question about O.A.L.?????

[dschow]

What is the function of the O.A.L. Why is it different for different bullet types and weights. I was wondering if this measurement can be played around with or is it in concrete. What will this do to the load if it is lengthened out or shortened? Just wondering.

Thanks
DS

 

[CamoWildcat]

To answer your questions would take a lot of writing. Most reloading manuals cover OAL (COAL) and I would suggest reading any of the popular manuals.
Changing seating depth changes available case capacity which changes pressure which changes velocity. Changing seating depth varies how much the bullet 'jumps' before reaching the lands. Some rifles like a long jump - some do not.

 

[remingtonman_25_06]

SAAAMI specs are the OAL you see in books. The length depends on a lot of things, but usually lighter bullets for caliber cannon be seated out far enough to touch the lands because they have such a short bearing surface, I believe. What most people do is seat the bullet out as far as the magazine will allow.
A neat little trick I do is take a fired case out of your rifle. Make a small indent on the very end of the neck where you would seat the bullet. Make just a big enough dent to hold your bullet of choice into place. Now slide the round into your barrel and close the bolt. The rifling or lands will seat the bullet close to the lands. Open the bolt and measure with good set of calipers. Repeat a couple times to get an idea of the measurement. Back off .010-.015 and start from there with that bullet. Thats what I have been doing lately and wow, I can see an improvement in my groups and especialy my velocity spreads over the crono.

 

[X ring 7mag]

I won't add to the other 2 comments, because both are right, but to answer why OAL changes between bullets is due to the ogive of the specific bullet...the first place on the outer diameter of the bullet that is actually of caliber. that is to say a bullet that comes to caliber on a faster taper should have a shorter OAL....which leads to how far you can play before you are in the lands of the barrel. as rem said .1 to .15 is the norm.

 

[zupspoon]

Please allow me to add my 2 cents...it's true that max OAL is set by SAAMI, but BEWARE!!! It does NOT mean that every different bullet style will have adequate bullet-to-rifling clearance. I learned this the hard way after loading some rounds for a newly acquired .280. I loaded some new cases with a relatively light charge to form the cases to the chamber, and I seated them at max OAL specified in the load manual. I went to the range and set up the chrono just for chits and giggles, and after firing the first round knew something wasn't right. The recoil seemed to be more than would be expected, and the chrono showed quite a bit more velocity than expected. More recoil plus higher velocity = more pressure. The only thing I could attribute this to was the bullet being stuffed into the rifling, so I went home and assembled a dummy round to measure the clearance, and sure enough, the bullets seated at max OAL were jammed into the rifling. In 30 years of reloading I've never had this happen before. The rifle is a stock 700 BDL, and has never been modified. Never again will I seat a bullet in ANY round without first checking clearance on the ogive with a bullet comparator. Ya just never know....

 

[JDMAG]

ALSO just incase you didn't realize this from any of the previous posts, make sure that the round will fit in your magizine, after you find the ideal OAL. It is disapointing when you find the best load\primer\bullet\brass\OAL, shooting one bullet at a time, then finding out that they don't fit in the mag when you try to load 3 or more at a time into your favorite rifle.
Please don't ask me how I know this. :roll:

 

[zupspoon]

Please allow me to add my 2 cents...it's true that max OAL is set by SAAMI, but BEWARE!!! It does NOT mean that every different bullet style will have adequate bullet-to-rifling clearance. I learned this the hard way after loading some rounds for a newly acquired .280. I loaded some new cases with a relatively light charge to form the cases to the chamber, and I seated them at max OAL specified in the load manual. I went to the range and set up the chrono just for chits and giggles, and after firing the first round knew something wasn't right. The recoil seemed to be more than would be expected, and the chrono showed quite a bit more velocity than expected. More recoil plus higher velocity = more pressure. The only thing I could attribute this to was the bullet being stuffed into the rifling, so I went home and assembled a dummy round to measure the clearance, and sure enough, the bullets seated at max OAL were jammed into the rifling. In 30 years of reloading I've never had this happen before. The rifle is a stock 700 BDL, and has never been modified. Never again will I seat a bullet in ANY round without first checking clearance on the ogive with a bullet comparator. Ya just never know....