Sendero seems to have a tight chamber


Well-Known Member
Sep 23, 2008
The tolerances must be extremely tight in my 300 RUM. Even with factory ammo, the bolt can be hard to close, and it is cratering primers even on starting loads.

When I measure my fired brass, the measurments are the same as full sized brass. So is this a good thing, or bad ?

Here is a pic of the primers

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The same damned thing is happening with my Ruger77 (300wm). I was using a brand new box of Hornady SST's during deer hunting and I put one in, and thought 'man that sure seems tough'. When I ejected the cartridge at the end of the hunt, the case was just scratched to hell. It looked like somebody ran a blade over it a few times. And these weren't just light scratches, either. I could actually feel the gouges in the brass.
Your primers are cratering due to excessive clearance between the fire pin and hole. If you look at the radiused perimeter of the primer it is nice and round and not at all flat. You have mild chamber pressure with those loads.

You may have a minimum headspace on the chamber, that is a good thing, or you could have some debree in the chamber. Or an ejector button that for some reason is not going all the way in. All easy stuff to check. Run a pc of brass into your FL die and see how it chambers with no powder or bullet seated. make sure the shell holder makes firm contact with the die.
I don't know if this will help, but I have a sendero that I bought back in August brand new. Got it out of the box put a scope on it and tried to put bullets in it. Would not close the bolt. I tried the whole box of factory shells and 3 out of 20 would chamber. Sent the gun to remington they had to finish ream the chamber and replace the extractor. Then when I got the gun back Shot it a few times and went to clean it and the bolt face was all scared up from the bottom of the cases. Looked to see what was doing this and the bolt has a lip on the end of the bolt where it meets the barrel. So I sent the gun back and haven't heard anything yet on it.
After readjusting my die so that all the slack was out of the shell holder, now my sized brass will chamber. So I guess it is just a min spec chamber.

The firing pin hole is around .091" best I can measure it.
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