I posted this at a couple other sites but thought that it might be good to post it here as well. I read the following article from Varmint Al's reloading page and it made sense to me. I just bought 500 pieces of brass and have already trimmed about 200 of them to minimum length. It just so happens that based on my chamber depth as measured according to the procedure in the article, minimum length is about .015" shorter than my chamber will accomodate. If you were me, would you finish trimming all the brass to the same minimum length or would you trim to chamber length on the remaining brass and use the minimum length stuff for plinking and save the chamber length stuff for serious accuracy work?
From the following link... http://www.varmintal.com/arelo.htm
MEASURE THE CHAMBER LENGTH.... Here is another accuracy aid. I purchased the Sinclair case length measuring plugs for .17, .224, and 6mm calibers. These are very simple steel cylinders turned to the bullet diameter, leaving a rim slightly less than the case neck OD. To use, you merely drill through the primer pocket (so you can later push the plug out) on an expendable cartridge case and neck size it. Trim the case length about 0.100 inch short so the case mouth will not touch the rim of the plug gauge. Insert the Sinclair plug gauge as if it were a bullet, leaving it long and then chamber the case. The plug will be pushed deeper into the case neck and when you extract it, you can measure the chamber's actual length with a dial caliper. I usually find that the factory recommendations for case length leave a 0.050 inch to 0.070 inch gap between the end of the case and the actual length of the chamber. Click here to see a drawing. This is a factory safety concern and you can get high pressures by forcing a long case into a short chamber. The factory wants to be on the safe side. But like everything else, if you want the best accuracy, you can minimize this gap down to 0.005 inch and still be safe. You will get better accuracy and find that you can use much longer necks, in most cases, than the factory recommendations specify. The extra case length will better allow you to load the bullet farther out to touch the lands. I have found that, typically, factory .243 Win brass, is already 0.050 inch too short and there is no way that I can think of to lengthen it. I don't trim to the lengths specified in the loading manuals, but use my measurements as a guide. All of this sounds like a lot of trouble to go through compared to walking into a store and asking for a box of 30-30's, but it makes a big difference in the confidence level of your accuracy potential. If you have a lathe, the dimensions of the plug gauges are given for a few rifle calibers on my Mini Lathe Page. They are very easy to make. Check out Fred's page for more info on making tight-neck and long-neck brass.
From the following link... http://www.varmintal.com/arelo.htm
MEASURE THE CHAMBER LENGTH.... Here is another accuracy aid. I purchased the Sinclair case length measuring plugs for .17, .224, and 6mm calibers. These are very simple steel cylinders turned to the bullet diameter, leaving a rim slightly less than the case neck OD. To use, you merely drill through the primer pocket (so you can later push the plug out) on an expendable cartridge case and neck size it. Trim the case length about 0.100 inch short so the case mouth will not touch the rim of the plug gauge. Insert the Sinclair plug gauge as if it were a bullet, leaving it long and then chamber the case. The plug will be pushed deeper into the case neck and when you extract it, you can measure the chamber's actual length with a dial caliper. I usually find that the factory recommendations for case length leave a 0.050 inch to 0.070 inch gap between the end of the case and the actual length of the chamber. Click here to see a drawing. This is a factory safety concern and you can get high pressures by forcing a long case into a short chamber. The factory wants to be on the safe side. But like everything else, if you want the best accuracy, you can minimize this gap down to 0.005 inch and still be safe. You will get better accuracy and find that you can use much longer necks, in most cases, than the factory recommendations specify. The extra case length will better allow you to load the bullet farther out to touch the lands. I have found that, typically, factory .243 Win brass, is already 0.050 inch too short and there is no way that I can think of to lengthen it. I don't trim to the lengths specified in the loading manuals, but use my measurements as a guide. All of this sounds like a lot of trouble to go through compared to walking into a store and asking for a box of 30-30's, but it makes a big difference in the confidence level of your accuracy potential. If you have a lathe, the dimensions of the plug gauges are given for a few rifle calibers on my Mini Lathe Page. They are very easy to make. Check out Fred's page for more info on making tight-neck and long-neck brass.
