Jim in Houston wrote:In the FAQ section of the Bushmaster website they indicate the the chrome lined barrels require no break-in. Here is the quote and its reference:
Question / Issue
What is the proper "break-in" procedure for a chrome lined AR barrel?
Answer / Solution
After firing a couple hundred rounds, the chrome lining will "polish out" from its light, flat gray, factory-new look to a brightly reflective, polished appearance. During this break-in period, excessive cleaning with solvent or brush should be avoided as that will only prolong the time (and number of rounds) it takes to achieve the final "bullet polishing" of the barrel.
Direct Link to This FAQ
http://www.bushmaster.com/faqs/?f=23
My 450b is the only chrome lined bore I own. If I had been given the choice, I probably would have preferred getting it with a stainless barrel. In defense of chrome lining, I must say it cleans up faster after a range session than any of my Stainless or CrMo bores. I did a break in on it like I would those other material bores, but I believe it was as much a reason to shoot it 50 times on its first outing than an essential measure. Prior to that first outing, I did what I do to all new barrels I've bought in polishing it with JB paste before I ever put that first reload down it. For me, that's a standard procedure to remove any left-over factory crud. No point in driving that stuff into a nice, new bore. It's been a while now, but IIRC, it didn't dislodge any significant crud when I did the 450b. Quite a departure from other off-the-shelf new barrels that produced frog hair fine slivers and tiny chips. Since I always take my cleaning rig to the range, I cleaned between each load experiment and of course, at the end of every range session, I gave it a thorough cleaning with Kroil, both brush and patch, while the bore was still warm. So, my particular 450b did truly have a long honeymoon of a break-in. All that having been said, it wasn't until somewhere between 200 and 250 rounds that I noticed a significant change in the way the patches got easier to push through and it taking less of them to get them to come out clean after a range session. The groups did not improve. They were good right from the get-go, if I did my part. These mortars throw their lumps much more forgivingly accurate than more finicky, light, hyper-velocity pills in smaller calibers. At least that's my opinion. I do not consider myself an accomplished marksman with black rifles and if I can get sub-MOA groups, then I suspect anyone can with this caliber. For folks spoiled by quality bolt rifles like I was, you learn quickly that black rifles are not so easy to shoot well. But if you have to learn and want to see reasonable groups quickly for your effort, the 450b is a great choice for a first AR caliber.
Hoot
