A couple of quick thoughts. One is the bipod. Getting really tight groups with a bipod takes skill. Many sporting rifles with whippy stocks do best with the front bag under the magazine floor plate. Your stock shouldn't be like that, but it's worth a try. Read Bugholes from Bipod for technique hints.
The second is, when I have a barrel that just doesn't shoot, I try recrowning it. I saw an article by a couple of fellows who bought Dave Manson's crowning tools and wound up doing crowns for $15 for a dozen or so club members to help pay for it. They said about half the rifles shot tighter groups afterward, while the other half stayed the same. Small crown errors are common. It's easy to address, so it's worth doing it. The fancy tools are nice, but you can also just lap one in.
That link is to my write-up, for which I made a lap from a ball bearing. But M. L. McPherson just squares his muzzle with a file and square, then uses a marble as the lap. I'm less sanguine about the reliable precision of using bolt heads and variable speed drills, but many have had success that way. The method I describe takes less than 10 minutes after any squaring you might choose to do, so I don't see a reason for the power tools.
Per McPherson, what I've seen photos of is him shortening a barrel, so he has a hacksaw, the file, the square and the marble and lapping compound with him at the range. He is then tuning the rifle to the ammo, rather than the other way around. Read the Secrets of the Houston Warehouse. You may decide to try trimming your barrel to 21¾", the magic number from those experiments, IIRC (but read the article to verify that, as it's been awhile since I have). That trimming presents you with the opportunity to recrown at the same time.
Finally, I would be sure to have a systematic approach to finding loads. If you can access a 300 yard range and have a good spotting scope, the old Auddette ladder may serve you pretty well. These days I use Dan Newberry's method most of the time, because it works at 100 yards, where an Auddette ladder need more range to let you clearly identify vertical dispersion. If you shoot one of Newberry's OCW round robins, record which shot is which one on every target. Last year a member did that with a rifle he could not make shoot, and by noting that the first shots on each target were almost always highest and most left, and the last shot was almost always lowest and most right, we figured out heat walking was occurring in the barrel, messing up what would otherwise be good groups. At that point, replacing the barrel is probably best. You could also try cryo-treating.
Regarding group sizes, try overlaying groups as Bart suggested. Figure a single 5 shot group tells you 95% of future five shot groups will fall within about +50% and -33% of the size of that one group, as shown in the chart below as dotted blue lines, and that 5% of groups will fall outside those limits. As soon as you collect several groups and overlap them, you have a group with the sum of all those shots, and that shot number applies and the limits get much narrower. The reason this happens is that as you increase the number of shots in a group, you offer more opportunities for outliers to appear, if they are going to. If they don't, your confidence increases that they won't show up often, and that narrows the likely limits of the group size.
The second is, when I have a barrel that just doesn't shoot, I try recrowning it. I saw an article by a couple of fellows who bought Dave Manson's crowning tools and wound up doing crowns for $15 for a dozen or so club members to help pay for it. They said about half the rifles shot tighter groups afterward, while the other half stayed the same. Small crown errors are common. It's easy to address, so it's worth doing it. The fancy tools are nice, but you can also just lap one in.
That link is to my write-up, for which I made a lap from a ball bearing. But M. L. McPherson just squares his muzzle with a file and square, then uses a marble as the lap. I'm less sanguine about the reliable precision of using bolt heads and variable speed drills, but many have had success that way. The method I describe takes less than 10 minutes after any squaring you might choose to do, so I don't see a reason for the power tools.
Per McPherson, what I've seen photos of is him shortening a barrel, so he has a hacksaw, the file, the square and the marble and lapping compound with him at the range. He is then tuning the rifle to the ammo, rather than the other way around. Read the Secrets of the Houston Warehouse. You may decide to try trimming your barrel to 21¾", the magic number from those experiments, IIRC (but read the article to verify that, as it's been awhile since I have). That trimming presents you with the opportunity to recrown at the same time.
Finally, I would be sure to have a systematic approach to finding loads. If you can access a 300 yard range and have a good spotting scope, the old Auddette ladder may serve you pretty well. These days I use Dan Newberry's method most of the time, because it works at 100 yards, where an Auddette ladder need more range to let you clearly identify vertical dispersion. If you shoot one of Newberry's OCW round robins, record which shot is which one on every target. Last year a member did that with a rifle he could not make shoot, and by noting that the first shots on each target were almost always highest and most left, and the last shot was almost always lowest and most right, we figured out heat walking was occurring in the barrel, messing up what would otherwise be good groups. At that point, replacing the barrel is probably best. You could also try cryo-treating.
Regarding group sizes, try overlaying groups as Bart suggested. Figure a single 5 shot group tells you 95% of future five shot groups will fall within about +50% and -33% of the size of that one group, as shown in the chart below as dotted blue lines, and that 5% of groups will fall outside those limits. As soon as you collect several groups and overlap them, you have a group with the sum of all those shots, and that shot number applies and the limits get much narrower. The reason this happens is that as you increase the number of shots in a group, you offer more opportunities for outliers to appear, if they are going to. If they don't, your confidence increases that they won't show up often, and that narrows the likely limits of the group size.
