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Posted: 9/4/2015 1:03:50 PM EDT
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My friend got left a rifle in 1995 that hadn't been bored out yet for any certain cartridge, but the bore was .308.. took it to a gunsmith and they gave him the options and he chose 30-06. He doesn't know squat about rifles, so when he test fired it last in 1995 he probably didn't notice this. He left the rifle with me while he was overseas and I reloaded a few light rounds to test it and we shot it today. If the pic works, you can see a sort of step in the cartridge about 1/3 way down from the shoulder. It looks like it was first bored a little larger to that depth, then they finished boring it to 30-06, which is a little smaller than the original boring. So the case fire forms to have this stepped ridge in the case body.
I assume it's safe to shoot like this? Also think I could probably still reload for it, but case life may be shorter due to the ridge? What say you? 
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How does it feel when you full length size one. I would think the the larger side will be getting sized a lot by looking at the blue print.
If this is what's happening the extra expansion and subsequent re-sizing will definitely lead to premature case failure. If it was mine and I for whatever reason did not want to have it fixed the only way I would consider using it would be to neck only size the brass so the case body will not be "worked" any more. There are a few options for fixing it but all require gun smith services unless you are capable and have the tooling to do it yourself. Motor |
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More just seeing if there's any reason it wouldn't be safe to fire with full strength loads. Being able to reload was more a curiosity. I haven't tried full length resizing these yet and probably won't. I told him if he wants to shoot (he doesn't hunt) to just get the low power rounds for his plinking.
I thought about neck only sizing, but I don't even have -06 dies (and don't have an -06). I had to borrow the two die set from another friend as well as a few cases for test shots. Prob too late to take it back.. |
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The .30-06 case tapers from .470" at the base to .436 at the start of the shoulder.
If the base measurement is still .470", then the issue is not enough taper along the case wall when it was short chambered, creating a step when the .30-06 chamber was completed. The .30-06 Ackley Improved tapers from .470" at the base to only .453" at the start of the shoulder and the shoulder is farther forward. Consequently, I'd measure the diameter just before the step and measure that distance from the base and then do a little trigonometry to see how the taper compares to the .30-06 AI. If the base measurement is still .470 and the diameter just before the step is small enough to fall within a .30-06 AI case dimension, I'd just get it reamed to .30-06 AI - which may have been the intention in the first place given the reduced taper. ---- If you leave it as is, there's no real harm, provided that you only neck size the cases. If you full length resize it will work the brass excessively and you'll get cracks in the body of the case near the start of the step where the brass is being worked the most. Case life would probably be around 3-4 reloadings with near maximum loads, and a little longer with lighter loads. |
| Not a gunsmith but have some machinist experience. Looks to me like they used two reamers, one a rough cut and the other the finish cut. The reamers didn't match and the first tool over sized or went too deep?. I agree it looks like a perfect opportunity to have case separation issues at the spot of the diameter change. I'd find a good gunsmith and remove the barrel and have the chamber recut and headspaced or a new barrel installed. Looks like a good gunsmith would have test fired and found the problem? |
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I can't see the pic, but I assume it is a hybrid of 308 and 3006 chamber reamers.
As long as the bottom 1/2" of the cartridge case is well supported, I would not think of this as unsafe. I used to get a huge number of partial/full case head separations in my M1A until I started sizing brass carefully and segregating lots by the number of times the cases were fired. How about doing an experiment, of loading and firing 5 or 10 cases to failure? I would venture to guess you may have some case body splits, but lose the majority of cases to "old age" - loose primer pockets, case neck splits, loss to the brass God at the range. In a bolt gun, the risk of a body split to the shooter 1.5" up the case base is neglible. |
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