I recently had my rifle rechambered by the gunsmith who built it, going from 280ai to 284 Win so it's a little more optimal on a Tikka. I'm going to leave this gunsmith nameless, as the intent of this post isn't to bash, and I'll give him the benefit of the doubt that maybe it was somehow a misunderstanding. However, I feel it should have been handled differently. The intent of this post is to provide some information about the issue and how it was diagnosed, so it might help someone in the future if they experience the same circumstances. And a tip of the hat to the gunsmith that listened, and fixed it.
I'm typically not a "close to the lands" guy, but after consulting with the original gunsmith, he recommended throating it to be 10 thousandths off. I sent a dummy round with a 165 Sierra TGK seated with the boat tail edge just above the neck shoulder junction as close as I could optically gauge, as the 284 has a fairly short neck, and we agreed that would be "touch". I received the rifle and loaded some rounds, immediately noticing about half of the 100pcs of new Peterson brass either had resistance, or would not close. I picked out a couple that had no resistance, and loaded them with a charge only 2gr above book min to start. I also noticed that "touch" was actually a pretty engraving jam, so I seated them 10 thousandths off of my measured touch. First shot locked the bolt up, and after beating it open, stuck the case.
I'm not a gunsmith, but I spent almost a decade in welding/machine shops building stuff to print, everything I could measure was below min tolerances on the SAAMI drawing. I immediately contacted the gunsmith and thought maybe it was headspace, but something was tight. I sent him the fired case, and a couple new pieces. He sent his PTG gauge off, and called me when it returned and said they spec'd it, and it passed. His irritated response was "The gauge passed spec, and the bolt closes on the gauge. You'll just have to size all your brass accordingly." I asked about the pressure issues and maybe if it was due to the short throat, and he said it shouldn't be and I just need to size my brass. I asked about throating it out more to make me feel better and he said he would have to charge me full labor price and cerakote again because he couldn't get the barrel loose without scratching it. After receiving the rifle back, with now uniform sized brass I was still getting bolt lift and click on extraction with a min book charge. For the sake of sample I shot the remaining 12 loaded cases just to see how it shot, not good.
I contacted Kinport Peak Rifles who I have used in the past and has always been very helpful with answers in regards to rifles or loads. I sent it to him with a few fired pieces and a dummy round to add about .070" to the throat for peace of mind. Within 2 weeks he text me with a picture stating "got it". The fired brass was .0035" smaller than his reamer above the web area.
After receiving the rifle my initial measurements showed the throat had exactly .070" cut out of it. I was able to run it up to book max with 2 different powders before any pressure signs. The first group is with H4831SC at book max. Obviously this barrel doesn't like that powder. Second group is with H4350 just below book max, avg velocity 2860fps. That will do for now until I can try another bullet.
Moral of the story is it never hurts to get a second opinion. Justin at Kinport Peak was very quick to respond to all questions, and communicated with me while diagnosing and fixing it. Highly recommend consulting with him if you have any issues, or are planning a build.
I'm typically not a "close to the lands" guy, but after consulting with the original gunsmith, he recommended throating it to be 10 thousandths off. I sent a dummy round with a 165 Sierra TGK seated with the boat tail edge just above the neck shoulder junction as close as I could optically gauge, as the 284 has a fairly short neck, and we agreed that would be "touch". I received the rifle and loaded some rounds, immediately noticing about half of the 100pcs of new Peterson brass either had resistance, or would not close. I picked out a couple that had no resistance, and loaded them with a charge only 2gr above book min to start. I also noticed that "touch" was actually a pretty engraving jam, so I seated them 10 thousandths off of my measured touch. First shot locked the bolt up, and after beating it open, stuck the case.
I'm not a gunsmith, but I spent almost a decade in welding/machine shops building stuff to print, everything I could measure was below min tolerances on the SAAMI drawing. I immediately contacted the gunsmith and thought maybe it was headspace, but something was tight. I sent him the fired case, and a couple new pieces. He sent his PTG gauge off, and called me when it returned and said they spec'd it, and it passed. His irritated response was "The gauge passed spec, and the bolt closes on the gauge. You'll just have to size all your brass accordingly." I asked about the pressure issues and maybe if it was due to the short throat, and he said it shouldn't be and I just need to size my brass. I asked about throating it out more to make me feel better and he said he would have to charge me full labor price and cerakote again because he couldn't get the barrel loose without scratching it. After receiving the rifle back, with now uniform sized brass I was still getting bolt lift and click on extraction with a min book charge. For the sake of sample I shot the remaining 12 loaded cases just to see how it shot, not good.
I contacted Kinport Peak Rifles who I have used in the past and has always been very helpful with answers in regards to rifles or loads. I sent it to him with a few fired pieces and a dummy round to add about .070" to the throat for peace of mind. Within 2 weeks he text me with a picture stating "got it". The fired brass was .0035" smaller than his reamer above the web area.
After receiving the rifle my initial measurements showed the throat had exactly .070" cut out of it. I was able to run it up to book max with 2 different powders before any pressure signs. The first group is with H4831SC at book max. Obviously this barrel doesn't like that powder. Second group is with H4350 just below book max, avg velocity 2860fps. That will do for now until I can try another bullet.
Moral of the story is it never hurts to get a second opinion. Justin at Kinport Peak was very quick to respond to all questions, and communicated with me while diagnosing and fixing it. Highly recommend consulting with him if you have any issues, or are planning a build.
