All,
reloading some 416 Rigbys and the bullet dia. are 0.4180". I then measured woodleigh, barnes, and hornady and they all measure 0.4160". This got me thinking about min/max bullet dia.,case neck thickness. What is the expected tolerance for these dims? Thanks much for the help.

rgds,

steve

What bullets are that big?

If they are cast lead then they should be fine and probably more accurate than lead of .4160 diameter. (.417 is a common nominal diameter for lead "416" bullets, and .418 is not uncommon. I used .418 cast lead in mine.)

If they are copper jacketed lead core, then you'd have to ask why they're so big. I'd be tempted to send them back.

If a fired case neck measures bigger than the resized and loaded case neck, then it would probably be safe to shoot even if thin copper jacketed lead. (If it's a monolithic solid or heavy-wall leadfilled "solid" don't even try them.) Start load development at least 10% low (maybe even 15%) if you feel like experimenting.

Don,

thanks for the reply. These are "soft" copper jackets over lead. I will talk with the manuf. today but i suspect these are designed this way. 18/20 rounds chamber with no force, two would not due to neck (the brass is on the thicker side, around 0.037"). I was concerned about swaging in the barrel but have since put this worry away.

rgds,

steve

They certainly won't cause any problem, if they chamber freely.

If 2/20 require force to chamber the round, then you should probably measure your cases and neck ream the offenders. be sure to check all your hunting rounds for chambering.



You want to be sure the case neck can expand slightly when fired. Note that on work-hardened brass the spring-back effect can still mean the bullet is a tight fit in the fired case. On freshly annealed brass a bullet should slip into a fired case with no more than two finger pressure on even a benchrest rifle (my opinion).



Just as a note: Most dangerous game rifles are made with generous chambers so that even a max cartridge will chamber easily under field conditions (.i.e dusty rounds, etc.) You typically do not want a tight chamber on DGR rifles.

Don,

I appreciate the feedback. The bullet manuf. sizes his bullet a little over due to the soft copper, anywhere from .4165 to .417, so my measurement could be off slightly.
I checked the necks of fired cases for this rifle and an A^2 416 i have and both measured about 0.001 to .002 over max. specs.

I got lucky. I chrony the 18 fired rounds and if i plot out the velocity you can notice random pressure increase correlated with minor scrapping on the necks. Fortunately, these are low pressure practice loads with soft bullets so the increases were not great. I am posting this as a reminder how easy it can be to get into trouble with 1/1000s of inches. Thanks again for the interest.

rgds,

steve

PS the brass measurement above is for 2 walls.