To recap..........

I showed up at the Tucson 1000 yd range with a varmint rifle in 6mm Rem. 14x Leupold scope, HS Precision stock, trued 700 long action, Pac-Nor #5, 27" long with a 1x8 twist and in a three-groove rifling configuration. I shot off my Hoppes front rest and Protektor rear bag on 8 Jan. I became hooked.......

Since the barreled action was showing promise, and I needed to limit my budget since we are building a new house, I thought about how I might ease into this in a cost effective manner. I have now learned that like all other shooting pursuits I have engaged in, there is no cost effective way to "ease in" to this.

The plan was front rest, stock, scope, and a load with 115 grain MKs. I figured that would get me through the year. Well, I did all that and pushed my original budget a bit, but it was all working. Then last night, after mounting the scope, I started in with the new bullets. I started by checking seating depth. I started with some 107 MKs to see how much the throat had moved. I figured there would be some erosion, and I wanted to see how much.

Would you believe .300"? That is not a typo. The throat had eroded a full 3/10ths of an inch in the barrel's 200 round life. I assume most of that happened at the match, when I was shooting 10-shot groups in heavy rifle.

I was stunned. The barrel now has as much freebore as if I had bought a 240 Wby. I realize the 6mm Rem is a tad high case capacity for a 6mm, and I know Pac-Nor barrels are soft, but come on, .300" in 200 rounds?

Fortunately, Jerry (the local 1000 yd rifle machinist who is moving in a month) hasn't packed his lathe up yet, Bruno's is only a 2.5 hour drive, and Bruno's had a Krieger 6.5mm, 1x8.5 LV barrel blank in stock--along with some 6.5x284 brass and most of the other stuff I need.

If I had checked this rifle's throat right after the match, I wouldn't have even ordered the scope and stock. I would have bought another Tucson shooter's 308 Patriot light gun (on a 700), and then bought a much lower end scope. Such is hindsight.............

Oh well, I guess I'll be better off with a new Krieger barrel in 6.5x284 and the Nightforce scope, right? (Just say yes, I don't even want to consider the alternative.)

All this bring up some thoughts on throat erosion.

Three times now I have fired strings and gotten barrels hot, and each time the throat has eroded excessively.

The first was several years ago, a factory Rem SS Sendero in 7mm Rem Mag. I started shooting 5-shot groups. I'd shoot five in a row, then let the barrel cool. In 400 rounds the throat moved about .040". I heard that is not uncommon for that chambering. I got rid of the rifle and got another SS Sendero, this one in 300 Win. After 825+ rounds, the throat had moved maybe .010". I started shooting three-shot groups and didn't shoot the barrel when it was more than lukewarm.

A couple years ago I was messing around with a 338-06. It too was a Pac-Nor barrel. The 338-06 isn't know for throat erosrion, but when I kept it hot for a few rounds it too erodoed noticably (like .010 in 80 rounds), whereas when I kept it cool, the throat didn't move. On this barrel, I was careful and stopped the experiment after noticing the throat movement, and kept form hurting the barrel.

I guess my issue is whenever I shoot barrels when they are hot, I seem to erode the throat excessively.

Several years ago I started using Rem Bore Cleaner, which like JB Bore Paste, is a non-embedding abrasive cleaner. I have very good luck using it with several rifles. I remember reading a test in Precision Shooting a while back how that RBC was so fine that all it did was polish the 600 grit lapping marks, and as such the author said it would not harm a bore.

Now I am wondering if I should be routinely using RBC or JB Bore paste.

Thoughts?

Blaine

Last edited by Blaine; 01/17/05.