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"Micro-Groove" muzzle loader?

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Old Hawkeye

50 Cal.
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Just acquired an unfired Investarm built (1979) 50 cal. Hawken style rifle imported by Armsport. Most of my ML shooting has been with shotguns & smoothies, so I'm not all that knowledgeable about the different kinds & types of ML rifling. Twist is 1:48. This rifle has a barrel unlike any I've ever seen on a ML. It looks similar to Marlin's "Micro-Groove" rifling, very, very shallow with 12, yes TWELVE lands. It also seems to have a "tight" bore as well. I tried a PA conical & the narrower skirt end could barely be started in the muzzle & a .501" diameter conical with a flat base wouldn't even start by hand. Does anybody have a rifle with this type barrel &, if so, what is your preferred bullet? The rifling is so shallow that I doubt a patched ball would even engage the lands, but I'm not a PRB shooter so don't know for sure. They lands are so shallow that looking down the bore near the muzzle, at first glance, you think it is a smoothie. Only when you drop a bore light in the barrel do they become clear. The PA conical is so tight to start with I am hesitant to push it down the barrel for fear it will get stuck. Was going to get some TC Maxi's to try, but thought I'd ask here for advice & insight first. Thanks in advance!!
 
That is intriguing.
A sizer of some kind maybe needed.
I guess once a lubricated bullet is started it is then sized and should ram home.
Personally I would sit the bullet on a lubed wad to soften previous fouling on the way down and help keep it soft just after firing.
 
A couple thoughts on your post. I have had experience with the Marlin micro-grooving. My results cannot be expressed on a family friendly forum, especially since it was a no-no rifle. Yes, I have had experience with a 12 groove ml rifle. It was (reportedly) a pick-up from the Battle of Gettysburg. We would call it a rifled musket. It was .72 caliber and had twelve round lands and tops in the rifling. I forget the twist but it handled a prb of .715" quite well. Having a very long Nock type breech my minimum safe charge was 120 gr. FFg bp. It kicked like a Yankee mule but was accurate. Probably no help with your situation, just sharing.
 
The early CVA imports had a very shallow (.002) deep groove 1/48 rifling and they shot round ball resonably. I refreshed several to .006 deep groves and they shot better. The micro grooves should shoot mini's well but they will need to be sized
 
Although not as shallow as your description, some of the first year TC Hawkens came with 12 lands and grooves. I'm guessing they changed to 8 because it would be less expensive and same time producing.
 

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Although not as shallow as your description, some of the first year TC Hawkens came with 12 lands and grooves. I'm guessing they changed to 8 because it would be less expensive and same time producing.
What projectiles did you shoot in it?? Was there anything it liked or disliked? Glad to see other barrels like it are out there. Wonder if TC used Investarm barrels early on in their ML production?
 
Quite frankly it's a recent purchase and have yet to shoot it. All though there is a lot of speculation of who made Some of the TC barrels I've never heard Investarms mentioned. You mentioned yours Investarm was made in 1979, the TC Hawken was first built in 1970.
 
I don’t think TC would have used a Investarms/ Lyman barrel on their guns..
Some Folks report early TC guns as having Sharon Barrels on them but I don’t recall any having Investarms barrels.... not from the factory anyway.
It seems that I have put Investarms barrels on a TC as well as TC barrels on Investarms stocks without much modification ... If memory serves me correctly only a small modification to the hooked breech on a couple were needed.

I owned a couple of Investarms muzzleloaders over the years but don’t recall how many lands the barrel had.
They were one in 48” twist and shot ok with lower powder charges. (60-70 grns fffg)

The problem I had with the shallow rifling was if you didn’t swab , after 2 or 3 shots accuracy fell off.
I found this to be consistent when shooting patched ball or bullet.

Especially when shooting bullets....
 
Every rifled musket I have seen has shallow rifling, most shot minies reasonably to exceedingly well, depending on the size of the minie ball and rate of twist.

The 1-48 twist shallow rifling seem to shoot heavier minies better, the slower shallow rifling work well with prb.

I would try Lee's REAL bullets, using an over powder wad of some sort. They usually require some force to start the top ring in the bore and use a range rod to drive it home, but shoot well.

Another option is to get a sizer and size your conical down to fit, but they MUST be a tight fit.
 
Actually, I used an 8" section off a .444 Marlin Microgroove rifle barrel (left over from shortening a 24" bbl) to make my first muzzleloader (a handgun) in the mid-60's.

It shot pretty good using PRB's correctly sized for the .444's bore( .429").
 
Round about 1975 my first rifle was bought out of a drugstore on the east side of Houston, a .45 "Kentucky" with narrow land rifling with geometry that looked about like a Remington .22 near as anything else. It shot great though until I wore it out.
 
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