I realize for the 7 rem mag that the maximum case length is 2.500 and that most of the manuals suggest a trim to length of 2.490. New Nosler brass measures 2.483 +/- .002. If I set my trimmer to 2.483 +/- .001 and repeatedly trim all my cases to this length am I losing anything. In other words is the actual trim to length important for accuracy as long as they do not surpass the maximum and are all trimmed to the same length before reloading?
The new brass should not need trimming at all. When it eventually stretches to beyond 2.5" then you will need to trim it to 2.49. I doubt you are losing anything at all by continually trimming to 2.483 but at the same time, I don't think its necessary.
AFTER you fire form and resize your brass, set your trimmer to just true up the mouth of the shortest piece of brass you have --assuming it's below 2.490-- and trim the rest of your brass to that length. Then when you have fired it enough that it exceeds 2.490, use that measurment to trim to or trim to your original setting. There is nothing magic about 2.490 and you are losing nothing by going below it. When you seat your bullets, ignore the case length, of course, and work to your COL.
Trim your cases anywhere between the max and "trim to" length. Ain't no factory sporter made that can tell any difference between case lengths within a few thou of each other.
Posts: 1615 | Location: South Western North Carolina | Registered: 16 September 2005
I've read on certain sites that you want your brass trim-to length to be .005" shorter than your actual chamber length for best accuracy. A Sinclair gauge is available to acertain your chamber length as chambers may vary.
Does anybody think that accuracy would degrade by trimming too short?
Does anybody think that accuracy would degrade by trimming too short?
Not I said the "short trimmer"
/////////////////////////////////////////////////////////////////////////// "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill
Posts: 28849 | Location: western Nebraska | Registered: 27 May 2003
I think for short neck cases like the 7mm Rem Mag the longer the case neck is kept the better. Sinclair makes a chamber lenth gage case insert that will measure the exact length of your rifle chamber. You can then trim from the exact measurement.
Posts: 2627 | Location: Where the pine trees touch the sky | Registered: 06 December 2006
Do you have a gauge for each caliber you load? Is it worth buying them? On Varmint Al's page he has instructions for making the "poor man's gauge" by sawing off part of the neck of a case, seating a bullet in the case, slipping the sawed off ring over the bullet and chambering a few times to get a measurement.
I've tried it and the little piece of sawed off neck gets deformed enough and won't fit nicely over the bullet to where you can chamber it without it rubbing the side of the chamber neck.
Trying to visualize the dynamics of a cartridge firing, I can't see how a case trimmed a few thousands short is going to change anything. This assumes you have enough neck to hold the bullet. Look at the .300Win Mag. When it first came out, all of the "experts" damned it far and wide because of the short neck. But it's still hanging in there. Killing stuff and winning 1000 matches.
Here's what Varmint Al says about it as to being an accuracy aid:
quote:
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.
wasbeeman, I have to agree with you. If the bullet is kissing the lands or backed off the same amount from round to round, and the inside neck diameters are the same from round to round I don't see how a few thousands in length makes any difference at all. But then again, I've been wrong before...actually quite abit
I don't think so. By the time the bullet has left the neck of the cartridge, it is engaged in the rifling of the barrel. IMO, anyone that isn't shooting Bench Rest, especially someone in a hunting situation, that suggest putting the bullet into the lands is an accident looking for a place to happen. The insurance of having the bullet moving before it contacts the lands insures a more constant pressure and allows for slight differences in COL. Bench shooters who are the advocates of this are doing it under a much more controlled environment and they have taken into consideration the added pressure the act generates. Bench shooters rarely take a round out of the rifle after coming into battery so the chance of having an action full of powder is rather remote. And too, ramming the bullet into the lands is no guarentee that the bullet will be rammed in straight. Luckily, the rifle has 18-24" to work that out. I mean, if a fellow want to tinker around so he can say "my cases are .0005" longer than saami". More power to him. But if he's looking for the straight road to the Jeruselem of accuracy, he'd be better off putting his time into dry firing or range time.
You guys use just a standard set of calipers to measure over all brass length? I was going to buy the digital on on Midway USA that is on sale right now.
If I said they didn't have digital when I got mine would it make me a bad person?
Who is this Varmint Al? I just re-read the quote from him and he talks about accuracy CONFIDENCE. I have to kinda agree with that. Anything you do that makes you "think" you're a better shot, usually helps make you a better shot.
That's only half the story. I'll bet he ain't heard of me neither.
I just sorta skipped around on that page. It's just a re-hash of the things that the super anal do. Some of it is needed; a lot of it is a big laugh. And he throws in a couple of little quirks (.0005" longer than saami) to make himself sound like some sort of guru. Thank you very much, I'll just go back to reloading with my rock and rusty nail.
I don't think so. By the time the bullet has left the neck of the cartridge, it is engaged in the rifling of the barrel.
Not necessarily. Some chambers have a long leade -- precisely to be a guard against chambering over-length brass into the lands.
A few thousandths in length on new brass is inconsequential so long as it's not over max.
But for accuracy, fire formed for the chamber, neck-sized and trimmed to the gnat's butt uniform is the formula. And then you want to figure out where the sweet spot is on bullet seating off the lands.
Varmint Al discusses all this stuff, and he's right.
No, the idea of the long leade was a Roy Weatherby innovation (dont know if he was the very first or not)That allowed you to load to much higher pressure as the bullet was moving quite a ways before it engaged the rifling. I don't know that any of his cartridges had a actual space/time in which the bullet was totally unsupported between the cartridge neck and the rifling of the rifle. Maybe Varmint Al can tell you.
By any road, what we're discussing is the the portion of the chamber that the neck of the cartridge fits in. Not the leade. I'm not going to get bogged down making chamber cast but I'd be very surprised if the various rifle manufacturers didn't make that a bit long to guard against the neck of an over long cartridge pressing into the bullet. But certainly not so long that the bullet at any time between the neck and the rifling would be totally unsupported.
But, as I said, if you're the type that wants to tinker around so's you can say "my brass is .0005" over saami, knock youself out. If you think it makes you a better shot, it probably does.
