where on sammi drawing does the freebore start and end

[Shawnba67]

I was looking at the sammi drawing and for my 243 win it shows what looks like the end of the brass at 2.055 and then a sharp 30 degree taper to dimension at 2.0816 then what looks like the end of the leade at 2.259. So i can handle the basic math part just curious which dimensions i need to use? And id .026 is the correct sammi freebore for 243 win??? thanks

 

[JohnW...ski]

My reamer drawings have a dimension that is called out as "lead", and is ahead of the 45 degree angle that is the transition from the neck to the throat, at the beginning of the 1 degree 30 minute throat taper to the bore diameter. The SAAMI drawing you are looking at does not appear to have any lead, the 2.259 dimension is the end of the throat at the .237 diameter bore dimension.

 

[BoydAllen]

It has been a while, but if I remember correctly the SAAMI .243 chamber does not look like those that have a parallel freebore ending with the leade angle at the origin of the rifling. What the original .243 design has is a continuous angle that runs from the end of the case neck part of the chamber to the top of the lands. The OD in front of the case neck is larger than the typical parallel freebore so that the point where the bullet would contact the rifling is about the same place that it would be if a typical target configuration was used. Some years back a friend who had been a factory engineer for Savage told me that he had asked one of the Remington engineers about how their .243 chamber throats were designed. The reply was that rather than follow the SAMMI drawing they had use the same one that that they used on the .244/6mm Rem. which has a parallel freebore.

 

[rcw3]

A SAAMI 243 WIN chamber has a -0- freebore (i.e. no freebore at all).

It's a big funnel with no freebore - it's one of the anomalies in SAAMI chamber designs.

 

[Shawnba67]

A SAAMI 243 WIN chamber has a -0- freebore (i.e. no freebore at all).

It's a big funnel with no freebore - it's one of the anomalies in SAAMI chamber designs.

Thanks Boyd also.
Well at least I'm not a dumb as I was starting to think I was. I probly spent 10 minutes looking at that darn drawing. Lol Thanks much

 

[GrocMax]

The funnel style freebore is also present in the SAAMI 300 WinMag. Its a little confusing when you first look at it.

 

[Richard Jones]

SAAMI ain't always correct, either. Check out the 25WSSM and tell me what you see wrong.....

Never knew that about the .243. Thanks to Boyd & Mr. Whitley.

 

[Shawnba67]

So if the sammi funnel where to be thought of in terms of regular freebore, Where would it fall ie- .000, .090, .140 ??? Just for my curiosity