Since the original post didn't mention whether the gun was a standard "off the shelf" make, or a specialized, custom built gun, I guess this leaves it up in the air a little.
Basing the query on a standard everyday rifle (which I think most would've assumed), on which my opinion is based, it isn't a safe load by acceptable safe standards.
Can it be done in a custom gun ?....I'm sure,....but my question to that would be "not if it could be done", but "why" ? Especially when safety "could" be an issue, and there's several other calibers that can do it safely. 3800fps using a 40gr. bullet would be of no benefit.
Ole,
Not to flame you or nothing, but based on what you mentioned regarding the "McPherson article", he's full of hot air.....period.
Here's some numbers straight off my Sierra software;
40gr bullet...
3800fps muzzle velocity....1282fpe.
300yds......351fpe.....-17.12" bullet drop.
55gr bullet...
3600 muzzle velocity....1582fpe.
300yds.....690fpe.....-16.05" bullet drop.
Almost double the energy at 300yds, 200fps. slower at the muzzle, and a little more than 1" less drop at 300yds.
Ballistically, the 40gr bullet would have to be pushed between 4100-4200fps. to match the 55gr. bullet's muzzle energy at 3600fps. That being said, the 40gr. bullet's downrange 300yd. energy, even at 4200fps., would still be only 444fpe., in comparison to 690fpe. for the 55 gr. bullet at 3600fps.
Since it's weight is lighter, even at a higher velocity, it sheds it's speed faster due to it's lighter weight based on wind resistance against that lighter weight. The reason for it's greater bullet drop.
Although it's lighter weight is a "pro" regarding initial muzzle velocity in certain cases, it's a "con" to it's downrange energy & ballistics in most instances.
For both the 55gr. bullet, and the 40 gr. bullet (at 3800fps) to have the same energy at the "mentioned" 300yds, the 55gr. bullet would only need a muzzle velocity of 2900-3000 fps.
In comparison to the 40gr's bullet having a muzzle energy of 1282fpe. at 3800fps, the 55gr. bullet would only have a muzzle energy of 1026-1095 at that lesser speed, but it would carry that energy much farther than the 40gr. bullet due to it's heavier weight....i.e., more momentum.
Somewhere at about 215yds., energy wise, those two bullets, at those grossly different velocities (40gr/3800 & 55gr. 2900) would change hands and the 55gr. carries it's energy further, although at it's much lower velocity the drop would be 25", or so.
Putting them in the 40gr/3800fps., and the 55gr/3600fps. perspective, approximating what you mentioned, the 55gr. bullet stomps all over the 40gr. bullet from the muzzle on out. No comparsion.....
No offense, but I'd rather "err" on the side of published ballistic charts, than Mr. McPherson's findings.
Like I said.....for the two bullet weights to even be remotely competitive, the 40gr. bullet would have to be doing at least 4100-4200 fps, which out of the Swift, it can be.
Now, using Sierra's maximum listed velocities for strictly the .223, comparing the 40 & 55 gr. bullets, the 40gr. at 3500fps. and the 55gr. at 3200fps.
40gr......1088fpe muzzle./ -20.14" @ 300yds + 289fpe.
55gr......1250fpe muzzle./ -20.52" @ 300yds + 526fpe.
Energy is almost double, and you'll never see a difference in drop. No matter how hard you "hotrod" the 40gr. in the .223, or even remotely how unbelievably it can be pushed, the 55gr. bullet can best it at several hundred feet per second less.
To make the two bullets even remotely competitive at all, the question would have to be " Is a 223 Rem/40Vmax/4000+ fps possible ??"
The simple answer is definitely not......
Off topic........is it me, or does anyone think (based on their photos) that Rem. Shooter & GuNut are huntin' buddies ? LOL
Take care,
Bob