9mm ammo question

i just bought a box of magtech 115gr full metal jackets. it lists muzzle velocity at 1135fps and energy at 330ftlbs from a 4in vented test barrel. how do i figure out what id get from a 16.5in barrel?

Chronograph.

Past that, it's hard to tell. Loading a 9mm with slow burning powder and then using a 16.5" barrel (like from a pistol caliber carbine) can get some impressive results. I'm not sure how magtech loads their rounds, though.

dont suppose ther eis some type of formula to give me a rough idea? im just curious since ill be shooting it out of a hi point carbine.

couldn't you figure out the exceleration from 0 to when it leaves the barrel, and then assume it continues to accelerate at the same rate (which it should, because the time is too short for it to start losing energy and decelerate), and then figure out what the speed is when it leaves the longer barrel? i'm sure a physics major could do this in a few minutes. wish i had sat in more classrooms these past few years... lol

I get right at 1100 to 1130 fps out of my P7 with 115 grain bullets loaded over 5.5 grains of WSF. It is a stout load, but you can always shoot less powder if you wish.

The only way to know is to chronograph your load.

it lists muzzle velocity at 1135fps and energy at 330ftlbs from a 4in vented test barrel. how do i figure out what id get from a 16.5in barrel?

Somewhere in the nieborhood of 1300 FPS or so from your 16" barrel, if it gets 1135 FPS from a real 4" barrel.

A couple of loads that gave me 1167, 1146, & 1168 FPS from a TZ-75 with a 4 1/2" barrel gave me 1308, 1333, & 1351 FPS from my AR's 16" barrel.

I have faster and slower loads, but those looked like they would match up close to your 4" barrel output.

dont suppose ther eis some type of formula to give me a rough idea? im just curious since ill be shooting it out of a hi point carbine.

That would be impossible to do. Variables such as fast vs slow powder, how tight or loose the bore is, conventional vs polygonal rifling, etc.

I pick up 100-150 fps in my Hi point vs my Glock 17 with a wide variety of loads. Subsonics stay subsonic. Your results may vary but not by much.

thanks guys

This chart was copied from a post in the reloading section.

@biggiesmalls

Bullets stop accelerating the moment they leave the barrel. Well not exactly the acceleration is negative due to friction so they actually begin to lose velocity the moment they leave the barrel.

thx 357 dont suppose they have a ft lbs chart too?

Here is the energy formula.

E = m • v^2 / (2 • 32.1739 • 7000)

Just input the bullet weight in grains for m and velocity in ft/second for v and you'll get foot pound out.

Some data I have complied:

Ruger PC9 Ballistics: from www.grimjaw.net/ballistics.htm
Rem Golden Saber 124gr +p jhp 1397 1406 1414 1389 1409 1397 1416 1416 1414 1384 avg 1404.2 s.dev 11.736
Speer Gold Dot 115gr jhp +p+ 1544 1643 1629 1653 1650 1641 1658 1652 1657 1620 avg 1634.7 s.dev 34.144
Winchester Ranger 127gr jhp +p+ 1368 1400 1413 1382 1392 1411 1389 1390 1370 1388 avg 1390.3 s.dev 15.004
Rem 115gr jhp +p+ 1577 1595 1568 1589 avg 1582.25
Fiocchi 115gr fmj 1307 1395 1344 1389 1381 1380 1340 1384 1373 1405 avg 1369.8 s.dev 30.151
Fed Premium Hydrashok 124gr jhp 1229 1307 1291 1319 1290 1308 1309 1287 1291 1299 avg 1293 s.dev 24.806
To calculate energy: E = W(eight in grains) * V(elocity in fps) * (V(elocity in fps)/450450).
JA
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February 1st, 2007, 02:20 AM
I have never shot any 40 carbines but I have chronographed 9mm and 45acp pistols/carbines. Both resulted in 150fps or less increase in velocity with factory loads in the carbines due to the fast burning rate powders used in factory ammo. Using the slowest medium buring rate powders I could find to make reloads resulted in a velocity increase of a maximum of 230fps. The limited case capasity and pressure limits of cartridges designed for semi auto pistols precludes the use of the slowest burning rate handgun powders that really show large increases in velocity in the longer barrels of carbines.
Handloading 357 magnum cartridges really showed some amazing results due to being able to use the slowest burning rate handgun powders in the large volume of the 357 magnum cases. Depending on bullet weight the results were 400fps-800fps increases in velocity in a 18" barreled carbine versus a 6" barreled pistol.
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From: FirearmsTactical.com
9mm 147 grain Federal HydraShok JHP, 11/27/90 (Marlin M9):

Test Gun Barrel Length Velocity Bare Gelatin Clothed Gelatin
Penetration Expansion Penetration Expansion
Marlin M9 16.5" 995 fps 21.35" 0.37" 15.60" 0.60"
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From GlockTalk: Joe Mamma
Temperature: 40 degrees F
Ammo Description (Product Code) average velocity with G-17, average velocity with Kel-Tec Sub 2000
Federal Hydrashok 124 gr +P+ JHP (P9HS3G1) 1167, 1321 fps
Federal NATO, 124gr FMJ (M882)1114, 1231 fps
Winchester USA Brand ("White Box") Hollow Points 115gr JHP (USA9JHP) 1149, 1305 fps
Winchester USA Brand ("White Box") Hollow Points 147gr JHP (USA9JHP2) 1020, 1117 fps
CCI Blazer Brass 115 gr FMJ (5200) 1120, 1299 fps
Sellier & Bellot 115 gr FMJ (80166-00902) 1162, 1296 fps
Geco/Dynamit Nobel 124gr (23364-12585) 1129, 1256 fps
Magtech 147gr "FMC-FLAT" (891798-001347) 969, 1096 fps

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From GlockTalk: WinstonSmith
A friend of mine in Kentucky just did some chrono measurements on the Keltec Sub2000 and a Kahr PM9 with a 3" barrel. All measurements at 15 ft from muzzle and at 64 degrees F. Here are the results:
Win 147 gr JHP - Five shots through the SUB-2000:
1111 FPS
1139 FPS
1119 FPS
1136 FPS
1130 FPS

1139 FPS - High
1127 FPS - Average
1111 FPS - Low
28 Extreme Spread
11 Standard Deviation

Win 147 gr JHP - Five shots through the Kahr PM9:
938 FPS
923 FPS
910 FPS
934 FPS
915 FPS

938 FPS - High
924 FPS - Average
910 FPS - Low
28 Extreme Spread
11 Standard Deviation

Maybe there is some intermediate barrel length that would do even better but the 16" barrel is clearly faster than the Kahr PM9 or Glock 17.

Of course its faster.
But not that much faster.

Given enough barrel length, pistol ammo will reach a point of diminishing returns rather quickly.

As noted, slow burning powder will give better results in a longer barrel.

But it is impossible to know what powder the factories use, so it is impossible to predict it with any formula.

rcmodel

I know that this is not 9mm but...using .40S&W magtech 155gr JHP's I get ~1175fps from my CZ40B and ~1350fps from my Keltec sub2000.