Lead ?

[Kurt]

Gary

They have a 45 degree transition into a .050" free bore into a 2° 30' lead unless they got a new reamer since 9-18-01

I might add. The case mouth is .4810" and the free bore throat is .460" in diameter.

[Lumpy Grits]

Thx for the info, most grateful.
ALL, that I shoot out of my .45-70 and .45-90 Shiloh's are GG.
The most accurate I have is the PJ #45001 Creedmoor. Cast 30:1, shot as cast after pan lubing with DGL.
I also have a 'Money Bullet' mould cut buy PJ to Dan T specs. Dan T gave this mould to me many years ago. Never a ring either or with the Steve Brooks Postell I have. These are also shot 'as-cast'.
I seat to just cover the top GG.
Never have any 'rings' in either gun and I'm burn'n 3F Goex.
Respectfully,
Gary

[TexasMac]

Here’re the Miroku Mfg. Browning BPCR chamber casts and some specs. Miroku cut the chambers per specs provided by Browning.

The .45-90 has a 12.75 degree transition step from chamber to bore. It has a 0.150” freebore and a 1.5 degree leade angle. As noted by the photo, the chambers are identical, which should not be a surprise since Miroku cut both chambers.



The .45-70 has a 12.75 degree transition step from chamber to bore, which continues to the top of the lands, resulting in a leade angle of 12.75 degrees. There’s no freebore.



The .40-65 also has a 12.75 degree transition step from chamber to bore. It has 0.0100” of freebore and a leade angle of 1.5 degrees.



Wayne

[TexasMac]

When I shot it last (.376 bullet in a .376 groove diameter barrel) with a Walter's Wad at the base I got these lead rings. Time before that same loading but no rings. I suspected they might be because I'd left the bell on the case neck. I had done that because they chambered fine and I thought maybe they'd help center the full-lenght-sized cases in the chamber better that way.
Something in the bell remaining encouraged the rings because today I didn't get but two rings (in all three sessions there is no leading in the bore). This time I layed the bell back down with my sizer.

SgtDog,

I also bell the case lip to ensure the rear of the bullet is centered in the chamber, and have had not rings or problems. It's been my experience that lead rings are the result of a sharp transition step from chamber to bore along with exposed lead just in front of the case lip under the transition step. To eliminate the rings position the bullet so that a lube groove is just in front of the lip. When the bullet obturates the lube rather than lead will fill the transition step preventing lead rings. I hope that makes sense.

Wayne

[Martini2]

Last Sunday I fired a match with new to me Ruger number 1 45-70. these chambers are known to have generous free bore. The first 2-3 loads with GG bullet seated out to reach the lead had a grease ring still attached to case rim. I guess it was due to squeaky clean oiled bore/chamber. After chamber warmed up cases extracted without lube ring. To reach even close to lead my 457124 bullet were seated way out with 1st grease groove exposed. I use a fairly hard Beeswax and Carnauba wax blend that requires heater pad under the sizer. The lube stays in place fine and thanks to the above thread it is clear that a lube ring probably filled the gap and went to work for that load.

[Iron Coyote]

Wayne
Thank You for posting pictures of your chamber casts. Always nice to have a visual image of what's going inside.
Very nice casts.
Thnx Lots
Bob

[SgtDog0311]

Wayne, Great pictures!! I've got some decent casts but I can never get pictures like those... and I'd say your surfaces look a good deal better than my cerrosafe surfaces. Wonder if you heat it hotter or what. I trap air bubbles and such.

You are clear as a bell on the lube groove technique. I do it on a 40-63 whether I need to or not... just the way things work out. Transition step on that that one probably has a bit more wear on it even if it’s the same angle... given it’s age. In that one I again use a groove size, but this time because that’s all the chamber would tolerate, and with reamed cases at that!
   

I have got rings before on a 32-20 and one a 38-55. Some work on the throat eliminated them. In both cases you could drop a bullet in the chamber, tap it incrementally deeper and see lead being plowed. The tapered throat would not tolerate an oversized fit till we relieved the throat a bit.

IF YOU WERE going to modify a throat angle for an optimal transition to groove size for accommodating an oversized cast bullet, what angle would you prefer... and could you utilize the same angle in a variety of calibers (speaking to cast bullets running from 1100 – 1500fps here). I've worked on throats for both the 38-55 and a 32-20 already mentioned but that was solution shy of a ‘throat reamer’. Always wondered, had I got a throat reamer what angle would I have been looking for... optimal speaking.

[Kurt]

Here is the throat I have in my Browning BPCR .40-65

[TexasMac]

Wayne... IF YOU WERE going to modify a throat angle for an optimal transition to groove size for accommodating an oversized cast bullet, what angle would you prefer... and could you utilize the same angle in a variety of calibers (speaking to cast bullets running from 1100 – 1500fps here). I've worked on throats for both the 38-55 and a 32-20 already mentioned but that was solution shy of a ‘throat reamer’. Always wondered, had I got a throat reamer what angle would I have been looking for... optimal speaking.

SgtDog0311,

You’re asking about a subject that I'm no expert on so I have to let someone (possibly Kurt) respond that has more experience with testing different angles. So, just to be clear, what angle are you referring to, the transition step angle from the chamber to the bore or the leade angle? I’m assuming you are referring to the transition step angle. Kurt’s photo displays a modified transition step angle (compare his Browning .40-65 cast to my unmodified Browning .40-65 cast). The relatively shallow angle takes up most of the original freebore.

One consideration is the type of bullet, i.e. grease groove or paper patch. Kurt, correct me if I wrong but I believe you modified the transition step for PP bullets, is that correct.

Another consideration in my mind is how the overall cartridge length matches up with the chamber length. Given an ideal condition where the case perfectly matched the length of the chamber plus head clearance and the case did not shorten when fired, a 90 degree transition step angle could be considered optimum. But in the real world it’s almost impossible to get a perfect match, leading to tradeoffs, one being an angular transition step.

BTW, the bullet diameter should not matter concerning lead rings. If the cartridge can be chambered the bullet can’t be oversize. When fired, typical BPCR-type cast bullets will obturate to fill the case neck, any exposed chamber neck, the transition step and the bore.

Wayne

[Kurt]

Wayne.

A little back ground on my .40-64 Browning BPCR.
I picked this rifle up used at a very good price. Shooting it when I first got it the would throw shots all over the paper. I made a chamber cast and found the throat was oval several thousands like a undersized pilot was used. You could even see it looking at the cast.
I had Manson make a throating reamer with a 4 degree/1.5 degree compound reamer from the chamber wall. That cleaned out .236" of the bad throat, freebore and all. This concentric taper improved the accuracy shooting PP or GG bullets and made this a fine accurate rifle.
I don't consider that concentric throat a PP throat, I call it a lead bullet throat. Check out the match .22 rimfire throats. They are a lot flatter then my 4 degree. They run as flat as a 1.5 degrees and they don't use a patched bullet.
I like my patched bullets couple thousands over bore diameter, this pushes the ogive tight into the concentric throat for perfect alignment. It is a plus for a PP bullet over a GG. A GG the way it is now designed with a reduced step from the shank to the ogive it gains nothing as far as aligning the bullet to the bore unless you cam the driving bands into the lead and this is lost if the bullet is seated in the case with a bunch of runout. This is were a action like the 44-1/2 Stevens where the block will cam the tight bullet into the lead. This is ideal for a groove diameter PP bullet where you can seat that bullet like a bore diameter patched bullet and get all of the benefits of a groove diameter patched bullet.