Bullet seating depth .308 Win

When I seat my SMK 168 bullet depth according to cartridge specs, the bullet is not in contact with the lands in my barrel. I know this is likely to increase pressure, but will I have increased accuracy if the bullet in not seated as deeply and does touch the lands and grooves when chambered?

 

Generally a "jump" to the lands will have lower pressures than a bullet seated into them.

Think of it as a running start before you have to do the hard work.

In some cases rifles are more accurate seated closer or into the lands though. Also in some cases a round loaded to this length will not fit into a magazine and you must load them one at a time.

To define the "some cases" part, you just have to test different loads with your rifle.

 

I can't seat any grain bullet within a country mile to the lands in my Rem 700 BDL. To do so, the bullet won't be near enough at all to having at least a caliber's worth of seating in the case neck of my 30.06.

If it affects accuracy I ain't complaining . I sneezed on shot#5 , but shots 1 and 2 are no more than .380" c2c.

The second pic is the depth tool I made using one of my fired cases. That's a 165 gr out touching the lands.

Andy

 

There is no set rule on seating depth. Will you rifle be more accurate with the bullet touching the L&G's, nobody knows. Each rifle is different and extensive testing is usually required. Any change with your reload can make a fifference. Try different powders and different charges until you find the right combination for your gun.

 

"...the bullet is not in contact with the lands..." Shouldn't be.
However, like joem1945 says, there's no set rule. Every chamber is slightly different. Even two identical consecutively numbers rifles have slightly different chamber dimensions. And there's absolutely no guarantee seating 'just off the lands' will make any difference.
Seating 'just off the lands' is a load tweaking technique that is 100% trial and error to find the exactly OAL your rifle prefers. Really doesn't make a lot of difference in a hunting rifle anyway.

 

The cartridge has to fit the magazine and fit the chamber. Reloading gives you to opportunity to do both. The big ammo manufacturers have to produce cartridges that will fit the vast majority of all similar type chambers. Use a type of measuring device that will allow you to find that point which is some .005 off of the lands and enjoy your reloading and shooting. I don't set OAL to jamb into the lands but do understand the implications and some advantages of doing so.

 

.005 off the lands with some bullets will have them falling out of the case, as I was surprised to learn.

There is a lot of conflicting information in reloading. One minute your told to seat just off the lands, and the next your told the COAL must be a certain dimension which is nowhere near "just off the lands."

I can see why people get confused.

 

I finally came across my first rifle that would not let me seat to the lands, a Rem 700 VTR.

To the OP, seating up to the lands generally can cause an increase in pressures, where as giving the bullet a running start will almost always produce lower pressures in comparison.

GS

 

168 SMKs are very tolerant of a jump to the lands in my experience. I experimented with seating depth and did not find a noticeable difference so I just seat those to mag length. VLD style and other secant ogive designs like the AMax (and some SMKs) often do shoot better close to the lands. Of course this all can depend on the individual barrel and how the leade is cut so it doesn't hurt to experiment some.

 

Cheapskate measuring absolute max OAL for a specific bullet...

I hope I can explain clearly enough. NOTE: As our buddies said above, all different bullets have different nose and ogive shape, one-size-OAL-fits-all doesn't work. You gotta remeasure when you switch to a different bullet.

Using two dowels and a razor blade.

Make sure chamber is empty. Close the bolt. Run a dowel down from muzzle until it stops against the bolt face. Mark the muzzle on the dowel with the razor.

Now remove the bolt, drop your bullet into the chamber. With a different dowel inserted into the chamber, gently hold the bullet against the rifling lands. Now put the first dowel down into the bore until it stops at the tip of the bullet, and mark the muzzle on the dowel again.

The difference between the two marks is your absolute maximum OAL for that particular bullet.

You can use a cleaning rod or other metal rod and a marker, if you can mark to the nearest 0.001". I can't do that with my old eyes, but perhaps you are accurate down to the 1/1000 inch.

The tools made by Hornady and others do the same thing, this dowel method is just for us frugal cheap-o cheapie cheapskates who want to do the same thing at no cost.

Plenty of good folks will tell you to stop being cheap and just buy the tools. Just smile a big grin and nod your head in agreement. The tools work great. So does the wooden dowel. The gun doesn't know the difference, it will give you the same measurement either method.

 

That's good stuff Ants, I kind of like the dowel concept. I'm gonna give that a try next time.

The only thing I might change, is instead of using a razor to mark the dowel, I think I'll try something that makes contact with and stops against the muzzle. Maybe a zip tie snugged up around the dowel, so the indexing point is less prone to visual interpretation, but rather stops with hard contact against the muzzle delivering a repeatable assessment.

I've learned more good stuff and outside the box ideas here at THR, than I have any where else.

GS