58 caliber hunting loads???

I had a 58 caliber underhammer follow me home this evening.

I measure the bore at .570 and the twist at 1 in 80".

I'm wondering what charges this rifle will require for good roundball accuracy.

Also pondering what charges it may require to shoot flat enough for deer out to 100 yards, without any "hold over".

First 58 caliber that I've owned and slowest twist in my stable, hence, the questions.

Would like to hear back from any 58 caliber shooters/ hunters.

Many thanks, Skychief.

With that slower twist and your desire for no hold-over at 100 yards, you're likely to be in the 100-120 grain (2f) realm. Depending on barrel length to a degree of course. It's likely your slow twist is going to want at least 100-110 grains of 2f for accuracy.

Try sighting in at 75 yards and watch your drop at 100 yards. Down at 80 grains of 2f in my light 28" 1:48 barreled Investarms 58, a 75 yard sight in results in being about 8" low at 100 while close to 2" high at 50. Pretty loopy. No question of "killing power" on deer within that range at 80 grains and probably less. But the trajectory might or might not be a bugaboo for you.

At the other extreme my 36" barreled GRRW Hawken with its slow twist (don't recall the zact number) demands somewhere around at least 110-120 grains to start seeing its stellar accuracy. Sighted in with 120 grains at 75 yards, it's barely an inch high at 50 and 4-5" low at 100. It's favorite load is in fact 140 grains of 2f. That isn't a whole lot flatter than 120 at 100 yards and not much of a recoil beast due to the weight of the rifle (12+ pounds). I shoot 120 in it most of the time, though I'd certainly bump it if trying to shoot further than 100. Might even sight it in right on at 100 in that case, depending what I learned about the resulting trajectory closer with that.

Good score. The 58's are real effective and real addictive!

Barrel 42" 1-66 twist round radius rifled flint.
thick mink oiled patch. poa @ 85 yards
105 gr. 2F Goex
or 90 gr. 2F Swiss
accurate... repeatable....1.5" groups.

Enjoy finding your happy load.

My experience with underhammer rifles is confined to only one that I've owned for well over half a century. Since I don't know how yours is built all I can advise are the results of my own shooting an underhammer. This barrel is "gain twist" and a .45. The normal load has been 60 grains of 3F and has taken deer and bobcats. What I noticed is that when going very much over this load, (an accuracy load) the hammer would start blowing back enough to bring it to half cock. This started at around 70 grains. With the long sleeves of a hunting shirt or coat, I never burned my arm. Different story come summer. I'd say just start on looking for accuracy and see how the rifle reacts.

My .58 has a .570 bore and is marked as 1:75 ROT. It works most consistently with 60 grains FFFg. I know the larger bores are supposed to like FFg, etc, etc but this one has a clear preference. My 50 yard groups are about 4" high, 75 yards are about dead-on and 100 yards are 4" low. When deer hunting I usually know the range from my stand or use a rangefinder. What I do is use a 6 O'clock on 50 yard animals, point-of-impact hold at 75 yard animals and level on the back of a whitetail or hog at 100 yards. The velocity is right in the 1200 fps range. While I understand if you are trying to get "more" out of a load, my point is not to be discouraged in the event your rifle tells you it wants a load in the 60-70 grain range. It is still do-able.

Thanks for all the replies!!

I found time to shoot the rifle only 20 shots or so.

Tried just 70 grains of 2f with a .570 ball. It was a tight fit with pretty thin patching.

At 35 yards it made a ragged hole with 5 shots. Yep, not much of a test, but shows potential.

I rang my 60 yard gong a few times for good measure.

I liked the throaty roar she made with even this modest load. :thumbsup:

Even if not real fast, I'm convinced this load would spell trouble for a whitetail within a hundred yards. That heavy ball would get a lot of work done!

Looking forward to shooting it more once the weather clears.

Would appreciate any more commentary about these 58's.

Best regards, Skychief

Good score. I'm wondering about that tight bore. In that era GRRW was making and selling barrels, and they were "choked," tighter at the muzzle than at the breech.

I have a GRRW 58 cal, and it's at its best with a .562 ball. Still tight at the muzzle with ticking patches, but the rod virtually falls to the breech, it gets so much easier after that.

Same is true with the .570's, once you get a little past the muzzle using a thin patch.

Your description certainly rings a GRRW bell, in any case. And that's a good thing. Far and away the most accurate muzzleloader I own.

Forgot to add this, if in fact your barrel is a choked GRRW: Seems like the faster you go, the better the accuracy. If you're getting fine accuracy at lower vels but want to flatten the trajectory for any reason, don't hesitate to start pouring the powder to it. My GRRW is at its best with 140 grains of Goex 2f, but I generally shoot it at 120 grains. Trajectory is almost as flat, and the group is only opening up around half an inch at 100 yards.

How tight are my groups? When old eyes cooperate I'm getting 2-2.5" at 100 with 140 grains and 2.5-3" with 120 grains.

Ditto for me Brown Bear. My Bobby Hoyt re-bored Browning Mountain Rifle to .58 shoots quite flat. with 120 grains of 2f in the 1:66 twist 30" barrel. It is not likely I will ever shoot at game beyond 75 yards where I hunt due to the thickness of the cover and my ageing eyes.

BrownBear and fyrstick, thanks for the replies!

The bore doesn't feel choked to me BrownBear. If I had to guess, I would say the barrel may well be of Numrich manufacture.

I've been told here that the outfit in Maine that built the gun, bought out Numrich Arms, builder of the "Hopkins and Allen" underhammers.

Sure don't know for sure who made the barrel, all the same.

Best regards, Skychief

Forgot to mention that I've not had the forestock off the gun yet. If I find a makers stamp under it, I will pass it along.

Did GRRW always stamp their barrels? :hmm:

Just FYI, 80 grains of 2Fg right at 3 drams, 95 is 3.5 drams, and 110 grains is just about 4 drams of powder.

As the sage advice from BrownBear suggests, try above 80 grains. That slow twist will not fail you. :wink:

I'd try 80/90/100/110 and see if you have any grouping differences with those four loads at 75 yards. Pick the most accurate, and then try a +/- increase of 5, so say if you found that 100 grains of 2Fg worked very well at 75 yards, try 95 and 105. OF course, the higher you go, the more it will smack your shoulder. :grin:

Then with your new pet load, try a 100 yard target and see the impact difference. Ideally (imho) you want to see it "on" at 100 or perhaps an inch low, and dead on at 75...with it being perhaps 2" high or less at 50. That way, if you see the animal, as you say you won't need any "hold over", you just light up the sights and let her go!

Then reload, wait about 15 minutes, and go and collect your [deer, elk, moose] probably pretty darn close to where it was when you fired. A 279 grain .570 ball with a 90 grain load or higher will probably be doing at least 1400 fps.., and that's more than 1200 ftlbs. launched at the deer.

LD

I like your thinking LD :hmm: .

I will be playing with it more and will test some other charges and check POI's at those ranges.

Right now, I'm wrestling with options for new sights for it.

Thanks for your thoughts, Skychief

In my "long gone" .58, I cast .562" ball from a Lyman mold; that size worked really well.

Thanks hanshi. I've been doing a bit of arithmetic and will have a .562 mould soon.

Appreciate it bud, Skychief

Skychief said:

I've been told here that the outfit in Maine that built the gun, bought out Numrich Arms, builder of the "Hopkins and Allen" underhammers.

Click to expand...

That and the lack of choke tells me you're probably on the money. Dunno enough about their barrels to guess if they're usually a little on the tight side.

Another "dunno," but at one time LEE made a .562 mold. Got one as a "cheap" trial of .562 for my GRRW and never felt the need to upgrade to steel.

Thanks BrownBear. I can buy a new Lee mould for about $25 locally. Hard to pass up. I have both Lyman and Lee moulds and get along fine with either. I like the spurs left by the Lee better in fact.

Take care, Skychief

I have a 1-70 twist and shoot 120 GR KIK 2F with handcast 570" RB and pillow tick patching. I am sighted dead on at 100 Yds and anything deer size fro 0-125 is dead hold on. Very accurate. When my eyes were better I shot a 5/8" 3 shot group at 100 Yds off a bench.

Thanks Idaho. Great information. That rifle would shoot!

Best regards, Skychief. :hatsoff: