different max o.a.l. for new box of bullets

[hunter30]

I used hornady c.o.a.l. gauge to determine my O.a.l. with sierra matchking bullets. after that box of bullets was used, i bought a new box of the same lot. i double checked my o.a.l. using the hornady c.o.a.l. gauge and this new box of bullets. with this new box, my o.a.l. is .020" longer. this is measuring to the ogive. is this common? should i adjust my o.a.l. so that it matches the bullet jump of my last loads, or leave them the same o.a.l. as the previous box, which would intern increase my jump by .020'? will any of this effect my muzzle velocity? Thanks for any advice.

 

[Catfish26]

It is common to get different lengths. I try to buy in boxes of 500 to help. Even then I still sort the bullets to +/-.003. Buy the Hornady Lock-N-Load Comparator Body and the correct insert for your bullets. This will keep things equal if you measure to ogive every time. And yes the closer to the lands you get the more pressure and speed.

Hornady Lock-N-Load Bullet Comparator Body

 

[AZShooter]

I thought the hornady c.o.a.l. gauge was used for locating the engagement point where the bullet meets the lands. The longer .020" difference would have to be the wear the throat encountered due to firing.

Even if the bullet has the ogive that is closer to the bullet tip, the seater cup would engage the ogive of the bullet, seating it so the cartridge base to ogive measurement would remain the same.

You will have to adjust the seater die to maintain the same jump to rifling to compensate for throat wear. My 1000 yd shooting buddies have rifles that show throat wear for every match.
They routinely measure with the hornady gauge then adjust their seater dies to maintain the same bullet the same engagement distance away from or into the rifling.


For grins did you measure the new bullets from base to ogive? It would require the bullet comparator or similar.
Alternate device for measuring which you could make if you have a drill press:

http://www.sinclairintl.com/reloadi...r-hex-style-bullet-comparators-prod34262.aspx

 

[Bigeclipse]

I thought the hornady c.o.a.l. gauge was used for locating the engagement point where the bullet meets the lands. The longer .020" difference would have to be the wear the throat encountered due to firing.

Even if the bullet has the ogive that is closer to the bullet tip, the seater cup would engage the ogive of the bullet, seating it so the cartridge base to ogive measurement would remain the same.

You will have to adjust the seater die to maintain the same jump to rifling to compensate for throat wear. My 1000 yd shooting buddies have rifles that show throat wear for every match.
They routinely measure with the hornady gauge then adjust their seater dies to maintain the same bullet the same engagement distance away from or into the rifling.


For grins did you measure the new bullets from base to ogive? It would require the bullet comparator or similar.
Alternate device for measuring which you could make if you have a drill press:

http://www.sinclairintl.com/reloadi...r-hex-style-bullet-comparators-prod34262.aspx

this is interesting. I never thought about throat wear. So just a quick question, if you had a hunting rifle load out to 500 yards for example. How many shots through the rifle before you would start checking to adjust your overall length again? I know this would change with different calibers and wear rates but lets say for example a non mag cartridge such as 308 or 3006 and a mag cartridge such as a 7mm mag or 300 mag....thanks for any info!

 

[AZShooter]

Sometimes we get too involved in the details when it isn't necessary. I shoot many of my rifles that I KNOW are getting throat wear without changing seating depth. I have been using the same OAL for a 257 Weatherby and 6mm-284 for hundreds of rounds with no change in POI or group size. My theory is that the barrel harmonics are remaining the same or close so impact/group remains the same.

The 1000 yd guys chase the throat because they are attempting perfection and want everything the same every time.

I remember the old days when we used to just choose a seating depth for a bullet and then add powder till we got the best group. Absolutely no measurement of jump to rifling, OAL or another detail. Many rifles shot wonderfully and our ignorance didn't hurt us. I think the attention to details trickled down from BR guys and the long range hunters picked it up.

BTW if you choose to shoot the hybrid line of Berger bullets you can go back to the "seat it at any depth" so it fits magazine and feeds then add powder till you find the best grouping. I swear these bullets are very friendly as advertised. Have used them in 6mm (105 gr and 95 gr), 7mm (168 gr and 180 gr), 30 cal (230 gr) and 338 (300 gr) in just this manner.

I'd say choose a seating depth work up a load and shoot the rifle till it tells you that you have to tweak seating depth or powder charge to get that small group back.

 

[Mikecr]

IMO nothing for LRH trickled down from benchrest, especially point blank BR. I'm sure very few competitors actually full blown test for best seating.
You could do full seating testing(like Berger's recommended) without ever measuring MaxOAL, as all that matters are the results per CBTO. Best would be logged/used of course.

What I've seen so far, with best seating off the lands, is that it never needs to be adjusted again -for same bullet & barrel. That is, no chasing is needed.
But where you change bullets, bullet lots, and barrels, you need to retest.

 

[Bigeclipse]

IMO nothing for LRH trickled down from benchrest, especially point blank BR. I'm sure very few competitors actually full blown test for best seating.
You could do full seating testing(like Berger's recommended) without ever measuring MaxOAL, as all that matters are the results per CBTO. Best would be logged/used of course.

What I've seen so far, with best seating off the lands, is that it never needs to be adjusted again -for same bullet & barrel. That is, no chasing is needed.
But where you change bullets, bullet lots, and barrels, you need to retest.

when you change a bullet lot...will you load up like 5 of your old load and test. If good, then call it good. If bad, then maybe slightly adjust powder or seating depths + and - a bit to see if it improves? Do you do a full blown load test from scratch? Or something else?

 

[MagnumManiac]

I agree with Mikecr. I used to chase the lands in my 1000yrd rifle barrels, but where do you stop?
I took the approach of retesting after every match for velocity changes if throat wear was evident, then adjusting the charge weight to compensate for the velocity loss. It has worked for quite a few barrels now and can prolong a node even though the barrel may be on it's way out. By keeping velocity in the node dissipates the negative effects of throat lengthening, and I have never seen evidence that the haze cracking in the throat as it lengthens has a detrimental effect on accuracy, but does foul easily.

Cheers.
gun)