Groove Bullet - Diameter for bore or groove?

[roscoe]

What is the rule of thumb for the correct diameter of a grooved bullet?

Should it be bore size, slightly over bore size or maybe the groove size?

[BRUCE MOULDS]

roscoe,
if a groove bullet is a greaser, there is one simple answer.
its diameter should be a neat sliding fit into a well fireformed case.
keep safe,
bruce.

[Travelor]

From what I have read, the bullet should be sized .001" over slugged bore diameter.

I'm open to be corrected.....................

[Tom Myers]

From what I have read, the bullet should be sized .001" over slugged bore diameter.

I'm open to be corrected.....................

And corrected, ye shall be.:bigsmyl2:

We are probably dealing with a case of semantics here. Many times the concept of BORE and GROOVE are unintentionally interchanged.

Usually, the grease groove bullet should be sized to at least 0.001" over GROOVE diameter and not large enough to expand a fired formed case when seated.

[country gent]

While Paper patched can be wrapped to bore or groove dia, they are done both ways. The grease groove is normally cast or sized to .001 or .002 of groove dia ( the large dia) this helps facilitate the bullet sealing the bore well and saves on bumping up of the bullet. Other things to consider is nose fit in the bore length and alloy

[Don McDowell]

The correct diameter for a greaser is something from groove diameter to .002 over groove. The nose on a greaser is best to be just under bore diameter to prevent leading due to the lack of lube on the nose, and to make chambering easier.

[roscoe]

Thanks for the information This is what I needed. Having been reloading since the late 60's, I have never worked with black powder. Wow what a difference and learning curve. This forum has really helped me out. Thanks again

[BRUCE MOULDS]

roscoe,
the 001 to 002 sizing rule is an urban myth, suited to smokeless and hard cast.
with black and the alloys that suit it, here is what happens when you light the fire.
the powder ignites, and before anything else happens the case obturates to the chamber wall at the same time as the bullet bumps up to fill that dimension.
the smaller the bullet, the more it bumps up.
then it starts to move forward through the transition/ leade area, being swaged to barrel dimension as it goes.
having the bullet at the diameter of internal unsized case reduces most of the bumping up, eliminating one deforming action and thus aiding accuracy.
this is also why having a loose chamber can reduce accuracy.
save the time and money sizing bullets because it is more work for less accuracy.
not having bore riding noses also helps accuracy because they bump up into the rifling and being unlubed can potentially add lead to the bore.
keep safe,
bruce.

[Gunlaker]

I've found the same as Bruce with respect to bullet sizing. The biggest that fits the case usually works best for me. If the chamber is a good one then it'll shoo well.

I also agree with Don about the bullet noses. As an example I have two of Steve Brooks Creedmoor molds. They are nearly identical, except one has a nose that is about 0.001" under bore diameter, and the other is at bore diameter ( and just a little heavier, maybe 10 grains or so ). The slightly smaller nose does not significantly lead the bore, but the larger nosed bullet will led the bore.

Chris.

[BRUCE MOULDS]

chris,
you make a good point about chambers.
shilohs have tight chambers, and are noted to be good shooters.
we know that bullets bump up prior to moving from an experiment done by William metford in the 1860s
he drilled a hole in a barrel and threaded it in order to screw in a pointed rod.
the point came out in a groove and was screwed in such that it stuch out about 1/2 the depth of the groove.
it was placed such that it was a known measurement from the base of a loaded bullet.
the recovered bullet had a scratch mark on it the length that proved the bullet had bumped up prior to moving.
this was done with a bullet containing tin and antimony, so not a soft bullet.
one of the reasons metford liked harder bullets was to minimize bumpup to only what is necessary.
chronograph (pendulum in his case) testing proved that the softer the bullet, the lower the muzzle velocity.
this is because the softer the bullet, the harder it bumps into the rifling, increasing velocity robbing friction.
never be afraid to experiment with alloy.
keep safe,
bruce.

[Gunlaker]

That is an interesting experiment. F.W. Mann did some interesting experiments showing essentially the same thing.

I might do a little bit of alloy experimentation this year. The low antimony/low tin alloy that Michael Rix has been using, and written about by Dan Theodore, sounds very promising for pointy bullets. Do you have any idea of the alloy composition used by Metford? Did he write a book by any chance? I only have the North American perspective on this stuff.

I'd like to be able to get rid of all leading in my grease groove shooters, but never seem to quite achieve it. I'm at this very moment removing lead from one of my rifles :-). I used to think that my rifles did not lead, but it as because I wasn't looking hard enough. Interestingly, of all of the BPCR rifles I own, my Badger barreled C. Sharps rifles are least likely to lead. This is by a big margin too. This of course excludes my paper patched rifles :-)

Chris.

[roscoe]

roscoe,
the 001 to 002 sizing rule is an urban myth, suited to smokeless and hard cast.
with black and the alloys that suit it, here is what happens when you light the fire.
the powder ignites, and before anything else happens the case obturates to the chamber wall at the same time as the bullet bumps up to fill that dimension.
the smaller the bullet, the more it bumps up.
then it starts to move forward through the transition/ leade area, being swaged to barrel dimension as it goes.
having the bullet at the diameter of internal unsized case reduces most of the bumping up, eliminating one deforming action and thus aiding accuracy.
this is also why having a loose chamber can reduce accuracy.
save the time and money sizing bullets because it is more work for less accuracy.
not having bore riding noses also helps accuracy because they bump up into the rifling and being unlubed can potentially add lead to the bore.
keep safe,
bruce.

I understand what you're saying here for the most part, but I'm a little confused on what size you're saying the bullet should be. It sounds like you may be saying the less it has to bump up the better, so are you saying the closer the bullet is to groove size and not "over" groove size the better?

[Gunlaker]

Rosco, basically the idea is that no matter what, the bullet is going to get as big as the case is inside. So lets say your case is 0.460" inside, but your groove is .458". In this case a .460" bullet will be distorted less than a .458" that gets bumped up to .460" in the case, and then swaged back down to .458".

I've got two rifles just like that and they both like .460" bullets best. I'm sure that smeone has the exact opposite experience, but that idea work for me.

Chris.

[roscoe]

Rosco, basically the idea is that no matter what, the bullet is going to get as big as the case is inside. So lets say your case is 0.460" inside, but your groove is .458". In this case a .460" bullet will be distorted less than a .458" that gets bumped up to .460" in the case, and then swaged back down to .458".

I've got two rifles just like that and they both like .460" bullets best. I'm sure that smeone has the exact opposite experience, but that idea work for me.

Chris.

So are you getting the bullet diameter from a fire formed case?

[martinibelgian]

No, much easier... If the unsized bullet fits the fireformed case, then don't size it, but use it as cast - much simpler, no? Whatever the dimension is, when the hammer hits the primer that bullet will indeed set up as big as it will possibly can. Which actually is the diameter of the fireformed case + springback of the brass.

[BRUCE MOULDS]

roscoe,
what gert and chris said.
but that is why good chambers are important.
if you can finger seat a bullet 0.001 to 0.002 bigger than groove in a fired case with a little friction, that is the optimum.
for those buying a reamer, the place to start is to buy your brass and barrel
from here you can establish bore and groove diameter, and neck thickness of brass.
so you know what the bore ride of the nose needs to be, what 0.001 bigger than the groove is, and can easily calculate the neck diameter of the chamber.
now you can order the reamer and a mould.
if this is put together by a competent gunsmith you will have a shooter, and will have great accuracy for little work.
keep safe,
bruce.

[BRUCE MOULDS]

chris,
it seems to me that metford was constanly experimenting and had no final perfect alloy.
what is clear though is that he preferred a harder alloy for groove diameter pp bullets than for bore dia bullets.
he also had a lot of trouble getting lead/tin/antimony bullets to retain constant hardness.
he referred to bullets "ripening" which seems to mean aged and stabilized.
I have been making some notes on metford's alloys, and will post either here or Shiloh when it is clearer in the brainbox.
keep safe,
bruce.

[roscoe]

Bruce, thanks a lot for the information. I re-read all the post here and you pretty much told me what to do on post #2. Sometimes you just can't see the forest for the trees. I'll try this out. Thanks again.

[Gunlaker]

Thanks Bruce. It would be interesting to hear about his experiments. I think I've seen just a litle bit of that posted here once. If I remember correctly it was a guy named David from ResearchPressUK... He has some really interesting articles.

Chris.

[Lead pot]

Antimony in bullet alloy is a plus, but the balance using it in a PP bullet patched at bore diameter or slightly under bore diameter the percentage of the mix can be a problem without a good wad seal under the bullet to hold the gas back for reducing gas cuts and getting enough upset to get enough engraving for proper rotation. This is something you don't have to worry about using a groove diameter GG or PP bullet. Just .8 oz of antimony and 15 oz tin mixed in 18 lbs. of lead will hold the bullet nose profile with minimal setback and expand well enough to fill the grooves for good rotation better then 1/16 T/L alloy.
Here is what that 523 gr PP bullet patched to bore diameter will look like shot with a 89 gr load of 2F powder from a .45-2.4.
Kurt
http://i22.photobucket.com/albums/b302/940Leadpot/IMG_0223-5.jpg (http://s22.photobucket.com/user/940Leadpot/media/IMG_0223-5.jpg.html)

[BRUCE MOULDS]

kurt,
yet again the similarity between a money bullet and a metford bullet becomes obvious.
the shape must just work for long range!
we owe you a great deal for sharing your experimental findings so generously.
chris,
I have not found a book by metford.
however, if you keep delving deeper into david's website "research press", there is an amount of good stuff in there.
the recent purchase of "the target rifle in Australia" revealed two essays of metford's.
if you go to "archive.org" there are a number of free online books from the era.
they include
the book of the rifle
modern observations on rifle shooting
long range rifle shooting
trajectories of American hunting rifles
full text of irish riflemen in America
and the one I must thank gert for suggesting
modern sportsmans gun and rifle vol 2
this last one has some of metford's writing, as well as info on shooting dirty, wads, etc.
there is a wonderful picture of the 461 gibbs cartridge with a metford bullet.
most of these books are American, but the last one is british.
if you get into the book and find the format unfriendly, find the feature that allows format change to that of a book, and you click on the page to turn it.
keep safe,
bruce.

[Lead pot]

Bruce.

I think the left bullet I swage is closer to the Metford.

http://i704.photobucket.com/albums/ww43/Kurtalt/IMG_1641-1.jpg (http://s704.photobucket.com/user/Kurtalt/media/IMG_1641-1.jpg.html)

[Gunlaker]

Thanks Bruce. I have several of those books, but not all. I'll have a look.

Chris.

[BRUCE MOULDS]

kurt,
the bullet on the left could be accused of not being dissimilar to a sharps long range bullet of the early years,
its nose does resemble one of metford's bullets.
he had a short range lighter bullet possibly more for hunting using the 461 gibbs cartridge.
the bullet was however shorter than the bullet on the left.
the nose of his long range bullet was more like the bullet on the right., but its base was cupped.
keep safe,
bruce.

[Old-Win]

Kurt,
Bruce is correct about the bullet on the right closely resembling the Metford bullet. A now retired mold maker copied the .461 Gibbs to create the first rendition of the money bullet. I just cast up 140 Sharps greasers for Lodi. Are you planning on going now that the weather has warmed and we can get our old bones on the ground? Bob
http://www.jpgbox.com/jpg/50711_600x400.jpg (http://www.jpgbox.com/page/50711_600x400/)]

[Lead pot]

Well Bob. Cant get a better comparison then that from an original. Thank you. Kinda hard to invent a new bullet when they where already in use over 100 years ago. :)

Bob I don't know yet if I will make Lodi. Kinda teetering between Lodi and Alliance this year. They both fall on the same weekend this year and I like both.
I haven't loaded anything yet for either. I been holding off for the new CPA .45-90 to get done and I been loading for Alma Mich. for the coming weekend. Talked to Gail at CPA and they are putting the final touch on the rifle so it makes the 12#2oz weight that I want this rifle to make. So when I'm close to her shop I will run over and pick it up.

[BRUCE MOULDS]

old win,
what a wonderful cartridge!
metford claimed that it could be shot dirty with great accuracy, and pictures of plots would suggest that the accuracy was there.
there is a plot where 50 consecutive shots hit the 36" (?) bull at 1000 yds, and another where 14/15 shots held 12.5" vert at 1000 yds.
it is believed that metford's ammo used a groove diameter bullet.
with regards his claims of no lube, we must ask the question whether beeswax on its own is a lube, because he used a beeswax wad under the bullet.
Stonehenge also mentions the use of a beeswax/tallow wad, using different proportions according to ambient temperature, comparing india's hotter times to Canada's winter.
could the powder he used and barrel dimensions be different than today.
modern practice for accuracy is a neat fit for the bullet as it is chambered, and a neat fit in a clean barrel will not fit into a dirty barrel.
in the 461, a lot of the bullet is in the neck of the case, so little freebore would be required, negating some of the above problem.
the brits preferred bottlenecks, believing that a greater percentage of the fouling was kept in the case and not in the barrel.
Stonehenge does however mention blowing into the breech if necessary, and gert has mentioned the use of blowtubes by the brits.
humidity in Britain is certainly greater than australia and certain parts of America.
without inspecting any of these brit match rifles, the question comes to mind as to whether they had some taper in their origins in order to function reliably dirty, and relied on the cupped base and wadding for an initial gas seal.
keep safe,
bruce.

[Lead pot]

There is no doubt in my mind looking at that shell that that PP bullet is seated in the case to be shot at groove diameter and with the ogive taper drops down to the case mouth so it will feed in a fouled chamber.

[BRUCE MOULDS]

yes kurt.
and that long neck is more than sufficient to hold all sorts of lube wads as well as the bullet shank.
the brits felt, along with the above mentioned wads, that felt was a very good gas seal, as is or soaked in something, or a combination.
they wanted their felt wads to be things like 0.020+ bigger than the internal diameter of the case neck .
no thicker than 0.090 made it easier to load the cartridge than a thicker felt wad.
keep safe,
bruce.

[Travelor]

OK, guys help me a little. Not shooting the same quality gun or cartridges, but still looking to shoot to the guns potential which I have read is 1" to 2" at 100 yards..

Gun is a Ruger 77/357 - 18.5" barrel 1:16 twist using a Weaver T-36 scope in a Boyd's laminate stock (I have checked and the recoil area is snug and the barrel is free floated. The barrel slugged at .3575".

First I shot a hard cast Lyman 358156 HP SWC GC 150 grain bullets sized to .357" = ugly groups.
Then a NOE 360-180 GC hard cast bullets sized to .358" = ugly groups.
Then a NOE 360-180 GC hard cast bullets sized to .359" = better but still not great.
Then the hard cast Lyman 358156 HP 150 gr GC SWC sized to .359" = much better but no god ring yet. Load was 14 grains of 2400 and SP magnum primer.

Based upon the above posts it would seem that the bullets be bumping up in size to fill the barrel even though the bullets may be undersized based up the "urban legend" of needing the bullet to be .002" over or sized to .3595".

[martinibelgian]

Having a rifle with a - knackered - Metford barrel, I'm wondering about dimensons: seems like the bore has a serious taper to it - like making the bullet bore dia. at the breech, but groove at the muzzle. This of course judging by my example, which is a Field Patent Military Breechloader with a Metford barrel. Unfortunately, the barrel is too far gone to be 'reconditioned' and put to use. I don't even know the correct cartridge to be used - it just mentions 52 bore.

[martinibelgian]

FWIW,

Take a look at the .45 Turkish - remarkably similar if not so extreme.... Logn neck, gently sloped shoulder. Looks to be an ideal BP cartridge configuration.

[Don McDowell]

Traveler, yes bullets that are to small will fill the grooves, smokeless or black, not sure where that urban myth about only bumping with blackpowder came from.... Won't go into the stuff about how most of my 45 caliber rifles .457 groove shoot best with .458-.459 bullets.My 44's with .446 groove shoot best greasers with .448 cast from 16-1..
You may want to adjust the powder charge. The best accuracy isn't always found with maximum charges.Sometime changing primers can make a big change in group size, as can crimp and seating depth.
Also when looking at large lousy groups, the first place to start looking is doing some lead prospecting in the barrel, and especially at the throat.