K31, little help please

happydude

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Doing some loading for a friend, but having a little trouble. I'm using resized .284 Win brass, trimmed as per a Lee 7.5 S case length gauge, and loaded with Hornady .308 150grn BTSP interlock bullets. The problem is, seated to the crimping grove they will not chamber. At all. To get it unstuck required quite a bit of force and one helluva surprise as the dummy round ejected backwards into my face. Ouch. Moving along, I seated the bullet to the min OAL of 2.790 and that worked much better, but the last 1/4" or so of the cycle still required a pretty good push and resulting 'click' noise. Finally, I seated one lower than recc'd overall length to 2.775 which chambers fine without resistance. Having never shot a K31 or any straight pull, I'm not sure how much resistance to expect. The other problem, since the bullets at BTs, seated to 2.790 a good chunk of the Boat Tail end of the bullet is sticking into the shoulder and case area which makes me a little nervous. I'm not a fan of seating bullets lower than recommended, and I'm also not keen on seating a bullet with part of it sticking out into the shoulder/body area of the case.

I have no problem buying different bullets but if there's another issue I'm not considering let me know.

Excuse the terrible pics, it's the best I can do.

Here's one seated to a shade under minimum spec (2.775 - min OAL with H335 load is 2.790).

Photo2.jpg


And one loaded to the crimp grove, 2.910, and this was was well cam'ed over when sizing.

Photo1-2.jpg


And one of the bullets,

Photo3.jpg
 
The only thing I can think of is the profile of the bullet. In your second photo, you can see more bearing surface of the bullet. K31's do have a short throat, and if your bullet has a "stubbier" profile (short nose), loading to length may be pushing it into the rifleing, causing the resistance.
I have some 150 SP's loaded to 2.75", seated to the cannelure and they chamber just fine. Also have 175 HPBT's at 2.915 and they chamber the same.

A bit from Surplusrifle.com about reloading for the 7.5 Swiss.
The olgive of the Swiss bullet doesn’t increase in size to .308 until a lot further back; so the long bullet of Swiss GP-11 ammunition doesn’t interfere with the short throat. Most US made bullets reach .308 diameter much closer to the nose of the bullet.

(E) :cool:
 
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