Muzzle Velocity General Rule?

[Myles]

This might be a dumb question, but is there a general rule regarding how much an increase in barrel length increase muzzle velocity? For example, hypothetically, using the same 9mm ammo, out of a 3-inch barrel average FPS might be around 1100. Out of a 4-inch barrel, can we make an estimation as to how much it will increase by without using a chrono?

[Steiny]

Im not sure on pistols but I know 5.56/.223 rifles (common AR's) loose approx 20FPS per 1".

[Myles]

Thanks, Dave. Good to know!

[gunfixrjoe]

The difference is negligible and will go unnoticed unless shooting over a chronograph.

[Myles]

The difference is negligible and will go unnoticed unless shooting over a chronograph.

Got it. Yeah, figured I wouldn’t BD able to tell a difference without a chrono. Just not sure if there is some general guideline or rule when it comes to barrel length and velocity.

[gunfixrjoe]

There are a ton of variables there to have a set guideline really. Variables that include, barrel length, powder type, bullet weight, primer, etc..... Every combination of these will likely provide a different outcome with a given barrel length for every cartridge. With each variable, there's an optimal combination that will provide the best efficiency, accuracy, and velocity. Change one aspect and the best barrel length might need to change, longer or shorter...

Did I over-elaborate? Lol.......

[Myles]

There are a ton of variables there to have a set guideline really. Variables that include, barrel length, powder type, bullet weight, primer, etc..... Every combination of these will likely provide a different outcome with a given barrel length for every cartridge. With each variable, there's an optimal combination that will provide the best efficiency, accuracy, and velocity. Change one aspect and the best barrel length might need to change, longer or shorter...

Did I over-elaborate? Lol.......

Lol...I'm tracking. I was just wondering if all variables are equal, and the only thing changed is barrel length, is there some kind of general rule in regards to how much velocity increases or decreases. (Basically, I'm just being lazy and don't want to use my chrono!)

[gunfixrjoe]

Understandable!!! I'll research some more for you, but it will be different for every cartridge to a degree. Are you only wondering about 9mm?

[Myles]

Would be awesome if you have any info handy!

Yes, just 9mm.

[AVRDefense]

I wouldn't worry about it too much, Myles. Just shoot em in the dick.

[Myles]

I wouldn't worry about it too much, Myles. Just shoot em in the dick.

Haha!

I’m creating some new ammo recipes for competition and need to get the right power factor. I was just too lazy to break out the chrono when I posted. With my G19 I’m slightly below the requirement, but with a longer barrel on my G34, it will increase velocity this power factor. I just didn’t know if there was a general rule.

for those interested, after doing some research, there is no golden rule and one should really chrono. But, if one can’t, an average range is an increase of 25-37 fps for every added inch. this is not a rule though.

[gunfixrjoe]

Haha!

I’m creating some new ammo recipes for competition and need to get the right power factor. I was just too lazy to break out the chrono when I posted. With my G19 I’m slightly below the requirement, but with a longer barrel on my G34, it will increase velocity this power factor. I just didn’t know if there was a general rule.

for those interested, after doing some research, there is no golden rule and one should really chrono. But, if one can’t, an average range is an increase of 25-37 fps for every added inch. this is not a rule though.

Excellent. Sorry I didn't get anything back to you.