Hello and thanks in advance for your help. I am just about to reload my first 20 rounds of .308 ammo. I have purchased the RCBS precision mic and competition dies. The precision mic gives me a reading of .025 in my rifle (Remington 5R). This is the spot where the bullet touches the rifling (correct?). The instructions say to try .010 less, .020 less and .030 less to find the most accurate. Is it really ok to make the bullet "jump" up to 30 thousandths? That seems excessive. The oal of the factory ammo is 2.800 inches. After loading to .010 less I get an oal of 2.760 inches. The Sierra reloading manual lists the coal of the .308 as 2.800. I'm confused:o Thanks again!

Paul

Welcome to the forum vikinghater. Rules are simple, be nice and join in.

Lots of times in a factory chamber you simply cannot get a bullet within .01 or even .03 from the lands and most of the times your magazine length will determine seating depth unless you want to run your bolt gun as a single shot. Most factory rifles have a chamber cut for the longest commercial bullet available.

I'd try loading to your manuals specs and see how it shoots. Often the bullet jump to the rifling won't have near the effect you think it does. Just remember the basic rule about seating bullets is seat one caliber deep in the case.

Welcome. You say; "...spot where the bullet touches the rifling (correct?). ...try .010 less, .020 less and .030 less to find the most accurate. Is it really ok to make the bullet "jump" up to 30 thousandths? That seems excessive."

Why do you consider .030" of the lands "excessive"? Some (factory) rifles shoot certain bullets best when they are seated as much as .100" off the lands. I find that my most accurate rifles (six) shoot best when seated from .020" out to maybe .060" off the lands.

Only my Marlin 336/.35 does very well (5 into 1.25"/100) when touching or even nearly touching the lands and I think it could do better if I tried more load development. The other six are in 22-250, 243, 6mm International, 30-06, 308, 7.65mm. ???

Thats another thing that makes reloading so interesting - finding just the right 'everything' for a particular rifle/load. It can also make things expensive & time consuming :)

Personally, I have never achieved best accuracy in any particular gun with bullets well off the lands but have had several that shot quite well with bullets up to .1" off. Lots of accuracy folks single load & let the lands seat the bullet. This requires reducing one's loads so pressure doesn't get out of control. Many picky handloader-hunters who prefer not having to worry about bullet creep & loading down due to pressure keep their loads ~ .001-.003" off the lands - depending on which measurement produces the best accuracy. For what it's worth, when working in mere thousandths off the lands, finished rounds need to be referenced from the bullet's ogive instead of going by COAL because the ogive is not always the same distance from a bullet's tip - even with 'match' style bullets.

I am just about to reload my first 20 rounds of .308 ammo. I have purchased the RCBS precision mic and competition dies.

I reloaded good ammo for 30 years before I owned a set of calipers. Don't get so bogged down in minutae that you forget the important stuff.

You are new to hand-loading. Load simple and have fun! That tool from RCBS is rather advanced I think.

The "shallow end of the pool" has warm water. Play there!

Cheezywan

It's a good tool and I have several. Used properly, it will save you money on components and range time and that is not a bad thing at all.

A little advice - check your loaded rounds for concentricity. There are tools for this but you can roll them across a tabletop and see if the tips wobble. That makes a big difference, too.

Have fun and good luck.

I have found over the years to start at .050" off the lands and work your way down.

I have some rifles that simply love anything I throw at them, while others are very selective.

In developing a hunting load, first determine the bullet you are going to use. Get the OGIVE reading for the bullet in your chamber. This is where the bullet contacts the rifling. I use a resized casing with no power or primer. I seat the bullet in the casing and find the point where I get movement after closing the bolt. Using a precision MIC or other measuring device I record this reading for that particular bullet for this gun. I do this until I get three identical readings. At this point I check to see if the bullet will fit my magazine. Remember this is a hunting rifle. At this point I have two options, I can adjust starting at .050" off the lands because I have no Magazine restriction or I seat the bullet deeper to accommodate the Magazine and have to live with the distance.

I have some factory rifles that can only get as close as .237" due to magazine restriction for a particular bullet.

I have also found that round nose bullets contact the lands much sooner that pointed bullets. In all cases making for a much shorter jump to the lands. I put together a pet load for a Marlin 336c in 35 Remington with 200gr round nose that will maintain a (3) shot 1/2 MOA. Simply just awesome.

Just always have enough bullet seated in the case neck a minimum of its diameter, especially for a hunting rifle.

Hope this helps and good luck. SP357

vikinghater (http://shootersforum.com/member.htm?u=17543) http://shootersforum.com/Image1.gif
I find the part of the mic that is used to measure the case useful but the part to measure to the lands I don’t like (the fake cartridge). I’d suggest making a dummy cartridge (no powder no primer) with an OAL measured to the bullet tip at 2.800. Also take a marker and color the bullet (this makes seeing the marks from the lands easy). Then chamber the dummy cartridge then extract it and see if you can see marks on the bullet from the lands. Most rifles won’t be able to touch the lands when loaded to mag length (2.800 in your cartridge) but if the rifle you have is the one I think it is you may be the lucky exception. If you can reach the lands at mag length I would only go .010 less in increments of .002 or .003. You can use the mic as a comparator to make measurements from the ogive once you establish where the lands start.