Solid/live pilot chamber reamers

Here's one for the ultra-accuracy bunnies here.

Putting all prejudice and preconceived notions to one side, is there any practical difference in the accuracy of chambers cut with a solid pilot reamer or a live pilot reamer?

Bear in mind that this is not going to be a bench rest/long-range rifle, and will have a SAAMI-spec 7.62 x 39 chamber on a .300"-.308" barrel, so is likely to do no more than one MOA tops, more likely 1.5-2.

Here is the "received wisdom" from the bench rest lot so far:

Live pilots are better, even though there is one more place for play in the system
solid pilots can scratch the lands (this I find unlikely, though not impossible)
some people swear by solid pilots although they are the minority

My thoughts are that it won't make the blindest bit of practical difference in my case, particularly as the portion just before the lead has to measure 0.3138 so as to accept .311 bullets (although the rifle will probably only ever fire one, and that will be its proof round.)

The thought of a custom reamer specified exclusively for .308 bullets has crossed my mind, but then would the proof house call it a wildcat and stamp it with something other than 7.62 x 39, landing me in a world of hurt back in the Netherlands?
By the way, I've gone for a 1:10 twist barrel, which is the same as the military standard, so that I can shoot light loads with sufficient stability, and maybe some "whisper"-type loads with heavy, Jacketed bullets. Had I only intended FMJ, I think I might have gone with 1:12 which is closer to what the Greenhill formula gives. Interestingly, 1:12 is what the colt 7.62 x 39 AR 15 uppers have. I believe the military spec is 1:10 because that's what Russia was already using for Mosin-Nagant barrels, even though it was over-twisted for the spitzer bullets.


I would have thought that a solid pilot reamer would have less play. I can't see the pilot damaging the leade as long as it was driven in concentrically...

Having said this, there are a number of pilots I know who would benefit from a reaming with a scratchy tool...

... and yes, most of them are solid..


War Hero
Congratulations on the most obscure topic I have ever come across in shooting! And I mean that most sincerely. It beats my current concern about setting sights on the Lee Enfield with and without the bayonet fixed.
used both, never noticed any difference.

in a lathe a reamer (of any shape or type) is allways self-centering.
allways go overboard with clean high quality cutting oil.

the idea of using rotating/removable pivots is so you get a 'perfect' fit between rifling lands and the pilot. as long as you have carefully measured the bore and have the correct pilot fitted to reamer.
the ploblem is between bbl makers theres sometimes a difference in land height, at max only of a thou or two, but if you dont check, the rotating pivot may be a bit too tight and will damage the first 1/2 inch of rifling ( the most important bit!), and you end up with a bit shorter barrel then normal because you have had to knock just over a 1/2 inch off and do the job again. :roll:

been there done that got the t-shirt. ( barrel wrecker of the week comp winner ect ect)

edit to add -
another good one of mine was trying to fit a .30 cal browning MG barrel to a P17, the customer is a real eccentric type and imported the unused still in grease bbl.
I rethreaded it to fit the action, and on reaming to headspace I discovered that .30cal MG barrels have a 6 inch hardened liner in them just in front of the chamber. que one broken 30/06 reamer. :x


I wouldnt worry too much about the proof house, if the barrel is .308 as per US specs and the chamber can be as well as lonng as the rifle is stamped as such by whoever does the work. European barrel makers use a .311 tube and the US lot use a .308 tube. In fact RCBS ship both expander balls with their die sets and also Sierra note that both .311 and .308 bullets in either barrels have no visible effect on either accuracy nor pressure!

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