Minimum Overall Cartridge Length

[jhenshey]

I have been reloading for several years now, but have just recently begun reloading for long distance shooting. I have read how it is important to determine the "jump" to the lands that a particular rifle likes and provides its best accuracy with. This requires measuring the length of the chamber and subtracting the desired stand off distance from the lands. Now for the question:

Does anyone know of a reference for minimum overall cartridge length? The only reloading book I know of that provides it is the Lee reloading manual, which doesn't contain data for the cartrige I'm trying to develop right now (.338 Lapua).

Everyone stresses how pushing the bullet too far into the case can raise pressures to dangerous levels, especially with max loads. I raise the question because in long range shooting you often use max loads and excessive pressue can obviously be very dangerouse. So if this is so important why don't reloading data publishers include a minimum overall cartridge length to keep us away from these dangerous pressures?

Thanks for any help you can provide. I'm new to this forum and look forward to the vast amount of knowledge and experiene that I'm certain is available here.

Regards,

Jon

[billnourse]

Get a Hornady "Overall Length gauge". This will give you the length of your round with a particular bullet set against the lands. You can then start loading with different overall lengths to determine what works best in your rifle. I usually start with .020" off of the lands, except for Barnes bullets. Barnes recommends .050" for their bullets.

Bill

[steve4102]

Everyone stresses how pushing the bullet too far into the case can raise pressures to dangerous levels, especially with max loads.

This is the case in straight walled pistol cartridges and not so much in rifle rounds. If fact in many instances just the opposite is true. Barnes did a study awhile back on OAL and how it affected accuracy and pressure. What they found was in most cartridges tested the shorter the OAL the less the pressure. Here is the article, scroll down to "From the Lab"
http://www.barnesbullets.com/resourc...rnes-bullet-n/

There is also this chart that shows the same thing.

[jhenshey]

Thanks Bill, I do have the Hornady overall length gauge and used it the other day to make up some rounds for my .338 Lapua. The thing is, when I pushed the bullet into the chamber, I didn't apply enough pressure so the bullet wasn't sliding all the way into the lands. As a result I got a drastically shorter reading and seated my bullets way too deep. I will pull them and re-seat to the proper depth, but it raised the question, how deep is too deep?

I was just looking for an answer from test data that shows seating depth's affects on pressure.

Regards,

Jon

[jhenshey]

Thank you, Steve. That was a very interesting article and just what I was looking to find out. I'm not as worried about the pressures of the cartridges I loaded too deep, but I will pull the bullets anyway for reasons of increased accuracy.

Some of the bullets are seated 0.160 too deep and I was looking to test the accuracy of .010 .015 and .020 from the lands. Since my pressure concerns are reduced, I will also test farther away, maybe to .025 .030 and .035 just to see what the affect is. I know the article mentioned that starting a bullet down the barrel farther off the lands had a negative affect on accuracy, but each gun is different and I really want to find the "sweet spot" for this particular gun.

Thanks again,

Jon