I have guys asking me all the time what I recommend to "tune" up there factory rifles. In all honesty, there are many things that many recommend for factory rifles but in all honesty, there are very few things that will bring you solid returns on a factory rifle.
My recommendations that will get you the most return for your investment:
- Trigger replacement or tuning.
- Skim bed the stock to the receiver.
- Recut crown to true match specs.
- If not opposed to, have a quality muzzle brake
installed. This will take care of recutting the crown at the same time as the crown will be recut when installing the muzzle brake correctly.
If the barrel is contacting the stock anywhere, then floating the barrel should also be done but this is generally not an issue with the Sendero rifles.
Some recommend lapping the lugs which can help to some degree but I generally prefer to to that only with a barrel replacement because you do effect headspace measurement when you start lapping lugs.
Some recommend receiver accurizing, this is a waste of time unless your going to replace the barrel and recut the receiver threads. There is no way to PROPERLY accurize a receiver without making the receiver threads larger in diameter. If someone tells you they will fully accurize your rifle and reuse the factory barrel, tell them "Thanks but no thanks" because they will not be doing the work they are advertising they will be doing.
As far as load development, There are many 7mm bullets that have proven themselves very accurate and consistant even in large capacity, high velocity magnums. I would recommend the 160 gr Accubond, 175 gr SMK and 180 gr Berger. In my testing, the 168 gr berger is not overly happy with velocity much over 3250 fps. In the 7mm RUM, you should not be at this level of velocity but you will be close. Still, stepping up to the 180 gr will lower velocity ceilings to a point that is much more friendly to the standard Berger bullet designs, plus you get a boost in ballistic performance with the higher BC and better terminal penetration with the added bullet weight. Some rifles with factory length barrels can get you into the 3100 fps range with the 180 gr Berger.
Powder wise, Retumbo is probably the best all around powder I have tested. Many will work though. Reloader 25 works very well and Ramshot Magnum also has proven very useful as have Hodgdon US-869. Still Retumbo has shown the best consistancy of all powders tested.
Primers, I recommend only one, the Fed-215 large magnum rifle primer. Not saying other primers will work, I simply go with the hot Federal primer for all large capacity magnums.
Tips for longer barrel life, GET OFF PAPER AS SOON AS POSSIBLE!!! This is a very low expansion ratio chamebring, kind of like the sports cars of the gun worlds. You do not drive them as every day drivers, you do not take them on long trips, you use them for specialized applications where there performance outshines standard chamberings.
Get your load developed, find the top end velocity and top accuracy will generally be a grain or two under where the bolt lift begins to get heavy to open. Prove the load will shoot under 1 moa at 100 yards for three shots. Preferrably under 3/4 moa or 1/2 moa but even a 1 moa load at 100 yards with these bullets driven to these speeds will generally hold tighter moa groups at longer range.
Do not waste barrel life looking for "greener pastures". Find a load that will work and zero the rifle where you want it at 100 yards, then get off paper targets ASAP and move on to practical field practice shooting. That being, practice as you would hunt. Find a target of opportunity, small rock or something similar at unknown range, range it figure the drops and start testing your drop chart.
You can get more practice from 10 shots in practical field practice shooting then you can with 100 rounds shooting on paper at 100 yards trying to find that magical load.
Get a load that works and get out and shoot in the field testing your drop chart. This will save your barrel dramatically compared to punching holes in paper at 100 yards.
Once zeroed, test at 500, 750 and 1000 yards if possible. If your drops match up with these 4 different ranges, it will match up over the entire trajectory to the longest distance and a bit farther. This can be done with practical field testing as well with a very limited number of rounds down the tube and very little barrel wear.
My personal lightweight 7mm Allen Magnum has WELL over 700 rounds down the tube, it has killed several dozen big game animals at ranges from 400 to 950 yards and it still puts first shot placement within 1/4 moa of my point of aim with no sign of slowing down. This wildcat will get you 125 to 150 fps more velocity then the 7mm RUM so you will easily get more barrel life then my 7mm AM.
Do not get the barrel hot and keep shooting. A few rounds through a hot barrel will do the same damage of 50 rounds through a cold barrel.
Hope this helps.