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fiatdad
09-02-2023, 09:34 PM
I was wondering why BPC calls for 20 to 1, to 40 to 1 lead alloy. I have shot everything from pure lead to range lead to Lyman alloy.
I noticed a bit of difference in the filling of the mold but accuracy seems fine.
I size to groove diameter so bumping up does not seem necessary. Why why are the soft alloys preferred?
Thanks
Nick

Winger Ed.
09-02-2023, 10:17 PM
With the slower BP speeds & pressure curves, they obturate('squish') and seal the bore better.

Bent Ramrod
09-03-2023, 10:33 AM
With a well-made barrel with standard chamber and leade (and no “issues” with either), and a boolit design like the Ideal 457124 or 457125, sized a thou or so above groove diameter, you should be able to get acceptable practical accuracy out of anything that can be melted and cast: wheel weights, range scrap; whatever is most easily and economically found.

It’s when you want the maximum accuracy potential from your rifle that you have to start worrying about the alloy it “likes.” Trick boolits with odd noses like Moneys or Postells may need a certain hardness to keep their less-well-supported (by the bore) noses from slumping to the side when the cartridge is fired and the boolit is started up the barrel. Bore-diameter paper-patch boolits, whose shanks need to slug or rivet up to groove diameter while keeping the noses on the bore centerline, seem to need a more critical balance of hardness and ductility.

I was able to mine a military range back when I first started BPCR shooting. I would sequester the .45 hardball bullets and use the lead from those to cast my Ideal numbers and later my Paul Jones Creedmoor boolits. Whatever the alloy was, it was easily castable, soft and consistent and was very accurate in whatever I was shooting it in. Of course, all the noses were fat enough to center in the leade and bore of the rifles.

Postell boolits, designed to load through a ring of BP crud ahead of the chamber, needed something harder, so I would cast those with the rest of the range scrap; miscellaneous Linotype and wheelweight combinations. They all worked surprisingly well. You’d have to ask somebody else about Money boolits; I’ve never gotten as good results from them as the Creedmoor design, whatever the hardness.

Paper patch boolits seemed to operate in a relatively narrow range of hardness. There is where I finally started getting some use out of the hardness testers I’d picked up at gun shows. But in the absence of direct measurements, alloys like 16:1 seemed to cover the hardness requirement adequately. Mine have Creedmoor-type noses, though; one of the old-fashioned designs with the short, round nose might tolerate a wider alloy spread, as there is less to project out front and possibly slump.

Nowadays, I have to mostly buy lead (*sob!*), so I more-or-less reproduce the hardball lead with 20:1. I could probably go with less tin, but it’s a simple calculation to use up the dregs of the 16:1 alloy I’ve cast the paper-patch boolits from.

Chill Wills
09-03-2023, 02:02 PM
With the slower BP speeds & pressure curves, they obturate('squish') and seal the bore better.

So, my question is, if the bullet is already a 0.001" or greater than the hole they are going to enter, so where do you want them to squish into?

Winger Ed.
09-03-2023, 05:14 PM
So, my question is, if the bullet is already a 0.001" or greater than the hole they are going to enter, so where do you want them to squish into?

Like so many other things, it doesn't matter even a little bit what I want.:bigsmyl2:
You're mileage may vary, and people are always trying to re-invent the wheel:
But soft alloys or more or less pure Lead has seemed to work best in BP
loads & firearms for the last few hundred years.

When I cast for my .45-70, I put just enough wheel weights in the mix so it casts well and I get a good fill out.
And, it has worked real well. I don't know why, but it does better than the hard alloy I use for .30 rifle.

I just write things like that off to 'People a whole lot smarter than I am already figured this out',
and let it go at that.

Brimstone
09-03-2023, 06:23 PM
Also with some bullet designs, the groove is engineered to partially close under ignition forces.

The same forces that obturate a patched bore rider in a muzzle loader or breach loader, same force that obturates the .458 bullet to a .462 Trapdoor bore, also partially closes the grooves to make grease move to useful purposes rather than, as the theory goes, just rest idle in the groove towards the muzzle.

fiatdad
09-03-2023, 09:08 PM
Thanks, I get good accuracy for the ranges I can shoot. I have been digging a mountain
of range lead. With the weight of BP bullets my pure lead is going down. I will save it for Minies and balls

indian joe
09-03-2023, 09:16 PM
Also with some bullet designs, the groove is engineered to partially close under ignition forces.

The same forces that obturate a patched bore rider in a muzzle loader or breach loader, same force that obturates the .458 bullet to a .462 Trapdoor bore, also partially closes the grooves to make grease move to useful purposes rather than, as the theory goes, just rest idle in the groove towards the muzzle.

I've dug a lot of boolits out of the dirt - dont see any sign of lube in the grooves - I woulda thought the rotational force would be sufficient to a) keep the lube forced against the rifling as the boolit travels downbore b) throw off any thats left on exiting the muzzle ----with all but the stickiest and hardest of smokeless lubes ......................

Dave T
09-08-2023, 07:32 PM
I shoot more black powder cartridge handguns than rifles. I've found softer bullets, like 1-20s in the 45 Colt cartridge, not only shoot better but do not lead the bore or even the forcing cone. That was enough to convince me.

YMMV,
Dave

Larry Gibson
09-09-2023, 10:51 AM
I was wondering why BPC calls for 20 to 1, to 40 to 1 lead alloy. ............ why are the soft alloys preferred? Thanks
Nick

The composition of lead to tin alloy for the best accuracy depends on the bullet weight (mass), the expected velocity and whether a lubed bullet or a PP'd bullet. If shooting a lubed bullet at or over groove obturation is not an issue. The bullet will actually be less than groove diameter as it will ride over and be swaged down by the layer of lube in the barrel. However, if obturation is wanted the alloy softness needs to match the bullet weight (mass). A lighter weight bullet will need a softer alloy with a given velocity (acceleration).

As to velocity (acceleration) bullets 400 - 500+ gr of 40-1 or 30-1 do best down around 1000 fps+/-. If pushed to 1100 - 1200 fps then a 20-1 is most often best. With velocities of 1250 - 1500+ fps a 16-1 alloy was proven the best after extensive testing by Frankford Arsenal back in 1880 - 1882. That was with the 45-70 with the new 500 gr bullet. It was found the 405 gr bullet with the 70 gr powder charge did not adequately obturate [obturation was the thought of the day as they used .459 sized bullets in .460 - .464 groove diameter barrels]. However, with the mass of the 500 gr bullet [still sized at .459] over the same 70 gr powder charge the bullet did obturate. The 16-1 alloy then gave the best accuracy. The 405 gr 45-55 carbine bullet was of a softer alloy that did allow sufficient obturation with the 45-55 load. No, the dish [it is not a hollow base], does not and is not intended to act as a hollow base as with Mine' style ML bullets.

With all that said a 20-1 alloy is often recommended because it is useful over a broad spectrum of BPCs. It may, or may not, be the most accurate alloy in your rifle with your load. Only testing will determine the correct alloy.

Lead pot
09-11-2023, 03:44 PM
If one would make an effort to find out what an alloy does fired with real black powder and there is a difference between powders used on how the bullet obdurates with different alloy hardness. When a bullet leaves the muzzle looking good it will shoot good if the one sending it down range does. :D
The first two the left one was fired and the unfired one is the same unfired. The bullet is a 715 grain .50 cal. creedmoor nosed from a Paul Jones mould. The fired bullet has completely changed in profile and it was cast soft with 1/40 L/T and it shows signs of stripping and it shortened .097" in length.

317843317844

The 9 are all the same shot with different alloy hardnesses. The first is unfired.
A GG hard alloyed bullet at groove diameter with a good wad under it will hold the gas back just fine because it's a tight fit on the bore.
The Hollow point rebated hollow based bullet is one I worked with a few years back to see how a rebated boat tailed PP will perform over a flat base normally used. That bullet is a mix of 1/16 lead, tin, 5% antimony and patched to bore diameter and it filled the grooves very well. The problem with this profile design was protecting the base from damage.
The alloy temper is a shooters choice, what ever he is satisfied with the results.
For me 1/16 L/T or 1/18 L/T/Antimony is my choice. I only shoot the PP bullets.

indian joe
09-12-2023, 12:12 AM
If one would make an effort to find out what an alloy does fired with real black powder and there is a difference between powders used on how the bullet obdurates with different alloy hardness. When a bullet leaves the muzzle looking good it will shoot good if the one sending it down range does. :D
The first two the left one was fired and the unfired one is the same unfired. The bullet is a 715 grain .50 cal. creedmoor nosed from a Paul Jones mould. The fired bullet has completely changed in profile and it was cast soft with 1/40 L/T and it shows signs of stripping and it shortened .097" in length.

317843317844

The 9 are all the same shot with different alloy hardnesses. The first is unfired.
A GG hard alloyed bullet at groove diameter with a good wad under it will hold the gas back just fine because it's a tight fit on the bore.
The Hollow point rebated hollow based bullet is one I worked with a few years back to see how a rebated boat tailed PP will perform over a flat base normally used. That bullet is a mix of 1/16 lead, tin, 5% antimony and patched to bore diameter and it filled the grooves very well. The problem with this profile design was protecting the base from damage.
The alloy temper is a shooters choice, what ever he is satisfied with the results.
For me 1/16 L/T or 1/18 L/T/Antimony is my choice. I only shoot the PP bullets.

Am I seeing this right? So the nose has actually subsided into the body of the boolit ?

I tend to like soft boolits but you won me with this !!!

Chill Wills
09-12-2023, 12:22 AM
Am I seeing this right? So the nose has actually subsided into the body of the boolit ?

I tend to like soft boolits but you won me with this !!!

Yup! [big grin} you go soft enough and the bullet reforms into a wad cutter.

Lead pot
09-12-2023, 09:39 AM
LOL, even if they turn into a wad cutter they will still shoot good :D

317859

Chill Wills
09-12-2023, 01:18 PM
:mrgreen:

Yes! Kurt, I remember you posting that years ago go. I have always admired the lengths you go to learn, as well as share.
Not having done that test, no wadcutters in my mold stable, I am going to guess, if you doubled the distance you shot this target, the group would look VERY different. An issue of form stability.

Lead pot
09-12-2023, 01:56 PM
Chill our right. The longer range would put those into the ground or over the hill.
Those are swage cores I use, not cast.
I shot a lot of bullseye with the S&W Mod 52 38 master that uses the full wad cutter and it shot very well.

farmbif
09-13-2023, 09:53 AM
I alway thought that I was using pure lead in a cap and ball gun because when loading the cylinder because the ball is just a bit bigger than the cylinder its getting loaded into and harder alloy is not necessary when shooting at the velocity that a black powder gun produces. its not like your trying to shoot at 2000 or 2200 fps when bullet sizing to bore adequate lube and even a gas check is necessary

JSnover
09-14-2023, 07:46 AM
I've dug a lot of boolits out of the dirt - dont see any sign of lube in the grooves - I woulda thought the rotational force would be sufficient to a) keep the lube forced against the rifling as the boolit travels downbore b) throw off any thats left on exiting the muzzle ----with all but the stickiest and hardest of smokeless lubes ......................

I think it depends on the lube and the velocity. I've dug a lot of bullets out of the berm with most or all of the grooves filled.

Lead pot
09-14-2023, 09:58 AM
To settle your curiosity on how much lube stays behind in the bore and how much gets spun off the bullet just split a 20' length of 4" or 6" PVC pipe and band it back together and shoot a round through it. You will see the strips of lube stuck on the wall a and it will begin inside two feet and ends inside of 15 feet and you will see the land impressions on the longer pieces :D
Or if you don't want to use the pipe just shoot over fresh snow and you will see the lube.

Shoot into a strong wind and it ends up on your glasses and spotting scope :bigsmyl2:

indian joe
09-18-2023, 07:32 PM
To settle your curiosity on how much lube stays behind in the bore and how much gets spun off the bullet just split a 20' length of 4" or 6" PVC pipe and band it back together and shoot a round through it. You will see the strips of lube stuck on the wall a and it will begin inside two feet and ends inside of 15 feet and you will see the land impressions on the longer pieces :D
Or if you don't want to use the pipe just shoot over fresh snow and you will see the lube.

Shoot into a strong wind and it ends up on your glasses and spotting scope :bigsmyl2:

learning is fun sometimes -----like Chill Wills I am amazed at the imagination - the stuff you do to figure things out - dunno how old you are but for sure there is a big kid hiding in there someplace !!!

we shot lube cookies under the ball in a army colt one time, they turned into tracer rounds and lit the paper target on fire (not kiddin) -walker with a full charge wouldnt do it - fun but kinda hazardous in our climate

indian joe
09-18-2023, 07:35 PM
Yup! [big grin} you go soft enough and the bullet reforms into a wad cutter.

hmmm --I have a slab of linotype lurking about someplace might be time to use a bit of it in the pot !
Thanks ....

Chill Wills
09-18-2023, 08:27 PM
I have been told you can just throw some blue pills in the lead pot.

Lead pot
09-18-2023, 09:39 PM
learning is fun sometimes -----like Chill Wills I am amazed at the imagination - the stuff you do to figure things out - dunno how old you are but for sure there is a big kid hiding in there someplace !!!

we shot lube cookies under the ball in a army colt one time, they turned into tracer rounds and lit the paper target on fire (not kiddin) -walker with a full charge wouldnt do it - fun but kinda hazardous in our climate

You have to quit thinning that lube with the 180 proof corn :D

Knocking on the door of 85 in a couple days, but between the ears I'm still 26 :D
A little Lino is a good thing. It holds the profile very well. I found anything over 1/16 lead tin is a waste of tin. My alloy I use 1/18 that is a 1# roll of 95/5 no lead solder with 18# lead. sometimes I use 1/16.
Been using the solder because when I retired from the Plumbing trade 23 years ago I had a bunch unused left on the shelves

indian joe
09-19-2023, 01:13 AM
I have been told you can just throw some blue pills in the lead pot.

havent tried them yet --- done the red pill thing ages ago

indian joe
09-19-2023, 01:20 AM
You have to quit thinning that lube with the 180 proof corn :D
nah that woulda helped I think - lube cake was sticky enough to hang off the back end of the ball - nothin fancy just beeswax and neatsfoot but FF powder and I bet some grains of that got absorbed into the cake

Knocking on the door of 85 in a couple days, but between the ears I'm still 26 :D

I've got ten years and a couple months on you but thats just a number - its the between the ears bit that counts

A little Lino is a good thing. It holds the profile very well. I found anything over 1/16 lead tin is a waste of tin. My alloy I use 1/18 that is a 1# roll of 95/5 no lead solder with 18# lead. sometimes I use 1/16.
Been using the solder because when I retired from the Plumbing trade 23 years ago I had a bunch unused left on the shelves
a mate gave me a two foot bar of lino (50 pound I think) still got most of it

Larry Gibson
09-19-2023, 08:55 AM
hmmm --I have a slab of linotype lurking about someplace might be time to use a bit of it in the pot !
Thanks ....

Linotype is very rich in antimony. The last thing you want in a BP alloy is antimony. You are adding about twice as much antimony to the alloy as tin if you do that. Same thing with adding COWWs only to a much lessor degree. Tin is all you want to add to lead for a BP alloy.

Chill Wills
09-19-2023, 11:23 AM
Linotype is very rich in antimony. The last thing you want in a BP alloy is antimony. You are adding about twice as much antimony to the alloy as tin if you do that. Same thing with adding COWWs only to a much lessor degree. Tin is all you want to add to lead for a BP alloy.

I couldn't disagree more. That idea is 100% demonstrably wrong.

Lead pot
09-19-2023, 12:05 PM
Oh come on guys :D Some shooters that have posted in the past and said that antimony was poison shooting black powder are turning around :DD
When bullets with a mix of lead/tin/antimony clear the muzzle looking like the straight shank and the DD and they don't hit the point of aim, it's not the bullets fault. :D
318089318090

Don McDowell
09-19-2023, 12:36 PM
I recall in the early 2000's a bunch of accolades went to BPTR shooters shooting straight wheel weights. There are a couple of alloy recipes that use wheel weights and a touch of lino, along with lead that has a good reputation. I have shot some lino hardball alloy in the bpcr's but bullet sizing and matching diameter to the throats is critical coupled with a great lube, or you can get some leading.
Joe try a touch of lino in your alloy if you have it, you might just find that it works a plumb.

Lead pot
09-19-2023, 01:09 PM
I shoot with a friend that uses a mix of 9+1 WW/Lino a very hard alloy rich in antimony and I seen him shoot a 99 at 800 using his .40-65. The last shot missed the 10 ring by less than 3/4" cant remember the holes through the X ring but close to the same that went into the 10 ring.
My 95/5 no lead solder is running out and I will most likely get any more for what it costs now compared to the $5 $6 I paid for it 24 years ago :D but on the good side my Son gave me 600 pounds or more of dip solder scrap from where he works and I have several buckets of old WW left in the shed that will get used when my alloy runs out I'm using now. But it will be a while, still have a couple hundred lbs I ingots left. :D
Larry looking at your avatar, I see that you carried that pig also. :D

Larry Gibson
09-19-2023, 07:14 PM
"Larry looking at your avatar, I see that you carried that pig also."

Yup, sure did, among numerous other weapons. The M60....what's not to love......:drinks:

indian joe
09-20-2023, 02:24 AM
I recall in the early 2000's a bunch of accolades went to BPTR shooters shooting straight wheel weights. There are a couple of alloy recipes that use wheel weights and a touch of lino, along with lead that has a good reputation. I have shot some lino hardball alloy in the bpcr's but bullet sizing and matching diameter to the throats is critical coupled with a great lube, or you can get some leading.
Joe try a touch of lino in your alloy if you have it, you might just find that it works a plumb.

I'm cheap - solder is real expensive - ww was free - as was our soft lead - and the lino
mostly we have shot WW + little bit of lino + however much soft lead it took to soften the mix to 3B pencil - by the sound of it I need to go harder than that ?
Accuracy has been good at shorter ranges (100-200yards) - had some problems further out - the LEE 500 3 R gets the wobbles in wind at about 400-450 - figured that was partly lack of twist as much as the profile (shooting it in a 20twist) I have put that one away, as much as I liked the flatter trajectory it brought, gone to a 460 grain CBE that looks a copy of the Lyman postell shape (which seems not really a Postell at all) Just enough lube on the CBE to do the job = 28 inch barrel '76 winchester and my sharps has also been shortened to 28"
A lesson I learnt years ago with a 22/250 and long bullets - if you are standing at the edge of the cliff with bullet stability it takes very little change to go from bullseyes to catastrophic failure - that pointy LEE is edge of the cliff !

Don McDowell
09-20-2023, 09:03 AM
Joe if you're not shooting past lets say 500 yards/meters, staying on the softer side of alloys probably doesn't hurt much. It's when you start stretching out beyond that that a good rigid bullet that holds nose shape gets important. I think the biggest problem with the Lee bullet is it's simply not quite balanced with those 3 lube rings. If a person is looking for a similar profile bullet there are a couple I've experience with that will do well in a 45-70 to 1000 yards, when cast from 16-1 or even #2 alloy or similar, are the 525 gr money bullet from BACO and their original postel copied directly from an original Ideal bullet mould from 1882. Keeping in mind the original postel was designed to make the trapdoor rifles competitive to 1000 yards. Not sure where in the progression of the reinterest in bpcr that dead soft alloys became the standard, but heck even the govt manual for the Springfield rifle and Colt revolver call for bullets alloyed at 16-1. Remington concludes in their 1875 catalog that bullets from hard alloy will do better when shooting long range than the soft alloy. Looking thru the 1878 Winchester catalog it is intesting to see the various cartridges listed there with powder charge and bullet content, with quite a few of surprisingly use 11-1 for alloy.
In your 76 the Saeco 645 bullet might prove to be a quite a good bullet.
Bottom line is if you have the linotype available, throwing a little bit in the mix may or may not hurt, and it may just help a struggling bullet. One just doesn't know till you try it.

beltfed
09-20-2023, 05:24 PM
A picture is worth a thousand words:
What Lead Pot said:
9+1 COWW//Lino bullets at 800yds:
318137
beltfed/arnie

indian joe
09-22-2023, 08:10 AM
thanks Don --500 - 600yards is about all I will do I think and that not often in competition - have the room to play at home but I get some frustrated going back and forth to the target - eyes and scope not up to confidently spotting holes anymore.....................................

Don McDowell
09-22-2023, 08:47 AM
Joe that's one of the reasons I really like my Caldwell target camera. It will give you a good picture of the target even at 1000 yards. They say it will work up to a mile but I've never tried it.

freakonaleash
09-22-2023, 10:14 AM
thanks Don --500 - 600yards is about all I will do I think and that not often in competition - have the room to play at home but I get some frustrated going back and forth to the target - eyes and scope not up to confidently spotting holes anymore.....................................

I drive my tractor back and forth.

Larry Gibson
09-27-2023, 09:20 AM
Sure you can shoot cast bullets in BPC firearms that have antimony in the alloy, never said you couldn't. What often happens when you do is leading. Such appears to be somewhat common these days as expressed in https://castboolits.gunloads.com/showthread.php?460463-Barrel-getting-some-lead. My experience is I get zero leading with a binary alloy of lead/tin. I have shot 100+ rounds w/o wiping or cleaning of duplex loaded 45-70s with 20-1 or 16-1 alloys out of all three of my TDs w/o one speck of leading. I have frequently fired 20+ rounds out of my M1884 TD of a replicant 1882 load w/o wiping or cleaning with zero leading. As soon as I try a ternary alloy of lead/tin/antimony I get leading. That also is the experience of many old timers from whom I learned not to use a ternary alloy with antimony in it.

Lead pot
09-27-2023, 10:56 AM
What is helping you with the TD is the slow twist and the transition from the chamber into the throat. I have a couple trapdoors with good bores and they shoot just fine, but I find some lead fouling when I clean them. I use the Gov. and posters bullets mostly cast with 1/20 T/L alloy in the Trapdoors and mostly shoot dirty (load/shoot and repeat :D )

Larry Gibson
09-27-2023, 06:15 PM
Don't know about your TDs but mine and all I've looked at has little, if any, "throat". Mostly the leade comes right up to the chamber mouth or very close to it. Any transition of the bullet from case/chamber to that leade is rather abrupt. What I do know is with both original TDs, my two H&R TDs and a couple replica Sharps, RB and '85s I shot is that if there is any antimony in the alloy then some leading [mostly long streaks of it] can be expected with BP loads.

With my 1873 45-70 loads with Lee 405 HB bullets or my M1884 with a Rapine 460500 bullet loads I've settled on the 16-1 alloy Frankford arsenal found best back then. For my 45-55 Carbine loads with the Lee 405 HB bullet I fall back to a softer 30-1 alloy. My BP lube is simply 6 parts beeswax to 5 parts virgin olive oil.

indian joe
09-28-2023, 05:32 AM
Don't know about your TDs but mine and all I've looked at has little, if any, "throat". Mostly the leade comes right up to the chamber mouth or very close to it. Any transition of the bullet from case/chamber to that leade is rather abrupt. What I do know is with both original TDs, my two H&R TDs and a couple replica Sharps, RB and '85s I shot is that if there is any antimony in the alloy then some leading [mostly long streaks of it] can be expected with BP loads.

With my 1873 45-70 loads with Lee 405 HB bullets or my M1884 with a Rapine 460500 bullet loads I've settled on the 16-1 alloy Frankford arsenal found best back then. For my 45-55 Carbine loads with the Lee 405 HB bullet I fall back to a softer 30-1 alloy. My BP lube is simply 6 parts beeswax to 5 parts virgin olive oil.

Larry - no leading problems at my place - but I am shooting new barrels
mix is about 50/50 soft lead and wheelweights with a tad of linotype - test is just scratch it with a 3B pencil
not much tin in that mix. - gets good expansion in soft dirt at 100yards

I like that LEE 405 HB but I modified it some
milled the nose flat for safety in my tube mag guns and lost the HB so I could use a wad under it still weighs 405gr
Also modded a second one by lengthening the base plug - lost one lube groove and driving band it drops at 335 grain
Its a nice profile and nice big lube grooves

Gray Fox
09-28-2023, 10:18 AM
Larry:

How do you apply your lube? Do you pan lube, water melt, cool and make a lube cookie, or what? thanks, GF

indian joe
09-29-2023, 06:16 AM
The composition of lead to tin alloy for the best accuracy depends on the bullet weight (mass), the expected velocity and whether a lubed bullet or a PP'd bullet. If shooting a lubed bullet at or over groove obturation is not an issue. The bullet will actually be less than groove diameter as it will ride over and be swaged down by the layer of lube in the barrel. However, if obturation is wanted the alloy softness needs to match the bullet weight (mass). A lighter weight bullet will need a softer alloy with a given velocity (acceleration).

As to velocity (acceleration) bullets 400 - 500+ gr of 40-1 or 30-1 do best down around 1000 fps+/-. If pushed to 1100 - 1200 fps then a 20-1 is most often best. With velocities of 1250 - 1500+ fps a 16-1 alloy was proven the best after extensive testing by Frankford Arsenal back in 1880 - 1882. That was with the 45-70 with the new 500 gr bullet. It was found the 405 gr bullet with the 70 gr powder charge did not adequately obturate [obturation was the thought of the day as they used .459 sized bullets in .460 - .464 groove diameter barrels]. However, with the mass of the 500 gr bullet [still sized at .459] over the same 70 gr powder charge the bullet did obturate. The 16-1 alloy then gave the best accuracy. The 405 gr 45-55 carbine bullet was of a softer alloy that did allow sufficient obturation with the 45-55 load. No, the dish [it is not a hollow base], does not and is not intended to act as a hollow base as with Mine' style ML bullets.

With all that said a 20-1 alloy is often recommended because it is useful over a broad spectrum of BPCs. It may, or may not, be the most accurate alloy in your rifle with your load. Only testing will determine the correct alloy.

Larry why the "hollow base" on that boolit ? Its puzzled me some -- Youre right its not gonna work like a minie - was that just to balance the projectile?

I modded that mold - milled the nose dead flat and bigger enough it would no longer protude into a primer pocket - then took the tit off the base plug sos it casts flat base - still comes out neat 405 grain (sometimes we get stuff right by accident)

It shoots fine anywhere within its useful range - might do a little better with a boolit like that blue one in Lead pot's post but you would need to be having a good day to see the difference .