[critters]

I am new to the forum, but I have been a gunsmith for 30 years, taking over my father's business. I do a lot of barrel work and have cut and crowned many barrels. I usually use either an 11 degree target crown or a straight recessed crown. I have sold a number of Marlin 7's to customers and two years ago I bought one for my daughter. It is an XS7 youth in .308. I shoot 42.5 grains of 4895 behind a 165 Remington core-lokt in Winchester brass with a Federal primer. I worked up this load with the original 22" barrel, chronographed it at 2549FPS average. I then cut the barrel to 18" as was my intention all along. The same load now chronographs at 2395FPS and shoots a five shot group at 100 yards in 7 minutes of .689" average. I used to bench rest shoot in hunter and varmint classes, so you can believe the numbers. I have cut a number of .308's down to 18". Remington 788's, Stevens 200's, XS 7's. Almost every one shoots better than factory, which I think is due as much to shortening the barrel than any craftsmanship involved. Don't get me wrong, the last thing the bullet sees is that crown, so that in my opinion is the most important part of the barrel and has the greatest effect on accuracy. If your crown is fixed properly now, you will be pleased with the results, I am sure.

 

[critters]

Having not seen the gun myself, I hesitate to second-guess a smith I don't know. I would find it difficult to believe a factory throat would not be correct in configuration, although I have seen factory headspacing that was incorrect. Looking down the barrel from the action end, you should see the shoulder taper, the case neck ring(or step) a short bit of smooth bore, and then the lands should taper up from there. That bit of smooth bore into the rifling is the throat portion of the chamber, and the rifling should not continue all the way through it to the case neck step. Throating reamers have a long gradual taper that eases into the rifling, however the lands should remain crisp throughout the taper until it reaches bore diameter. The rifling lands should form the grooves in the bullet, rather than cutting them. When this tapered portion of the rifling at the throat becomes eroded, the bullet tends to smear into the rifling rather than the rifling forming nice clean grooves in the bullet. This is a common condition in cartridges such as .220 swift and 6.5'06 that can be loaded to real barrel-burning velocity. It can effect accuracy to a degree, but nowhere near as much as the crown. I personally washed out a Swift barrel in under 500 rounds, but then I was a kid, and I was doing a lot of pretty wild experimentation. I had just read Ackley's book, had an old Apex Swift barrel, a good '98 Mauser action, and dad had a reamer. A set of dies, some old shells, an assortment of every .22 bullet I could find, and I was busy for half my summer between 11 and 12 grade.
An extended throat, known as "freebore", has been used by some, most notably, Weatherby. The thought is to reduce resistance on the bullet, letting it get moving before entering the rifling. I have never been a fan. I personally adjust my seaters so the bullet just contacts the rifling when chambered.

 

[critters]

Glad to hear it has worked out for you. The way you described the original crown job, I was certain it would once it was corrected. I have resurrected dozens of "worn out" shooters by cutting 1/2-3/4" off the end of the barrel and recrowning. Enjoy your 7, they are one of the best new guns I have seen on the market in years.