Where to start with a 45cal 1-18twist load

[bob243]

This is something pretty new to me, but I am putting together an underhammer with a GM 45cal 1-18twist barrel. My intent is for shooting at a 300yard target.

Can someone offer me some insight on where to start with a decent load for this? I heard mentioned that a whitworth bullet is pretty popular with this, but when looking there is a few, and I am not sure which one. Also is there a place I can get a bag of these bullets to try out before investing in a mold?

 

[BrownBear]

Haven't done it with a muzzleloader, but coincidentally my 45-70 has a 1:18" twist. Accurate as can be with 60 grains of 3f and 500 grain bullet. Recoil is mild, and without the confines of a brass case, I'm betting you could bump the charge quite a bit, especially with 2f.

 

[jmforge]

I know a guy who shoots a Rigby replica with 540 gr slugs and 120 grns of 1.5 F ofr Ff for target loads, but he uses a false muzzle and has to start the bullet with a leather mallet and that is after "engraving" the rifling into the bullet using a piece of barrel as a sizer.

 

[Idaho Ron]

I have a Lyman "whitworth" mould. My gun is a 1-18 twist GM. It shoots the whitworth bullet good. I use Lars White label lube it is a BPCR lube, and it works very well. I don't use these bullets much because my Lyman peep can not get to 300 yards with this bullet.
I do use a Paper patched Lee 459-405-HB. I size them to .451, then I patch them. I size them again to .451 and they are ready to shoot. I use 80 gr of Pyrodex P for that load.
Here is a couple of groups I shot to show the difference between a paper patched bullet and a naked one. I plan on using this rifle this year for my deer hunt. Ron

 

[ResearchPress]

...but he uses a false muzzle and has to start the bullet with a leather mallet

Sounds like the bullet is way too big. Bullets loaded into British match rifles are usually a much looser fit and certainly do not require a mallet to start them. Just under bore size will be adequate with little more than the weight of the ramrod to seat them.

Charge seems very high too, but I guess if thats where he finds best accuracy and is content with the recoil then it's his choice. I only up my 90 grain load of 2F to 105 grains when I get back to 1200 yards.

David

 

[jmforge]

He told me that he uses lighter bullets for hunting, maybe in the 350-375 grain range with a similar powder charge that don't require all of the hassle, but apparently, the "troublesome" target load is a genuine ultra long range tack driver. I guess you go with what works. He used to build muzzle loaders before he switched over to knives full time, but he still uses this Rigby copy that he picked up in the 80's. Must be an exceptional rifle.

 

[ResearchPress]

This is something pretty new to me, but I am putting together an underhammer with a GM 45cal 1-18twist barrel. My intent is for shooting at a 300yard target.

Try 85 grains of Swiss 2F with a 530-560 grain bullet. I use paper patched bullets.

You'll want a bullet just under bore size. Note that many of the bullets for the black powder cartridge rifles are groove diameter (eg .457) and may need sizing down of you choose one of these.

You'll also need to source platinum lined nipple if you don't have one. Others can erode quickly leading to loss of pressure and accuracy.

Contact Joe Hepsworth at http://www.jcunard.com/.

David

 

[ResearchPress]

There's no reasn why match rifles can't take loads of 120 grains, but there's a trade off with recoil and accuracy. If your friend (as he obvioulsy is) is content with the recoil then fine. I'll stick with my 90 grain load which still wins me matches at 1000 yards.

David

 

[arquebus]

David has given you some excellent advice. I used to shoot a Navy Arms 'Rigby' .451 with a 1:21" twist, but all my shooting was at 100 meters. Even so, the method is still the same. I used a Lyman #457121PH bullet mold that cast a 475gn bullet, with 65gns of Goex 2Fg & a felt wad between powder & bullet. I sized the bullets to .451" using a Lee bullet sizing die which made the bullets a hair under the bore size....the bullet would glide down the length of the barrel with just a little help from the loading rod.

 

[bob243]

Ok, this is starting to make sense to me..
What do I need to get for a paper patch? Does it basically work the same as PRB?

 

[paulvallandigham]

Basically, most people buy paper that is .001" thick, like Onionskin, cigarette papers, etc. You can find the paper sold by some of the suppliers. Dixie has carried the product for years. YOu want a paper that holds together when wet, as MOST shooters wrap wet paper around the bullets to get a tight fit, and then let the paper dry before going to the range.

 

[paulab]

bob----- Buffalo Arms sells bullets, paper, p.p. template etc. Watch out though, every time I look through his catalog I always seem to find something I can't do without. My gibbs likes .450 diameter bullets cast at 24:1 and 90 grains of swiss 1 1/2 powder. Don't forget, you'll need to get a quality rear vernier sight and globe front sight. Using the standard barrel sights will be a handicap.I just shot mine at 300 yards last weekend. Group size was 4 inches tall and 8 inches wide. You REALLY have to watch the wind if you want to shoot good groups at 200 yards and beyond. My group was shot in a fishtailing tailwind which made the group twice as wide as it was tall. Good luck on your project and keep us posted. paul

 

[Vbull]

This is something pretty new to me, but I am putting together an underhammer with a GM 45cal 1-18twist barrel. My intent is for shooting at a 300yard target.

Can someone offer me some insight on where to start with a decent load for this? I heard mentioned that a whitworth bullet is pretty popular with this, but when looking there is a few, and I am not sure which one. Also is there a place I can get a bag of these bullets to try out before investing in a mold?

Bob243,
You've recieved some good advice above. I have now built 2 of the underhammers for use in long range competition. Both use Green Mountain .45 cal. 1:18 twist barrels. I've used both paper patch and grease groove bullets. The heavier #6 barrel shoots a 100 gr. charge of Swiss 1.5 with a Pioneer Products (Fred Leeth) grease groove bullet that drops from the mold at .450" using 40:1 alloy. It weighs 540 gr.

The lighter #5 barreled rifle shoots both the Leeth bullet and a Steve Brooks paper patch bullet that weighs 520 gr cast 40:1 and patched with 8lb. tracing paper. It measures .4485/.449 after patching. I prefer the grease groove bullets. Powder charge for this rifle is 80 gr. of Swiss 1.5 for 200 - 600 yards and 95 gr. when shooting long range (800 - 1000 yards).

The heavier rifle weighs just under 15 lbs while the lighter one weighs 12.5 lbs. On a good day, accuracy is right around 2 moa. Good luck with your rifle. Frank M.

 

[Dphar]

This is something pretty new to me, but I am putting together an underhammer with a GM 45cal 1-18twist barrel. My intent is for shooting at a 300yard target.

Can someone offer me some insight on where to start with a decent load for this? I heard mentioned that a whitworth bullet is pretty popular with this, but when looking there is a few, and I am not sure which one. Also is there a place I can get a bag of these bullets to try out before investing in a mold?

I would shoot a 500+ gr bullet, 70-100 grains of FG or 1.5F Swiss. No real need to exceed 530-550. A 400-450 *might* work OK at 300 but the heavier bullets usually shoot better past 200 yards.
Either PP or GG. A good GG bullet is easier to get consistent accuracy from than the PP. The paper is an added variable. Its also a lot more work.
I would use a 1:40 to 1:30 Alloy and be careful of nose design. Bullets designed for use with Smokeless powder can produce very poor results in BP rifles.

It might take quite some time to get a load worked up bullet guns can be pretty finicky.
I would alos make a drop tube to drop the powder through. Have it end just above the point the bullet base will occupy in the bore.
This should improve the accuracy. And no a rifled bore does not function as a drop tube.

Concentrate on uniform bore condition, everyone wipes and does so EXACTLY the same way shot to shot.
Use EXACTLY the same powder charge and always go to the range with 2-3 nipples. Preferably hard stainless. Platinum lined is best but are about 80 bucks.

Dan