Seating depth question

LawrenceN

LawrenceN

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I'm getting conflicting information from friends and even manuals as to the correct seating depth of bullets. One school of thought says that the bullet should just touch the rifling when it's seated at the correct depth. This of course means that you'd have to set your seating die each time you use a different bullet as the ogive varies depending on the weight and manufacturer. The other opinion is that the bullet should sit just off the lands a few thou and actually jump to engage the rifling.
I'm not new to reloading. I've been doing it for a while and my current method is to lightly seat a bullet in an unprimed case that ready for powder and primer. I put a bit of lube on the bullet so it won't bind on the rifling, and set it in the rifle and slowly close the bolt. I gently extract the round and then measure the overall length of the cartridge and set my seating die accordingly. I record the length in my reloading log, and I do this for each different bullet that I load.
So I'm putting 'er out there to you guys who have reams of experience and I'm wondering what your thoughts and experience tells you. I'd appreciate different input and the logic underlying the other methods. Thanks in advance.
 
This is a chicken and the eggs question but i'll give you my train of thought First the gun, my gun likes the bullet touching the lands so I TRY to load this way I have read all the literature out there and tried both ,then I came to this conclusion for myself One every gun is different Two the seating die is it custom made to the bullet your using Three Are you pulling the lever on the press at the exact speed and force every time Four and the thing I found to be the biggest variable is the bullet are they made to the one one thousands that I am measuring Even if I wanted I dont think I could make the perfect lenght rd every time There are some that do do this I believe and measure every round to get that perfect rd So I now load so the bullet is just of the lands and I still get that one round every 100 that needs a little push to chamber
My suggestion to you is try both methods see what works for you and your set up .
 
Touching or lightly jammed into the lands works right up to the point when there is a situation on the range that requires you to unload and make safe. Having the action full of powder in the middle of a match is not something that you would want to do twice. If you are touching or lightly jamming the lands in a hunting rifle, bring a good cleaning kit with you.

When I am starting to develop a load for a rifle I do start with the bullet touching the lands. This way you will be able to see very quickly if the loads are too hot, because you will be at max pressure seated to the lands. Once the desired load is found, start seating the bullet deeper by .005" at a time. I find that .020 off the lands works in several target rifles shooting a 155 gr match bullet.

Some bullets like SMK's or Nosler Competition bullet will shoot just as well touching the lands as they do loaded with a big jump. I know lots of TR shooters that are jumping Berger 155's, .040" off the lands.

Seating different bullets to get the same amount of jump or seating to your desire seating depth from one bullet to the next is the reason I only use Redding competition seating dies for my match ammo.
 
Thanks Maynard. After 40+ years of shooting, trust me, I know the dangers inherent to seating a bullet too far out and binding on the rifling. Outside of the increased pressure curve that can result, I've seen the actions full of powder and listened to the fascinating range of cussing that some folks are capable of. As I'd mentioned, I load just off the lands (usually by about .05 thou.) but interestingly enough, I loaded some 7.62 X 39 ammo way off the lands and finally got hunting acceptable groups. I'm going to retry some rejected loads and see if they also benefit from that set back.
 
I tried playing with seating depth and found that the first and foremost criterion is that the loaded round fits into the magazine. In all my 30 cal. rifles this means the the bullets are seated way off the lands, generally close to the COL specifications given in the reloading manual. It depends somewhat on the ogive of each bullet type, of course.
 
In my 30-06 bullets are .020" off the lands and feeds from the mag. My 7mm-08 everything is seated to the mag length no idea how far they jump but it is accurate.
 
If you are starting out, I suggest you use 20 thou off the rifling. In many guns I find this much more accurate than touching.

Because there are minor variation of where the ogive is and in seating depth, round to round, by using 20 thou off, all those variations disappear.
 
Ganderite said:
If you are starting out, I suggest you use 20 thou off the rifling. In many guns I find this much more accurate than touching.

Because there are minor variation of where the ogive is and in seating depth, round to round, by using 20 thou off, all those variations disappear.
Click to expand...

If you measure coal length from the ogive there shouldn't be any variation
 
hometownhero said:
If you measure coal length from the ogive there shouldn't be any variation
Click to expand...

Ganderite is mostly right, seating 20 thou off the lands will in most cases erase the effect caused by variation in ogive within a lot of bullets. You're right only if you measure and finick with measuring and adjusting every loaded case to get every ogive seated to the same depth. Realistically nobody does this.
 
So many guys with different results. David Tubb (10-11 time National Champion) says he "soft seats" his bullets for best long range use. That's using minimal neck tension and letting the bullet seat "softly" into the lands. Jim Carmichael (spelling?) was a great writer/hunter/shooter with many decades of experience. He had a rifle (7 Mauser?) that he all but gave up on for accuracy till he seated the bullets WAY off the lands. I once used a Rem 700P that had to be loaded from the mag and restricted the OAL to be .100 off the lands but performed very well out to 900. (I've seen Maynard shoot, he knows his stuff and can perform on targets at distance)
 
I do my process slightly different also, and depending on rifle/application.

It comes down IMO basically to pressure which vary and are changed with a)seating depth and b) charge weight. The degree to which influence I do not know, I cannot test such variables.

For a rifle with a magazine I ensure the seating depth allows for use of the magazine.Then, do my testing with loads and chose one, haven't had to vary depths yet as accuracy has been adequate.I will however record my OAL with a comparator and I will find the lands just to know what distance I am.

If I am doing one with no restrictions I will go with the manufactures recommendations and then vary my jump or jam after I have optimized my charge weight.If I have no information I will find the lands and do a +/- of 0.005 , 0.010 , 0.015 , 0.020. or whatever number I/you decide to use for increments.





Here is an example above of finding a weight, then varying depth.

So many differences between components and rifles, pick a system you like and are comfortable with and stay consistent, get a comparator for the few $$ they are and I like to use a magic marker to find the lands, works for me, YMMV.

I adjust my dies every time I use them so leaving them for a particular bullet never really bothered me for the few seconds it takes to find your mark or to change for ogive differences.
 
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