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 22" 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.

22" barrel, Avg. Velocity = 2150fps.

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

16" barrel, Avg. Velocity = 2078fps.

22" 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. roger

I've read where the general "rule of thumb" is 25fps per inch of barrel length.

The results your getting is some what more than that.

If you look over the FPS/Inch column on this page of load data it shows that there is no hard and fast rule. Case capacity, bore diameter and powder burn rate all influence how much is lost or gained per inch of barrel length.

It would be real interesting to see how different load intensities and different powders behave in those same two barrels. (Hint, hint!)

I don't suppose you just happen to have a decibel meter lying arround?

Great link, Gerard. It confirms my notion the effect of case capacity to bore diam has.

bartsche, according to your results, barrel make is not skewing the results. I assume those would both be made with the same reamer? Are 'fast' and 'slow' barrels a function of chamber dimensions perhaps? We know that different bullets don't have too much effect which would indicate that the bore itself is predictable.

The problem though is you do not have apples & apples. Two diff. barrels & chambers are not likely to give representable velocities. The only way to know for sure is take one barrel & test it, then cut 1" at a time off & test it each time. I've seen same length barrels give 150fps diff. w/ identical loads. I've seen 22" barrels have higher vel. than 24" barrels w/ identical loads. Just too many variables.

quote:

Originally posted by fredj338:
The problem though is you do not have apples & apples. Two diff. barrels & chambers are not likely to give representable velocities. The only way to know for sure is take one barrel & test it, then cut 1" at a time off & test it each time. I've seen same length barrels give 150fps diff. w/ identical loads. I've seen 22" barrels have higher vel. than 24" barrels w/ identical loads. Just too many variables.

I hear what you're saying ,Fred, and agree with your approach. The fact is I'm not trying to prove anything. I'm giving you raw data based On what I got. If you find it ify, OK. If you find it informative that's nice too. Personally I think it is quite indicative of FPS. increase/IN.

And yes both barrels were chambered with the same reamer. roger

quote:

The problem though is you do not have apples & apples. Two diff. barrels & chambers are not likely to give representable velocities. The only way to know for sure is take one barrel & test it, then cut 1" at a time off & test it each time. I've seen same length barrels give 150fps diff. w/ identical loads. I've seen 22" barrels have higher vel. than 24" barrels w/ identical loads. Just too many variables.

I recall someone, I think Rick Jamison did just that a few years back although I remember what cartridge he used. He took a full lgt barrel and cut an inch at a time recording the velocity useing a handload he made up for the purpose. It seems he found the lenght vs velocity difference varied, and at one lenght actually recorded a faster velocity then the 1 inch longer barrel showed. Likely the extreem spread of the load had something to do with it.

quote:

Originally posted by Ol` Joe:

quote:

The problem though is you do not have apples & apples. Two diff. barrels & chambers are not likely to give representable velocities. The only way to know for sure is take one barrel & test it, then cut 1" at a time off & test it each time. I've seen same length barrels give 150fps diff. w/ identical loads. I've seen 22" barrels have higher vel. than 24" barrels w/ identical loads. Just too many variables.

I recall someone, I think Rick Jamison did just that a few years back although I remember what cartridge he used. He took a full lgt barrel and cut an inch at a time recording the velocity useing a handload he made up for the purpose. It seems he found the lenght vs velocity difference varied, and at one lenght actually recorded a faster velocity then the 1 inch longer barrel showed. Likely the extreem spread of the load had something to do with it.

I think I read that one, maybe a 6.5 something military & cheap. It was interesting that some length showed significant loss, some none & some even a slight gain.
Hey bartsche, I wasn't condeming the experiment, it's just many guys think it's just about bbl length & we know there are many other variables affecting vel. Even chambering w/ the same reamer will have a slightly diff. chamber size as you've slightly worn the reamer from another chambering job.
One reason I let guys shoot over my chronograph. They are all sure their fav. load is at least 100fps faster than it really is. The chronograph doesn't lie.

Well, FWIW, I think it quite a revealing result because two different barrels of different manufacture but cut with the same reamer show predictable barrel length differences. (That 25 fps per inch applies to 308/303 Brit proportioned cartridges pretty much what bartsche measured).

Here ya go! Apples to Apples.
http://www.accuratereloading.com/223sb.html

quote:

Originally posted by steve4102:
Here ya go! Apples to Apples.
http://www.accuratereloading.com/223sb.html

Holy Crap! It's a good thing the FEDS didn't see this posting of an illegally short 10" barrel. Didn't Randy Weaver get in big trouble for some miniscule amount under the legal minimum of 16"?

quote:

Originally posted by Ol` Joe:
...I think Rick Jamison did just that a few years back ... He took a full lgt barrel and cut an inch at a time recording the velocity useing a handload he made up for the purpose. It seems he found the lenght vs velocity difference varied, and at one lenght actually recorded a faster velocity then the 1 inch longer barrel showed. Likely the extreem spread of the load had something to do with it.

Hey Ol` Joe, I did not read the article, so my comments are based only on my impression of jamison. I used to think he was quite a Reloader back in the `60s-`70s. Then I noticed he pulled the old "Bogey the Load Data" so the 300WinMag ALWAYS outshines ANYTHING it is compared to, after I had worked with a few 300WinMags.

So, this is pure speculation, but I'll guess he only fired 1-2 shots after each reduction in barrel length. And reported what he saw, which was a normal Load Variation due to some off-the-wall Powder/Cartridge combination he selected.

No way was it a 300WinMag, or it would have stair-stepped perfectly - to hear him tell it.

I HATE IT when some fool gets me to believe him. Sure makes a person cautious.

quote:

Originally posted by steve4102:
Here ya go! Apples to Apples.
http://www.accuratereloading.com/223sb.html

Very interesting. The only issue I have w/ the accuracy data is each cut & recrown would have to be identically done in order to have a neutral affect on the accuracy. The vel. data is good stuff though, thanks.

quote:

Originally posted by steve4102:
Here ya go! Apples to Apples.
http://www.accuratereloading.com/223sb.html

Super experiment. roger

quote:

Originally posted by onefunzr2:
Holy Crap! It's a good thing the FEDS didn't see this posting of an illegally short 10" barrel. Didn't Randy Weaver get in big trouble for some miniscule amount under the legal minimum of 16"?

I really don't think the United Arab Emirates cares about barrel length.

Saeed: What, if any, are some of the more interesting gun restrictions or laws in your country? (ie. barrel length, full-auto, concealed carry, etc.)

-Kenati

With quickload you can vary the length of barrel and see the effect.

Barrel length is more important to 7mmMag than to 45acp.