OAL on rifle loads

[onlybrowning]

I am wondering two things about OAL. Is it as important to find the maximum (closest to the lands) OAL for the gun as some people say it is. I have heard both arguments. I also want to know the best way to dertermine the best length for my rifle.

 

[6mm4me]

My method

I use a dummy round, no primer or powder and lube the inside of the neck in a sized brass and seat a bullet long. Then I chamber it in the gun and close the bolt, this seats the bullet touching the lands. Then I eject it and measure the OAL and subtract 5/1000's and adjust die to that OAL. I don't like a lot of "jump" but really can't comment on accuracy gained or lost. But I do want uniformity in shell to given rifle.

 

[Bullet94]

onlybrowning Quote – “I also want to know the best way to dertermine the best length for my rifle.”

You will have to try different seating depths and see which one shoots best in your rifle.

What kind of rifle are you shooting?
What cartridge are you shooting?
Do you want your cartridges to feed from a mag?

 

[somerled]

Bullet94 points out some variables one has to consider.

Some bolt action rifles with short actions or magazine-fed rifles put limits on the OAL. Some manufacturers have built rifles with long throats and short actions in the past.

I usually try to use the OAL listed for a particular bullet in the better reloading manuals. I don't go much shorter as it increases pressure. But if you load the bullets too long and contact the rifling origin (or even worse force the bullet into it) the pressure goes up.

Often the best accuracy in a given rifle is found when the bullet is seated so it is is just short of the rifling origin. But that always isn't the case.

With some cases, particularly shorter necked ones such as the .300 Win. Mag., some bullets aren't secure enough seated long. Just chambering a round will shift the OAL. The bullet will usually move deeper into the case. I've particularly had trouble with boat tail bullets. The bullets with long bearing surfaces work better in cases with short necks. I've also heard of cases when long-seated bullets pull out of case necks when an unfired cartridge is extracted from the chamber.

Another thing to consider is: Will these cartridges be used in another rifle? If so, you should avoid loading the bullets long.

 

[onlybrowning]

Oal

I am shooting a Browning A bolt II in .308. The load in particular is a Nosler Ballistic tip 150gr over 43.5 grains of H-4895 in Remington brass with Federal 210 primers. The length listed in the Lyman 48th edition book is 2.78" and I loaded them to 2.800." It is not touching the lands and I do not think that it is even close to touching, but the 150gr bullet is relatively short, so I want to seat it deep enough to be consistent. I know that my .270 of the same make does not contact the lands even if I seat it out farther than I am comfortable with (3.400"). Sorry for being long winded but I want to be thorough.

 

[somerled]

You're okay seating so the overall length is 2.8 inches. That is the maximum for the short-action cartridges such as the .308. You may encounter feeding problems going longer. Of course, you can work with seating some longer to see if they group better while not sacrificing reliability.

An old Hodgdon manual I have here shows a max. of 44 grains for a 150 grain bullet. Other manuals show 150-grain bullets of similar profile as the Nosler ballistic tip seated at around 2.7 inches overall.

Sometimes a combo will not develop the best accuracy until reaching optimum, safe pressure levels. Seating long will reduce pressure (unless the bullet is actually engaging the lands when chambered). So moving the bullet farther forward may actually hinder accuracy using the same powder charge. Perhaps that is why data shows the 150 grain bullets seated deeper.

Reloading is challenging because all of the variables involved. I never did well at it until I got a chronograph and starting keeping logs.

 

[kingudaroad]

If you have an extra 30 bucks laying around, These chamber measuring tools from Stoney Point really do the job.