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Old December 6, 2012, 11:26 PM   #15
Senior Member
Join Date: July 15, 2012
Location: Wonderful, Windy Wyoming
Posts: 133
The point I was making was missed, and I'm sorry I caused people to waste time responding. I'll clear this up in excruciating detail right now.

1. When a gunsmith starts showing people what bores actually look like through a borescope, many customers recoil in horror.

Increasingly, I think that a gunsmith showing most customers what barrel bores actually look like is a mistake, unless we're pointing out some specific damage eg, pitting or throat erosion. Showing customers what a new rifled bore actually looks like (as compared to what they perceive from either end of the barrel held up to the light) just seems to invite all manner of obsession by customers.

I've seen bores that looked like what the OP photographed there.... and worse. Much worse. An example: I've got a barrel on an AR-15 that looks like it was reamed by a bionic beaver... and yet it shoots what I would consider pretty well for what it is. BTW, this barrel won't even pass military go/no-go gage requirements, especially the barrel straightness gage. The price was right - dirt cheap. So I slapped it onto a carbine and ran some ammo through it. I figured "OK, it's $50. Let's experiment and see just what a failed barrel looks like on paper."

I can group five rounds from just over 2" to about 2.75" at 100 yards off the bench, depending on how hard I work at it and the variance in the bulk ammo. This isn't bad at all for a carbine length barrel on an AR, with iron sights, with Walmart bulk .223 55gr ammo. Actually, all things considered, I'm quite pleased with those results. A $50 reject barrel, carbine length, iron sights that shoots that well? I lucked out when I bought that barrel, IMO.

It truly does look like hammered crap on the inside. I won't and don't worry about what it looks like - the results on the paper are what I look at. Does it foul? Oh hell yes, does it foul - mostly powder fouling with some copper on top. You can clean it for an hour to get a clean patch.

2. I don't worry too much about what a mass produced barrel looks like until it shows me something is wrong. "Wrong" can be:

- it doesn't group
- it shows me evidence of high chamber pressures
- it fouls very quickly - like gobs of lead or copper in 50 rounds.

Now, if I'm paying a premium for a custom barrel that is supposed to be lapped and very well finished, then I might complain if the bore is rough. I paid for something better.

3. What I was suggesting was that if someone is worried with what a barrel's machining marks look like before they've even shot it, they can cure the "problem" by lapping away the marks. A couple of hours and they have reduced the marks, ergo, no more problem, right? If they haven't shot it yet, they wouldn't notice a difference in accuracy. That was uncharitable of me, for which I apologize.

Starting with 800 grit is actually starting rather fine. Barrel lappers usually start down around 320 to 400.

4. Bart then went into the details of air gaging barrels, which while significant to someone who can shoot as well as Bart, flies over the head of most shooters at about Mach 2. The vast majority of shooters aren't anywhere near as serious a marksman as someone like Bart and are nowhere near as methodical and consistent in their evaluation of contributing factors to rifle accuracy - ie, if you gave them two rifles with variances in the bore diameter or rifling consistency that were identical in all other aspects, would the shooter be able to a) notice the difference in accuracy and b) properly attribute the cause of the difference? I'll bet "no."

If you're in the accuracy game at Bart's level, you're most likely not buying an inexpensive, mass-produced barrel. You're quite picky about your barrels - and your barrel maker(s), and your bullet makers, and your brass, and your primers, etc. And you're most likely not mounting your accuracy barrels on a Mauser - which, as much as I love Mauser actions for hunting rifles, I have to admit that they're not the go-to action for accuracy work.

5. I'll touch briefly on the issue of air gaging.

Air gaging barrels is all very well and nice, and there are lots of barrel manufactures who claim to air gage their barrels... and then the details of what they DO once they've air gaged a barrel start becoming thin.

Do they simply set a criteria for variance along the bore, and reject any/all barrels that exceed these criteria? What are these criteria?

Do they sort/select their barrels into two groups - the barrels that gaged with very high uniformity, and then "most everything else" and reject the worst of them?

Do they lap out the tight spots to obtain more uniform bore diameters?

Or... do they do something else? Like sell their rejects to a customer with a lower quality criteria, which then are sold at a low[er] price with no name attributed to the barrels? This is how I got my AR barrel - it failed acceptance criteria, so it ended up in the aftermarket with a dirt-cheap price on it.

They could do any of these things... but many mass-production barrel manufactures are rather quiet on what they do after they've air gaged their barrels. For guns where I'm really worried about accuracy, I buy barrels from companies that tell me what their criteria are and what they do with the information. This usually means paying a premium for the barrel and waiting a fair bit of time for delivery...
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