How to determine velocity from rifle vs pistol

[shibbershabber]

I recently picked up a 357mag carbine and mostly shoot my own cast bullets and am concerned about leading the barrel.

I load them to about 950fps from a 6" barrel & my 38spl is about 840fps from a 6"

Is there a way to determine what that velocity will be out of a 16" bbl?

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[Arne K]

Here you go: BBTI - Ballistics by the Inch :: .357 Mag Results

 

[shibbershabber]

Those charts were all defensive rounds and varied quite a bit.

I think I'll just put a handful of them through the chrono and see where I am at.

 

[P7M13]

Those charts were all defensive rounds and varied quite a bit.

I think I'll just put a handful of them through the chrono and see where I am at.

Makes sense. I thought your original question odd.
The 16" barrel is from a locked breech '94 or something, right? I would expect an additional boost from the chamber seal in the carbine, and then 20-40fps faster per inch.

 

[CHLChris]

Powder speed makes a really big difference, though. Slower is better for rifle barrels if you really want to maximize your carbine load versus a handgun. You really need to put a ladder together and chrono all the loads. BBTI is only about factory ammos.

 

[shibbershabber]

Yeah, air cooled WW cast bullets coming from a Rossi 92 16"... Hardness Im guessing BHN of 10

I have my pet loads for 38 & 357 and have loaded several hundred rounds... Id hate to have to make a new load for the rifle.

Using Unique powder, btw

 

[Stomper]

The answer is clear.... sell the rifle.

 

[Certaindeaf]

Those loads probably won't make a difference, matter of fact, they'll likely lose speed with that longer barrel. Regardless, shoot a few and peep down the bore.

 

[OldBroad44]

Insufficient data. How the velocity of a bullet is affected by barrel length depends not just on bullet weight and speed but other factors including burn rate of specific powder. For example, a commercial load designed for short barrel .38s may gain some speed with a few more inches of barrel, but very little, then lose speed in long gun. Basically they use a very fast powder that contributes its all in a short barrel. It will generally be only a little faster in a standard revolver barrel. It may then actually be slower in a rifle barrel than a revolver barrel because friction of bullet in barrel costs speed in the longer barrel.

Commercial .357 or .44 loads designed for hunting usually have slower burn powders that work very well in 6 to 10 inch barrels. You lose a lot if you fire these load in a snubby. There is usually enough unburned powder left even from a 10 inch barrel so they are significantly faster in rifles.

You need to just run your loads through a chronograph shot from your rifle and find out. There is no way you can predict based on data on commercial loads since you arent using the same powder as those loads. Even bullets matter, since some are slightly bigger for the caliber and cause more friction.

The Buffalo Bore website is interesting because for many calibers and skus they give the velocity from several barrel lengths. And they have load purposes listed, such as short barrel loads. And monometal loads. And they include Marlins for relevant calibers.

 

[Arne K]

In reading your OP, it appears that your main concern is leading and not trying to squeeze out max velocity? Your 950fps loads are exceedingly mild (I'm assuming a standard target bullet ~158gr) and you will likely see 1100 to 1200 fps in your 16" barrel. You shouldn't have any worries about leading until you start running loads that hit ~1500fps in your 6" gun. I cast bullets for most pistol calibers and some rifle. Gas checks become important as you approach 2000fps. In most cases, accuracy suffers before leading is a problem.

 

[orygun]

If the 357 Mag loads were much hotter, I'd say you could expect a 500 fps gain by shooting them in the 16" barrel.
Since they are not and the 38 Specials are only about 100fps behind, I'd say you will see approx a 350fps boost.

 

[ageingstudent]

In reading your OP, it appears that your main concern is leading and not trying to squeeze out max velocity? Your 950fps loads are exceedingly mild (I'm assuming a standard target bullet ~158gr) and you will likely see 1100 to 1200 fps in your 16" barrel. You shouldn't have any worries about leading until you start running loads that hit ~1500fps in your 6" gun. I cast bullets for most pistol calibers and some rifle. Gas checks become important as you approach 2000fps. In most cases, accuracy suffers before leading is a problem.

I've seen no mention of it but powder coating makes quote a difference also. Bullet hardness vs velocity is less of an issue with a good coating. It acts much like a gas check. I've got some coated 12 bhn alloy that I am driving at 1800fps in my .351SL (almost identical ballistics to a .357 carbine) with 4227 and AA 5744 that show nary leading. Slightly oversized to seal the bore from gas leakage seems to be more of more importance. No smoke and much cleaner to load and fire than traditional lubed bullets. A soft alloy flat nosed .358/158 (in my case sized to .352) really makes a jackrabbit do backflips. It's not fair really.

@Certaindeaf have you tested out those .358 PC projectiles I gave you yet? Wondering if your experience is similar?

 

[Certaindeaf]

I've seen no mention of it but powder coating makes quote a difference also. Bullet hardness vs velocity is less of an issue with a good coating. It acts much like a gas check. I've got some coated 12 bhn alloy that I am driving at 1800fps in my .351SL (almost identical ballistics to a .357 carbine) with 4227 and AA 5744 that show nary leading. Slightly oversized to seal the bore from gas leakage seems to be more of more importance. No smoke and much cleaner to load and fire than traditional lubed bullets. A soft alloy flat nosed .358/158 (in my case sized to .352) really makes a jackrabbit do backflips. It's not fair really.

@Certaindeaf have you tested out those .358 PC projectiles I gave you yet? Wondering if your experience is similar?

I worked up a carry load with those hard wadcutters so those are all kinda gone.
I sure like the powder coating.. super clean and don't crud up the seater die like tumble lube etc. does.

 

[ageingstudent]

I worked up a carry load with those hard wadcutters so those are all kinda gone.
I sure like the powder coating.. super clean and don't crud up the seater die like tumble lube etc. does.

I have a bunch more of those wadcutters I don't shoot them as much as the 105 swc and 125 rnfp. Pm me your address and I'll send you a few handfuls.