.308 what gained by 30" bbl

People have been shooting 147-gr. bullets from 30" .308 barrels with 1:13 and 1:14 twists to keep them supersonic through 1000 yards since the 1960's. It's the only way those bullets will leave at 3000 fps at normal safe pressures. All normal stuff for Palma rifles where .308 ammo with bullets not heavier is required by the rules.

I've shot 155's in .308 barrels from 22 to 32 inches long; all the same ammo lot. Muzzle velocity was from about 2800 to over 3100 fps.

The British Commomwealth countries did this first with converted SMLE rifles. It was not until 1991 that it became the norm in the USA for Palma rifles shooting the Palma course of fire.

Kraigwy is referring to .308 chambered free rifles used in the Olympics in 1958 by USA military team members. The barrels had 1:11 twist and 2200 fps reduced loads shot 168 very accurate with mild recoil through 300 meters. Max loads with 190's in those barrels put them out at 2550 fps with much better accuracy but with more recoil. Better scores were shot at 300 meters from 3 positions using reduced loads with 168's.

Competitors use long barrels to shoot bullets faster. Metallic sight radius made longer has little effect on accuracy.
 
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Yes, Jimro, I was referring to F T/R because nobody would bother to set up a 10 kg "belly benchrest" .308 for F Open.

I am a long way from winningest and I shoot a 28" barrel, largely because PacNor charges by the inch for anything longer.
There was the one guy, either F T/R or Palma, I disremember which, who had bought a barrel so long that he could not find a gun case for it. At least 32" maybe more.

There is no bullet weight limit to Palma shooting as run by the NRA in the USA. If you want to go abroad and follow international "Fullbore" rules, there is. Which is why Berger makes a 155.5 grain bullet, the maximum Fullbore is 156.
 
There is no bullet weight limit to Palma shooting as run by the NRA in the USA?

There is if the match rules limit bullet weight. That happens.
 
Oh, note that in the link I provided in post #9, it was found that the average FPS gain per inch of barrel, in barrel lengths from 28" to 33" is only EIGHT fps!

So yeah, those are hardcore diminishing returns- and that's with 6BR - my guess is even less with .308 win.... maybe 6 per inch??

From 33" to 47", I'm sure even less per inch on average.
 
I was just quoting some old guy name of Salazar and his cite of the NRA rulebook. Is he wrong?

The NRA High Power Rifle Rules set forth the requirements for rifles to be used in a Palma match or the Palma Rifle category of a long-range match. The pertinent rule, Rule 3.3.1 reads as follows:

3.3.1 U.S. Palma Rifle
(a) a rifle with metallic sights chambered for the unmodified .308/7.62 mm NATO or .223/5.56 mm NATO cartridge case.
(b) any service rifle with metallic sights chambered for the unmodified .308/7.62 mm NATO or .223/5.56 mm NATO cartridge case.

"That's it, the entire rifle rule, the whole enchilada. The rule is notable for what is left unspecified: bullet weight, rifle weight, trigger pull weight. All of these things are unrestricted. As long as you're shooting a rifle with metallic sights chambered in .308 or .223, you comply with the Palma Rifle rules, in the U.S.A. at least."
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If the match rules limit bullet weight without reference to Fullbore, then they are playing by what we IDPA shooters call "tribal rules."
 
44AMP said:
I remember reading, back in the 70s, where some wag calculated the barrel length needed for efficiency, if you necked the .50 BMG down to .30 caliber.
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I got bored a couple years ago and set up QuickLoad with a .50BMG necked down to .243.

Max fps limited to 65,000 psi with a 55gr Nosler occurs at 84" barrel length, using 123.5gr of H50BMG... 5807fps.

Heavier bullets like a longer barrel. QuickLoad says it could get a 115gr Berger VLD up to 4,808fps in a 108" barrel, using 107.3gr H50BMG.

How awesome would that be?:D

MPBR of 465 yards with +-3" and only 24" low at 710 yards:eek:
 
I keep building longer and longer. The rifles keep getting faster and faster. My newest 1k toy has a 33" barrel on it. 33" of barrel and then 4" of brake.
I usually use .284 Winchester. The .308 Win. has never done too good in the matches around here. .284 Winchester and 6Br Norma are dominant on still days. On the windy days the big 6mm wildcats take the money home. The 6.5 x 284 is always a force to be reckoned with. One of the Gunsmith recently started shooting a 338 Lapua necked down to .30 cal. I believe that in extreme conditions it will definitely be the rifle to beat.
 
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People have been shooting 147-gr. bullets from 30" .308 barrels with 1:13 and 1:14 twists to keep them supersonic through 1000 yards since the 1960's. It's the only way those bullets will leave at 3000 fps at normal safe pressures. All normal stuff for Palma rifles where .308 ammo with bullets not heavier is required by the rules.

I've shot 155's in .308 barrels from 22 to 32 inches long; all the same ammo lot. Muzzle velocity was from about 2800 to over 3100 fps.
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I have not been doing well at 1000 yards with my 175's or 190's out of a 26 inch 308 with a 1:10. Target pullers tell me the bullets are subsonic when they hit. Bud's are recommending 155's and longer barrels. I have lots of 155’s. I also have a box of new 308 blanks all in the 1:10 twist. Will this work? Or am I going to have to bite the barrel blank and order a 1:11, 1:12 or a 1:13?
 
Slamfire, I don't think your barrel length and twist is a problem. Here's why.

I've shot 168 to 200 grain HPMK's from a 26" 1:10 twist .308 barrel that held 3/4 MOA at 1000 in accuracy tests. Won my share of matches doing it. Same thing with 180 and 190's from a 1:12 twist 24" 7.62 NATO M1 barrels.

Military rifle teams shot Sierra 180 HPMK's from 1:10 twist 22" M14 barrels with much success winning and record setting.

Therefore, I think there's a different fly in your rifle/ammo ointment. Most likely a twist flaw or irregular barrel bore and/or groove dimension.

Have you slugged the bore to ensure its groove diameter is at least .0004" smaller than bullet diameter?

What muzzle velocity are those bullets leaving at?
 
Have you slugged the bore to ensure its groove diameter is at least .0004" smaller than bullet diameter?
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No, I have not.

What muzzle velocity are those bullets leaving at?
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I am of the opinion that the barrel is tight maybe the chamber. Barrel is stamped “308 Palma” which should be the reamer used.

I chronographed these loads in the barrel, decided nothing strange was going on, the nickel plated brass shot a five shot one hole group at 100 yards, and shoot well in other 308’s.

I cannot push these 175’s faster than the max load or I have to get a cleaning rod to knock the case out of the chamber. I have also had to cut my 190 grain Varget loads by a grain, from 44 grains to 43.0 (Fed cases, Fed 210S) or I have had pressure problems.

26” 1:10 Wilson barrel.

175 SMK 41.0 grs H4895, wtd lot 4501, Nickle R-P, Tula7.62 OAL 2.750"

10-Jan-14 T = 51 °F

Ave Vel = 2540
Std Dev = 17
ES = 35
Low = 2522
High = 2557
N = 5

175 SMK 41.5 grs H4895, wtd lot 4501, Nickle R-P, Tula7.62 OAL 2.750"

14-Jan-14 T = 51 °F

Ave Vel = 2619
Std Dev = 29
ES = 67
Low = 2576
High = 2643
N = 4

easy bolt lift, five shot one hole group at 100 yards.


I swapped scopes, am now using a 24X Weaver. There was nothing wrong with the take off scope as I shot well with it on a 223 at 600 yards. It may be that I don’t shoot this 308 well, or, more likely, I am a horrible 1000 yard shot
 
Slamfire,

I have not been doing well at 1000 yards with my 175's or 190's out of a 26 inch 308 with a 1:10. Target pullers tell me the bullets are subsonic when they hit. Bud's are recommending 155's and longer barrels. I have lots of 155’s. I also have a box of new 308 blanks all in the 1:10 twist. Will this work? Or am I going to have to bite the barrel blank and order a 1:11, 1:12 or a 1:13?
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Depending on atmospherics even a 175 SMK will go subsonic before 1k. The trick is that the 175 SMK handles the transonic velocity zone a lot better than the 13 degree HPBT bullets like the 168 SMK and "new" 180 SMK.

The 155s will get there supersonic, as will Berger's 168gr Hybrid. Reported BC is higher than the 175 SMK and results have been good from by buddy shooting them through a 1:11.25 5R barrel.

If you really want to try a 155gr bullet, try the 155 Lapua Scenar or Sierra 155 Palma.

Jimro
 
A Sierra 175 SMK leaving at 2600 fps will be supersonic at 1000 yards.

The 175 has a higher BC than the 155 Palma. Check a Sierra website for BC's on both.
 
Depending on atmospherics even a 175 SMK will go subsonic before 1k. The trick is that the 175 SMK handles the transonic velocity zone a lot better than the 13 degree HPBT bullets like the 168 SMK and "new" 180 SMK
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I have had 168's tumble, even older Hornady 190's. That was a surprise, I finished a string with 190 SMK's, switched to the Hornady 190's, same everything else, and the Hornady's tumbled! Some hit the berm, about seven feet below the previous zero. Went back to 190 SMK's. The 190 Hornady's shot well at 600 yards, look the same, no idea what was going on.

When my target pullers tell me that your bullets have gone subsonic, I believe them. Maybe it’s the wind, maybe the humidity, but that’s what they told me.
 
Slamfire- try some RL-15. You will pick up speed with out pressure. RL-15 is great in 308's. You shouold be able to get low 2700/FPS with a 175 gn.
 
Bart B,

A Sierra 175 SMK leaving at 2600 fps will be supersonic at 1000 yards.

The 175 has a higher BC than the 155 Palma. Check a Sierra website for BC's on both.
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You are mistaken.

175gr SMK, 2600 fps muzzle velocity, 59 degrees F, 29.92 inches mercury, the bullet will go subsonic at 980 yards. The muzzle velocity has to be 2,650 to reach 1k and still be at mach 1.001.

You can check it out at JBM Ballistics if you don't believe me.

A Sierra 155gr HPBT Palma or Lapua Scenar at 2,950 fps in the same conditions is still supersonic at 1k.

The speed of sound is not a constant, as the air gets thicker the speed is higher. http://www.engineeringtoolbox.com/elevation-speed-sound-air-d_1534.html

Jimro
 
I heard any barrel over 7' is illegal in NY....
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"Weapons of war" don't belong "on the streets" - dontcha know!?

Never could figure out what they meant by that. Never saw a select-fire M4 for sale at the local shop, let alone did I ever find same out "on the streets" - I looked....checked gutters and everything for those M4s and RPGs. What the hell are the antis even talking about?
 
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