Re: Objective research on Barrel Break-in procedures
I've been initializing new barrels for probably close to two decades by now. Over that time, various approaches have come into vogue and then been supplanted by others.
Originally; I didn't know any better and just unpacked them and shot them. Never recognized any issues, but again, I didn't know any better. Nowadays, I'd clean the rifle thoroughly before shooting it. The first time I tried that, I got out an amazing amount for grit and crud. I'll never take a chance on running bullets through that kind of junk again.
When the shoot/clean process came to my attention, I figured it was a great idea and followed it religiously. When abrasives were incorporated within that, I even developed my own technique that involved coating bullets from loaded ammo with mild, non-imbedding abrasive, like Rem Clean or JB Compound.
I don't think I did any harm, and I chose my technique/materials so as to limit the potential for harm. I wrote it up here, and I sure lots of folks followed my lead.
I haven't done it lately, but I still think it has a place in intializing barrels where rough bores are involved. Viewpoints vary on whether a rough bore equates to diminished accuracy. I don't know whether either argument is better but I do believe a rough bore encourages copper fouling and that copper fouling degrades accuracy once it reaches a certain level. Hence, honing a bore can postpone accuracy degradation due to cumulative copper fouling.
Another argument favors removing initial tooling marks associated with the throating proces of barrel making. I think it's a valid argument. I think that judicious use of abrasive honing techniques can hasten a barrels's stabilization, to where the copper fuoling rate steadies down to more or less a constant rate. I personally believe that until this status is achieved, load development is a waste of time, good components, and bore life.
Basically, we are talking about wear rates that bring the bore and throat from the newly cut condition to a worn and constant condition. Whether this is down overtly through firepolishing, or by hand lapping/honing, the net effects are quite similar, or at least can be when done judiciously.
But, this accelerated wear rate can be skipped and substituted with regular wear from customary shooting followed by post shooting session cleaning, and we'll essentially arrive at the same status, differing only in the number of shots accumulated in the process.
Up to this point we're mainly just doing the same thing over shorter or longer lengths of time and numbers of shots.
There is, however, another factor that I don't see being discussed as part of this argument.
Barrel life isn't determined by barrel wear or friction. It is determined by the number and degree of heat and pressure cycles the barrel's throat experiences.
For the sake of argument, a process which stabilizes the barrel earlier in the sequence of heat and pressure cycles <span style="font-style: italic">should</span> permit a longer sequence of 'good' shots within the allotted/fixed total number of cycles the barrel can sustain.
By this argument, a quicker break-in process <span style="font-style: italic">should</span> allow more lifetime where the barrel's performance is consistent, before the heat and pressure cycles accumulate to end the barrel's usefulness.
If I were to lend a contribution to this argument, that would be it.
There was also a question about a formula for extended bore life. Logically, my answer would be 'anything that decreases the punishment the throat is subjected to by heat and pressure'. In essence, use tamer loads. It's my personal belief that hotloading and bore life expectancy are diametrically opposed.
Very simply, if the chambering you're using does not generate the performance you seek while running moderate pressures; then that chambering is inadequate and needs to be replaced by one with more case capacity. Hotloading (IMHO) is just a matter of trying to achieve the improbable while simultaneously opening some cans of worms that nobody really needs opened.
Greg
