Inconsistent COAL

[highcotton]

Well, being that we are snowed in I decided to get on with the AB load work for my son's 260. To clarify, Dr. Mike, snowed in occurs in SC when you have anything over 4 in of winter precipitation. I primed the Lapua brass, dropped my powder charge, and seated the first bullet. Adjusted the seater die to the 2.812 length I was looking for and then took my comparator measurement. The comparator length needed was 3.276. Proceeded to load various powder charges and began to notice inconsistency in the COAL, with measurements running from 3.274-3.281". I am loading virgin Lapua brass that I ran through my resizing die prior to loading. I am using a Forster Micrometer die set that I have used for all previous load work for this rifle. I finished loading all the test rounds I planned to work with by constantly adjusting the die. I have really grown to like the Forster die sets, and have them for 3-4 different calibers I load. Not sure it's a die issue- I really don't know how to explain the differences. I did notice it took more "handle" to seat bullets, but nothing excessive. I have used these dies to load the REM brass I was loading prior to acquiring the Lapua I loaded today with absolutely no issues. Any ideas what I have done wrong?
HC

 

[joelkdouglas]

HC, I have noticed quite a bit of variance in AccuBond measurements. Can you measure from cartridge base to ogive instead of OAL? You should see those lengths tighten up.

I'm torn about the AccuBond. Some boxes I have had shoot very well, and others not nearly as well. In total I can normally get Partitions to shoot as well on average as Accubonds, even though some boxes of Accubonds shoot very, very well.


However, Accubonds do normally shoot MOA or better, despite the measurement differences. I would like to see Nosler tighten the AccuBond standards.

 

[DrMike]

HC, enjoy the snow. We aren't snowed in until there are at least 30 cm, and then only until we can get the truck warmed. You haven't done anything wrong. Your seater stem is likely not cut for VLD, which means the bullet "rocks" as it is pushed in. Measuring off the ogive will give you a more consistent OAL, and switching out your seater stem for a VLD stem will assist in making a more consistent cartridge.

 

[ElmerThud]

'began to notice inconsistency in the COAL, with measurements running from 3.274-3.281". I am loading virgin Lapua brass that I ran through my resizing die prior to loading'.

HC, after running the new cases through your sizing die, did you then measure & trim to the same length all the new cases? I think the measurements you quote (3.274-3.281") are comparator not COAL - is that right?

I have noticed if cartridge cases vary in length, so then also will the seated round vary...I haven't yet figured out why this happens, it just does. I'm not an engineer so maybe someone out there can tell me. Dr Mike also puts his finger on the positioning of the point of the bullet in the seating die. A very valid point often overlooked. Best of luck sorting the problem out - ATB

 

[highcotton]

Thanks for the replies. Yes, I am measuring to the ogive with a Hornady comparator. And I guess looking back I should have, but checking the case length after resizing didn't cross my mind- I was thinking new brass, and Lapua at that, wouldn't need it . After resizing I assume now it should have been checked. I have heard of the need to change seater stems with the Bergers, never had a problem with the AB's before. The only bullets seated with this die previously were BT's.

 

[rick smith]

Cartridge length does not change comparator length since you are measuring from base to ogive. New brass often will give different measurements even if they are neck sized. After firing the problem disappears. The Accubonds should not be a problem with a Forster seating stem. I seat Bergers with several of mine and they were acquired prior to Bergers being introduced. Expanding the necks and then neck sizing, with new brass, will help. Also the consistency of seating pressure helps maintain good measurements. Rick.

 

[tim629]

i had a few run long on my 280ai w/ 160 accubonds, try running them through the press again and see what it does, brought my long ones right down with the others

the few that were shorter coal than the others I just put them all to the same depth and decided they would be a test to see how coal affected my rifle/bullet/powder combo

 

[muleman]

HC, enjoy the snow. We aren't snowed in until there are at least 30 cm, and then only until we can get the truck warmed. You haven't done anything wrong. Your seater stem is likely not cut for VLD, which means the bullet "rocks" as it is pushed in. Measuring off the ogive will give you a more consistent OAL, and switching out your seater stem for a VLD stem will assist in making a more consistent cartridge.

Mike,
Would it be better to use a VLD seater on ABs, LRABs and BTs?
Thanks

Scott

 

[DrMike]

I've not found the VLD seater necessary on the BTs, but my impression is that it may be beneficial on the ABLR bullets. It doesn't hurt on the BTs or the ABs, however.

 

[muleman]

Thanks Mike for confirming my observations!

Scott

 

[woods]

Proceeded to load various powder charges and began to notice inconsistency in the COAL, with measurements running from 3.274-3.281".

HC

Don't know if this has any bearing but if you go from loading bullets without powder compression to loading bullets that compress the powder, you will gain OAL. The more compression the longer the OAL and you will need to readjust your seating die