Thank you for this. Yes I understand gas guns are typically very dirty. I have several and have been reloading for them for 25 years or so. I do regular bore and action cleanings. I scope the bores regularly. This gun was cleaned down to bare metal in the bore and chamber and 15 shots were fired before I fired the group shown in post19. After the deep cleaning I shot 3 shots with some of my standard reloads, then 3 shots of 17.9gn 296 with the SMK then 9 shots of some more standard reloads (17.9gn 296, 125gnSST) without any issues. There is/was no carbon ring per se but there was a carbon buildup in the chamber itself. If you read upthread you saw that I have never had this issue until I started trying load development with the 125 SMK. First I thought it was the brass, then the bullet, then the dirty chamber now I think it's a combination of factors that I cannot nail down. I am confident in my loading technique, post 12 shows my case prep. All charges are hand weighed on a scale that has loaded 1000s of rounds for years without incident sometimes riding the ragged edge but not this time. These should be very mild loads. Maybe this particular barrel just does not like this particular bullet. We should find out this coming week... I have a new barrel coming tomorrow.
Good luck with your new barrel Hope you find the 125gr. MK bullets as accurate as many other people do with a new chamber.
Thanks Dellet... Base to ogive of the 125 SMK touching the lands in this rifle is 1.594. I am loading into the cannelure at 1.524. Look at the top of my second picture post 12. Below are some borescope pictures of the chamber: first is at the end of the leade where the lands start. second is end of the chamber, third is chamber itself showing some black spots that seem to be staining from the carbon buildup i cleaned last week. I took the mirror off of the bore scope because it seems to show better this way. With the mirror on its barely visible and does not appear to have any thickness. The barrel/ chamber has not been cleaned before I took the pics.
If thats the case I may just put the SMKs up on the shelf. The barrel swap idea was just out of curiosity, I'm not really expecting much out of it as it was on sale at Midway for about 40 bucks. lol. I will work up a load with the SMKs with it just to see but will go back to my original one as I have 300 Sierra Pro Hunters and about100 Nosler BTs loaded for it that run just fine and stay about 3/4 moa. Fun aside about this gun. I was at the "range" working with a different gun. I had just watched a youtube video called "Minute of Angle Challenge" where some dude was going to public ranges and paying people 50 bucks or so if they could put three shots into one moa. On the video no one could except the host (of course). I had my 300 BLK that day as always and realized I had 6 different loads for it in my ammo can. I put up two of those three group targets and shot the six different loads. All six were sub moa. Its been a good gun for me. I purchased the upper right after they came out and have shot a couple thousand rounds through it killing untold numbers of wild hogs and probably 10 deer. Thanks again dellet for all your help.
Not certain if it applies here, but there have been a couple of times over the years that manufactures of shall we say, price conscious barrels, sharpened them a time or two more than they should have. The popularity of cast bullets and sub-sonic shooting caused havoc in those barrels because of the diameters always being oversize.
I wouldn't take too much credence in my original post about only 4-5 loads on these cases. I have been lacking at keeping up with the number of times each case has been shot. I know some of the original 200 or so RP cases I started with are getting tired which is one reason I started converting LC and PMC brass. When I get ready to resize these I see if I can push the primer out easily by hand. If so they go into the bin. I get an occasional one I cull this way. When I get ready to load I check primer pockets with a go-no go gauge and occasionally cull a couple this way. I am sure as you said that I probably have higher pressure than normal due to the short chamber.
Yessir, been a member there for a while... don't post much there.
