I've been working up loads for .223 Ackley Improved. I've started a web site to post load data from others.

I keep seeing load data for 40 gr. bullets where velocities are in excess of 4000 fps. Try as I might with various powders, I get about 3750 fps and start showing pressure signs or "bore capacity" indicators. The velocity just sort of flattens out at this speed and no amount of increasing the charge seems to increase the velocity.

Remington 700 PSS, 1:9 twist, rechambered "stock" barrel. 22.5" length.

Chronographing with an Oehler 35P "Proof" printer and two screens.

Am I crazy, or is everyone else fudging their data?

Genghis;

Welcome to the "Howja do that?" club. I've been an experimenter and wildcatter many years and have several computer programs for determining internal ballistics and so far none of them predict those kinds of velocities unless the barrel is in the 30" plus range and the pressure is just sorta REAL HIGH.

I also don't understand some of the claims for case capacity. There isn't much body taper to the 223 case so how do you get any improvement, were only talking about 0.020" more dia tapering to 0" in about 1.2". Someone help me with the math, please. I have enough trouble getting a 40 grainer going 4000 out of my 26" 22-250 and it has almost twice the capacity of the 223. Believe me, I want to chamber me a barrel for a 223 AI just as soon as I can get some REAL data not just dream data, not that I don't believe.

Makatak

I'm really not sure. I have rifles (a certain 284 Win comes to mind) that are consistantly faster then the books say they should be. Faster then it should be with factory ammo too. I also have a 7mm-08 that comes nowhere close to what the loading manuals say it should do, no matter the load. So I guess I agree that there are fast and slow barrels. I also think that people are optimists, so what do i know. - Dan

FWIW, my .222 is fast, my .303 & .35 Remington are "book", aand my .30-06 is slow. The .30-06 shows pressure signs before the .222 does.

Bye
Jack

I always though a fast barrel had to do with the smoothness of the bore. Now I don't know.
1) An eary M700 Rem. in 7mm mag with factory ss barrel. Look at this barrel with a bore scope and it's as smooth as a Hart barrel(great shooter to)
Right at 3200fps. with a 160gr. Nosler
2)A new M700 SS VS in 220swift, this barrel also is real smooth in the bore scope. It shoots right around 1/2in. But oh is it slow, best velocity I have come up with is just over 3700fps. with a 55gr. bullet and 45.5grs of IMR4350. About the same with H414.
3) A Rem M700 in 223/Hart barrel. Great shooter, velocity-just over 3600 with a 40gr.VMax. And that's a very warm load.
4) A 6.5X257IA built on a Sako L579/ Douglas barrel that can be a copper fouler(rough bore). This little rifle weights 71/4lbs. with scope , shoots under an inch almost always, and gets 2975fps. with a 140gr. Sierra. This is not a smooth barrel but is quite accurate and I consider it to be a very fast barrel.
Some barrels just spit out a slug faster then other for reasons unknown.

Gentlemen -- I experience the same speed disparity with a pair of my rifles. The rifles are .358 STA chamberings, one a Winchester custom stainless steel barrel and the other a Lilja custom stainless barrel. The Winchester barrel is very consistently 75 to 150 fps slower than the Lilja barrel, on every bullet I have ever shot through them. I load them identicaly and after nine months of shooting them, the difference is always there. I have also noticed that on certain days the speeds may vary up to 100 fps. Just this past weekend while shooting the Lilja first I noticed an approximately 100 fps slower average speed than a few days earlier. I was using a 270 gr North Fork bullet at speeds of approx. 3000 fps. The temperature was only 5 degrees different, the load, bullet, primer all the same. After shooting the Lilja and noticing the slower speed, I shot the Winchester and it was also about the same amount slower. The accuracy was excellent on both. My brother-in-law who witnessed both sessions, scratched his head and asked me to explain the difference, I was at a loss. I chronograph 95% of my shots and have noticed on different days I would have slower or faster readings, therefore I average several sessions to determine the true speeds. Normaly those differences are not as much as 100 fps. Maybe someone out there can explain this, if so please do so. I can understand the difference in barrels and those speed variences, but why the difference in speed on different days that seemed to be about the same puzzles me. Good shooting.

[ 06-11-2002, 17:17: Message edited by: phurley ]

I'm not sure how much, if any, difference there is in barrel "speed". Obviously a barrel will polish out eventually after a few rounds, even if the bore is pretty uneven to start.

Some years back I had the bright idea of exactly duplicating a rifle in 338 Win Mag. The "parent" gun had a Douglas barrel. I took a new M70 and cut a couple of threads off the barrel and rechambered with the same reamer as the parent, figuring I could use the same loads in both rifles thereby minimizing weight to pack in to hunting country. Surprise! While the chambers were as near identical as they could be there was significant disparity in velocity with the identical loads. Turned out that the new rifle had a bore diameter .0004" larger than the Douglas barrel thus even with less friction and resistance it was a good deal "slower" than the other barrel. Less sealing of the projectile as it was pushed out, I figured.

I think the majority of these differences in velocity are due to the minute differences in bore diameters that are difficult to measure and identify. After all, if the metal is the same, the friction should be quite comparable in most barrels. I think it's those small differences in bores and chambers that account for most of these differences, not the barrel itself.