There are several other things you might consider for analytical tools before you go and assume it's all about your run-out. You might have a look at your throat wear, using a Hornady "Stoney Point" COAL gauge. This will help you indicate how much jump your bullets witness before land engagement. Since you're shooting a bolt gun, you might be willing to seat the projectiles to within 0.020" of touching. Next, you MIGHT be willing to cast your chamber with cerrosafe. This would provide you an accurate mould of your chamber, throat and leade. With these numbers, you might be able to figure out if your guidance in the throat is too excessive in diameter, compared to the diameter of the projectile. Or, you COULD also witness if the chamber was perhaps cut "off-square".
Next, you could lap your barrel. If you've never done this one, I'd encourage you to do it, just for the experience. Here's how: Take the barreled action out of the stock. Scope off too. Mount the barrel, muzzle up AND at AT LEAST 45 degrees, in a soft-jaw vise. You want the barrel pointed a little bit "closer to the ground, than closer to the sky". This way, when the lead pours off the head of the muzzle, it won't form a "mushroom head". OK, now, insert a cleaning rod with a wrap jag on it, within ~ 2 inches of the muzzle. Now, heat up some lead. Wheel weights will do. Molten. Pour that lead down into your muzzle, and let it harden. Absolutely enable the extra lead to pour off, onto the ground. If you form a mushroom head, discard this "lap" and start again. So, once you've finally got a lead lap that'll pass back into the bore, and is secured upon the wrap jag, remove the barrel from the vise, and tighten it back up horizontally. Now, slowly move that lap to and fro, feeling for any tight or loose spots in your barrel. If anything, it is acceptable to feel a tight spot at the muzzle, and everything else should be looser. You should not generally feel any "skips", nor should you feel any tighter spots than that at the muzzle. You may go a step further, and place some clover lapping compound on the lead, and work the barrel over for a while. If you choose, you may remove "odd" tight spots with the lapping compound.
I have lapped numerous barrels over the years, to include black-powder guns, and barrels that folks thought were absolute junk. It IS possible to give new life to these old work horses, but be warned: If there's an overly worn throat, or misalignment in the chamber/bore, lapping won't help.
Good luck!