Lead ?

[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