Long and short barrel ammo diff?

[MoreCowBell]

I alternate carry between 5" 45 and 3" and between 4" 357 and 2-1/4"
I hear all the time that the short barrels lose so much velocity that ammo choice needs to reflect that. But I see little if any real data on the subject.

So yesterday I loaded up a 5" and 3" 1911, a Glock 22 and 27, also a 4" S&W Model 65, a 2-1/4" SP 101 in 357 and a 1-7/8" 38 Airweight Smith.
Plus 18 varieties of ammo, mostly various PD HP rounds. What wasn't magnum was mostly +P. Some of the better known semi-exotic was included.
Went to the range and chrono-ed all that stuff at ~10', three rounds each.

According to my results there is about a +/- 10% velocity drop between the long and short but the difference between light and heavy loads was inconclusive.

I'd like to also calculate impact force before I tabulate and post the data.
Anybody got the formula for getting lbft from bullet weight in grains and velocity in fps?

Thanks
cb

 

[Ol` Joe]

This will tell you what you want to know as to your bullets energy.
http://www.handloads.com/calc/quick.asp

The only difference in loads deemed as "short barrel loads" is that the flash is at times a bit less. The velocity is never far enough from anyother load of same bullet wgt to matter IMO.

 

[Duo]

i think your experement has a few too many vectors, you should have just used a single handgun with interchangable length barrels and only used one brand and two different loads I.E. heaviest and lightest. further conclusions could then be drawn from there. as for your problem with colecting data on that matter, simply firing the gun from a set distance from a block of ballistic gel or something along those lines could give you some more data

at any rate, i'm pretty sure that the idea of using the heavy load is short barrel is for compensation. the theory being that since you loose a bit of preasue build-up in short barrels you compensate it by using heavy rounds in an attempt to increase the initial acceleration.

however, as for the difference between the muzzel velocity between short and long barrel, unless your comparing a 1" to a 14" your not going to see any real jaw dropping numbers. the majority of a bullet's velocity comes from the inital acceleration.

 

[MoreCowBell]

Duo:
Actually velocity loss from 4" to 2" averaged about 10%. And impact energy loss was everywhere from 15% to 40% on the few I've calculated so far.
This was more trials than experiment. I used what I had and carry. I'm not going for theory here, I'm going for fact.
This was about impact energy. I get to penetration and expansion question later.
I'll try to have some data tabulated for analysis by the weekend.
Joe:
Thanks for the Taylor KO formula. Like practically everything anyone ever says on the boards it's been argued and flamed but I think it has some validity, I might add it to my spread sheet whenever I get around to making one. That'll give more people something to quibble over ha ha.
cb

 

[Shadan7]

You may also find our project of interest: http://www.ballisticsbytheinch.com/

Cheers -


Jim D.

 

[CombatArmsUSAF]

I know Gold Dot Short barrel load has a different hollowpoint that is supposed to expand better at lower velocity than a standard GDHP. But that load was designed to be shot out of a 2 inch barrel.

 

[jfh]

You did run your ammo over a Chrono, right?

A number of us started working on "short barrel reloading" for revolvers a little over two years ago. Early on, the goal was designed to meet fairly specific criteria: to develop a (cheap) practice round that felt like--'replica recoil'--the Gold Dot Short Barrel 38+P 135-gr. ammo, or the GDSB 357 Magnum 135-gr. ammo. Later, some of us also worked with "FBI-type" loads--that is, practice rounds that would roughly match that FBI 38 Special round with the 158-gr. LSWC-HP bullet.

In those two calibers, some of us also fired sample amounts of factory ammo. Those GDSB rounds, for example, as well as such exotic items as the Buffalo Bore 20A (a 158-gr. LSWC 38+P round that does over 1000 fps out of a 2" barrel).

For factory ammo, the GDSB ammo appeared to be the most-carefully tailored, I think, to effective SD use in carry guns. That 135-gr. bullet works well from about 850 on up through 1050 fps before fragmenting, and the Speer factory rounds run about 860 fps on up to 1020+ fps when fired from the nominal 2" and 4" barrels.

From what I see in factory PD ammo, the issue is what loads are available that will meet carry criteria, not necessarily Self Defense criteria for in-home use. In sum, marketing and promotion carry the day, not necessarily performance criteria. I'd love to see a factory PD round called the "FBI 900"--which, IMO is about what the shooter of a lightweight revolver can resonably shoot ten times as-fast-as-possible in an Old Fuff "Quad Five" drill (5 shots, 5 yards, 5" group, 5 seconds) and still have a usable shooting hand.

I'll be curious to see what you come up with.

Jim H.

 

[Jim K]

Actually, it has been done many times, usually by using one gun and several loads. Each load is fired with a long barrel, an inch cut off the barrel, the same series of loads fired, another inch cut, and so on. With factory ammo, velocity can vary as much as 100fps in a 50 round box, so handloads are used and carefully controlled.

Overall, the results will depend on the gun and load, but a good rule of thumb is 50fps per inch of barrel.

Jim

 

[rhinoh]

Had the head of the disassembly pin break off a Kel_Tec PF9 while firing. KT promptly mailed me a new one, no questions asked.


Added in edit- ok this is weird, this post was supposed to go in the handgun parts failure thread! Don't know how it posted here...since there is no delete function I guess it stays unless a mod can remove it.

 

[MoreCowBell]

Duplicated in post #11 when meaning to edit. Not entirely in the 21st century yet lol.
cb

 

[MoreCowBell]

Sorry the titles and spacing went awry. I didn't make a spread sheet, just typed the data into my local gun forum then when I tried copying it over here it got squeezed. I guess it's a different forum engine. For the original you're welcome to take a look in Carolina Gun Talk/General Firearms Discussion/Short barrel power loss trial/post #6.


SURVEY SAYS:
Velocity Energy Energy Diff
ft/sec (short fps) lbs/ft(short lbs/ft)
.45 ACP Llama 5"(Kimber Ultra CDP 3")

Federal HST +P 230grain 936 (831) 447 (352) 79%

Aguila 230 FMJ 832 (761) 353 (295) 84%

Winchester White Box 230 FMJ 804 (734) 447 (275) 61%

CorBon Pow'r Ball 165 +P 1172 (1021) 503 (381) 76%

Remington Golden Saber 185 HPJ 1049 (931) 452 (356) 79%

Federal Low Recoil 165 Expanding FMJ 1097 (948) 441 (329) 75%

357 Magnum S&W 65 (4" Ruger SP101 2-1/4")

Remington 180gr SJHP 1173 (1053) 549 (443) 81%

Winchester 158 JHP 1242 (1090) 541 (417) 77%

MagTech 158 SJSP 1099 (993) 424 (346) 82%

Hornady 140 FTX LeveRevolution 1279 (1185) 508 (436) 86%

Speer Gold Dot 125 GDHP 1396 (1268) 541 (446) 82%

38 Special S&W 65 4" (S&W 442 1-7/8")

Federal HydraShok 129gr +P JHP 944 (885) 260 (219) 84%

CorBon 125+P JHP 970 (898) 261 (224) 86%

Hornady 110 FTX +P 1029 (934) 258 (213) 83%

40 S&W Glock 22 5" (Glock 27 3")

Winchester Personal Protection 165gr JHP 929 (885) 323 (287) 89%

Federal 155 Hydra Shox JHP 1175 (1100) 475 (416) 88%

Speer Gold Dot 165 GDHP 1134 (1049) 471 (403) 86%