.357 mag velocity ?

[hillbillydelux]

I have been reloading for a long time now however, I just recently got a chrony. I usually trusted the published velocities but now that dang chrony has just disproved everything I thought I knew about MV. Each reading was the average of 5 shots. All shots were within 10 fps of each other.

Test #1
Ruger SP101 3" barrel
- 125gn JHP over 17 gn 2400= avg 1450 fps.
- 135gn JHP over 15.5 gn 2400= avg 1448 fps.
- 158gn JHP over 14.5 gn 2400= avg 1451 fps.

Test #2
Ruger vaquero 5 1/2" barrel
- 125gn JHP over 17 gn 2400= avg 1480 fps.
- 135gn JHP over 15.5 gn 2400= avg 1434 fps.
- 158gn JHP over 14.5 gn 2400= avg 1361 fps.

This is definatly not what I expected. I also tested several different pistol/rifle calibers just to make sure my chrony was reading correctly. Any suggestions on why this is?

 

[ants]

Those velocities look good to me. Were you expecting higher or lower?

And the spread of 10 fps is phenomenal to say the least.

Did you have the muzzle close to the chronograph? You need 15 feet or more.

 

[Oyeboten]

...darn it...and I almost bought a pound of 2400 at the Gunshow a few days ago too...$43.00, and I demured...


Now I wish I had bought it...I was not familiar with it's applications, till now.

 

[hillbillydelux]

It was at least 15 feet away. From everything I have ever read longer barrel= more velocity and heavier bullet = lower velocity. I guess thats what I get for trusting someone else and not checking for myself earlier.

 

[ArchAngelCD]

Oyeboten,
It's good you didn't pay $43 for a lb of 2400, it should be less than $20 but recently it has been ~$25. A price tag of $43 is way too much especially since it seems the supplies are starting to come back slowly. In a few months you will be able to buy 2400 for ~$20 again. (I miss the $14 days) Most of the stores aren't over $25 even now.

 

[The Bushmaster]

10 fps ES for 5 hot groups? Unbelivable...How are you charging the cases with powder? You weighing everything?

You should, normally, get higher velosities from a longer barrel, but the barrel from one gun may not act the same as another barrel. I have three .357 magnums. A 2 1/2" S&W, a 4 3/4" Colt and a 6 1/2" Ruger. The ruger is the fastest of the three and the S&W is faster then the Colt. Go figure...

I imagin that the cylinder to barrel gap has a lot to do with it too. The S&W is tighter then the Colt and the Ruger is the tightest of the three.

 

[rcmodel]

You are actually getting slightly higher velocity then I would have expected.

As already noted. the shorter barrel is faster then the longer barrel, just because!

Could be the SP101 has a closer barrel/cylinder gap, tighter chambers, tighter throats, slicker bore, etc, etc.

In all, it's prefectly normal for two identical guns to vary that much, let alone to different ones.

rc

 

[hillbillydelux]

Yes I do weigh each load as I do not trust the powder thrower to be accurate enough. They are all loaded on a rockchucker. Maby im just being silly but im kind of obsessive about making sure every load is exact, every case is measured for exact length, crimping is done seperatly, primer flash holes are uniformed, bullets are weighed in lots... Well you get the idea. Yes it takes forever but my father in law taught me to reload some years ago and he was a bench rest shooter so I guess it just stuck. I have found that most of my loads have very little velocity spread (aside from a stinking AR Every other gun I own holds true to the long barrel=higher velocity and heavier bullet=less velocity. But the .357 mag threw me for a big loop.

RCmodel, I checked the barrel gap on both pistols and you may have something there. I can barely slide a piece of paper between the cylinder and cone on the sp101. The vaquero definatly has more of a gap. Also the sp101 has had more rounds than I care to count through it and the vaquero only a couple hundred.

Thank you all for the feedback. Is starting to make some sense now.

 

[VegasOPM]

Barrel gap is probably the biggest factor in velocity differences in revolvers. I'm betting that the Vaquero has a noticably bigger cylinder gap that the SP.

 

[Steve C]

Its quite unusual to get higher velocity, esp the figures you recorded, from a 3" barrel vrs a 5.5" barrel. My own experience is that shorter barrels universally deliver lower velocities though I have an 8-3/8" S&W M27 that produces velocities only equal to 6" barrels.

The assumption is the chrono was correct however some things can affect the readings. If the chrono wasn't set at least 10' away from the muzzle of the pistols you may have been measuring the powder and smoke rather than the bullet going across the screens. However, measurement are measurement and if the ruler is correct then that's the way thing are if they can be reliably duplicated by others (the scientific method of experimental validation).