16" barrel

PhilOhio · 04-27-2009, 12:55 PM

Although it has been dormant for a couple months, this thread caught my eye because I've spent a lot of time playing with long 9mm barrels, and might be able to steer some of you away from frustrating dead ends. Since it looks like others here are like me, having almost more fun playing with the technical stuff than with the guns, I thought I'd share it.

I'm brand new, having found my way to the site in the course of looking for a nice matching S/42 which I can afford to buy and shoot; still haven't found it. I already have a very nice 1917 artillery and a circa 1930 Dutch Luger from Indonesia, with a somewhat gruesome operational provenance which I can personally verify back to the mid 1940s.

But back to long barrels. Please STAY AWAY from the 16"+ blank barrels which Numrichs advertises as being for "9mm/.357". I say that because I noticed Postino mentioned 9mm Numrich barrels. There is apparently something wrong with the twist rate, and bullets cannot be stabilized. That may be why they became available to Numrichs. I wasted a great deal of personal time and effort finding this out (bought two), building a semi-auto Sten barrel. Bore diameter is correct, but at least half the bullets keyhole (lead, jacketed, standard weights). No amount of tinkering with powder types and weights can correct this, as far as I could determine. Somebody just made a mistake, and now his mistake is being sold.

I cut the second Numrich blank into a few pieces, to see if pistol barrels could be made to work. No, they couldn't. So don't buy these blanks in hopes you can make a Luger barrel that works. I believe Numrichs is still advertising these 16" blanks. They must have a ton of them. It takes a lot of work to profile a nice Luger barrel. Then you go out to shoot it...total keyholing and accuracy disaster.

Luger Doc: Do you have a source of affordable 16"+ 9mm blanks of the correct twist rate for 9mm Para, and with an O.D. of .725" to .750", to roughly duplicate the diameter of Sten barrels?

Postino,

You posted your logical guess as to how pressure and velocity probably drops off significantly in a 16" 9mm barrel...quickly reaching a point of diminishing return. I would have thought the same, until I began experimenting a year or so ago with scrap barrels and a chronograph, etc.

To explore the bullet friction/barrel length/pressure relationship, I began by experimenting with a scrap of .22 RF barrel 10" long. A vintage High Standard Supermatic pistol was my test bed. I drilled 1/16" diameter ports, two at a time, starting about 1/2" back from the muzzle. For each new pair, I would go backward about 1/8". Each time I would chronograph a few rounds, expecting velocity to drop quickly. But I was getting no statistically significant velocity reduction.

To make a long story short, I finally stopped drilling ports when I was 4" ahead of the breech end. There were 100 holes. Standard velocity Federal .22 LR rounds, which had originally measured slightly over 1040 FPS, did not go below about 1000 FPS at the end of the drilling. So after building up pressure and velocity in 4" of barrel, with all that pressure instantly removed, the additional 6" of barrel friction only reduced bullet velocity by about 40 feet per second. I must say that I was astonished!

With 9mm Para, my standard load is 4.5 gr. Bullseye and a cast 120 gr. round nose lead bullet. This gives you 1150 to 1200 FPS in pistol length barrels. It will be somewhat faster, not slower, in a 16" barrel, because powder is still burning and barrel friction is most certainly not slowing the bullet. To do that, you would need an extremely long barrel, considering what I found out with the .22 experiment, and considering the volume of gases generated; it's a few liters, and that's lots more than the volume of a very long barrel. So sometimes what seems to make a lot of sense, when you theorize, turns out to be very different in practice.

FYI: I've also made about 3 - 4 9mm barrels of 10.5" length for the quick change barrel and caliber conversion setup on my registered 1928AC Thompson. Works flawlessly, and of course velocity is always higher than with pistol barrels between 4" and 6".

With all semiauto pistols, Luger Doc has put his finger on the main problem, barrel weight. You have to keep it to the very minimum to get the gun to function, without some way of boosting recoil. Which is another long subject familiar to you suppressor people.

But it's all about fun, and I'm having a lot of it, reading the many technical contributions from some of you Luger experts. I'm renewing my interesting in them, after years of having just left mine sitting in drawers most of the time.

04-27-2009, 12:55 PM	#6
PhilOhio User Join Date: Apr 2009 Location: Ohio Posts: 145 Thanks: 5 Thanked 17 Times in 14 Posts	Although it has been dormant for a couple months, this thread caught my eye because I've spent a lot of time playing with long 9mm barrels, and might be able to steer some of you away from frustrating dead ends. Since it looks like others here are like me, having almost more fun playing with the technical stuff than with the guns, I thought I'd share it. I'm brand new, having found my way to the site in the course of looking for a nice matching S/42 which I can afford to buy and shoot; still haven't found it. I already have a very nice 1917 artillery and a circa 1930 Dutch Luger from Indonesia, with a somewhat gruesome operational provenance which I can personally verify back to the mid 1940s. But back to long barrels. Please STAY AWAY from the 16"+ blank barrels which Numrichs advertises as being for "9mm/.357". I say that because I noticed Postino mentioned 9mm Numrich barrels. There is apparently something wrong with the twist rate, and bullets cannot be stabilized. That may be why they became available to Numrichs. I wasted a great deal of personal time and effort finding this out (bought two), building a semi-auto Sten barrel. Bore diameter is correct, but at least half the bullets keyhole (lead, jacketed, standard weights). No amount of tinkering with powder types and weights can correct this, as far as I could determine. Somebody just made a mistake, and now his mistake is being sold. I cut the second Numrich blank into a few pieces, to see if pistol barrels could be made to work. No, they couldn't. So don't buy these blanks in hopes you can make a Luger barrel that works. I believe Numrichs is still advertising these 16" blanks. They must have a ton of them. It takes a lot of work to profile a nice Luger barrel. Then you go out to shoot it...total keyholing and accuracy disaster. Luger Doc: Do you have a source of affordable 16"+ 9mm blanks of the correct twist rate for 9mm Para, and with an O.D. of .725" to .750", to roughly duplicate the diameter of Sten barrels? Postino, You posted your logical guess as to how pressure and velocity probably drops off significantly in a 16" 9mm barrel...quickly reaching a point of diminishing return. I would have thought the same, until I began experimenting a year or so ago with scrap barrels and a chronograph, etc. To explore the bullet friction/barrel length/pressure relationship, I began by experimenting with a scrap of .22 RF barrel 10" long. A vintage High Standard Supermatic pistol was my test bed. I drilled 1/16" diameter ports, two at a time, starting about 1/2" back from the muzzle. For each new pair, I would go backward about 1/8". Each time I would chronograph a few rounds, expecting velocity to drop quickly. But I was getting no statistically significant velocity reduction. To make a long story short, I finally stopped drilling ports when I was 4" ahead of the breech end. There were 100 holes. Standard velocity Federal .22 LR rounds, which had originally measured slightly over 1040 FPS, did not go below about 1000 FPS at the end of the drilling. So after building up pressure and velocity in 4" of barrel, with all that pressure instantly removed, the additional 6" of barrel friction only reduced bullet velocity by about 40 feet per second. I must say that I was astonished! With 9mm Para, my standard load is 4.5 gr. Bullseye and a cast 120 gr. round nose lead bullet. This gives you 1150 to 1200 FPS in pistol length barrels. It will be somewhat faster, not slower, in a 16" barrel, because powder is still burning and barrel friction is most certainly not slowing the bullet. To do that, you would need an extremely long barrel, considering what I found out with the .22 experiment, and considering the volume of gases generated; it's a few liters, and that's lots more than the volume of a very long barrel. So sometimes what seems to make a lot of sense, when you theorize, turns out to be very different in practice. FYI: I've also made about 3 - 4 9mm barrels of 10.5" length for the quick change barrel and caliber conversion setup on my registered 1928AC Thompson. Works flawlessly, and of course velocity is always higher than with pistol barrels between 4" and 6". With all semiauto pistols, Luger Doc has put his finger on the main problem, barrel weight. You have to keep it to the very minimum to get the gun to function, without some way of boosting recoil. Which is another long subject familiar to you suppressor people. But it's all about fun, and I'm having a lot of it, reading the many technical contributions from some of you Luger experts. I'm renewing my interesting in them, after years of having just left mine sitting in drawers most of the time.