Originally Posted by elkaholic
I have a 721 rem wih a 27"NBRSA Lilja barrel, H-S Precision stock. It's in 300 ultra. No matter what I shoot or what I try, I can't get much less than 1.25 MOA. I have skinned the bedding, lapped the bolt etc. etc. The previous barrel was swapped for the same reason. I suspect that the barrel and action are not square? What do you guys think??
First, revert to fundamentals.
Everything you've done thus far is the baby steps that takes a good rifle to the level of exceptional.
(assuming its done correctly mind you)
I compare this to a car that runs poorly. if it's missing and sneezing out the carb pulling the heads off and having them ported/polished, and titanium valves installed are more than likely not going to solve your driveability issues.
You have a heavy contour barrel made by Dan Lilja on a Remington. A combination that is very common and time tested. This is a good thing because it tells you that it should shoot just fine. First ensure your bullet weight is appropriate for the twist rate. Rather than regurgitate info visit Lilja's site and review the barrel twist/bullet size chart.
If you don't know your twist rate, measure it. Get a cleaning rod, mark the rod where it bisects the tang after the patch has a good purchase into the bore. Put a flag made of tape on the shaft right in front of the cleaning rod handle. Push the rod through until the flag rotates one complete revolution, then mark the cleaning rod again. Measure the distance between the first mark and the second and you know the twist rate.
1-10, 1-12, etc. (Whatever it is. Chances are its probably a 1-10 as this is the most popular for 30 caliber.
Now get yourself a quantity of factory loaded premium quality ammunition. Ammunition companies devote considerable time and resource to ensuring that their stuff works in a broad spectrum of guns.
Make sure your optics are mounted securely and that the parrallax is set for the distance you are shooting.
Next go shoot a five shot group. Then have someone else shoot it and compare. It could be the guy pulling the trigger. (As painful as this can be to admit, it's true sometimes) If the gun is squeeky clean shoot the first five rounds right into the berm and ignore where they go. A barrel needs to be fouled for real world testing.
Now shoot for record.
Here's a "Chad's top 11 reasons guns shoot like crap list":
1. Parallax in scope
2. Guard screw torque (40 inch pounds is all it takes)
3. The barrel isn't screwed on tight (As dumb as this sounds, I've seen it)
4. The recoil lugs bottoming out in the stock
5. The tang of the receiver is hitting the stock and preventing the recoil lug from making contact with it's register in the stock
6. The bolt handle is touching the stock
7. The rings/bases are not tight
8. The chamber does not have sufficient clearance between the case neck and the chamber wall. This is borderline dangerous because pressures elevate violently if the neck cannot relax enough to let go of the bullet. You should have a minimum of .0025" all the way around. (.005" ID larger than the case neck OD with a bullet seated-more on this below)
9. The magazine box is bottoming out against the receiver mortises preventing the action from nesting in the stock properly
10. Recoil lug is not clocked properly (easy to do on a Remmy) and its binding the action when it's pulled up tight in the stock
11. Too tight on the headspace.
Regarding chamber dimensions: Yes, I realize bench rest guys run their stuff to the extremes when it comes to minimal tolerances. Bench guns are also very application specific firearms that operate in a controlled environment. A .261" neck 6PPC "trailer queen" bench gun is allot different than a 300RUM hunting rifle.
Check all this and then check it again. If none of this results in any kind of satisfaction then it may be time to box this up and ship it to someone who can dig into it a little deeper.
Last note. How do the primer strikes look on the cases? A weak striker spring will also wreak havoc on groups, but this is typically seen at further distances. (400 yards and beyond)