I've dealt with mostly every barrel manufacturer that you can think of, except McGowan until now. I'll try to keep a long story short(ish)
My buddy built a 416 wildcat that he had chambered in a different barrel for a while. It absolutely always shot like dog poo and he kept asking me to shorten the barrel because he figured he had a harmonic issue due to barrel length (not my call, but his.) I took the cut off piece and did a cerosafe cast to find that the bore was .4185 which explains his problems. He would never pony up for a barrel but I had a favor to return because he purchased a special order blank (dont remember the brand) for my 50 caliber airgun and surprised me with it so I ordered a McGowan blank, 30" long 1:10 twist that took about 8 weeks to come in. Got it all set up in the lathe and indicated in perfectly.
Here is complaint number 1. Excessive run out is an understatement.
https://youtube.com/shorts/0HS3dhcvk0c? ... DnjSD4Kkal
But I got it chambered, threaded, contoured, etc.. and put on the rifle. I noticed when I was machining it that it turned incredibly soft (keep in mind)
He takes it out to the range and for the first time in 2 years the rifle shot just under an MOA at 185 yards! Big improvement. He also chronographs every round and has been using a Lab Radar that a friend let him borrow.
Problem 2: After about 20 rounds he started running into an extraction issue with no signs of over pressure anywhere excess for a swell ring where the brass sits in the back of the chamber. So he bulged the chamber in 20 rounds of his regular loads that he's been using, same velocity, etc...
The only reasoning we could come up with was the barrel being soft after I remembered how it machined in the lathe. I Google for a local place that does heat treating and ask if they test rockwell hardness and the guy says he does and that he'd do it for free. He was also only 2 miles away so my buddy took over a piece that I had parted off the blank before the other machine work. The barrel only has a hardness of 20 rockwell C and is supposed to be prehardened 28-32
They sent an annealed barrel. I'm pretty sure it's too late to get my money back but this sucks. And sorry for the novel but I figured the whole story was pertinent.