Measuring the coal for that rifle. You can take an empty case (no primer - no powder) seat a bullet out. Drop in chamber and slowly close bolt pushing round into chamber. When the bullet hits the lands it will be pushed back into the case. Close the bolt then slowly extract the round. You can then measure from case head to the scratches on the bullet where it hit the lands. Now you know the distance. Reduce that number by .002" or .003". Check and make sure it will fit the magazine. Now this measurement will only work for those particular bullets. Ogives change on bullets so if you changed bullets back to the process.