was playing with QuickDesign (which looks to have fallen out of favor here as last post was years ago)
for 416 Rigby and Swift A-frame and the collison check shows that for almost the full
length of the bullet shank from the case mouth collides, ie bullet larger than the reamed chamber.

Then looked at the CIP specs for leade angle, chamber diameter at the case mouth and bore (land diameter)
and in just 20/1000" or so from the case mouth, the chamber is at the bullet diameter of 416!

Am I missing something here or just to many Tequila shots over the Winter?

thank for any help.
Steve

Are you explaining that the 416 chamber in question has a freebore of bullet diameter (.416) for .020 length before the tapered leade starts?
Sounds reasonable...

The chamber diameter at the case mouth is 0.4169 and at 20/1000 is then 0.4160.and bullet shank goes another say 200/1000” while the chamber diameter is now smaller than the seated bullet diameter.!

I can't imagine anyone making a reamer that cuts a throat/leade the exact size of the bullet. They are always .0005 larger. Half a thousandth.

My early Ruger .416 Rigby has a very short throat which gave me problems with the early Swift bullets. I had to keep the OAL of my reloads well short of the max. OAL listed for the cartridge. I don't know if Ruger cut their chambers to any standard but it really needs to have its throat extended a bit.
C.G.B.

Here is the 416 Rigby Saami Chamber spec. and Swift A-frame measured diameter.
I assume the +0.002 diameter Saami refers to max. chamber and the listed diameters are min.
The plot is from the case mouth to the bore diameter and A-frame seated at the cannelure middle
giving an OAL of 3.60", well short of the 3.75 max length.




and the collison plot from QuickDesign that started me down this rabbit hole.

SAAMI drawings were not made for the swift bullets; you will need a throater. This chamber was designed for traditional tapered ogive bullets. This interface issue is common with old chamber designs (and many new ones too) and new monometal and bullets with less ogive taper.
Easy fix. Get a throater.

thanks dpcd, will look at throating out to 150/1000 to 200/1000.
Been looking at the Swift bullets shot start pressures which is 10777 psi vs
normal bullet 3600 or so and even more than solid copper according to quickload and now their ogive with it's funky shape.
Great bullets, just need a bit of love to use.

DPCD is correct--use a throater to allow your specific bullet, seated to your COAL, to be used. The reason for this is neither SAAMI, nor CIP specify bullet profiles in their standards, as this is an impossible task that would never be up-to-current manufacturers' offerings.

When SAAMI standardizes a new cartridge, it relies on dimensional and pressure-test data from the designer/maker. This data, and the format in which it is presented, must meet SAAMI's standards for testing methods and statistical reliability.

It should be noted that CIP and SAAMI have a close working relationship, with most cartridges standardized by CIP accepted by SAAMI, and vice versa. Generally, CIP dimensions are identical to those published by SAAMI, WHEN METRIC/ENGLISH CONVERSIONS AND MEASUREMENT LOCATIONS ARE TAKEN INTO CONSIDERATION.

Specifically, there are rounding errors in metric/english dimension conversion. Further, SAAMI "base" diameter measurements are usually taken .200" from the bottom of the cartridge vs variable locations for CIP. This difference in base location affects body taper calculations. When actual lengths are used, however, body tapers, between CIP and SAAMI, are usually identical.

SAAMI and CIP, in establishing cartridge and chamber standards, do an excellent job of ensuring your CZ 550 will accept 416 Rigby ammunition made by Federal, and your Remington 870 will safely fire Czech ammo when both firearms and cartridges are made to industry specs. And yes, maximum body length of cartridges usually exceeds minimum chamber body length. The system works in practice, likely due to manufacturers' tendency to produce middle-of-tolerance brass, and gunmakers' tendency to cut middle-of-tolerance chambers.