I agree. Right now I'm trying to get some info on what the depth of the groves are i.e. shallow .008-.010 or deep .012-,016 and with there being an odd number, 5. of lands and groves one can't do the standard. I am thinking that since GPR have .012 deep groves this one may be the same.Since InvestArm made the standard GPRs for Lyman, I'm guessing that's pretty much what it is. I don't know if Lyman requested any spec changes or not.
I'm sure you've seen by now on here; go to Lyman website.I agree. Right now I'm trying to get some info on what the depth of the groves are i.e. shallow .008-.010 or deep .012-,016 and with there being an odd number, 5. of lands and groves one can't do the standard. I am thinking that since GPR have .012 deep groves this one may be the same.
I was looking for information on the original St. Louis Gemmer rifles recently with a Google search, and the first thing to pop up was this link to Muzzle-Loaders dot com: InvestArm Gemmer Hawken Rifle
This rifle looks like the Lyman Great Plains Rifle, but rebranded with a different name. I then looked up InvestArm, and found what appears to be the same rifle, but they call it their Hawken Muzzleloading Rifle Model 160
I can't say for sure, but it looks to me like Muzzle-Loaders dot com may have come up with the "Gemmer" moniker themselves. I didn't find anything about a Gemmer rifle on the InvestArms site. However, InvestArm did provide this table:
View attachment 62844
Strangely, they list this rifle in .45 caliber as well as .50 and .54. Muzzle Loaders only lists the .50 and .54, and as far as I know, the original GPR was not offered in .45. Neither Muzzle Loaders or InvestArms provide the rifling depth, but this table does at least show the number of grooves and rate of twist. I thought it odd that the .45 has twelve grooves! I think Pedersoli puts 12 grooves in some of their target pistols. Maybe its an Italian preference. Five grooves is also an unusual number in the muzzleloading world. I don't know how many grooves were in the original Great Plains Rifle.
So, Lyman has apparently moved forward in their alliance with Pedersoli in producing the Great Plains Signature rifles. The Model 160 from InvestArms looks like the old GPR as well as the Muzzle Loaders "Gemmer" rifle. We could assume they are both the same as the original GPR, but the potential buyer will probably have to go directly to the source to know for sure.
Incidentally, the InvestArm website also has a chart showing maximum loads, but I'm not going to paste it here. I think their chart shows the loads in grams rather than grains and I don't want to contribute to the confusion.
Anyway, that's about all I've found on it.
Hi.. Yeah I've seen all of that too. Personally I think they're all one and the same ML i.e. GPR and Gemmer. I'm waiting for Muzzle-Loader to call me tomorrow. I also sent Investarms an email also asking about the groove depth. I'm also thinking that if the GPR grooves are .016 then hopefully the Gemmers are too. .016 tgroove depth gives you mor eopinions for round ball 0490-.0495. IF however they come back and say that the grooves are shallow I MAY rethink about getting a .50 or .54 cal GPR kit
I have not. I've tinkered a bit with original and reproduction guns, but have not assembled one from a kit.Got another question. have you built an ML from a kit?
I agree. I think .016 is wrong. I thought I had read some where that the groove depth for a GPR was .012. I'll have to recheck.I have not. I've tinkered a bit with original and reproduction guns, but have not assembled one from a kit.
However, there are plenty of people on this forum who have, and some of those kit builders have done remarkable work. One gentleman in particular, @Loonhaven , has made some exceptionally fine firearms out of ordinary Lyman rifles and pistols, although I don't recall whether he started with kits or if he rebuilt factory finished guns. It would be worth your while to search for his posts on this forum.
I had not heard previously that groove depth was .016" on the GPR. That is really deep, even for a muzzleloader. The only barrels I know of with grooves that deep are the ones with round-bottom grooves from some of the custom barrel makers. Some shooters consider this to be "too much of a good thing," while others like them a lot. I have no personal experience with them. I had heard something more like .010" deep for the Lyman round-ball twists, and around .006"-.007" for the faster twists. That's unofficial, though. We will be interested in hearing what you find out in your correspondence.
I sent Investarm another email asking them for the measurements of the lands and grooves in their .50 cal Gemmer Hawken rifle. Some might think that I'm over thinking it and if I'm going to order one just order it. They might be right but I'm not going to be happy if the lands and grooves are shallow. If they're .010-.012 great.Investarms is very high quality stuff. How they might relate to Pedersoli or not is
a good question. I was told that Investarms is the brand for a firearms group.
My favorite shooter is an Investarms Hawken style carbine with leather straps.
There was a guy who was the"go to" for details with IFG on obscure questions
involving Italian brands and specs. Investarms has a website and they have
manuals that are general and combined. Whatever the depth of rifling, your
buying decision should center on quality and reviews from people who own
and shoot the rifle you are considering.
If you are shooting a patched round ball you don't need to concern yourself with lead fowling. For a round ball .008-.012 deep grooves are good. If they are too deep, your patch might not seal well and let the gas escape past the ball and ruin your accuracy.The rifling can be too deep and lead to lead fowling. Rifling depth does not determine
quality. It has to be sufficient to spin the projectile gradually but not strip the lead or
jacket. I would trust the manufacturer's engineers.