.008" !?I don't know what Wilson is calling the "bullet seat". The short freebore ahead of the case mouth, maybe? As for the "throat not being cut correctly", the bullet needs to enter the rifling squarely. If the 'funnel' (the angled throat) is cut more on one side than the other, the bullet would upset and not enter the rifling squarely, which would create a non-concentric condition of the bullet, causing inaccuracy. The use of a fixed pilot reamer might case this. There is play between the pilot and the bore, sometimes as much as .008". That's .004" on each side. The scaring caused by the fixed pilot happens when the very fine chips collect between the pilot and the lands. Even being slightly out of alignment of the reamer to bore can mean the reamer cuts on 1 side more than the other. The use of a reamer with removable pilots where the pilot is no more than 1/2 thou smaller than the bore helps eliminate this condition, but it can create other issues if the holder doesn't have enough 'play' to allow self alignment . Another 'condition ' that might exist that can cause issues is the reamer only cutting on 1 or 2 flutes. Not all reamers that are manufactured are of equal quality. You can see where only cutting on 1 - 2 flutes might bring 'issues'. If a guy is gonna' use a solid pilot reamer I'd suggest pre-boring, with a boring bar, before using the reamer. That would help 'guide' the body of the reamer where you'd not be dependent on the pilot & bore and the built in clearance between those. It may not take a 'ton' of money to set-up a chambering operation. It's knowing the fine points of the process and of the tooling to have a successful out come. First is the cost of the lathe, then the cost of the tooling. A guy could get by with an old fashioned rocker tool post off of e-Bay and make his own 'floating' reamer holder, if he wanted to save some $$. HS turning tool blanks aren't outrageously priced if you look around, and you don't discard them when they dull, you just re-sharpen them. With the cost of a removable pilot reamer, it will pay for itself with the first chamber cut and I have worked at a discounted hourly rate for that 1st one. The 2nd chamber with that reamer profit begins to appear. With the 3rd, the initial cost becomes even lower,,,, and so on, and so on. As far as renting reamers, I have been mostly disappointed the 3 times I have rented in the past 27yrs. (I have only rented in the past 10yrs or so). I need to be able to trust my tooling. I have chambered both ways, between centers and thru the head. I have only used what has been called in this thread, "pricey" barrel blanks. I need to have confidence in the blank I am chambering, too,,,,,, as well as having confidence in what my lathe is capable of and confidence in my set-up and what I am capable of. If I was to use a 'tiny' lathe, like you have, I think I'd have to use a Bald Eagle type pusher. I may not be a "master" as some like to refer themselves as, but I have been machining since '74, and chambering since '91 when I cut my first chamber (a .280 Rem for a Win 70 while in gunsmith school. The machine was a '70's vintage South Bend Heavy 10. Not a 'large' lathe by any stretch, it only has a 10" swing but it does have a bit of weight and rigidity. The holder and reamer were both a Clymer. Solid pilot on the reamer.) I cut a very good chamber 1st time. I had confidence in that little South Bend, the tooling, and my abilities with my machining back ground. We were taught to pre-drill and then pre-bore before reaming.
I went and measured a solid pilot I have in 300rum. The pilot measured 2.9988". I'd be interested to see which brand of reamer and which cartridge you found the .008" different
