I have about 1,200 rounds thru my 6GT (Proof) barrel and never scoped it until recently. I clean approx every 300-400 rnds, stopping when the patches came out more or less clean. The gun shoots .5MOA or better, so figured all was good on the basis that it’s still grouping well. But without a scope, it’s hard to tell how clean it really is.
Recently I’ve been experiencing some pressure signs: a few blown primers and a few cases with an extractor mark on the case. No change to my load which is around 2,840 fps. Some of the brass in question came from a questionable batch of 1x fired brass that got on trade, but it also happened with a few cases of 3x fired (all by me) Hornady brass.
I’m trying three things: The first was to get a borescope and I’m pretty sure I had a carbon ring forming so I went after that with some C4 soaked on a bore mop and some nylon brush scrubbing. Based on what my borescope is now showing I think I got most of the carbon ring out of there. But the first 12” of the barrel still has what I think is baked on carbon. Being at approx mid-life on the barrel I figured it was time for a good cleaning, alternating patches and a bronze brush with just Hoppe’s. It’s looking better now, but by no means am I down to the bare metal. The other 2/3 of the barrel looks pretty good according to the borescope.
The other thing I’m trying is trimming my brass. Some of my cases were starting to get into the 1.730-1.732” range, so took it back 8-10 thou. I haven’t fired those yet, but felt like it was time to trim.
I also reduced my seating depth by .020” for an .040” jump (I was seating to .060” jump before). Back when I did my seating depth testing, the .060” jump yielded the best groups in the .3XX” and .040 was in the .5XX” so I went with the smaller group. But now my thinking is I would rather have a slightly larger group than over pressure… plus I’m sure my throat has eroded some in the last 1K rnds.
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