.357 Burn Length?

[tinkerfive]

There is a thread over in 'Sporterizing' that got me thinking about hanging a new barrel on my .357.

At present it is a 2" snub nose.

 

I'm interested in getting the most muzzle velocity and accuracy practical.

 

Apparently there is an inexpensive .357 barrel available that is 18" long.

 

I don't know about hanging an 18" barrel on a hand gun.

 

At what barrel length do you reach a point of diminishing returns?

 

For instance what length of barrel would it take to burn 80%,90%, 100% of the powder?

 

Thanks in advance!!

Tinker

[AzRednek]

If I remember correctly PO Ackley had much to say about barrel lengths and velocity in his books. I can't recall if he did any research with handgun calibers. Ackley's books out of print for years are still pricey on Ebay and Amazon but free if your library has them.

 

I'm guessing so don't relay on my specualtion. I recall reading something in a gun rag years ago. The difference in a 6 vs and 8 3/8 inch barrel was pretty much insignificant. Don't recall the numbers but I think it averaged something like 40-60FPS but the gain between 4 and 6 inch was a significant improvement. I think that article though was about 44 mag, might be different with 357.

[gun nutty]

The Hodgdon #27 Reloading Manual lists the .357 Magnum under both the rifle ans pistol sections. The test rifle had an 18.5" barrel, and the pistol had a 10" barrel.

 

For the pistol loads (starting):

 

14.5gr H4227 with a Hornady 158gr XTP - 1402fps

15.0gr H110 with a Hornady 158gr XTP - 1418fps

8.0gr HS-6 with a Hornady 158gr XTP - 1182fps

5.8gr UNIVERSAL with a Hornady 158gr XTP - 1026fps

6.2gr HP-38 with a Hornady 158gr XTP - 1108fps

 

For the rifle loads (starting):

 

14.5gr H4227 with a Hornady 158gr XTP - 1578fps

15.0gr H110 with a Hornady 158gr XTP - 1619fps

8.0gr HS-6 with a Hornady 158gr XTP - 1181fps

5.8gr UNIVERSAL with a Hornady 158gr XTP - 1059fps

6.2gr HP-38 with a Hornady 158gr XTP - 1095fps

 

 

Summarizing:

 

Barrel difference: 18.5" - 10" = 8.5"

 

For H4227: 1578fps - 1402fps = 176fps --> 176/8.5 = 20.70fps/inch GAIN

For H110: 1619fps - 1418fps = 201fps --> 201/8.5 = 23.65fps/inch GAIN

For HS-6: 1181fps - 1182fps = (-)1fps --> negligible loss/gain

For UNIVERSAL: 1059fps - 1026fps = 33fps --> 33/8.5 = 3.8fps/inch GAIN

For HP-38: 1095fps - 1108fps = (-)13fps --> 13/8.5 = 1.53fps/inch LOSS

 

 

Notes:

 

HS-6 improved on the rifle for same MAX load (1427 vs 1375) --> 52fps/8.5 = 6.12fps/inch

UNIVERSAL improved on the rifle for same MAX load (1147 vs 1133) --> 14fps/8.5 = 1.65fps/inch

HP-38 decreased on the rifle for same MAX load (1214 vs 1220) --> (-)8fps/8.5 = negligible

 

Barrels can vary considerably in performance; two barrels of equal length from different manufacturers, or even the same manufacturer, can vary in velocity and peak pressures.

 

The pistol barrel tested was 10", considerably longer than barrels on most revolvers. It was probably either a T/C or a test barrel. Cylinder gap on a revolver will also reduce velocities.

 

The calculations represent a linear relationship between barrel length and velocity. This is at best an approximation.

 

Analysis:

 

Looks like "slow" powders in the .357 Magnum yield an increase of 20fps/inch velocity in longer barrels; "fast" powders have negligible effects in the .357 Magnum as barrel length increases.

 

So, in terms of "burn length", powder selection also plays an important factor when trying to improve velocity by increasing barrel length. No surprises.

[pacrat]

Not a Lawyer, nor have I ever played one on TV.

 

Seem to remember it is illegal to exceed 16" barrel on a pistol just as it is illegal to have less than 16" on a rifle. If a pistol is fitted with more than 16" barrel it must also have a buttstock and meet 26" overall criteria making it legally a rifle.

 

Or something like that.

[tinkerfive]

Thanks for the replies!!

 

Sounds like I can take the 18" barrel and cut it in half at 9" and

be just about optimum and still have another 9" section for a second project.

 

 

Thanks again!!!

 

Tinker

[pacrat]

One more point on the not a lawyer thing.

 

Supposedly the ATFE measures all barrel lenghts from the breech face to the muzzle.

 

So if you have a revolver with what is known as say a 4" barrel ATFE would add the cylinder and cylinder gap to that calling it a approx 6 1/2" barrel. If someone screws a 16" barrel on a revolver they have broken the law by ATFE standards.

 

Or something like that