More barrel length vs. Velocity

30 July 2009, 07:58

For those who ask have much affect barrel length has on velocity.

Two 7.62 X 41s ( home grown )

Mauser With 16" Douglas barrel

Stevens Mod 200 with a Shaw 24" barrel

Load = 30.5 grains aa 2015

Case = reformed from .257 roberts, RP

Primer #34

#1 Bullet 150gr. RN. ABC., OAL=2.400"

16" barrel, Avg. Velocity = 2015fps.

24" barrel, Avg. Velocity = 2150fps.

#2 Bullet 150gr. BT., Balistic tip,

16" barrel, Avg. Velocity = 2078fps.

24" barrel, Avg. Velocity = 2205fps.

DELTA #1 bullet, 2150 - 2015 = 135 fps.

DELTA #2 bullet, 2205 - 2078 = 127 fps.

Comment: These were somewhat mild loadings and a minute amount of unburned powder was evident.

Same two rifles. Load = 34.7gr. I4895 compressed, SL-42 case #34 primer.

150grain BT bal.tip,OAL=2.590"

#1.Shaw 24" barrel, Avg. Velocity=2350 FPS.

#2.Douglas 16" barrel, Avg. Velocity=2195 FPS.

Delta Vel. = 155FPS.

150 grain RN sp Arizona Bullet Co. OAL=2.395"

#1. Shaw 24" barrel, Avg. Velocity=2310 FPS.

#2. Douglas 16" barrel, Avg. Velocity=2167FPS.

Delta Vel. = 143 FPS.

Hmmmmm. Seems like the rule of thump might just change with variables.

roger

30 July 2009, 10:23

tnekkcc

Some have experimented with 22LR and barrel length.
There is ammo that peaks at 16" and there is ammo that keeps getting faster all the way to the longest barrel, 26".

Quickload does a great job of predicting velocity changes with barrel length for the cartridges in quickload's library, but I lack the where-with-all to enter your wildcat's parameters.

30 July 2009, 17:05

Hot Core

Nice Test and I agree with your conclusion.

31 July 2009, 04:14

bartsche

MADE A MISTAKE and now will edit it. The Shaw barrel was 24"

roger

06 August 2009, 22:47

Allan DeGroot

The effect of barrel length is variable depending on the energy release curve of the propellant.

You see the least differences with quicker propellants
and a greater difference with the classic "slow propellants"
(IMR4831/IMR7828/H5010)

Also remember that there are "Fast barrels" and "slow barrels" that can really screw with your perception

then there are counterintuative effects you run into with
propellants like the RL propellants that are dual based and bring a lot of energy into play later in the burn cycle.

AD

07 August 2009, 13:59

Saeed

Gentlemen, you might find this of interest

07 August 2009, 21:45

bartsche

quote:
Originally posted by Saeed:
Gentlemen, you might find this of interest

Good stuff Saeed

roger

07 August 2009, 21:53

bartsche

Just a point of interest;the Shaw barrel took at least twice as long to clean as the Douglas barrel. In all fairness the Douglas barrel has had about 500 more rounds put through it than the Shaw. The Shaw ,however, really holds on to the copper.

roger

09 August 2009, 08:16

Krochus

If you're interested take a look at my data along similar lines

quote:
Over on AR15.com I offered to compile a bunch of data concerning how 7.62x39 preforms in diffrent bbl lengths. I figured I'd share it with you guy's first.

The rifles used for this test differed greatly from one another so please don't take this as "one size fits all" data.

The rifles used were as follows

1. A norinco 16.5" paratrooper SKS .310bore

2. is a 20" Model 1 Sales AR15 upper .310bore

3. a custom bolt gun with a 1/15 inch twist bbl that's 26" long and has a .308 bore

All chrony readings were taken at 12 feet with a model F1 without sky screens against a uniformly Grey overcast sky and an air temp of 55 degrees. Perfect chronographing weather.

Part 1 factory loads

154 grain WOLF sp

16' bbl........20" bbl........ 26" bbl
2042............2106............2273
2025............2110............2265
2015............2113............2261
2041............2125............2256
2033............2124............2250

avg velocity
2031............2115............2261

123 grn Monarch FMJ

16' bbl........20" bbl........ 26" bbl
2354............2432............2599
2345............2418............2595
2377............2405............2593
2315............2453............2548
2330............2422............2601

avg velocity
2344............2426............2587

125 grn Remington SP

16' bbl........20" bbl........ 26" bbl
2265............2261............2428
2238............2308............2444
2202............2304............2437
2191............2366............2485
2224............2264............2486

avg velocity
2224............2300............2456

Part 2 hand loads

for these loads the 26" rifle was omitted and the SKS had the gas piston removed due to slamfire and cycling concerns

170grn Sierra .308 diameter 30-30 flat point, magtech SR primer, 28.0grs H335

16' bbl........20" bbl

1921............1968
1924............1967
1931............1970
1936............1970
1896............1985

avg velocity
1921............1972

125 grn nosler b-tip, magtech SR primer, 25.5grs AA1680

16' bbl........20" bbl

2256............2359
2226............2355
2243............2361

avg velocity
2241............2358

The only real loser in all this is the anemic Remington ammo, this stuff just reinforces my assertion that anything METRIC factory loaded in this country is going to suck.

The most interesting find was just how fast and accurate these loads were when fired from as accurate platform as possible through a 26" tube

5 shot groups for the factory loads in the Stevens 200 were as follows
154grn Wolf 1.2"
123grn Monarch 1.37"
125grn Remington 1.0"

09 August 2009, 22:37

bartsche

quote:
Originally posted by Krochus:
If you're interested take a look at my data along similar lines

[/QUOTE]

I did!

and thanks for shareing.

roger

09 August 2009, 23:48

Saeed

I am playing with the idea of doing the same thing we did with the 223 with a 308 Winchester when I get the chance.

10 August 2009, 01:23

bartsche

quote:
Originally posted by Saeed:
I am playing with the idea of doing the same thing we did with the 223 with a 308 Winchester when I get the chance.

Sounds like a winner. I, in turn, this week will be doing it with two 6.5X55s , one with a 24" barrel and the other with a 30" barrel.

roger

10 August 2009, 06:59

Sagebrush Burns

I am presently doing load development on a pair of 270s. One is a Mauser with a 22" Shilen barrel, the other is a pre-64 M-70 with a factory 24". With identical loads the shorter barrel has consistently been about 30fps faster. Goes to show, you gotta chronograph 'em to know what you're talking about.

10 August 2009, 12:07

Saeed

Gentlemen,

Using two rifles introduces another variable into this.

I found this out when we got 5 Mannlicher rifles, all in 270 Winchester, with 5 scopes and Norma 150 grain SP ammo.

All the rifles were brand new, same make and model.

The velocity difference between them was 150 fps??!!

I am still scratching my head of why.

We have had 300 Remington Ultra rifles that had a higher velocity than a 30-378 Weatherby, but that is another story altogether.

11 August 2009, 21:51

KenOehler

The differences between the "identical" barrels and chambers is not surprising.

I recall many years ago visiting the Winchester plant where they fired some 225 Winchester reference ammo in a SAAMI spec test barrel. The velocity was some 200 fps under the assessed value. No surprise expressed, simply "That barrel must have a fairly large correction."

11 August 2009, 22:24

Hunt-ducks

Roger

Good test

and Just about what I figured all along.

I have spent a lot of time doing same with primers and cases.

12 August 2009, 00:35

KenOehler

To answer the barrel length vs velocity question, I would tend to trust using Hartmut Broemel's QuickLoad more than trying to do it experimentally.

Experimentally you will end up looking at the small differences between large numbers; this is risky at best and easily can be misleading.

Ken O

12 August 2009, 03:52

bartsche

quote:
Originally posted by KenOehler:
To answer the barrel length vs velocity question, I would tend to trust using Hartmut Broemel's QuickLoad more than trying to do it experimentally.

Experimentally you will end up looking at the small differences between large numbers; this is risky at best and easily can be misleading.
Ken O

Loud and clear ,Ken.

It would be silly to use these numbers I'm generating as a physical law. They can however, in the doing, aid in putting to rest the curiosity factor, give you some pleasure and stimulate folks like you to join in a discussion. It seems to be working. Glad I got my Mod. 35 before you gave up the ghost.

roger

13 August 2009, 00:14

fredj338

quote:
Originally posted by Saeed:
Gentlemen,

Using two rifles introduces another variable into this.

I found this out when we got 5 Mannlicher rifles, all in 270 Winchester, with 5 scopes and Norma 150 grain SP ammo.

All the rifles were brand new, same make and model.

The velocity difference between them was 150 fps??!!

I am still scratching my head of why.

We have had 300 Remington Ultra rifles that had a higher velocity than a 30-378 Weatherby, but that is another story altogether.

Exactly Saeed, it's why numbers from two diff rifles w/ diff. barrels is almsot meaningless, sorry Bartsche, because identical rifles can vary as much as 150fps.

13 August 2009, 02:46

Doc224/375

Allan DeGroot X2

Hypothetically speaking a 1:16 twist does little good in a 12" barrel .

If your shooting light bullets from a fast twist short barrel Good Luck !.

Roger : You failed to mention rate of twist not that it is that critical for velocity Stats but can effect

them some what.

Rather than type out a long winded blah of my BS : I borrowed this from Gunners Den .

What does the rifling twist rate do.

The rate of rifling twist determines the optimum bullet weight for a given caliber and speed of the bullet by applying the proper spin on the bullet to prevent the bullet from yawing and pitching.

Expressed in terms of the number of revolutions per inch of barrel length, this ratio is commonly expressed by designations such as 1:10, 1/10 or 1 in 10 twist, the 1 represents 1 twist, the 10 represents inches of barrel length.

So, a 1 in 10 twist is, 1 complete bullet revolution every 10 inches of barrel length traveled.

How do you know what rifling twist is right.

A good rule of thumb is that the heavier and longer a bullet is, the faster the rifling twist rate needs to be to stabilize it in flight, therefore a lighter shorter bullet needs a slower rifling twist rate to give proper bullet spin for correct flight.

Exception to the rule.

If an insufficient twist rate is used, the bullet will begin to yaw and then tumble; this is usually seen as "keyholing", where bullets leave elongated holes in the target as they strike at an angle.

Once the bullet starts to yaw, any hope of accuracy is lost, as the bullet will begin to veer off in random directions.

A too-high rate of twist can also cause problems. The excessive twist can cause accelerated barrel wear, and in high velocity bullets an excessive twist can cause bullets to literally tear themselves apart under the centrifugal force.

I leave the twist and length too professional barrel makers . One less headache .

13 August 2009, 03:47

bartsche

quote:
Originally posted by fredj338:
[QUOTE]Originally posted by Saeed:
Exactly Saeed, it's why numbers from two diff rifles w/ diff. barrels is almsot meaningless, sorry Bartsche, because identical rifles can vary as much as 150fps.

Don't be sorry ,Fred. these are just numbers that are being generated to be used or not as you will. I find nothing sacred here.
Todays findings are interesting to be sure.

Mod 200 Stevens 6.5X55 24" Shaw barrel.

Mauser Mod 96 6.5 X 55 30" barrel.

Load** 139gr. psp Prvi., 45.3 gr. DP85, PMC case, #34 primer.Oal=3.015", Shaw = 2718fps. avg.

Military = 2714 fps avg.

Load** 139 psp Prvi., 45.9gr. DP85, PMC case, #34 primer OAL=3.015" Shaw = 2720 fps.avg.

2. Military = 2707fps.

Something to be learnt here I'll bet. WAHH.

roger