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8milimeter
09-15-2011, 05:59 PM
I resently cut off on old barrel to make a case lenth guage. I cut it about .020 shy of the end of the chamber. What I noticed was that my trimmed cases were about .050 from the chamber end. So I picked thru all my fired cases and found a really long one 4.503 It still had over .030 clearance from the end of the chamber. I then put that long case in all my 30-06 rifles (7). The long case chambered without bottoming out.

My question is why do we trim our brass to 2.484-2.494 when most chambers have ample room for longer cases. It appears my rifles have .010 to .030 more room. I am sure I could safely fire cases at 2.500 and still have more then sufficient space for safety in my guns.

Opinions !!!

raymeketa
09-15-2011, 06:25 PM
8mm

Not everyone trims to 2.484 to 2.494. Some of us trim only as necessary to keep all cases the same length, making sure that our chamber is long enough to accept them.

And many of us have custom reamers that cut chambers with necks shorter than you'll find on most military and commercial rifles

Bottom line is - casual reloaders should trim to specs until they become experienced hand loaders. Case length is just one of many standard dimensions that have been established in order to keep some semblance of order.

JMHO

rcolarco
09-15-2011, 06:46 PM
Ray is exactly right. Case specs (including trim lengths) assume every rifle has a nominal SAAMI chamber. It's just easier to trim to spec than to size cases individually for each rifle.

Benchresters carefully size and trim cases for the closest fit possible to individual chambers. The outside of the case fits the chamber and the inside of the neck fits the bullet. Case prep between shots involves depriming, repriming, charging with powder, and seating a bullet. No resizing necessary. On rare occasions trimming may be necessary, but if you never size the case you may never need to trim it. This level of precision is wasted in a military rifle or a hunting rifle.

All my .30-06s are M1s, '03s, or bolt action hunting rifles, with the exception of one Remington semi-auto. I full-length resize all my cases in the same set of RCBS dies I have been using for 40 years, and trim to minimum length. I use good bullets. My latest hunting ammo shoots one-hole groups at 100 yards in my more accurate hunting rifles. It's an easy process to perform, and produces ammo adequate for my needs.

JohnF
09-15-2011, 06:48 PM
If you really want to know how much to trim, or even to find out if you need to trim, then get some Cerrosafe and make a casting of your chamber. It's not hard to do and will answer a lot of questions in order to tailor your handloads for your rifle and chamber.

ceresco
09-16-2011, 10:15 AM
Cerosafe casts will not get the cartridge base (think about it) and are very difficult to accurately measure shoulder to neck, etc. Sinclair sells an inexpensive plug gauge that you use with a modified case to actually check the available chamber neck. Works in all 308 cal cartridges. Just get one if you really want to know. There is always a safety factor over the listed case length but actually measuring it on my rifles produced a wide range. In general 2.500 is pretty safe unless you have a special chamber. Good Shooting...

aka108
09-17-2011, 08:16 AM
Most of my rifles have some military heritage whether bolt action or semi auto. I neck size the cases for the bolt actions and full length size for the semi autos. So far as case length goes, I trim them with the Lee case lenth trimmers and have never experienced any problems. I trim about every 3rd or 4th loading of the case. Never measured case length as I believe Lee knows more about that than I do. Anyhow, keeps things in spec.

GarandGrabber
09-17-2011, 10:59 AM
Cerosafe casts will not get the cartridge base (think about it) and are very difficult to accurately measure shoulder to neck, etc. Sinclair sells an inexpensive plug gauge that you use with a modified case to actually check the available chamber neck. Works in all 308 cal cartridges. Just get one if you really want to know. There is always a safety factor over the listed case length but actually measuring it on my rifles produced a wide range. In general 2.500 is pretty safe unless you have a special chamber. Good Shooting...

Mostly the Garands with a TE of 9...:D You going to come up tomorrow?

Unclenick
09-17-2011, 04:26 PM
. . . I trim about every 3rd or 4th loading of the case. Never measured case length as I believe Lee knows more about that than I do. Anyhow, keeps things in spec.

That's probably in the ballpark. I've not tracked the exact measure in the .30-06 closely enough, but my .308 target shooting loads (shot in an M14) grew an average of 0.005" per load cycle (standard FL sizing; not a small base die and not limited to .002" shoulder setback). Both the .308 and the .30-06 have a tolerance of 0.010" either side of the Lee trim length. I'm guessing you may be letting them get about 0.010" over tolerance by waiting through 4 reloads, but I've yet to own a chamber without at least that much extra room.

The SAAMI chamber spec to the end of the neck from the breech face is 2.5020"-2.5170". Many seem to be longer, but 2.5095" would be the middle, and I expect you'll see a number of chambers aimed at that middle spec.

There has also been some discussion of never trimming the medium power cartridges. The idea is the case starts to headspace on the mouth like a pistol cartridge, so a long neck sees to it the shoulder never touches the end of the chamber, so the shoulder gets blown forward a little rather than all the expanding going rearward.

I have yet to feel sanguine about this "X-die approach" to trim length. I'd rather do it in an actual X-die than in the gun. I'd be more comfortable with the idea if my chambers had a 90 step at end of the neck, but most have a taper (3543' in .30-06) into the freebore, and some, like the .30-30, have a very gradual taper (15) that I'd really fear wedging a case mouth hard into. But a 90 step with perhaps just five thousandths of chamfer (to avoid shaving bullets) might do the trick. Be an interesting experiment, anyway. Until someone funds me to get the special reamer and guinea pig barrel, though, I'll keep doing and recommending normal trimming.

GarandGrabber
09-20-2011, 02:41 PM
All my .30-06s are M1s, '03s, or bolt action hunting rifles, with the exception of one Remington semi-auto. I full-length resize all my cases in the same set of RCBS dies I have been using for 40 years, and trim to minimum length. I use good bullets. My latest hunting ammo shoots one-hole groups at 100 yards in my more accurate hunting rifles. It's an easy process to perform, and produces ammo adequate for my needs.


Yes I think for all of us "casual" handloaders shooting milsurps this process is plenty. :)