Originally Posted by 308 nate
Here is what's happening. I built a couple 300RUMs for a friend of mine and he is having some problems with reloading. (no, he's not a new reloader)
New brass he can run 92grs. of Retumbo with 210 Berger's and just about 3200 FPS with no pressure and easy extraction.
Once the case is full length resized and loaded back up with the same primer, powder and bullets this load is too hot and sticks in the chamber.
It needs to be backed down to 90 grs. to be functional. reload number three is backed down to 89grs. (everything same as above.) to be functional. reload number four needs to be 88.5grs. to be functional. Velocity is about 3050fps and still a little bit sticky but will work.
Brass necks have been annealed after first firing, also done with brand new brass never annealed (other than factory).
Chamber reamer used is a match spec by Dave Kiff
there appears to be .003 clearance between the neck on a loaded round and the chamber neck. He says bullet seating tension is very consistent. I am trying to help him out and am quite frankly stumped! I haven't really loaded much for a 300RUM, never owned one and have only dealt with new brass.
Questions: Could a donut at the base of the neck be building up more on each shot causing the pressure increase??
Do I need more neck clearance on my chamber reamer??
I have build numerous 300RUM's with this reamer and have not heard of any problems other than these two.
So what are you guys doing to your brass?
Are you turning necks?
Are you reaming inside of necks??
Would sure appreciate your input and suggestions........
Giving someone like you advice Is unnerving but There is one thing that could be making the
difference that I have experienced and It would be worth a try.
Retumbo is a very unforgiving powder . It can be a great powder in some rifles and be terrible
in others. I have had it go critical with just a 2/10 grain increase while working up.
I normally work up in 1/2 grain increments and everything will be very linear (More powder,more
pressure and more velocity an then all at once they jump in velocity and pressure.
I have seen other powders do this and avoid them if I can because of temperature swings of
70 to 80 degrees in my part of the country.
There are a lot of good powders out there and I would recommend that you try one of them.
You may lose a little velocity but if the right powder is found the consistency will improve and
the load won't be as temperamental.
From what I have seen and heard your gunsmithing is second to none and the reloading
process sounds right so I would look elsewhere for the problem.
Just a thought
J E CUSTOM