bullet velocities ?

[rockyfatcat]

I didn't say wildly different, but yes, different. You can even get different results from the same brand and type of ammo from the same rifle if the ammo manufacturing lots are different. The difference may not mean much to most shooters, but if you are looking for maximum accuracy, especially at long range, those differences are important.

You said "You can fire the ammo from two weapons that are the exact same model and manufacture of rifle or handgun and get different results. "
You said Different not similar

 

[summer44]

Different results? I would expect Similar results, not exactly the same, and certainly not wildly different.

U would be wrong to expect that

 

[summer44]

Try this , take a new box of what ever bullets and weigh each one. They don't all weigh the same. Some as much as 10 grains. You can even take a box of bullets for reloading and the lead out of the same box doesn't all weigh the same. And that's with out getting into head space, cylinder gap, case hardness, variations in rifling, once you factor in all the variables you can very easily get more less 100 ft per second difference. Many people reload so they can control some of these variables.

 

[rockyfatcat]

Different results? I would expect Similar results, not exactly the same, and certainly not wildly different.

U would be wrong to expect that

http://www.massreloading.com/reloadsVfactory2.html

"The factory powder charge weights were nearly as precise as what I used in the handloaded ammo. The brass cases were also very consistent. The bullet weight variation was only slightly larger than what I measured in a sample of the match bullets used for the handloads.

With consistent charge weights, bullet weights, and cases, one would expect consistent velocity from the factory ammo as well. As it turns out, the velocity was quite repeatable with the factory ammo. The maximum measured velocity was 3410 FPS, the minimum was 3333 FPS. The resulting extreme spread of 77 fps would account for only about 0.1" of vertical shot dispersion at 100 yards. Clearly, something other than the velocity was to blame for the inaccuracy.

So what caused the difference in group size? The short answer is, "The bullets did, because they're not all the same shape." Table 3 shows the measurements of cartridge overall length for both the factory ammo and the handloads. This measurement represents the distance from the case head to the tip of the bullet."

So based upon this variation of manufacturered ammunition @ 77 fps, you're saying that the same ammunition fired through same the exact weapon (eg a series of say a dozen identical S&W model 15 revolvers) are going to produce wildly different different bullet velocities?

Having fired thousands of rounds of military issued .38 ball ammo through many different USAF S&W model 15 revolvers as part of an Air Force Base base shooting team. I would suspect something other than bullet velocity for issues at revolver distances.


It’s a poor craftsman who blames his tools.

 

[summer44]

http://www.massreloading.com/reloadsVfactory2.html

"The factory powder charge weights were nearly as precise as what I used in the handloaded ammo. The brass cases were also very consistent. The bullet weight variation was only slightly larger than what I measured in a sample of the match bullets used for the handloads.

With consistent charge weights, bullet weights, and cases, one would expect consistent velocity from the factory ammo as well. As it turns out, the velocity was quite repeatable with the factory ammo. The maximum measured velocity was 3410 FPS, the minimum was 3333 FPS. The resulting extreme spread of 77 fps would account for only about 0.1" of vertical shot dispersion at 100 yards. Clearly, something other than the velocity was to blame for the inaccuracy.

So what caused the difference in group size? The short answer is, "The bullets did, because they're not all the same shape." Table 3 shows the measurements of cartridge overall length for both the factory ammo and the handloads. This measurement represents the distance from the case head to the tip of the bullet."

So based upon this variation of manufacturered ammunition @ 77 fps, you're saying that the same ammunition fired through same the exact weapon (eg a series of say a dozen identical S&W model 15 revolvers) are going to produce wildly different different bullet velocities?

Having fired thousands of rounds of military issued .38 ball ammo through many different USAF S&W model 15 revolvers as part of an Air Force Base base shooting team. I would suspect something other than bullet velocity for issues at revolver distances.


It’s a poor craftsman who blames his tools.

8
I don't have 38 load data in front of me but 77 fps variation is going to be around 8 to 10 percent that's a lot in my opinion, most factory ammo is metered, or was I can't say for sure now. As any reloaded knows can can get a small variation in weight by metering vs weighing each charge. Out of a sig 5" barrel 220 10mm I get about 50 fps less than what is listed on sig 10mm ammo. Again 50 being avg.
My experience has been that I generally get less velocity than what is listed. I can't think of one time that I have gotten more. Also take a look hand load data from different sources list the same bullet, power and charge weight, yet don't list the same velocity. There are just to many uncontrollable factors.

 

[greg vess]

Usually a manufacturer will have a stationary rear breach loading test barrel. Length is varied depending on manufacturer but I would estimate 18 to 22 inches in length maybe more. Loads are then measured through this barrel and then a ballistics work up can be made and be uniform across the board of their different ammo profiles. The secret is the length of their test barrels. It could be the length of a bolt action barrel which is still within a real life scenario.

There are so many lengths of barrels on guns they will never hit the set velocity on every shot. It's just a speed that can be obtained with under the same conditions they were tested under. Which leads us back to the original question, what in the hell are those conditions? Good luck trying to find out. However, some manufacturers will give you a complete ballistics work up on a variety of barrel lengths.

 

[Ken Ford]

Some if not most publish their way of testing. Might have to dig though.

Example.
http://www.hornadyle.com/assets/site/files/Hornady-LE-Military-Application-Guide.pdf

 

[REDX]

http://www.massreloading.com/reloadsVfactory2.html

"The factory powder charge weights were nearly as precise as what I used in the handloaded ammo. The brass cases were also very consistent. The bullet weight variation was only slightly larger than what I measured in a sample of the match bullets used for the handloads.

With consistent charge weights, bullet weights, and cases, one would expect consistent velocity from the factory ammo as well. As it turns out, the velocity was quite repeatable with the factory ammo. The maximum measured velocity was 3410 FPS, the minimum was 3333 FPS. The resulting extreme spread of 77 fps would account for only about 0.1" of vertical shot dispersion at 100 yards. Clearly, something other than the velocity was to blame for the inaccuracy.

So what caused the difference in group size? The short answer is, "The bullets did, because they're not all the same shape." Table 3 shows the measurements of cartridge overall length for both the factory ammo and the handloads. This measurement represents the distance from the case head to the tip of the bullet."

So based upon this variation of manufacturered ammunition @ 77 fps, you're saying that the same ammunition fired through same the exact weapon (eg a series of say a dozen identical S&W model 15 revolvers) are going to produce wildly different different bullet velocities?

Having fired thousands of rounds of military issued .38 ball ammo through many different USAF S&W model 15 revolvers as part of an Air Force Base base shooting team. I would suspect something other than bullet velocity for issues at revolver distances.


It’s a poor craftsman who blames his tools.

77 FPS difference is a DISASTER. Revolvers and rifles are TWO different things. For example back in 2015 I used Factory Hornady 6.5 creedmoor for a PRS match because I was in a bind. I didn't notice that it was from 3 different Lots.

Day two of the Match my impacts were starting to go .3 Mils Low which basically cost me several stages. When I got back to GA I choreographed the 3 different Lots and from fastest to slowest was 93 FPS.

Plug the 93 FPS data into the Ballistic app and guess what .3 Mils different

 

[REDX]

You said "You can fire the ammo from two weapons that are the exact same model and manufacture of rifle or handgun and get different results. "
You said Different not similar

YOU CAN shoot the same ammo in two different rifles that are exactly the same and get different velocities. Most Productions guns are generically headspace so the .02-.04 of headspace can cause different velocities. Differences in the Barrels can cause different velocities.

 

[Flashover16]

It depends upon a set of variables. A 9mm round through a handgun with a 3' barrel vs. the same round through a 16" rifle barrel. One can be easily stopped by a level two vest. The other can easily go through a level 3 vest.

The velocity achieved with the additional 13" of barrel length adds up. This is why a 9mm round through a revolver is such a bad idea. The gap between the cylinder and the barrel robs significantly from the rounds total performance.

The manufacturer can publish data on a round. They rarely let you know what the variables they used are. Bolt action, barrel length, even if they use the same variable to bench test and verify load data.

YEP! additionally it is an average not every round that produces exactly that figure.
many test are from universal recievers and test barrels as well.
In the case of center fire ammo especially variables such as how accurate in the chrony, where is the chrony /lab located (25,000 feet on the side of a mountain), temperature at test time, powder type (and lot number) primer type (and lot number), type (exact) of projectile used, clean barrel/ dirty barrel, the variations are numerous that's why they vary a lot from manufacture to manufacture and what you will actually get IF you fire them over your chrony.
Kind of like why your Prius don't get the 78 miles per gallon that Toyota does when they test it.