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44magSr
Reply with quote  #1 
I am setting up for a new rifle I am currently having made in .243 Winchester. I am starting with new Winchester brass and was wondering how short is too short to trim them. My current 243 brass is trimmed to 2.040, .005 under SAAMI max length. My new brass measures anywhere from 2.034 to 2.040, the majority being under 2.040. I am trying to come up with a common mid length between the longest and the shortest so I can weigh them out and sort them after I trim them but I don't want to go too short. I am expecting them to stretch a bit when I fire form them but like I said I don't want to go too short. What lengths have some of you been working with and what is an average amount of stretch you have experienced. I feel a little foolish asking all this because I should have data on all this already from my other rifle and the brass I used in that rifle but when I started my long range shooting and loading this was a step I overlooked in the beginning.

Here is an interesting question, what do you think about fire forming before trimming? Thought about this using the Unique/Cream o Wheat method.
fdshuster
Reply with quote  #2 
44MagSr: I use the Sinclair Chamber Length Gauges, ( 2009-B catalog, page 32, item #G-243, $6.95) for all my chambers and take the actual chamber length measurement for that chamber. The number is recorded, and case lengths kept .010" shorter. The chamber length on any given rifle can and will be whatever was on the reamer that was used, and I've found some to be as much as .042" longer than maximum case length as published in some of the reloading manuals. On top of that, they tell you to trim .010" shorter than maximum, creating a huge gap in front of the case mouth, where a ring of carbon will buildup.
44magSr
Reply with quote  #3 
fdshuster, Thanks for the reply, I actually do have that chamber length Gauge, I just don't have the rifle yet, its currently in the works at my gunsmiths place. I was initially wondering about the case length because I want to weigh and sort them out but didn't want to trim them shorter than necessary before I got a chance to measure the chamber on that rifle. I am thinking I may just fire form them with the ole cream of wheat method first before I weigh and sort so I can see how much stretch I get when I do fire form them if any. I would think I would see some, not expecting a whole lot but want to keep them as long as possible til I get to check the new gun out. I may even be able to get some info from my gunsmith on how long the necks might be if I can get him to measure the neck cutting area on his reamer. Thanks again
fdshuster
Reply with quote  #4 
44magSr: I can understand you wanting to get started, and I feel the same way when I know a new rifle is on the way, but I don't do any serious work, of the permanent type 'til I have the rifle in hand. I always have the gunsmith include the empty,fired brass case from his test firing, when he delivers the rifle, and take my chamber dimensions from it, before doing any loading for that particular rifle.
44magSr
Reply with quote  #5 
fdshuster, Yeah I have to agree with you, I am just a bit excited about it and was hoping to get something started. However I did pull out the chamber length guage and measured my current rifle chamber and the neck is cut .032 longer than my brass. I am going to give my gunsmith a call and see if we cant set up the new rifle with a little less room than this and give me a bit closer tolerances. Thanks for the input about this if you had not said anything I would have totally forgot about this little step.
By the way, Have you ever used JLK bullets? I am setting up the new gun with a 1 in 7 twist for the 115 gr bullets and want to throw them into the mix and try them along with a few others?
fdshuster
Reply with quote  #6 
I'm using Sierra and Berger bullets, almost exclusively in all my BR match rifles, and some of the Varmint models. Just a few of the V-Max, so have no knowledge of the JLK bullets. There are so many choices of extreme high quality bullets available, it is mind boggeling. We are fortunate to have so many to choose from. When I was "active" with my 243's the Sierra 75 gr. #1510 and 85 gr. #1530 were 2 of my favorites: Varmint bullets that produced groups like Match bullets. Never used Berger's 'til the 6ppc in 1998, followed by 6BR's a few yrs. later. Regarding the existing chamber length: you could let the cases stretch and not trim them back 'til within .010" or so. I don't think there is any industry standard for chamber length, might be whatever the reamer maker decides to make it, otherwise why the wide variations in lengths? Couple of my chambers, same cartridge, differ by .028" in length.
JamesinAsheville
Reply with quote  #7 
44magsr I'd ask whoever is building the rifle to measure the reamers' neck lenght and you'll find you can run the brass longer than you might think. Fireform the brass then turn the OAL.
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