I've been reading (again) "Any Shot You Want" by Art Alpin, (A-Square Co. (Yes, I know that there was considerable controversy involved there, but that's all I recall so am not going there.) He discusses parallel and tunnel throats and how they affect seating depths and accuracy. He says that any standard cartridge will always have the same type of throat. Does anyone know where that info can be found? Diemakers? Sierra Bullets?

Talk to a reamer company; Dave at PTG knows all about designing reamers and can talk about throats and free bore. Also the SAAMI book on chamber and cartridge specs has all the throats in it, but do not expect gun manufacturers to follow it; there is no mandate to do so, therefor each maker has his own throat designs. Some, like Ruger, have many of them for the same cartridges.

The US SAAMI standards are supposed to provide safe pressures with SAAMI standard ammo. However production reamers can be manufactured to produce the largest possible throat and chamber so that the reamer can be sharpened several times before it is considered too worn to use. This sharpening process will make the reamer and the chamber smaller each time the reamer is reground causing variation in chamber and throat dimensions.

There are several different basic chamber/throat designs that are dependent on the purpose of the rifle.
A benchrest or competition rifle will often have a tighter neck and shorter throat.

A rifle designed for dangerous game hunting may have a long free bored throat. An example of this is the SAAMI 458 Win chamber. The factory chamber ensures easy chambering of a round that does not have to hit the smallest targets at long range.

A cast bullet rifle may have a tight neck and long tapered throat. Some BPCR variations even have a long free bore with the long throat.
The free bore pemits long heavy bullets without intruding in to the space needed for heavy black powder charges.

The best chamber and throat design can even vary for the same cartridge used in different rifles. A 6.5X55 chamber for a Ljungman autoloader might be very different than the same round used in a 300 meter free rifle.

YOU MEAN "FUNNEL" THROAT NOT TUNNEL THROAT.

A "Funnel" throat is a zero-parallel-sided free-bore throat.
It is just a leade angle from chamber case mouth to rifling bore diameter.

You better read Art Alphin again and pay attention to tunnel versus funnel at least this time.
His book is very good an not controversial at all.

Study some throats here, CIP specs from the reference section of this forum:

quote:

Originally posted by jeffeosso:
CIP
[QUOTE]Originally posted by Ol` Joe:
http://www.poliisi.fi/intermin...DE/$file/TABIcal.pdf

http://forums.accuratereloadin.../9411043/m/861105007

You are correct, RIP. Funnel is correct. Also, I did not mean that Alpin's book was at issue. It is quite good. He apparently ran into some legal and financial problems. As I understand, A-Square is out of business. That's about all I know, so I didn't want to address it.