SmallCaliberCentral

The Sinclair chamber gauges arrived today. Couldn't wait to check the chamber on my Thompson Center Precision Hunter .204. It measured out to 1.890". I'm not sure but the SAAMI drawing looks like 1.8626". I've been trimming my brass to 1.842" Guess I don't need to do that from now on. Looks like iI'll be leaving them at SAAMI max of 1.850. And I only cost me $57.82 to find out. Ok, so I bought a few other gauges, a 204 body die, AR-15 firing pin retainer keys, and a bubble level.

Anyone trim their brass LONGER than 1.850?

Interesting. I will have to get the gauge soon - coz I reckon I'll shoot much better knowing the throat length for sure
Plus I have been wondering if maybe mine has a shorter throat. Have a little trouble closing the bolt sometimes and guessed this may be one reason?
And I haven't bought any toys for a little while

Sth Oz Dan wrote:Interesting. I will have to get the gauge soon - coz I reckon I'll shoot much better knowing the throat length for sure
Plus I have been wondering if maybe mine has a shorter throat. Have a little trouble closing the bolt sometimes and guessed this may be one reason?
And I haven't bought any toys for a little while

Don't get chamber and throat length mixed up.Sure a longer chamber will extend the distance to the lands.but seatting a bullet to touch the lands does not give you
chamber length and trim length.That's where the Sinclair gage is used.

Joe O wrote:Don't get chamber and throat length mixed up.Sure a longer chamber will extend the distance to the lands.but seatting a bullet to touch the lands does not give you
chamber length and trim length.That's where the Sinclair gage is used.

Roger that Joe. I'm still a little rusty on terminology. I have the tool for measuring to the lands, and understand this differs with each bullet (and my throat does seem shorter there than most). The length I'm after is from bolt face to where the neck would touch/squash if too long ie max trim length. So this is "chamber length"?
I ordered the Sinclair tool this morning. I was surprised that it cost nearly a hundred bucks. But I was lucky to get a Forster trimmer and a few other little goodies thrown in for free

Good move Dan.You have it right for chamber length.Once you measure(average three tries),trim .010 below this measurement.You may find your brass is to short to get to within .010 of chamber length.I just square off the necks (to a uniform length)after the first fireing,when this happens.