Overall ctg length?

[fairview mick]

I recently got the new book by berger, on handloading etc. There was talk of overall length effecting the accuracy of the round, but they don't go into whether it is better to have the bullet go further into the chamber or not!!!
Is anyone familiar with this effecfting accuracy and is it worth the time to run alot of testing on oal of the round?
Thanks
Mickey

 

[243winxb]

http://www.bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/ Doing your own testing is the only way to know. The ammo must fit the magazine, if one is used. Start with the bullets base (full diameter, not boatail) at the neck/shoulder junction if possible. Then trying as many as 4 different burn rates of powder for the cartridge may tell you something. Like the 223 rem can use IMR powders 4198, 4895, 3031 and 4064. Then fine tune with OAL with the powder of your choice.

 

[mikld]

I have tried different OAL, distances off the lands, but it was near the last thing I did working up a load. For me, powder type, powder charge, primer type, brass and bullet came first. Some rifles preform better with the bullet .010" from the lands, some like .025", and some don't seem to care (old Schutzen shooters crammed the bullet into the rifling) ...

 

[Unclenick]

Take a quick read of item #3 at the top of this page for another example. Changing COL isn't really the objective. It is adjusting how far the bullets have to jump from the case mouth to the throat of the rifling when the gun fires. It seems to affect how well the bullet lines up in the bore. It is just another tuning factor, same as adjusting the powder charge, primer, and bullet choice; getting tools to improve coaxiality of the cartridges (reduce runout); getting the gun bedded, recrowned, lugs lapped or receiver trued to take advantage of all the cartridge tweaks and to realize its potential.

Unfortunately, nobody can tell you which way you well have to move the bullet to find the best spot. As the Berger article points out, with their VLD bullets some guns want the bullet in contact with the rifling for best precision on the target. Some want them backed 0.020" away from the lands, some want 0.050" off the lands, some 0.080", and some even 0.120". You just have to find the sweet spot for your gun and bullet choice, and expect to have to do it again if you change bullets.

 

[Bart B.]

Whatever cartridge length you choose to start with, the bullets will have .001" further to jump to the rifling every 10 to 20 shots. That's 'cause the barrel erodes away from firing. That distance can increase 1/10th inch without any significant loss of accuracy.

Best accuracy depends on the bullet's ogive shape and the rifling's leade angle. It takes at least a couple dozen shots per test group to verify any cartridge length setting is best.