If you've been following the thread on the Stewart Wilson AR10, this is an email about our rifle and barrel break in. Bear in mind that this is a long term builder who makes contract rifles for the military and is now the head field instructor for E.D.M.
Since beginning our series of tests he's now considering hBN in lieu of Moly, but also note that his Moly process involves definite post-session cleaning and maintenance of the barrel...... every time without fail.
Because of his promotion of the Sierra within the contract rifles, he has a deal with Sierra to supply him with any amount of 175 SMK Molys upon request.
From: xxxxxxx
To: xxxxxxxx
Sent: Sunday, August 09, 2009 6:15 PM
Subject: Yo!
Pierre, HBN is definitely viable. Go for it.
You can do your own moly process. You have to find
laboratory grade mds (moly). or, by all means, do the hbn process.
The article you highlighted is the preferred method for any of the processes. Good material.
The process on the barrel, probably requires some explanation. All of the properties applied, from the parent barrel material to the finishing process (electro-polishing) inclusive of the taper bore (there is a slight taper from breach to muzzle - about .0006" , that's six ten thousandths of an inch.) This achieves a couple of desired conditions: 1) linearization of the surface molecules of the bore surface {as you no doubt are aware from your machine tool background, every time a cutting tool touches the material a 'crust' is formed. This crust is what "barrel break in" is meant to correct. This is also, why 'break in' is minimal on your barrel}. Secondly, the taper configuration of the barrel, in affect, creates a freebore situation for the entire barrel length. Or, another way of looking at it is the barrel achieves a more uniform, or normalization condition for the bullet being pushed down the bore. All this achieves more even or consistent muzzle velocities which tightens standard deviation.
The point of all this is - barrel life!!. Instead of replacing that barrel every 3000 rounds or so, how about, well, I really don't know as yet. I have one of the first units built (my AR10s), a 24" version of yours that has 9700+ rds out of it and it is still a 1/2 MOA rifle!. There are those that have declared that we will have a wake for it when it's "shot out". The goal sought after was longevity. There was no data when I put the formula together some years back. It took time to demonstrate the objective.
Moly coating (or any process that augments the barrel surface 'normalization') is just part of the matrix.
I would hate to think that you would be waiting (in limbo) to shoot the rifle because of a shortfall of resources here. I am sure there is an answer somewhere with HBN. Let me know of the solutions you come up with. I used to have some moly, I am sure that I still do, - I just am unable to find it in all the crates scattered about in my life right now.
Keep me posted here.
Stewart
Original Message
From: xxxxxxx
To: xxxxxxxxxx
Sent: Saturday, August 08, 2009 5:33 AM
Subject: Re: Yo!
Good morning, Stewart.
I don't want to take a lot of your time with this, but I've determined that buying/waiting for Moly coated projectiles is going to be a three to five month wait, this accodring to Sierra.
Would you mind taking a brief look at the following link. I'm a 45 year reloader and avid projectile caster, so I doubt I
d have much difficulty with this process.
My question concerns the use of HBN in lieu of Moly, but if the Wilson AR10 requires Moly as the lubricant, then of course we'll use Moly. The link is here..
www.patentstorm.us/patents/7197986/description.html
Thanks for your help, and we're huge fans of this rifle. Despite parting with substantial cash to obtain it, we're honored to have it.
Pierre