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Old August 5, 2012, 01:28 PM   #26
Bigdog57
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I recently had similar problems, when trying some 165 gr.loads vs. my usual 150 gr. loads. I use the 'official' 2.790 COL that my loading data said fr the 150's, and they work fine. They listed the 165 gr. at 3.06, and I was getting failures to chamber all the way, and sometimes the bullet stuck in the lands! I reseated to the 2.790 mark, and all is well - no pressure signs, and my K31 loves the load! I finally have it shooting as good as with GP11.
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Old August 5, 2012, 02:25 PM   #27
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I would add that a spec for an older rifle may well not match the spec for a later design, even in the same chambering. Diopter's link shows a difference, and the first post describes using plug type gauges rather than slugging for which a 7.52 mm won't enter the muzzle. So that rifle clearly doesn't have The 1911 7.54 mm bore spec. So I don't think this is just a slug measuring error.

The taper is obviously substantial on the bullets Diopter measured. That the pressure ring at the bearing surface heel would be fat is no surprise, but the degree of reduction by the case mouth position is more than you'd expect in most modern bullets. Seem like that bullet might be designed to squeeze down the bores of even the late 1800's designs.
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Old August 7, 2012, 07:19 AM   #28
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My thanks to parashooter for the scans.

Links:
http://i45.tinypic.com/2lxv5n4.jpg

http://i54.tinypic.com/10hnk82.jpg


K31



K11


Bore mm LH RH Total K31 mm "
Min 7.5 + 0.15 + 0.15 = 7.8 = 0.307086614"
Max 7.57 + 0.15 + 0.15 = 7.87 = 0.30984252"


LG1911, K11 bore
Min. 7.54 + 0.13 + 0.13 = 7.8 0.307086614
Max 7.6 + 0.13 + 0.13 = 7.86 0.309448819

Last edited by diopter; August 8, 2012 at 01:04 PM.
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Old August 8, 2012, 11:38 AM   #29
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I'd be interested to know what document those are clipped from. (Also please be sure you have permission to reproduce them if there is a copyright currently in force, pursuant to the board policy.) At 0.15 mm, that's the highest land height number I've seen yet. If several folks with K31's would slug their barrels and mic the diameters of the lands and the grooves on the slug, it would be informative.

I'd still like to see what happens if the OP marks his bullet with a Magic Marker to see what the marking on the bullet looks like where it stops in the throat.
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Old August 8, 2012, 12:05 PM   #30
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Old August 10, 2012, 11:21 PM   #31
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What's cool about the K-31, is that you can easily use the rifle itself as a bullet seating gauge. Here's how:

Start by placing the cocking piece in the "half-safe" position:



Then make up a dummy round (no primer, no powder) using your chosen bullet, but seated long enough that you know that you are going to touch the lands before the bolt goes into battery.

With the cocking piece in the half safe position, the bolt rotation has no spring tension to fight against. Attempt to chamber the dummy by gently pushing the bolt forward using your thumb on the back of the bolt handle rod as pictured. You will be able to easily feel the point where the bullet touches the lands.

Take out your dummy, put it back into the press, and seat the bullet deeper by .005" to .010", depending on how patient you are. Retry closing the bolt as just described. Repeat this procedure until you can just get the bolt to go into battery with a gentle push. Now measure the C.O.L. This is the length that you are just touching the lands. Now seat the bullet a little deeper, say .020" to .050", whatever is your preferred jump distance.

You might try this procedure several times until you feel that you have reasonable confidence that you are getting a repeatable measurement and a good number for your C.O.L.

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