Barrel Length effects on .357 (SP101 & GP100)


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wacki
February 7, 2011, 12:14 AM
I'm considering a SP101 and GP100 in .357 and I have a few questions.


How much of an impact will these barrel lengths have?
I know they will impact the velocity of the bullet but I don't know by how much. Is there a chart anywhere?
Will these barrel lengths impact the spin rate of the bullet and therefore impact the accuracy?
How big of an impact does the site radius play at these distances?
Is there anything else I should consider?


Barrel Lengths in question:

2.25"
3.0"
4.2"

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Oyeboten
February 7, 2011, 12:21 AM
Hi wacki,




Some pretty good info here -


http://www.ballisticsbytheinch.com/357mag.html

SniperStraz
February 7, 2011, 12:24 AM
I was just looking for an answer to this question. I keep hearing people say that a 4in. bbl is the shortest they will go. I'd love to see some numbers so that I can make an educated decision.

Radium
February 7, 2011, 03:06 PM
here is a video i like that showed the speed out of a sp101 2.25"
im impressed.

http://www.youtube.com/watch?v=yqDysouNjL4

LKB3rd
February 7, 2011, 08:35 PM
I have a 3 inch security six, and it has stout recoil with .357, and I wouldn't go any shorter to shoot .357. If you aren't planning to conceal carry it, I'd go 4+ inch barrel.

Drail
February 7, 2011, 09:28 PM
You simply have to ask yourself, is this a target gun or a carry gun? If it's a carry gun, longer barrel length in the interest of any accuracy gains should be way down the list of features. I have carried 2.5 and 3 in. revolvers for years and barrel length doesn't matter at all in my opinion unless you're attempting to shoot tight groups at 25 yards. Bullet technology has improved over the years to the point that we now have many very good hollow point bullets that will reliably expand at the velocities generated by a snub. Personally I just carry big bores with cast SWC bullets. They work just fine at low speeds. In a .357 snub with lighter weight bullets (110 to 125 gr.) your main problem is from the bullet departing the barrel so quickly that the powder is not being completely burned and you get a huge flash. Very bad at night. My wife carries a S&W Model 36 snub loaded with 140 gr. or 158 gr. bullets and does not generate a lot of flash and blast. My advice has always been to not put your faith in your bullets to do the job, put it into your shooting skills. A 3 in SP 101 is a VERY GOOD choice for a carry gun. Don't waste your time on the 110-125 gr. high velocity stuff. It will teach you to flinch, blind you, and erode the forcing cone on your gun. Think 158 gr. loads.

WNC Seabee
February 7, 2011, 10:06 PM
I don't have a chronograph, but I do have an SP101 3" and GP100 4". The SP is a dream to carry AND shoot. It manages recoil very well.

With my 158 gr handloads, I get the same Point of aim/point of impact with both revolvers out to ~12-15 yards or so. Beyond that the GP does perform a bit better.

papa_bear
February 7, 2011, 10:16 PM
1. How much of an impact will these barrel lengths have?
A: A lot. about 200 fps per inch

2. I know they will impact the velocity of the bullet but I don't know by how much. Is there a chart anywhere?
A: A 3 inch .357mag is comparable to a 4.5" 9mm using 125/124 gr.

3. Will these barrel lengths impact the spin rate of the bullet and therefore impact the accuracy?
A: No, not at handgun distances

4. How big of an impact does the site radius play at these distances?
A: Negligible

5. Is there anything else I should consider?
A: Yes, Muzzle blast and recoil

357 Terms
February 7, 2011, 10:25 PM
200fps per inch ? NO! My chronograph says my hunting rounds (180gr XTP's) are going bout 1375 outa my 6.5 Blackhawk and 1600+ outa my 18.5 Marlin. There is no way there will be a 200 fps difference between a 3 in and 4in barrel.

GP100man
February 7, 2011, 10:44 PM
The difference on my GPs 4" -6" is an average of 50fps with `bout any load ya wanna run over the F1 , my findings are closer to 25fps /inch . Now ya gotta bunch that will jump in `bout powder burn rates & unburnt powder , & it`s true different powders will affect speeds acheived in different length barrels , that`s why we handload & some ammo suppliers now offer "short barrel" ammo !!

My personal findings is it takes at least 3" barrel to burn the powders avaiable to the handloader !

hirundo82
February 7, 2011, 10:50 PM
200fps per inch ? NO! My chronograph says my hunting rounds (180gr XTP's) are going bout 1375 outa my 6.5 Blackhawk and 1600+ outa my 18.5 Marlin. There is no way there will be a 200 fps difference between a 3 in and 4in barrel.

If you look at Ballistics by the Inch (http://www.ballisticsbytheinch.com/357mag.html), .357 loses a lot of velocity with short barrel lengths. They see 200fps or more of a loss with most of their tested loads going from 4" to 3", and the same when going from 3" to 2".

The gains per inch are much smaller when you're talking about 6" or longer (ie that's how long you barrel needs to be to get near-complete powder combustion).

papa_bear
February 7, 2011, 10:55 PM
there's always one.... this time two..... The velocity curve of the lengths he has listed 2",3",4" is about 200 fps per inch. The greatest variation in mv is below 5". Please check chrono results before posting misinformation. These forums really irk me when you have to defend every little word and sometimes typos.

What will really blow your minds, is that a 16" barrel has more velocity than a 17" barrel.......

SPW1
February 7, 2011, 11:19 PM
Another variable you have to keep in mind is all barrels don't shoot the same loads at the same velocity even if they are the same length. There are "fast barrels" and "slow barrels" that can cause pretty significantly different velocities, up to around 100-150 fps difference or so even at handgun velocities. This will upon occasion have the result of shorter barrels shooting as fast or faster than barrels a few inches longer but over all the longer barrels usually do quite a bit better in the velocity department. The main reasons a lot of people don't care for 357 barrels less than about 4 inches or so is that quite a bit of velocity is usually lost(a four inch 357 with warm to hot loads will often beat a two inch 357 with the same loads by around 150-200 fps though this does vary gun to gun) while at the same time muzzle blast and muzzle flip goes up quite a bit in a two inch barrel. A lot of people myself included figure the more controllable 38 special is better suited to the really short barrels than is the 357 for those type of reasons.

nofishbob
February 8, 2011, 09:09 AM
Note that in the tests at Ballistics by the Inch they say that they measured the test barrel from the breach face as on a rifle, not from the forcing cone as on a revolver.

Since COL for a .357 is around 1.6 inches, the effective test barrel length for the "2 inch" barrel is closer to 0.40 inches. No wonder performance was so low!

As the barrels get longer in the charts, the effect of the solid test barrel is less, but for short barrels, adding the approximate length of a cylinder to the data would get you closer to actual velocities.

Sure we can deduct some velocity due to the revolver's cylinder gap, but the referenced tests for short barrels are not representative of snub nosed revolver performance.

Bob

Gary A
February 8, 2011, 11:20 AM
nofishbob is right on the money and points out a real problem in trying to use BBTI to determine the performance of short barrels. The 3" Bond Texas Defender in the "real world weapons" chart is closer to expected performance from a 2 inch snubby. Not exact but closer.

paul105
February 8, 2011, 11:51 AM
You can also gain some useful insight by going to Buffalobore's website and clicking on the various .357 Mag loads they offer. Each load will show velocities obtained with different barrel lengths -- actual velocities from the owner's own guns.

http://www.buffalobore.com/index.php?l=product_list&c=1

Paul

357 Terms
February 8, 2011, 03:59 PM
Check out that link paul 105 put up Papa bear. Thats the kind of results i"m familiar with. Of course you may disagree.

Steve 48
February 8, 2011, 08:05 PM
I love my 3" SP 101. Its very accurate and managable recoil. The 3 " guns are the "rage" of revolver shooters around here. Easy to carry and shoot.

Walkalong
February 8, 2011, 08:14 PM
I shoot my 2 1/2" 686 at 100 yards all the time. Yes, it is harder to hit with that a 6" gun, but only due to the shorter sight radius. I like to shoot at clay pigeons on the 100 yard berm. Tough, but fun. Yep, a 4" gun is easier as well.

roaddog28
February 8, 2011, 08:28 PM
Don't waste your time on the 110-125 gr. high velocity stuff. It will teach you to flinch, blind you, and erode the forcing cone on your gun. Think 158 gr. loads.


I agree with Drail. Unless you plan on carrying go with a 4 inch barrel. Sight radius is better and most people will be more accurate with a 4 inch than a 2.5 to 3.0 inch barrel. Plus shooting 357s out of a short barrel revolver is at best unpleasent. If you insist on a 3 inch or shorter revolver then shoot +P 38 specials. Lots of options.

Like Drail said, shooting light grain high velocity 357s can result in bad habits. Forcus on accurately. It might be better to learn to shoot 38 specials than work yourself up to 357s. Again like Drail said, light grain and high velocity ammo is hard on any 357 revolver.

Good luck,
Howard

Drail
February 9, 2011, 01:08 AM
Good advice from roaddog. Learn the basics with a .22 Then learn to hit reliably with standard .38 Spls. Then work your way up to the +P stuff. This was how we taught NRA defensive pistol classes and it worked almost 100% even with women who had never held a gun before. I dearly love shooting snubs, but it is unlike any other type of gun to become proficient with. It just takes practice.

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