Not trying to be argumentative or anything.
But the OP was kinda general on the issue, and I tried to respond based on that.
As to calculators. Online or hand held or computer software. Many will round up or down to a nearest whole number. Depending on the person that wrote the code. So 447.7 or 448 is kind of mute.
The first OP opined a 140 gr RB so that is what I went with, regardless of what the original bullet may have been.
Also apparently nobody has any chronographed results of some actual loads fired from the gun at 40, 50, 60 gr with a 140 gr rb or a 200 -220 gr conical
so we could use real math for a real calculation.
also nobody that I know of has any of the powder that existed back then.
One does not now positively how it performed compared to todays refinements in BP making.
So on that point it would be pure speculation how powerful it was back then. more or less than todays??
While the Walker was designed as a horsepistol to be carried in saddle mounted holsters, there is no doubt it was also worn on the hip.
But the main point is terminology.
Let's just say it was a HANDGUN, as compared to a shoulder fired weapon or a mortar or cannon regardless of how it was holstered.
Then we have the word MILITARY. Most would conceive that to be the uniformed armed forces of the United States (or another country) .
The Texas Rangers were not that.(But see explanatory notes below-- that explains this)
Also in dealing with the performance formula. Note, any change in the velocity or weight, the change becomes exponential not linear.
But without a chronograph of how fast that heavier bullet is traveling, it's all conjecture and supposition.
A 38 or 357 bullet that weighs less, but is traveling perhaps half again as fast
will produce a much higher # per ft .
So one would want to keep either the velocity or the projectile as a constant.
But even that would not be correct.
So using the Walker as the basis
220 gr conical at 1200fps would be your base line
Is there any other side arm / handgun that offers a 220 gr conical that will
also produce 1200fps ? if not then the walker would be king.
But we do have modern guns that have a heavier bullet and can be loaded to reach or exceed that velocity.
But those are not commonly ISSUED to the military
So the Walker would remain king, except for the fact he used military
and the Rangers were not technically military.
If he had opened that criteria up a bit and said sidearm /hand gun ever issued to a USA military or police force then all other things being equal.
Then yes quite possibly it would remain the king.
But we can only guess at what the original load was and it's performance.
did they really use 220 gr conicals and was the velocity 1200fps unfortunately we just don't know for sure.
Colt did recommend only loading 50 grains of powder though.
My apologies for my brevity here
-----------------------
A few other notes should be included I guess.
It wasn't really the Texas Rangers. There's a lot of back and forth and new companies formed and disbanded at that time.
He had moved on to the Texas mounted vlounteers. and during that time period, he had offered his services to the US Army.
He was commissioned a Capt in the army. president polk ordered the treasury dept to purchase the Walker Colt, from Sam Colt, for Col. Walkers unit ( a volunteer company of scouts). So even though Walker was commissioned in the US Army, his unit was all volunteers.
But the Federal government equipped them.
Walker named his unit The Texas Mounted Rangers. But he was back and forth with the Feds. So much it becomes confusing during this time period.so lets see if we can basically chronicalize some events
----------------------------------------------
4/21/1846 authorized to form a volunteer regiment of scouts for Taylors army (texas not feds) = Texas Mounted Rangers
a volunteer unit attached to the US Army
june24 1846 was appointed brevet lt col with the 1st regiment TEXAS mounted riflemen but he delayed that appointment until his
previous enlistment expired in July.
At same time he accepted a commission as a Capt. in the regular Army with the First United States Mounted Riflemen so he was serving in dual capacity for a short time. but his federal service with the Texas Mounted Riflemen ended in a couple months anyway.
So now oct 1846 he is a Capt with the First United States Mounted Riflemen -------are you following this conglomeration?
It is now January 1847, he is in Washington, meets Sam Colt, they design the Walker colt.
Walker sees President Polk who orders the treasury to buy 1,000 of the revolvers for Walker to issue to his troops. So technically it is a United States Military issue.
While the guns are being made, Walker raised his company: Company C, First U.S. Mounted Rifles at Newport Barracks. april-may 1847
Tecnically they were USA Army, but the men called themselves Texas Rangers..............so now we must alter all the very above.
Technically the Walker Colt was issued to a Military unit of volunteers.
From approx june 1847 til oct 1847 his unit was in several campaign in Texas, and down to Vera Cruz, fighting Mexican Army and others.
BUT he did not yet posses the Walker Colt.
The Walker Colt was finally delivered to him . In October 1847, he Received his as personal gifts. but the rest were not delivered yet.
The remainder were delivered sometime after his death on October 9, 1847.
The Walkers were only made one year 1847. Thereafter they were redesigned slightly smaller and became the 1st, 2nd and 3rd model Dragoon.
This design was to corrct some of the shortcomings of the Walker.
maximum charge was reduced to 50 gr, to avoid ruptured cylinders ( even though they may of ruptured because bullets were inserted wrong).
shortened the barrel for better balance and to lighten it somewhat
improved the loading lever catch to prevent it's inadvertent dropping while firing. Which could be very disconcerting to the shooter especially on horseback.