, but I'm sure there's some, and often wonder if this is what gives that erratic accuracy at closer ranges (i.e. what perople refer to as "the bulet not going to sleep yet"). Your thoughts?

 

Hi MarinePMI,

 

severe transonic turbulence is reckoned to be a problem from around 1.2 Mach down to a bit below the speed of sound, so say 1,350 fps through the speed of sound (1,122 fps) to somewhere between that figure and 1,050 fps. If there is a problem though, it's more likely in a smaller band peaking as the bullet's speed reduces to somewhere around the 1,200 fps mark and is worst at just above the speed of sound itself. Some bullets are fairly badly affected, some seem to mostly ignore it. The problem is that in this speed range, the curved shape of the bullet both accelerates and slows the airflow around its various bits, so you get a mixture of supersonic air against one part of the bullet alongside to subsonic flows on other bits - result: turbulence. The best way of avoiding it is to have ballistics that keep bullets above 1,200 fps or thereabouts at the target - and that's the problem with .308W at 1,000yd, it's damn hard to achieve so you need the best mix of muzzle velocity and bullet BC that you can squeeze out of the cartridge, hence TR, Fullbore and Palma rifles universally adopting a 30" length across three continents, with some going a bit longer even to 31 or 32".

 

What happens in the barrel on the way up through the speed of sound and transonic speeds is rather different as you have no airflow around the bullet, it making a seal within the bore. The bore fully supports it through this period and the real issue is what 55,000-60,000 psi pressure up its backside does to it! I'm no scientist or engineer so don't pretend to understand the physics here, but people with the right background (like Dr Geoff Kolbe of Border Barrels) tell me they don't really know either. That's why rifle barrel and cartridge design has, unlike large calibre stuff like artillery pieces, evolved through several hundreds of years of trial and error and is even now unsuited to computer modelling. We do know that strange things happen to the bullet in the first few inches of travel under peak pressure and that the support of the barrel walls is essential. In the early days of smokeless small-bore (.30") military cartridges, government scientists cut barrels down to stub lengths to see what would happen - the bullets came out of the muzzle like flat pennies and cut 1" to 2" dia holes in the target. It is assumed that the bullet is in a near plastic state in the early part of its travel down the barrel, and in effect solidifies as pressures reduce - but that's probably a huge simplification of the processes involved.

 

Going back to the 26" barrel question, I've always argued that this length (and the metric equivaslent that works out at around 25.5") is the minimum you need for successful 1,000yd shooting, and it's barely adequate. You also need an action that performs with stout loads, Like Toni / Adrian's 48 odd gn of N150. The Sako TRG and Accuracy International type rifles meet those criteria, some factory rifles don't as their groups turn huge at peak pressures due to a poor lug lock-up. Toni's Remy 700 is obviously a good one (assuming nobody has worked the action over). And by the way, what a performance that was from Toni and her rifle and Adrian's handloads !!!!

 

There is another factor in addition to simple length and that's bore / groove dimensions. I've always assumed that one reason the AI and TRG etc jobs perform better than they should at long ranges is because they're given 'tight' bores as they have to perform well with standard 7.62mm machine-gun rubbish with its undersize bullets if the proper sniper fodder is unavailable in the wilds of Afghasnistan or wherever. This was an assumption until recently when I had it confirmed unofficially for AI models at any rate. Commercial factory .308s with hammer forged barrels may be closer to the SAAMI 0.300 bore / 0.3080" groove dimensions, so give lower MVs all other things being equal. There is throating too, which is said to be 'awful' (ie horrendously long) in current Remy PSS and VS barrels, again reducing MVs. .308W target rifles use slightly tight bores as well as 30" lengths to get their 2,950 - 3,000 fps from 155gn ammo.

 

Moreover, I would caution writing too much into what a good 26" barrel rifle like Toni's will do in a BR match at 1,000yd and how that transfers to deliberate shooting at marked targets. Toni's group shows what the rifle and ammo will do in 'precision' terms (group size) at long range, but BR shooters get their shots off fast - Gun Pimp with his twin-port left feed, right eject BR Light Gun gets his five off in 18 seconds! In deliberate shooting, the second part of the success mix is reading the wind and having a combination that is as little affected by it as possible as even the best wind-reader going can't call it right every shot. If you have two shooters of equal ability and using rifle/ammo combinations that group equally well, but one has his bullet at 2,750 fps and the other shoots the same model at 2,950 fps, the second guy will win all other things being equal - and the longer the range, and the more variable / stronger the wind, the larger the winning points margin. Simple ballistics! Also, the Match Rifle shooters who shoot .308W up to 1,200yd in the UK and longer ranges in Canada and Australia (1,500 at some range I can't spell or even pronounce in New South wales) and know a thing or two about ballistics at extreme ranges say that once you're in the transonic zone, even if the bullet behaves well, it becomes very sensitive to minor wind changes.

[MarinePMI]

Laurie,

 

Yes, I understand the effects as the bullet passes through the 1,200 fps mark, and the resulting turbulence. I guess my question was a bit vague. I was curious as to your thoughts on the bullet's behavior as it passes through the sound barrier the first time?

 

Just curious...

[brown dog]

Laurie,

 

Yes, I understand the effects as the bullet passes through the 1,200 fps mark, and the resulting turbulence. I guess my question was a bit vague. I was curious as to your thoughts on the bullet's behavior as it passes through the sound barrier the first time?

 

Just curious...

I was wondering what your thoughts were on the effect on the bullet as it passes through the transonic barrier the first time (since 1080fps would be the second one, right?). Just curious...

 

Everyone talks of the last one, as it does have the most effect, but I'd be curious what your thoughts were when it passed through the one that's around, what, 2160fps? I'm thinking it's negligible due to the velocity,

 

I'm a bit confused. I have the impression that you're saying that as it decelerates you think it goes through 2 sound barriers? Is that what you're asking?

 

There's only one 'sound barrier' -at Mach 1, after that, Mach 2, 3 etc are just descriptors to compare speed to Mach 1, there aren't 'sound barriers' at each one

[MarinePMI]

BD,

 

Okay, now that makes sense. I had always (I guess erroneously) thought that there were multiple "barriers" of sound waves condensing in on themselves and rebounding back...

[ChrisF]

I have a 308 , and am running Lapua Scenar 155gr @ 2896 fps ( has a 26 inche barrel & mag feed ) , and its OK at 1000yds , BUT I tryed it at 1025 metres & had NO real luck with it , it may have been just hard conditions/target to see impacts , or it may be they are going transonic and losing accuracy .

 

2300 fps , Please