David Halblom, you asked "How often do you find a choke in 6MM or 30 Cal. barrels. Or let me re-phrase, how often in ANY quality BR supplier, centerfire supplier? "
In my experience after having slugged thousands of barrels in the past quite a few years from most of the barrel-makers out there, barrels from some makers have never had a "choke", and other makers have had it to some varying degree. A slight choke is not a bad thing at all, but if it isn't in the right place, or if it opens up again after that (which does happen), then you are much more limited where you can crown it. I agree with Jerry that this may be more important in a rimfire, but a centerfire barrel with a slight choke will shoot just as well as one that is dead level all the way through.
I almost never see this with any of the cut barrel makers like Krieger and Bartlein - they are just usually exactly the same feel on the slug from one end to the other, so you can pretty much crown them anywhere you want in the far majority of cases. I can go for several hundred barrels before finding one of these that has any issues at all that I am concerned with, so I have come to prefer using cut-rifled barrels the majority of time, since I have had the least amount of issues with them.
I do use a lot of button barrels also, and barrels from some makers almost never have a choke, and ones from some other makers often have some degree of choke present. The ones I find almost always have a choke seem to be from the makers who purposely taper-lap the bore. If this is done correctly, it can be awesome. If not, then this can easily become an issue. But as long as they slug good I think button barrels, tapered or not, are just as good as cut barrels.
I think to get a choke into a barrel, whether done purposely or just as a result of finish-lapping, it has to be lapped there. This means the whole length of the bore behind the choke has to be lapped larger, and since this has to be done by hand in most cases, this is one of the reasons for a lot of the issues I have found in the past. When I found barrels from one particular maker all of a sudden start having issues a few years ago, I called and talked to the owner about this, and he said he lost one of his top lappers and was in the process of training a new lapper. This definitely explained the issues I was feeling with their barrels for awhile, and their barrels now seem to be just fine again.
If lapping the bore is done nice and evenly with either a smoothly tightening taper from the chamber to the crown (taper-lapped), or a straight bore transitioning into a gentle tightening up in the choke near the muzzle, they will shoot great and be a winning barrel. But too often I find where they are not even all the way through with loose and tight spots caused by uneven lapping, which I either re-lap myself or return to the maker. The other main thing I have found was they transition into way too much of a choke, sometimes between .0005" and .001", which is way too much in my opinion. When I find this, I measure to make sure the bore hasn't been lapped oversize behind the choke, and if not I crown it where the choke has just started tightening up. These will be match-winners also.
I often taper-lap factory barrels if they aren't too large inside already or bell-mouthed beyond where I want to crown them. This isn't all that hard to do and works extremely well in most cases if you slug them along with the lapping process to make sure you end up with a good even bore. I have explained in detail how to do this in my upcoming DVD also.
The importance of slugging barrels really came back to me this morning. I'm like Jerry, it has been a long time since I've had a problem barrel come through here since I almost always use the barrel-makers I have had the least amount of issues with. But I had a customer recently send me 2 barrels from one of the top barrel makers to put on his competition rifle. It has been a long time since I've used barrels from this maker, and have never had much issue with their barrels in the past, but boy did that change this morning. Both barrels were nice and even for the first half going forward, and one opened up just ever-so-slightly ahead of the half-way point. But it wasn't enlarged over .0001" or so (I could barely measure any difference on slugs from either end), and the slug from the loosest area near the crown area measured .3080", so I can lightly taper-lap it to remove the tighter area in the first half and be just fine. A lot of extra work, and some additional expense for my customer, but that's the only way to get his rifle to him soon.
The other barrel from this maker I have flat rejected and am refusing to install. It measures around .3084" at the crown end, which means it's too large inside to lap out, and it's reverse tapered to boot - no way would this barrel shoot good! The slug noticeably loosens up at the 20 1/2" mark and then loosens up even more at 25 3/4" - not good at all, especially since the customer wants a 30" barrel. So this has put a definite damper on my day (and played havoc with my schedule), but even worse, this is going to cause problems for my customer who is on a very short time-frame for needing this rifle. But I am sure glad I found this issue before spending all my time chambering and installing this barrel, and the customer having to spend much frustrating time and expense shooting load after load trying in vain to get it to shoot good. This is exactly why I feel slugging new custom barrels is so important!
Gordy Gritters
www.ExtremeAccuracyInstitute.com
