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tight neck ?

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grumpy04730 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote grumpy04730 Quote  Post ReplyReply Direct Link To This Post Topic: tight neck ?
    Posted: June/01/2009 at 09:01
Last winter I bought a Weatherby MK 5 lightweight in 280 Rem. After mounting a scope on it and firing it for the first time with Hornaday 139 moly light magnum ammo. it proved to be a real tack driver .3 to .4 3 shoot groups and fast over my Chrony 1 3200 fps avg. But when I went to reload for it a bullet won't fit into a unsized case I have never run acrossed this before so I take it this is not normal.  The brass shows no outward sings of high pressure but i'm a little leary of what it will do in warm weather. But on the other hand I don't want to send it back to the factory to have it rebarreled if I can get by with it .
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300S&W View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 300S&W Quote  Post ReplyReply Direct Link To This Post Posted: June/01/2009 at 12:23
  From the Hornady specs it seems your over the top with your velocity readings.
 
   There are a number of things you can do to get proper neck clearance but first off I would contact Weatherby and see what their response is. No need to spend more of your hard earned money when they should fix the problem for free. You may need to click,refresh,to connect.
 
"I ain't got time to bleed!"
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Duce View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Duce Quote  Post ReplyReply Direct Link To This Post Posted: June/01/2009 at 12:34

Have you tried it with the regular 280 ammo too? and does it do the same thing. It may just be the light mag ammo. I have an older Weatherby 240 and it is very picky about what it will shoot, if I drive the bullet to fast the accuracy goes down.

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Texas View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Texas Quote  Post ReplyReply Direct Link To This Post Posted: June/01/2009 at 13:31
Grumpy,
 
If the Hornady factory ammo will chamber without so much resistance that you notice or feel the resistance when you close the bolt handle on a chambered round, it is not really a tight-neck chamber and is just on the small side of the SAMMI spec. A factory round will not chamber in a benchrest-style tight neck chamber at all because the chamber neck ID id too small; i.e., the brass must be neckturned to even chamber in the rifle. If you really see a need to verify the chamber dimensions, take the rifle to a good gunsmith or send it to Weatherby and have a chamber cast made and measured, and compare the measurements to the SAMMI spec. Also, use a micrometer to measure the o.d. of the neck of a fired case vs. a loaded, unfired round from the same box of ammo. The fired case should be slightly larger than the unfired ammo.
 
Unless there are signs of excessively high pressure like a hard to open bolt or a flattened or leaky primer, I would just be greatful to have a tack-driving factory rifle and shoot it... my feel is that this rifle has a chamber cut on the small side which can be a real enhancement to rifle accuracy. This is also a good thing if you hand load, it means your brass will last longer from not being worked as much.
 
Hope this helps and good shooting,
 
Texas
"There are some things which cannot be learned quickly and time, which is all we have, must be paid heavily for their acquiring. They are the very simplest things..." Ernest Hemingway
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Oldtrader3 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldtrader3 Quote  Post ReplyReply Direct Link To This Post Posted: June/01/2009 at 14:01
Can you check I.D. and O.D. of the fired case and compare it to SAAMI specs?  Check at the base of the neck O.D. and at the mouth of the neck also.  They should be the same diameters?  The reamer may have worn or been sharpened with a taper? 
CDR3
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grumpy04730 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote grumpy04730 Quote  Post ReplyReply Direct Link To This Post Posted: June/01/2009 at 17:03
This morning I had a chance to call Sierra Bullets and talked to one of their ballistic techs He had Me measure some fired cases and seemed to think My chamber is SAMMI mininum spec. and I should be good to go. I talked for almost an hour learning two or three things i hadn't learned in 25 years of handloading. This is a very helpful service if you have a question.
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