Hunting cartridges tend to perform with a small jump to the riling giving the best combination of speed & accuracy. Determining the correct seating depth is tricky by far the simplest way I have found is to buy a Hornady OAL Gauge and bullet comparator.
Along with a good set of Dial Electronic Calipers. Projectiles can be accurately seated in out or against the lands of the rifling. The text below is a description of how the Hornady O.A.L. works is taken directly for Hornady’s web site as I feel they do a better job of explaining its operation than I could:
Here’s how the 0.A.L. Gauge works:
1. Thread the Modified Case onto the O.A.L. Gauge and slip a bullet deep into the case neck.
2. Remove the bolt from your rile, then slip the Modified Case/ Gauge assembly all the way forward into the chamber. At this point the bullet has not been moved toward the rifling.
3. Now, gently slide the internal plunger rod on the O.A.L. Gauge until it pushes the bullet into contact with the start of the rifling (throat or lead). You can feel the contact of the bullet with the rifling. Gently tap the plunger a few times to ensure contact with the rifling. Tighten the brass thumb screw to lock the plunger with the gauge and remove the assembly from the gun.
The result is the longest combination of case and bullet that can be fit into the chamber without a preload on the bullet. The results are easily measured with your calipers.
If you load bullets .020″ shorter than the result, the bullets will “jump” .020″ to the rifling ECT. This tool is simple use and gets the job done.
There are a couple of other methods to work up cartridges over all loaded length. One is to size a cartridge & heavily chamfer the in side of the neck drop your projectile of choose into the chamber of your rile and carefully close the bolt on a sized BUT UNPRIMED! case behind the projectile. (Without opening bolt) turn the rifle muzzle up & carefully place cleaning rod down the muzzle until it touches projectile tip. While placing a small amount of pre load on the cleaning rod lift the bolt handle and what should drop out should be a dummy cartridge with the projectile seated on the lands of your rifle. By measuring and then seating the projectile in an extra 20 to 30 thousandths of an inch you have created your own dummy cartridge with a small amount of jump to the lands.
You will be able to keep and use this in the future to reproduce your hand load only with this specific set of components. Keeping in mind this dummy round will only work if you use reputable manufactures dies like Lee, Hornady, RCBS & Lyman. The seating stems of these manufacturers seat the projectiles by pushing them only on the ogive of the projectile not the tips witch can vary in length. It is best to keep that dummy to reproduce your hand load because if you were to take measurement this can vary a lot as projectile tips can measure very differently from batch to batch or even projectile to projectile.
As a means of working out O.A.L. this method is no where near as good as the Hornady O.A.L. gauge. If you can afford the Hornady O.A.L. gauge buy it, all up it will save you a great deal of heart break and when you state that your projectiles are 3 thousandths of an inch off the rifling lands they will be exactly three thousandths of an inch off. So once you have worked out your rifle’s overall loaded length out, you can then seat your projectiles.
Take some time placing case into the shell holder and placing carefully lining up your projectile in case mouth before pushing the press handle down to seat your projectile. Consistency helps, do not push the handle down quickly on a couple of cases and then slowly on the next four. Slowly, and all the way to the press travel stop on the press you are using works best. When you have done this for your 20 test cases you will require a cool clear morning with little or no wind, a set of sandbags, a tarpaulin and of course a target set 100 yards away.
Load testing a bench rest would be better but this article is being written for hunters, not target shooters and most hunters do not have access to a bench rest if time is taken in setting yourself up you will be able to gain meaningful results to base your findings on. As mentioned above spend plenty of time setting yourself up. The more time spent in preparation will lead to time savings in having to repeat this experiment if you get inconclusive results. (Due to not being comfortable and not shooting well or the many other problems that can cause inconsistent results).
If each group of 5 different powder weights are carefully shot the result on paper should hopefully show the cases loaded with the group @46 grains 1.8 primer showing no signs of pressure. The group @47 grains 1.2″ primer starting to flatten. The group @48 grains 0.9″ further flattening. The group @ 49 grains only two shots 1.9″ flattened & cratered primer and excessive case head expansion.
STOP. (You would be best to cease firing the rest loaded at 49 grains) Some rifles will shoot better than others, some hunters will expect more than others hunters do. But looking at the groups listed above 46 grains shows a poor level of accuracy. 47 grains accuracy is getting better with a small level of pressure starting to show. 48 grains shows a good turn of speed with acceptable pressure levels and excellent accuracy. 49 grains pressure has increased dramatically to a level where the shooter should be thinking seriously about not firing the remaining three loaded shells and disposing of them safely or pulling the projectiles and dropping the powder to an acceptably safe pressure level and accuracy is starting to drop off.
We can see 48 grains is accurate and fast. I would reload 20 at 48 grains, retest and if the results were as conclusive as the first outing I would re-zero rile for this combination. It is that easy to develop a load specifically for the circumstances you are hunting. This can only add to your enjoyment and the sense of accomplishment you receive from hunting.
Warning: All the reloading data in this article should be used with caution. Never use the heaviest recommended powder charge until lighter charges of the same powder have been tried and found to be safe in each individual gun. All data contained herein is derived from various sources and is believed to be entirely safe when used in properly maintained firearms that are in good mechanical condition and chambered for the respective cartridge.
Since neither the author nor publisher have any control over choice of components, the manner in which they are assembled, or the arms the resulting ammunition may be used in, no responsibility- either expressed or Implied- is assumed for the use of this data.