How accurate is factory data

There are those with way more knowledge than I on the subject, but I will give you my opinion.
The only factory data that I have found to be close to whats listed on the box is Barnes Vortex ammo. Why, because they are located here in Utah. All of the other ammunition companies are located in areas that are typically lower altitude than Utah which means they have different everyday test conditions. Not to mention most companies like to exaggerate the performance in order to sell more of it and we have no idea what barrel length they are using to reach the desired number. On average, I have found factory ammo to be between 150-300 fps slower than whats listed on the box.

With regards to terminal ballistics, In most cases a lighter bullet can be pushed faster than a heavy bullet thus generating more energy over shorter distances. Ftlbs of energy is a formula of mass and speed. So to answer your question, yes. A lighter bullet can be pushed fast enough to exceed the terminal performance of a heavier bullet. Providing the bullet construction can handle the higher speeds. In your case, the 130gr Nosler BT has a SD. of .242 and with that type of bullet construction, I would refrain from pushing it any faster than 3000-3100 FPS. However, the Accubond that you are using has a SD. of .261 in addition to the type of construction it has, I would have no problem pushing that bullet at the same speeds or higher, providing they could be reached safely.
One final thing to consider is BC. Typically heavier bullets with the same construction, will have a higher BC than the lighter bullets. This means they will retain the energy they produce for longer distances. So a 130 BT @ 3100fps may outperform a 140 AB @ 2900 out to 400 yards, but beyond that the AB starts to pull ahead with regards to terminal ballistics.

150 to 300 fps slower? Wow. That is quite a drop off. I would like a little more truth in advertising from ammo producers. By far and away the most common barrel length for an '06 is 22 inches. So I think a test barrel for 06 factory ammo should be 22 inches. I dont care what the small handful of guys with a 24 inch 06 might be able to get out of this ammo. We probably worry way too much about these things though. I seriously doubt an animal punched through both lungs is going to care whether it was a 130 grain bullet leaving the barrel at 3100 fps or a 140 grainer at 2950. I was pretty disappointed, however, to find out that some 130 grain .270 ammo I have from sellier and bellot only.had a mv of 2800 fps. Thats pretty weak sauce for a 130 grain .270 win. Thats what a 165 grain 06 with 35 more grains of mass should get. But then again maybe thats a common mv from a 130 grain .270 and sellier and bellot is just more honest.

CCG, I totally agree I would also love to see more truth to their advertising. If you look in most reloading manuals, I believe the barrel length typically used for an 06 is 24". I also agree that animals aren't going to be able to tell at a reasonable distance the difference between the AB and the BT. I would say it becomes a little more apparent at extreme long of close distances. Within 100-300 yards the terminal performance of either bullet will be more than adequate.

Cheddar, I have to say when it comes to the reloading data, I get pretty close to the advertised speeds on the Nosler site. However, I've learned what brass renders faster loads with the same powder charge so its getting easier. For instance, if you used their data + barrel length + primer but used Remington or Winchester brass you will be slower than they advertise. Do the same but use, Federal or Nosler brass to be very close. Use Lapua or Norma brass and you will be slightly over. Not true 100% of the time but enough that I use it as part of my data. Better brass = thicker brass = higher pressure with the same charge = higher velocities per same charge.

Bo0YaA said:

However, I've learned what brass renders faster loads with the same powder charge so its getting easier. For instance, if you used their data + barrel length + primer but used Remington or Winchester brass you will be slower than they advertise. Do the same but use, Federal or Nosler brass to be very close. Use Lapua or Norma brass and you will be slightly over. Not true 100% of the time but enough that I use it as part of my data. Better brass = thicker brass = higher pressure with the same charge = higher velocities per same charge.

Click to expand...

This is all basically true, but since CheddarNut is calling himself green I just wanted to add a little bit. Let's say you work up a load trying to imitate factory ammo or a published load. If your handloads are anywhere above a start charge, DON'T just switch out brass to try to bump up speed a little. Lower the charge weight to a start load before you switch anything.

As for the original post, high velocity may improve terminal performance but if it isn't accurate it won't do you any good. With many loads, greatest accuracy will be near max pressure but not right at it. This is usually because near-max loads make for very full cases. Full cases=consistency as the powder is unable to shift around inside. But with many of my rifles, If I do a full-house load trying to chase velocity, accuracy suffers. Whether it's due to harmonics, bullet jacket integrity or whatever else, I don't know. A few of my guns and loads have been exceptions to this rule though.

A lot of people like to attribute the velocity differences between what manufacturers publish on the box and what you may get in your rifle to dishonesty on the part of the manufacturer. While "sprucing up the numbers" may happen to some degree I don't believe it's quite this simplistic and there are differences that can cause the discrepancy.

All SAAMI specs have an allowable tolerance for what is considered "within spec". Ammunition manufacturers must pressure test their data for the worst case scenario. Their pressure testing equipment uses minimal spec chambers, barrels, throats, etc. On the minimal side of things (tighter chambers, shorter throats with less freebore, tighter barrels) you get higher pressures and with it, higher velocity. This ensures that their ammo is safe in any firearm a customer may use. The standard length for pressure test barrels for many years was 26". Many still use this length, although you will now often see pressure barrels with lengths of 24".

Typical factory made firearms have chambers, throats, and barrels that fluctuate from minimal to maximum specs as tooling wears out over time. I believe that most large manufacturers don't try for the minimal allowed specs as this could severely limit which factory ammo a firearm will accept. The looser tolerances mean lower pressure and velocity, not to mention the 2-4" shorter barrels on typical factory rifles. You'll lose 25-35 FPS per inch of barrel (depending on the cartridge). So a 4" difference could easily equate to 100 FPS loss by itself.

If you really want to know, buy a chronograph. You can get a decent unit for $100-$120. Or find a friend and borrow his. It's really the only way to know what velocity your rifle and ammo are producing.