I don't know why they seem to bind up in dirty conditions although a lot of people seem to throw around the idea the bolt to receiver tolerances are too tight.
So are you saying if I use an off the shelf Defiance action from a reputable gunsmith on here it won't bind in dirty conditions? Because there's quite a few people who report having there actions bind when they get dirty.
Can you explain what a properly spec'd action means?
Why do certain other actions run just fine in dirty conditions without any special specs?
I think you are correct that there are a lot of people having issues with the bolts fitting too tight in the receivers. Long time issue with older Defiance, BAT and Nesika.
If you are having a reputable shop build the rifle and they know it will be used in tough conditions, they should be able to deliver a reliable rifle regardless. IF the action is delivered with tight fit between the receiver and bolt, the bolt body can still be adjusted slightly smaller as part of the build process. I know a few good shops regularly mentioned here that have done that.
When instructing classes and/or clinics we have also seen regular occurrences of otherwise good-to-go actions binding due to ridiculously long bolt handles. We have even seen Rem 700 based rifles with factory bolt/receiver fit be put in a bind when cycling due to extra long handles. One has to remember that the further you get your knob or contact point away from the bolt path, the easier it is to pull and push off that axis enough to bind the snot out of things. We often see such rifles having their bolts pushed forward for the first part of cycling with the shooter's thumb on the bolt shroud or closer down the handle to the bolt body.
Bottom line is that an individual can throw together a rifle that is a tack driver these days but if they expect to run it in severe conditions, they have to pay attention to what additional details are needed to accommodate. Ditto for many shops that build rifles with the intent of getting them out of the door quickly without looking at the bigger picture.
NOTE: More than anything else we still see way more triggers causing grief and way more operator induced malfunctions due to splitting atoms with COAL and zero tolerances between their ammo and barrel.
I believe most "off the shelf" Defiance actions are going to default to a 0.700 bolt body diameter. They did not allow deviations of that diameter in the past on individual orders for their own production labeled actions. Contact Mike or Norm to see what their current policy is.
On "branded" actions, they do allow variations not previously offered.
Bolts on all actions sent to my shop are 0.697" diameter and with a shortened handle boss/stem.
I send the bolts among other action components to Ion Bond and CeraKote the receiver inside and out. Rifles built on actions spec'd in this manner continue to work very well for me in Law Enforcement circles. North American Sniper Championship just finished in the rain and mud last week and several KMW sniper rifles ran there with no issues.
Defiance is not the only quality action out there. They offer me the consistency, delivery time frame and options I need to build the rifles I want to build for my niche. I can choose any maker of action I wish but do not feel that I am taking a back seat to anyone at all in choosing them as my supplier. Impact, BigHorn and others certainly make awesome actions as well.