I have a Bushmaster varmint upper, it does not like military type ammo, has anyone tried a RRA Varmint upper? I know with these types of barrels I should be reloading for it. But I just don't want to, I reload for everything else. I was hoping to find a heavy barreled, varmint type upper that also liked the military ammo. Any experiences to share?

Sorry, don't have any answers, but I would like to know of a good military ammo-digesting varmint upper as well.  Kind of takes the fun out of it if you have to reload or spend $1.00 a shot to get accuracy.  Anyone?

What doesn't your rifle like about milspec ammo?  What specifically happens or doesn't happen?

Talk to Bushmaster, they may be able to cut a M16 chamber into your barrel.  If the chamber is currently undersized and rough you'll have stoppages.  Polishing the chamber may be needed.  

If you want reliable operation the rifle should be cleaned and lubricated to dash-10 standards regardless of the barrel on it.

-- Chuck

Oh, Sorry, I was not specific ... It shoots all ammo very reliably, its just not very accurate. I wish I could just throw the same stuff that shoots into 3/4" to 1" groups in my other Ar15's and have it shoot AT LEAST as well in my varminter! My varminter wont shoot that ammo under a 2.5" to 3" group at 100yds. I am going to try some SS109's, maybe the heavier bullets will shoot better.

I believe the Bushy varminter normally has a 1-in-9 twist and the 62 gr SS109 might work better than 55's.  However, it also has a match chamber and heavy DCM type barrel that may not be chrome plated and may be a bit more finicky on bullet selection.  

With match or non-plated barrels you have to clean it more frequently and watch out for copper build up in the barrel like most other varmint guns.  Also, your upper may not be fully broken in yet.  Try a good barrel cleaning and see if things improve.  

Also, I seem to get a little better accuracy with military bullets at slightly lower velocities than US mil spec.  My SS109 handloads are more accurate at around 3,000 fps muzzle velocity than at 3,150 fps.  With the tight chamber, close tolerances and 24" barrel (?) of your varminter, you are probaly getting even more velocity than standard for M193. If you are set a using military type ammo, you might want to look at the test results posted on this site and try some of the milder stuff.

Finally, a couple of people are getting really good results with Winchester's 46 gr. HP in the Varmint Pack from Wally World, me included.  Then there are also Black Hills reloads from Georgia Precision.  Good luck!

Skid,
I have done some evaluation on the RRA and Armalite Varmit/CMP barrels with military type ammo of various types/mfgs. including reloading with military bullets. My conclusion is that if you want match/varmit quality results, use match quality ammunition. All the BS claims aside, you are not going to get 1" groups with mil spec ammo on a repeatable basis from any barrel manufacturer. 2"-3" groups is more realistic and it is a waste of time to shoot his quality of ammunition in a varmit quality gun.