And it would be nice if Lyman re-tested 40S&W loads using more typical .400' groove diameter test barrel.
.401" shown on page 362 and why some of their start charges are Hodgdon's max charges -
https://www.thehighroad.org/index.php?threads/40-s-w-load.852049/#post-11145208
Here's Lyman #49 40S&W load data which used .401" groove diameter test barrel.
- 180 gr Jacketed HP W231 OAL 1.115" Start 5.0 gr (927 fps) 20,400 CUP - Max 5.6 gr (1015 fps) 22,800 CUP
And here's Hodgdon load data.
- 180 gr HDY XTP W231 OAL 1.125" Start 4.1 gr (797 fps) 23,800 PSI - Max 5.0 gr (947 fps) 32,900 PSI
bds, you’ve made a spurious correlation. And you've done so because of an assumption. It looks like you're assuming that Hodgdon used a 0.400" groove diameter barrel. Where does it indicate barrel groove diameter on their website? So, bds, what is Hodgdon's 40 S&W barrel groove diameter? Please point me to that information. Maybe it's the same.
The problem is that your claim cannot be supported. There are so many things wrong with your claim that it is . . . well, I don't know how to address this except to point out the facts.
1) SAAMI specs for a 40S&W barrel groove diameter are 0.4005”. Technically, a 0.400(0) barrel would be undersized. 0.401” is within spec since tolerances are + 0.004” meaning anything between 0.4005” to 0.4045” is within SAAMI specs.
There’s squat data showing pressure (or powder charge weight) differences in handgun rounds where bullets are undersized or oversized.
2) Your claim for the 180 grain bullet is flawed. While the 231 results (5.6 gr v 5.0 gr) are consistent with your claim, it is just the opposite for Universal (5.5 gr v 5.8 gr).
All people have to do is look at the data for Universal and they’ll see that you’re wrong.
Plus, the manuals are using
two different bullets, and at different overall lengths. Lyman uses a Sierra 180 grain bullet, while Hodgdon uses a Hornady XTP bullet. Don’t assume they will produce the exact same results.
Lyman is using, for many of their 40 S&W loads, the old fashioned CUP measurements, and you can’t easily translate that into PSI, so the actually max pressures are not likely to be the same.
3) Let’s compare data with the same bullet, 135 grain Nosler JHP. Here, Lyman has lower maximum powder charges with 231 (6.7 gr) and HS-6 (9.0 gr). Hodgdon’s max loads are 7.0 gr and 10.2 gr, respectively. But again, they are loaded to different lengths. The Lyman loads to 1.085 and Hodgdon loads to 1.125. Thus one would expect that Hodgdon could add more powder before reaching max pressure limits, and the results are consistent with that.
4) You’re also probably not taking into account that the powders are from different lot numbers.
5) Lyman uses Winchester brass, and Hodgdon uses Hornady brass. But at least they are using the same WSP primer. Have you taken different brass into account?
When taking all this stuff into account, it’s difficult to imagine how you’re drawing your conclusion based on one powder and different bullets. Seriously.
No two manuals will agree. That’s reality. But to claim there is a problem with using a barrel that is 0.001” different is probably not valid. Data to support that requires that it’s done in the same lab by the same people with the same components, same, same, same . . . etc., the only difference being barrel groove/bore diameter. And, as pointed out above, your claim is contradicted when looking at other powders and bullets.
Feel free to contact Lyman and tell them about their oversize barrel. And you might want to tell them that their 38 Special and 357 Magnum test barrels are the wrong size, too - at least according to you.