TTL Question
- Thread starter ConRich
- Start date
Gene Beggs
Active member
Dick, it sounds like you're talking about my 220/6mm Beggs cartridges.
When fireforming, follow the method outlined in Mike Ratigan's book i.e., lube the cases well for the first firing. I use twenty grains of N133, Benchmark, 322 or 8208 with the bullets seated long and jammed hard into the lands. This prevents stretching in the critical web area. Cases fireformed in this manner will not tighten up in the web area later. After the first firiing, you can use a full charge of your favorite powder. In the 6mm Beggs, my hands down favorite is H4198. For the 220 Beggs, Benchmark.
After the first three firings, the 220 cases usually measure 1.515, the 6mm cases around 1.505. In either case, the necks do not run into the end of the chamber until they reach 1.530. After depriming, measure the cases and find the shortest. Trim all to that length and deburr with what Mikel Shilen calls a, "Rocket Ship." That is, an L.E. Wilson inside/outside neck deburring tool.
Unless you bump the shoulders back more than .001 you will probably never have to trim the cases again. If they should approach max length (1.530) trim to 1.515. Some question the wisdom of leaving .025 to .030 in front of the case neck in the chamber fearing this will build up carbon etc.,
decrease accuracy blah, blah blah. Forget about it; doesn't hurt a darn thing, I assure you. Better to have a little more room than necessary in this area than run the risk of crimping the case into the end of the chamber.What is the minimum clearance? Just so the neck doesn't contact the end of the chamber. How much is too much clearance? I would say with our little 220 and 6mm cartridges, about .035 is the max I would want.
Hope this helps.
Later,
Gene Beggs
Thanks Gene. My rifle is a 30BR and the brass has been fired about 10 times. I noticed that they are not all the same length now and thought about trimming them to the length of the shortest ones but didn't want to create a problem with the carbon ring.
Thanks for the help,
Dick
Thanks for the help,
Dick
A
abintx
Guest
Dick ...
Here is a similar question I once asked and the responses I received:
Chamber Length Safety Zone
Q: How many thousandths shy of actual chamber length does one establish as a safety zone, before assigning a trim "from" length, once measurements have established a rifle's true chamber length ???
Mike Bryant
A: I use .010" for each increment. For instance, if the chamber length is 1.570" from the base to the end of the neck on the chamber, then the maximum case length would be 1.560" with a trim length of 1.550". Don't let the cases get over 1.560" and you'll be in good shape.
Jackie Schmidt
A: I use a .010" window. 6mmPPC chambers have been shortened to 1.510". Since shooters fire cases to expand them, the cases come out close to 1.500". I trim them back to 1.490."
Here is a similar question I once asked and the responses I received:
Chamber Length Safety Zone
Q: How many thousandths shy of actual chamber length does one establish as a safety zone, before assigning a trim "from" length, once measurements have established a rifle's true chamber length ???
Mike Bryant
A: I use .010" for each increment. For instance, if the chamber length is 1.570" from the base to the end of the neck on the chamber, then the maximum case length would be 1.560" with a trim length of 1.550". Don't let the cases get over 1.560" and you'll be in good shape.
Jackie Schmidt
A: I use a .010" window. 6mmPPC chambers have been shortened to 1.510". Since shooters fire cases to expand them, the cases come out close to 1.500". I trim them back to 1.490."