NOT an expert.
However, there is a an OP book about Hacker Martin, well illustrated. Remember that he started building long before the modern longrifle scholarship started. So, you will find some eclectic styling choices mixed together on the same rifle, as he incorporated ideas and materials that he liked from different sources.
As well, I knew an old fellow who 'knew a bit' of Hacker Martin lore. He said that Martin and other ML gunsmiths of the time used old vintage parts: locks, trim, DST triggers that were readily available, taken off of broken or unusable guns. I specifically asked him about Martin's recycling another time, and replied [more or less] "that it didn't take a thing away from his reputation, as he did make his own locks, too. As well, there was no good reason back then, not to use perfectly good vintage parts in a new build."
The old boy was a late fifties and sixties regular at Friendship, and had built some few LR's himself. And, he'd sat around campfires down there swapping lore with the real oldtimers. And, he was always on the hunt for usable old parts, especially good English locks. A sound Manton flinter was cherished, I can tell you. So, while his statement is oral history regarding Martin in particular, even I am old enough to remember a M/L clan guy swapping in a vintage lock to replace some early poorly cast and finished replica lock.
As SDH and other will testify, we live in an abundance of resources for the average guy to assemble rifles from well-made quality mfg's that would have the old-timers pretty happy. Are the results equal to the supremo artistic technical tour-de-force efforts of a Bivins, Gusler, House,SDH, Mandarino and the other members of the Modern Pantheon? Of course not. But a person can buy a decent well-designed, sparking, tuned lock for a relative pittance today from someone like Chambers.
There just wasn't anything to compare to that for Hacker and his contemporaries, of which I'm aware. So, having a perfectly good lock to hand back then, was a real good step towards building a rifle. As most of you are prob'ly aware, parts re-usage is nothing new in the field of building fine guns. ;~`)
ENDORSE Jerry's advice: doublecheck ANY M/L -- old or new -- for loads in the bbl. Black powder WILL fire after a century of being tamped under newspaper wadding, topped with patched lead. A surprising number of those pieces were put away behind a barn door or in a pumphouse, stoked and ready to roar at the next chicken stealing varmint -- two or four legged. As my Black Swamp farming grandfather informed my father during the Depression, regarding tramps and Great-Grampa's habit of cracking a bullet past them on sight, "There's always room for one more behind the barn."
However, the family guns and other antiques, dating back from the post-Revolutionary migration to the Ohio River, and then North after the Civil War, and on thru the 20th Century were lost in the Flint,Mi/NW Ohio tornado of June 8, 1953. The twister got all four family farms and a cousin. I-75 and it's barrow pits run thru the land now.
However, an elderly neighbor in the small town in which I grew up, had a garage that literally was festooned with longrifles, hung from rafters,walls, and benches piled with pistols and other 'old stuff'. It was all just curio status goods back then. Never have lost my interest in those archaic longen-boomers, and their times. Wish the board members who pursue such items,"Happy Hunting
some useful sites:
* National Muzzle Loading Rifle Association -- www.NMLRA.org
* Coon 'N Crockett Muzzleloaders Club -- www.Coon-n-Crockett.org
* Armory Hill Living History Association -- www.armoryhill.com
* Kentucky Rifle Association -- www.kentuckyrifleassociation.org
* Hog Heaven Muzzleloaders -- www.hogheavenmuzzleloaders.com/index02.htm
* The Honourable Company of Horners -- www.hornguild.org
* `Kentucky Longrifle Virtual Museum` of original rifles and makers -- americanlongrifles.org/forum/index.php?PHPSESSID=d85qehjtvk2auti5n77o
* Cook Inlet Mountaineers ,muzzleloader/black powder shooting club -- www.cookinletmountaineers.org/home.html