There is some misinformation here.
First. The early rifles were not as massive as the later rifles. I have 2 Don King Flint Hawkens that he patterned after an original FS Hawken he had access to in the late 60s. Its as deep though the forend in front of of the lock with 1’” barrel as my 1 1/4” barreled heavy match rifle is.
The ETC rifle in Helena which likely dates to the mid 1830s at the front of the trigger guard bow in 1.854” including the barrel. The barrel is about 1 1/32 at the breech with a rapid taper to somewhere past the rear sight and a slight flair at the muzzle and its 39 7/8” and about 50 caliber. Compared to the much, later 20 years or so, club like Bridger rifle its pretty dainty. And as near as can be determined its a real “Mountain Mad” rifle and surely spent a season with a “brigade”. Nor does this rifle or the Petersen Rifle have a long tang/ long trigger bar and while they have hooked breeches neither has a “patent” breech. The ETC has a nipple lug that was part of the forging when the barrel was welded. The Petersen has a nipple seat that is apparently threaded into the side of the barrel and/or brazed on as it shows the line of brass at the joint. The forged nipple seat appears to be true of the fullstock that I think Don King used for a pattern. This rifle in pictured in Baird’s book on page 2 and 27.
Second. No the full stocked Mountain Rifles were not that large in the bore. Most Mountain Rifles were about 32 to the pound since this was a common trade ball size for the trade gun and thus even if you lost the mould you could get balls that fit or close enough. AND 54 was the most economical caliber suitable for the West. The 50 will work but its a little light. But calibers significantly over 54 use a lot more lead. 62 is about 19 to the pound. And the weight really goes up from there. A .67 caliber rifle is 16 to the pound.. This means that while its pretty easy to pack around 50 rounds of ammo for a 54, a pound and a half or so. 50 rounds of 19 to the pound is crowding 2 1/2 pounds. I have a rifle that used a one ounce ball and a decent supply of balls in the pouch is gonna be heavy. There is a large fullstock S. Hawken in Cody that is just a long, heavy, large bore “Kentucky” and yes it was stocked by the same man that stocked the FS mountain rifle in that was in the same display at the time we took them out and examined them at the Museum.
The rifle as DRAWN in the DGW looks like what I would expect an early Hawken fullstock Mountain Rifle to look like.
But it is DRAWN to have the long tang and a screw into the rear of trigger bar which is how the Atchison J&S Hawken rifle dated 1836 is made, it also has a hooked patent breech. I would not expect the 36 caliber rifle the drawing seems to be based on to have the long tang and trigger bar. And it, IMO would be a local trade or “squirrel” rifle. But this is all supposition. And the 36 caliber rifle probably is pretty small. But in drawing the rifle for the plan the artist and advisor if he had one may have enlarged it somewhat.
The gist of it is that if people are used to looking at a late Hawken like the Carson, the Bridger or even the Modena, the early rifles are generally going to be smaller and more like a Kentucky. But the rough use they were exposed to caused the rifles to grow in places and get pretty massive. Horses are notoriously hard on firearms. 1000 miles out out a broken rifle is an “inconvenience”. Also the use of steel barrels may have been part of it since steel of unknown alloy can be weaker than a good iron barrel when subjected to pressure and shock. So the barrels seem to have gotten heavier. And by 1820 or so the powder was a lot better than it generally was in 1770.
