Velocity vs. barrel length


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Win75
August 24, 2008, 10:37 PM
I have seen this somewhere and should know but I can't find the info right now. What gain in velocity do you get in a .223, .243, 25-06, etc. per each inch of barrel length past, say 22 inches?

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sarduy
August 24, 2008, 10:48 PM
1 inch = ~100fps

Strongbad
August 24, 2008, 10:52 PM
On big mags with slow burning powders, I'd say that sarduy's numbers are probably right. On the rounds you mentioned, probably less. Half that much maybe, just due to the quicker burn rate of the powders used. That's just my own personal rule of thumb mind you. A lot of things come into play. Dan Lilja did a test on this and has the results posted on the web. That being said, it's very very subjective. It's going to vary from chambering to chambering and gun to gun. Tightness of the bore, that kind of thing.

Ridgerunner665
August 24, 2008, 10:53 PM
243 and 25-06 can be as high as 70 - 90 fps per inch, up to 24 inches.

The 223 is less because its powder charge is smaller...it will be about 30 - 60 fps per inch, up to 24 inches.

You will get varying replies on this...but I have experimented with this a lot and thats what I have found to be the average.

308's are good to go with 20 inch barrels with the right powders...its all about efficiency, not larger capacity...the more efficient a round burns...the less powder and barrel it needs.

Ridgerunner665
August 24, 2008, 10:55 PM
The 243 suffers REAL BAD with barrels less than 22 inches...100 fps per inch easily. Over 22 inches though and it gets back into its comfort zone, the difference is not near so much.

Loomis
August 24, 2008, 10:58 PM
The only caliber I can comment on with some degree of accuracy without doing research is the 22LR. 22 long rifle ammo reaches it's max velocity in about one foot of barrel length or less.

Naturally, the bigger calibers will require more barrel to reach their max velocity. But my hunch is that most calibers will gain very little velocity from barrels longer than 22"

shadowalker
August 24, 2008, 11:17 PM
.308 / 30-06 is 20-25 fps per inch, my LR-308 with 16 inch barrel has is 20 fps per inch.

Here (http://www.loadammo.com/Topics/October05.htm)is an article with information on various calibers and velocity decrease per two inches of lost barrel, after 22 inches most calibers are only gaining ~ 25 fps per inch.

Auburn1992
August 24, 2008, 11:18 PM
Anyone know what the 7mm-08 is?

Ridgerunner665
August 24, 2008, 11:19 PM
Pretty much the same as 308...but I believe the 7mm-08 is at its best with a 22 inch barrel.

jmr40
August 24, 2008, 11:24 PM
According to a Remington ballistics chart I have:

2000-2500fps +/- 10fps/inch
2500-3000fps +/- 20fps/inch
3000-3500fps +/- 30fps/inch
3500-4000fps +/- 40fps/inch

This assumes that you start with a 24 inch barrel.

cliffy
August 25, 2008, 01:13 AM
A .223 Remington shines brightly at 22" of barrel length, yet rifling twist governs what weight bullets will do the best shining.

A .243 Winchester shines brightest at 24" barrel length, yet rifling twist governs what weight bullets will provide the maximum shine.

Caliber plus velocity plus a lot of other factors govern accuracy and striking force at any given range.

Powder and powder charges contribute to these other "factors" concerning velocity. A bullet that fails to leave to leave the muzzle at 3000 fps fails my tests automatically. Hence I don't like super-heavy bullets. Speed Kills: Medicrocy Wounds, with less than a well-placed bullet. Hydrostatic Shock is no Myth! Otherwise, we should all be using wheely-bows with arrows! cliffy

R.W.Dale
August 25, 2008, 01:24 AM
The quick rule of thumb is the more overbore the chambering the more you lose per inch of bbl.

243 and 25/06 will get hit really hard in a short barrel as much as 70 or 80 fps

308 and 30/06 not so much maybe 30 to 40

358 and 35 whelen hardly at all

rangerruck
August 25, 2008, 03:27 AM
I pretty much figure, any centerfire doing 3000fps, is going to gain no more than 50 fps, and leave it at that.

Art Eatman
August 25, 2008, 12:25 PM
Every now and then--every ten years or so--somebody gets ambitious and actually does some testing.

For starters, almost all ammo used to have published factory data as to velocity, and most data was taken from rifles with 26" barrels. There used to be foam-backed pads at gunstores with all this info on the top. You could lay pistols or scopes on them during "tire kicking" and not scratch the glass or the item. Winchester and Remington used to give them out by the thousands.

So time goes on and 26" barrels become uncommon. Today's data is commonly from 20" to 24" rifles.

Anyhow, when folks cut back an inch at a time, there is a certain amount of consistency in velocity reduction.

My memory has it from reading a couple or three articles over the years:

Maggies, around 100 ft/sec/inch.
'06-case type, around 75 ft/sec/inch.
.308-case type, around 40 ft/sec/inch.

As usual, "roughly". "Generally." "Rule of thumb."

NCsmitty
August 25, 2008, 01:43 PM
The sharper the bottle neck, the more you will lose. That's why straight case cartridges generally work better for shorter barrels.

NCsmitty

LAR-15
August 25, 2008, 02:02 PM
Most of your 'ultralight' and 'compact' rifles on the market have barrel of 18-22 inches.

Very few go down to 17 inches or less

This has to do with getting good performance from most centrefire rifle rounds

Shorter barrels just don't allow for sufficient powder to burn to get maximum performance and velocity

For 'magnum' rounds longer is better

R.W.Dale
August 25, 2008, 03:12 PM
Shorter barrels just don't allow for sufficient powder to burn to get maximum performance and velocity

When O when can we finally put this myth to rest.

With modern centerfire rifle rounds all of the powder that is going to burn will have done so in the first 3 or 4 inches of barrel. The whole faster powders for shorter barrels line is a complete myth. With rifle cartridges 9 times out of 10 the fastest powder for a long bbl will still be the fastest in a carbine. Just look at handgun data vs rifle data for 308 win. With most bullet weights Varget is usually the top performer regardless of bbl length. Be it a 14" ENCORE handgun or a 26" Savage 12fp

NCsmitty
August 25, 2008, 05:35 PM
krochus, you and I both know that your statement is a half truth because it does not hold true for all cartridges. The more bottle neck rounds need the slower powders with a longer barrel to perform at their highest efficiency. You put a 243 in a 14" encore and compare it to a 24" 243, and powder requirements will be different for optimum velocity. The slower powders offer a longer burn time to achieve this in a longer barrel. You know that, that's why they are called slower burning. You cannot blanket all rounds with your statement, if that was the case, everyone would be fine with a 16" barrel. Your comparison of the 308 is more the exception than the rule and that is a little flawed. It's just that Varget is a very versatile powder in that round.
I have a TC Contender in 223 w/14" barrel and my powder requirements run much faster powders, RE-7 & 4198, than the usual slower H-335 that's used in many 223 rifles.
So the statement that I'm making is that sometimes a faster powder will give better velocities than slower powders, when used in shorter barrels.


NCsmitty

TRGRHPY
August 25, 2008, 06:50 PM
Can anyone translate what the fps means in bullet-drop for a given round and distance? For example, 20fps may not sound like much of a difference, but IIRC at long distances it can mean enough to determine a hit or miss (which is the point of hand-loading...consistency). True? False?

cliffy
August 25, 2008, 09:24 PM
Joyce Hornady says, ". . . all the powder must burn within 95% of barrel length . . ." I use this as my guide related to burn rates. H4350 burns faster than RL-22. This knowledge assists me in component selection for maximum velocities concerning various bullet weights. Of course, I'm talking .243 Winchester here. Alliant RL-25 burns too slowly for maximum velocity in ANY .243 Winchester application. Powder burning out the end of the muzzle aides nothing velocitywise, but can create an extremely unstable, inaccurate bullet. .243 Winchester loads work well with many powders, but all within the proper burn rate range! My .223 Remington loads MUST use faster burning powders than any suited to .243 Winchester applications. I tried Hodgdon H4350 in .223 application and it's really slower in velocity then, say, Alliant RL-10x, yet a .243 Winnie light bullet screams forth at maximum velocity with the very same H4350! IMR 4350 actually burns slightly faster than Hodgdon H4350, and I prefer H4350 in my hot .243 loads. To each his or her own experiences, signed Cliffy.

Bartkowski
August 25, 2008, 09:43 PM
http://www.shootingtimes.co.uk/features/136776/How_important_is_the_barrel_length_of_a_rifle.html

Read that whole article. It is about .223 and .308 and the results are not what you might expect.

It says that the difference between a .308 with a 24" barrel and an 18" barrel is only 157fps.

XD-40 Shooter
August 25, 2008, 11:38 PM
Here's another good article on the subject, no velocity loss with .308 down to a 20 inch barrel. They also mention that they can go down to 22 inches on 300 win mag with no velocity loss.

http://www.tacticaloperations.com/SWATbarrel/

Loomis
August 25, 2008, 11:59 PM
Ha!

So I was right then. I just can't help it. I'm very rarely wrong with my hunches.

See my post #6

LAR-15
August 26, 2008, 07:41 PM
Yeah but if you go down to the US NFA minimum (16 inches) you get a loss.

Otherwise why bother making guns with barrels over 16.5 inches?

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