slower powders = higher velocities

Well Power Pistol is very on point because it’s the exception to the 125 gr FMJ data in Lymans. There it sits slower than Unique and faster than 2400 and it isn’t behaving data wise. So it seems to me it has some property not present in BE, Unique or 2400. As you say, its what Lyman got – I can accept that.

I use PP exclusively in 9mm – but that is getting off subject

HiBC is not the first to say that about me – I do tend to overthink – but I like calling it “paying attention to detail”

I do carefully work up all my loads, with a chronograph and that work lead me to 2400 and 158 Bayou’s Hi-tek coated LSWC. I shot quite a bit of 125 grain factory ammo when I first purchased a 6 inch S&W 686 and have flame cutting on the top strap to prove it.

Since then, I’ve stayed away from the 125 grain bullets.

My questions arise from discussions I have had with a friend who does shoot 125 grain bullets out of 3 and 4 inch 357 revolvers. He had noticed how low some velocities he recorded were, and since he does not tend to “overthink” issues – he dumped it on my lap to figure it out.

Thank you for the welcome, it’s a great forum – I’ve been lurking for awhile.

I’ve been reloading about 4 years now. The question arose with the 125 grain FMJ, because of his low velocities, but my interest is mainly for revolvers in general. The purpose is 100% target shooting and the goal is small groups at 25 to 50 yards. Barrel lengths are 3, 4 and 6 inches. We both have a good selection of handgun powders: BE, Unique, PP, 2400, HP-38, HS6, HS 7, Longshot, IMR4227, WST, H110. Also have decent stock of 38/357 bullets, mostly Hornady XTP’s in multiple weights. I generally shoot lead – he generally shoots FMJ’s and plated.

Loading process? Not sure what you’re looking for, but I reload for all of my guns. 38 spl, 357, 9mm, 45 acp, M1-30 Carbine, 223, 308, 7mm Mag, 30-06 and 30-30.
I use a Hornady single stage and a Lee Classic Turret

thanks for taking the time to reply – I appreciate the sharing of the information

I sent this before I saw your new post
 
Revolvers with 3 to 6 inch barrel lengths have slightly different requirements, but the powders are the same.
Burn rates are only part of the equation too. Some powders are bulkier than others and you use more or less to get the same velocities.
"...have flame cutting..." That's not caused by the bullet weight. It's caused by the powder. Hodgdon's H110(Win 296) Start loads, for example, are at higher velocities than the Max loads for other powders.
"...chrono data with velocities 300 fps lower than book velocities..." Perfectly normal. Book data is with the specific components, firearm and conditions found on the day of the test. Hodgdon's site for some odd reason used a 10", 1:18.75" twist, barrel and unnecessary magnum primers. Your 6" will never give the 1,881 fps of the H110 Start jacketed(H110 isn't a cast bullet powder) load they're showing. Something very odd about their site anyway.
 
You might want to verify that the 125 gr FMJ's are for 38/357 rather than 9 mm .That can make a difference of .001 or .002 in bullet dia.And that can matter to both less accuracy and pressure.

If you are searching for cast bullet accuracy,bullet fit is crucial.Ideal,bullets just drag through the cyl throat,and are bore dia to bore dia +.001.

Another FWIW,I have fired a LOT of full house .44 magnum loads through my Super Blackhawk.
Nearly all the bullets were cast of wheel weight.They ranged from 215 gr to 250 gr.SWC's. I cut the gas check feature out of my Lyman Keith mold,245 gr? I forget.It worked fine.
I never got leading.I loaded full Hogdon max from the old black manual.
It was accurate enough that sitting down,leaning against the truck,knee resting the hands,hitting qt oil cans at 100 yds was a high percentage shot.
I have also used H-110 in a 32 H+R with cast bullets,no problem.
In my experience,H-110 works fine with cast bullets,just load them stout,and use a good crimp.
Hogdon data used to show over 1800 fps with a 215 gr cast SWC in .44 Mag using H-110,BUT,it was not from a revolver.Universal receiver,test bbl.
I did not own a chronograph then,but I doubt we hit 1500.
I have chrono'd 1300 with 300 gr lasercasts and H-110.I cut the bbl to 5 in,too.
H-110 is an excellent 30 carbine powder,and with Mr Hogdon's way of naming powders,I would not doubt the 110 gr 30 carbine bullet played a part.
 
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This is not an easy question to answer. I recommend that all who are interested in this review AMCP 706- 150 “Interior Ballistics of Guns”. This AMC pamphlet is written towards artillery tubes which, if you have not noticed, are a bit longer than the barrel on a snubbie or a 6” revolver. The basic principles still apply, but any answer if far from basic.
 
I've not read the page after page of posts in the past 24 hours, but skimmed them.

There was a statement that getting efficient burn, in other words. having the entire charge of the slowest useful powder consumed rather than lost will show when velocity is peaking, and there is possibly the best round to use, unless all you want is power. Your pistol will start out with a certain velocity even if the barrel is taken off and you shoot directly from the cylinder, and with every centimeter of barrel length, the bullet will accelerate. Velocity peaks when it leaves the barrel. The pressure curve of the burning charge determines what acceleration takes place.

once read a tip on getting the best performance out of your black powder rifle. Load the thing, and shoot past, or through, a cardboard box. Check for unburned powder. Keep increasing in 3 to 5 grains of powder until a significant amount of unburned powder shows up in the trap. then back down until the unburned powder is reduced to just a few granules.

I'm sure that someone has mentioned that the only way to know what isi happening with your ammo is to borrow or buy a chronograph. ..

Test barrels were brought up. A test barrel is a bolt action receiver, and barrels are slipped in and out as test rounds are supplied. They may not even have actual ejectors like a traditional bolt, just a solid bolt face with pin.

The point is, that there are vented barrels and non vented. A hole has been drilled into the barrel that simulates the cylinder gap. It may be that 1/8 or so inches will simulate the gap around a cylinder.

I don't know why a vented barrel would be used on anything but revolver cartridges. It's doubtful that any traditionally semiauto cartridge would ever be tested in a vented barrel, while revolver cartridges of every sort should be. There isn't any reason for vented barrel testing with rifles. Even if the thing has a gas port, it doesn't represent the velodity that would be obtained in any other firearm.

My lord, it must get boring as hell running a test gun. Fire, change cartridge, step behind shield and pull lanyard. Do it again, all day long, letting the computer collect and report the data. doing nothing but pulling the string and listening to the gun go boom. Once or twice a day, you'll move to another station and gun, or replace a barrel. With pistols, there may even be universal barrels. most of the 9mm cartridges may be fired from the same chamber, it could work, if headspace requirements would allow it.
 
Haven't read all the responses but one thing that must be understood manuals list "peak" pressure velocity isn't directly related to "peak" it's related to pressure under the curve or dwell time. A fast powder will spike pressure but this pressure will also drop very fast leaving much less dwell time. Slower powders allow for more dwell time as the pressure curve is straighter however go too slow and it takes too long to accelorate bullet wasting much of your pressure as muzzle blast.
 
The vented test barrel that is used for many revolver caliber P&V measurements is shown on page 138 of the SAAMI manual.
http://www.saami.org/specifications_and_information/publications/download/205.pdf

The drawing for the .357 Magnum P&V barrel is on page 157.
It shows the dimensions for the straight barrel as used by Hodgdon and, in red, the vented barrel they should have used to give a better representation of a real revolver.

When it gets down to real mass production guns, there is a chart in many editions of the Speer manual showing muzzle velocity from a number of different .357 revolvers. There are wild variations from gun to gun.
 
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