velocity

[sako2]

Do you guy get the same velocity out of your reloads the data says you should get.

[Jim Watson]

I won't say never, but hardly ever at best.

[Rimfire5]

Unless you are using the same length barrel, the same primers, and are close to the temperature during the test that established the 'data', why would you even suspect that what you measured would even be close to the same.

Even if your barrel was the same length, you would also have to consider differences in individual barrels and chambers, even from the same manufacturers.
Then you also have to include the differences in the chronographs and where along the flight of the bullet you measured and where the 'data' was measured.

Actually, given all those variables, I would be surprised if you measured the same velocity as the 'data'.

[TX Nimrod]

Published loading data doesn’t “say” you should get anything. They are simply a report of what the manual publisher’s lab obtained using the specified components in a precision SAAMI-spec barrel of the reported length. It would be a minor miracle if anyone got exactly the same velocity as reported in the manuals. Reasons for the difference include:

Different barrel lengths
Different chamber and bore dimensions
Different powder and bullet lots
New brass versus used brass
Different case capacities
Different test temperatures
Accuracy of chronographs

The latter is important since not all chronographs will read identical velocities. When I shot a series of loads across my Oehler 33 and Labradar at the same time, average corrected velocities between the two varied by about 18 fps. These were high end chronographs, I wonder how a $60 chrono would have fared. Too, a string of five chronographed shots is not enough to obtain a statistical accuracy of over about 75%. This means that when comparing two 5-shot averages of the same load the two results will almost never be identical.

All of the above should demonstrate why you won’t get the same velocities as those published in the manuals.




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[74A95]

In the same range? Often. Sometimes it's more, sometimes it's less.

Same thing with factory ammo.

[Bart B.]

How the rifle is held against the shooter's shoulder can have a big effect on bullet velocity.

I've seen several dozen fps spread in average velocity across different people shooting the same stuff.

All published velocity numbers are not based on SAAMI spec test barrels and procedures.

[TX Nimrod]

… All published velocity numbers are not based on SAAMI spec test barrels and procedures

Absolutely correct, some data like Hornady uses production firearms for the published velocities, some like Speer do not. Speer have gone back to using 24” barrels for most of their published data instead of trying to match what they think is the most popular length. The velocity differences are real. Example, .30-06 with 150-grain bullets and 46.0 grains of H4895:

#14 used a 22” barrel = 2572 fps
#15 used a 24” barrel = 2601 fps

The bottom line is that published velocities - reloading data or factory ammunition - are in no way a guarantee of actual performance in a consumer’s firearm. There are far too many variables.




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[44 AMP]

Several here have stated many of the factors, including how the gun is held, that play a part in the differences in velocity readings. Here's the main point to remember.

EVERY gun and ammo combination is a combination of many, many different factors and ALL of them have a range of tolerances.

There is a bell curve at work here, and while the majority falls in the middle of the curve, there are results that are at each end of the curve.

Because the majority of results will be in the middle of the curve, reloading data is useful as GUIDELINES, they are NOT hard and fast results that you will get.

If you get exactly what they got, its serendipity, no more, no less. Do exactly the same thing tomorrow and you'll probably get a slightly different result.

That's another part of the key. Slightly different. Do not obsess over a handful or even a double handful of fps variations. Guns and ammo do that.

And for every "rule" you can think of, there is some exception, somewhere. I've seen a shorter barrel gun shoot faster than a longer barrel one. I've seen multiple guns with identical barrel lengths, shooting the same ammo, over the same chronograph in the hands of the same shooter vary in velocity as much as 100fps.

As previously stated, reloading data doesn't tell you what you will or should get. It tells you what they got. The expectation is that you will get something similar. Anyone who promises you that you will (or should) get precisely what they got is selling something.

Which is the main reason I retired my chronograph decades ago. The actual exact fps numbers are irrelevant to me. I shot enough different guns and different ammo to learn that I will get something close to the published speeds, allowing for different barrel lengths and all the other differences between individual guns and the published data so what matters isn't the speed number of FPS but how my ammo performs in my guns.

Only shooting wil tell you that. Getting as close to humanly possible consistent identical numbers in your ammo specs (all of them) provides potential, but doesn't tell you much beyond that. Only actual shooting shows you what actually happens with your gun, and your ammo in your hands.

Now, someone might come along and tell you how that prepping and sizing your brass is a certain way, and doing other things a certain way improves group sizes, some might even go so far as to say it "always shoots better" or "shoots better in all my rifles"...

To which my response is, "good for you! How does that help me put a deer in my freezer with my .308 Win Remington 600 carbine?"

The only honest answer is, "it doesn't".

There are just too many factors at work that are specific to the individual gun and the ammo being used to claim otherwise, if you're honest about it.

[74A95]

Members might find this article of interest;
https://www.ssusa.org/articles/2021/...h-and-velocity

[Unclenick]

One thing to remember about SAAMI pressure and velocity barrels is that they are held to the minimum drawing chamber size within half a thousandth of an inch. This is done to encourage a worst-case high pressure from each load so the maker is less likely to have his loads go over SAAMI numbers in his customer's guns. As a result, the center of the peak pressure bell curve, which is the average value for all guns, is going to be a bit below the published number even when barrel length is the same.

[jmr40]

It depends on the rifle. It is common to see 25-50 fps difference between 2 different rifles with ammo from the same box. And 100+ fps isn't unusual.

With some, (actually most), of my rifles the velocity that I get is pretty close to the predicted velocity in the load manuals. Factoring in for shorter barrel lengths of course. Most non magnum rifle loads are tested in 24" barrels and most magnum loads are tested in 26" barrels. Whereas most factory barrels are about 2" shorter than that.

I have 2 rifles in 30-06, both with 22" barrels. The Winchester is always less than 50 fps slower than predicted. Which is about right for the slightly shorter barrel. The Remington on the other hand is always about 50-100 fps slower than the Winchester depending on the load. And 100-150 fps slower than the load manuals predict.

The powder choice matters too. With some powders I've tried I was unable to meet the predicted velocity. With others I come very close.

[Unclenick]

For testing using production guns, that is so. For SAAMI P&V barrels, all, including the magnum barrels, are 24" except for the following 5 cartridges:

300 AAC Blackout: 16"
7.62×39: 20"
30 Carbine: 20"
350 Remington: 20"
44 Magnum for carbine: 20"

The reason to know the SAAMI numbers is that ammunition manufacturers will frequently state a velocity but no test barrel length. They all use SAAMI barrels for pressure and velocity determination, so knowing the SAAMI numbers tells you what barrel length they were tested in when none is given.

[reynolds357]

Originally Posted by sako2

Do you guy get the same velocity out of your reloads the data says you should get.

It's rare that I match published velocity.

[cdoc42]

44AMP, thank you for an absolutely practical and comprehensive answer.

[sako2]

Thanks guy's. My loads are usually 100-150 fps slower. Will a muzzle brake lower velocity. My barrel length is the same as the test barrel.

[reynolds357]

Originally Posted by sako2

Thanks guy's. My loads are usually 100-150 fps slower. Will a muzzle brake lower velocity. My barrel length is the same as the test barrel.

A brake will no lower velocity, buy you do not include brake in barrel length.

[Shadow9mm]

Rarely if ever. I look at it as a rough estimate, and a way to gauge progress when working up a load. For example. AA#7 in 9mm with 115g plated round nose. Max from hornady was 8.6gr. However in my 4in barrel gun there was no velocity increase after 8.0g.

8.0g gave the best velocity at 1176, and the manual listed 8.6g at 1200fps.

[74A95]

Originally Posted by Shadow9mm

However in my 4in barrel gun there was no velocity increase after 8.0g.

That's odd because A#7 is used for 9 Major.

https://www.ssusa.org/articles/2018/...-short-barrel/

[Shadow9mm]

Originally Posted by 74A95

That's odd because A#7 is used for 9 Major.

https://www.ssusa.org/articles/2018/...-short-barrel/

I was running a 4in barrel. May have fared better in a 4.5 or 5in. Also, not sure what primers they used. Looked through twice, did not see it. I would expect they would be using magnum primer for those heavily compressed loads with the high pressures.

[74A95]

Originally Posted by Shadow9mm

I was running a 4in barrel. May have fared better in a 4.5 or 5in. Also, not sure what primers they used. Looked through twice, did not see it. I would expect they would be using magnum primer for those heavily compressed loads with the high pressures.

I don't think any of those would have mattered.

I have 9mm data with 125 gr bullets, CCI 500 and #7 (up to 8.5 gr) and velocity just keeps going up and up.

[44 AMP]

I would expect they would be using magnum primer for those heavily compressed loads with the high pressures.

magnum primer in 9mm Luger? AA No.7?? no need. And likely no benefit. Magnum primers aren't about how compressed the load is they're about igniting difficult to ignite (slow) powders. AA No. 7 isn't a slow pistol powder.

And, my personal feeling is that anyone who is providing loading data without providing the primer, and case used or the gun it was tested in isn't telling us enough.

[74A95]

Originally Posted by 44 AMP

magnum primer in 9mm Luger? AA No.7?? no need. And likely no benefit. Magnum primers aren't about how compressed the load is they're about igniting difficult to ignite (slow) powders. AA No. 7 isn't a slow pistol powder.

Some 9 Major and 38 Super IPSC/USPSA shooters use magnum or small rifle primers to reduce primer flow - for their thicker cups. I have with my Major loads.

Originally Posted by 44 AMP

And, my personal feeling is that anyone who is providing loading data without providing the primer, and case used or the gun it was tested in isn't telling us enough.

That link provides the primer used.

[Unclenick]

The effect of a muzzle brake on velocity depends on how it is implemented. A radar engineer once shared a Doppler Radar trace with me of a 40 S&W round from a pistol, and it picked up about 3.5% of its peak velocity (about another 35 fps) from the muzzle blast after it cleared the muzzle. That agrees well with Harold Vaughn's magnetometer measurements of about 2.7% (82 fps) for a rifle in 270 Winchester (Rifle Accuracy Facts, last paragraph p. 165). Since a muzzle brake vents the muzzle blast pressure, you can expect to lose that 3-3.5% of so if the vents are located behind the muzzle, as with Magna-porting or other brakes that drill into the barrel. But if your brake extends forward from the muzzle, since the main effect of muzzle blast on a projectile is within a very short distance from the muzzle, you will still pick up most of that muzzle blast acceleration with that configuration. If memory serves, the Doppler plot showed the acceleration was mostly done in the first two or three calibers of travel from the muzzle.

[Don Fischer]

Take the ammo and shoot it in several different rifles using the same cartridge and you just might get several different velocities!

[DaleA]

How the rifle is held against the shooter's shoulder can have a big effect on bullet velocity.

From all the comments here this is apparently common knowledge.

This site, along with mirrors, weighing myself and scoring my targets keeps me humble.

This site is a great place to lurk and learn.