I have a .338-06. The rifle had never achieved the stated reloading manual maximum velocities with H414, best powder, or R15 or N140/150 powders. For 210 and 200 grain heads, the MV is a good 90+ god short of maax and the pressure signs, H414, appear well before max charge. I find Quickload more accurate predictor in my case.

What do people think - are there fast and slow barrels / barrel makers? The .338-06 wears a Oac or barrel.

Despite a defunct company named A-Square producing both .338-06 rifles and ammo for a while in the 1990s, the .338-06 is a wildcat. Or at least it has reverted to being a wildcat, since the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) does not list it.

As a result there are no standard chamber and throat dimensions--which can make a considerable difference in handload velocities and "pressure signs." You also don't mention your rifle's barrel length, which also makes a difference.

All of this also why published loading data on some other wildcats will vary considerably, both from other sources and results in specific rifles.

Weatherby made a few rifles in 338-06 as well as factory ammo. Looked into getting one but was never able to find either. I don't need a 338-06 now that I've got a CZ 550 in 9.3x62.

Data for wildcats is all over the place because of lack of standards and high pressure handloads.

The rifle has a Pac-nor 24.5 inch long barrel. It was chambered / reamed to the then A-Square SAAMI specifications as per A-Square published dimensions for cartridge.

I OAL my cartridges as per Barnes and Nosler reloading data books.

All good points though to keep in mind. I noticed before bullet manufactures give higher velocities than the powder makers. Probably realism tinged with product liability.

I have one that is the opposite. It is a Kimber with a 24in Brux barrel in 6.5 Creedmoor. It exceeds loading manual max velocities with mid range powder charges and Barnes Vor-TX ammo chronos over my Oehler 100fps faster than what is listed on the box.

If the barrel bore is slightly undersized or over sized it can for sure have an affect on MV.

We must live with the fact that different barrels give different pressure and velocity responses to the "same" loads.

Even industrial test barrels made to the same spec will give different responses. That's why the industry uses the elaborate "Proof Ammo" procedure. The assessed pressure and velocity of a given lot of proof ammo reflects the "average" response obtained when fired in different test barrels made to the same specification.

Your mileage may differ.

Some years ago when 338-06 was even more of an oddball, I did a bunch of load development with various powders and 225gr Hornady sp.It's my feeling 225gr in a 338 caliber is the 180gr of the 30 caliber. I found a magazine article using a wired barrel that limited out at 2650fps. So that became my bench mark. Not the 2700fps frequently mentioned. I was unable to get the 2650 with Win760. I found that Big Game worked for me and my rifle. Maybe try that. I got my first moose and elk with that rifle and load.

But I know there are slow barrels, I have one, a 6.5-06 . It maxs out at 2850 with a 140. I'm pushing the envelope at that. That's a ways from a more accepted 3000 .

Thank You all for your replies.

Now the how long piece of string / 64 K question:

Who in the experience of those with custom barrels in their rifles makes a consistent 'fast barrel'?

Or who cuts the closest tolerance barrel / chamber?