I got the RCBS small base dies so far they are working great and just as expected. Every piece of brass formed with them drops into the Sheridan gauge and seems to have a little bit of wobble just as expected.Ken70 wrote:OP, just buy the RCBS small base die. You only need the one die and not the set. That will get the case down to the smaller dimension your chamber obviously requires. If you got some Cerrosafe and a good micrometer that measures to the .0001", you could make a chamber cast and then measure it and find out how close to the blueprint it is. And measure the formed brass and see what you got.
Lee stated why they don't make a small base die; they feel it works the brass too much. Plus their dies seem to work for most users. Like others have said, 300 isn't the easiest round to produce. Especially if you're using different headstamps. You'll notice a lot of the vendors make a point of using only one headstamp, they've already found out about variances.
As to the Lee Precision dies, different brass, and variances, Lee Precision makes this product to reload rounds, no they do not say anywhere the rounds produced with their dies from 223/5.56 will fall into SAMI cartridge spec, and I am using a sizing die as a forming die, like many others are doing. I am saying nothing about using their dies to resize 300aac brass back into SAMI cartridge spec. I am specifically talking about forming 223/5.56 brass to 300aac brass that falls in SAMI cartridge spec. The fact that brass produced from 223/5.56 with a Lee Precision die will chamber in some rifles does not prove that the brass is in SAMI cartridge spec, just as my experience with the Lee Precision dies does not prove that I didn't just get a bad set of dies.
What my experience does prove is that Lee Precision will not stand behind their dies ability to form 223/5.56 brass into SAMI cartridge spec. Forming to the SAMI cartridge spec from what I have interpreted from the SAMI drawings means that the round should chamber in any chamber that is in the SAMI chamber spec. Link to the drawing again for reference.http://www.saami.org/PubResources/CC_Dr ... ackout.pdf
If you want to purchase 300aac dies for the intended use of forming 223/5.56 into SAMI cartridge spec 300aac and want to be sure they will work for that use, Lee Precision dies are not the way to go, as they will not back up this use. Will other manufacturers? That's a good question, I honestly do not know I found what worked for me and moved on. 400 mixed head stamp rounds with an RCBS small bass die and no issues. Factory ammo no issues. Brass produced with a Lee Precision die and measured in a Sheridan gauge 100% fail rate in the gauge check, 60-70% fail rate in my rifle, but this is my personal experience it may not be the experience of others. Could it have been a bad set of dies, sure that was my original thought, but Lee Precision did not offer to inspect them, they told me they did not support the use of their dies for forming 223/5.56 into SAMI cartridge spec 300aac. I do not seem to be alone in this experience either. Should others feel the desire to write some other companies to see if they would stand behind their dies ability to form 223/5.56 into SAMI spec 300aac and report back with their findings it would be beneficial information.
From my experience, understanding of the SAMI cartridge and chamber specs, and Lee Precisions response, I can say without a doubt that if you want to purchase 300aac dies for the intended use of forming 223/5.56 into SAMI cartridge spec 300aac and want to be sure they will work for that use/ have the manufacturer stand behind their dies to do that, Lee Precision is not the way to go.
Edited: for extra clarity on which of the two different SAMI specs I am referring to.