Fun With A Bullet Comparator

[IndispensableDestiny]

I use a Hornady bullet comparator to set my seating dies, measuring from the case base to the ogive on the bullet. Today I finally broke out a new box of Lapua .308 brass and a box of 175 grain Sierra Match Kings. I planned on seating the bullets to about .015 from the lands on my rifle.

I decided to measure all the bullets in the box of 100, from the bullet base to the ogive. About half the box measured .660, a third .655, and the rest .657 or .658. I sorted them into three sets and used the .660 bullets to develop a new load.

I was a bit surprised at the variance. I understand that the bullets are made on multiple dies and then mixed together for packaging. I wouldn't have cared but the difference translated to the seated OAL (to the ogive). The "short" bullets seated to the longest OAL. That makes sense. Make a drawing and you'll see why.

Anyway, I'm taking Friday off to test my rounds.

 

[Infantry23]

I admire your painstaking attention to detail! Have fun Friday enjoying the fruits of your labor.

 

[IndispensableDestiny]

I admire your painstaking attention to detail!

I weighed them all first. It's become an obsession.

 

[Pinecone]

To truely test, you need to do a doulbe blind test.

Segragate the lots, have someone else mark them as to which lot is which, without you knowing.

Then shoot the lots in a round robin fashion. Round 1 from Lot 1 on Target 1, Round 1 from Lot 2 on Target 2, etc.

Then figure out which was best. THEN have the person tell you which was which.

Best would be to have someone else entirely do the shooting, but that is not fun.

Funniesst story I heard was about a top competitor in long range shooting. Had a big match coming up, so as he loaded, he had two groups, "Perfect" ammo for the match, and "other" ammo for practice and such.

He went to the match and won easily. Got home and found he had taken the wrong group of ammo, he had taken the "other" and left the "perfect" at home.

 

[axshon]

I know what you mean about the comparator and calipers obsession. I am not convinced that it makes a hill of beans difference at 1000 yards on a .308 but using hand tools to produce ammo that precise scratches that itch for me. Theoretically if you had the same OAL with different seating depths you would have different pressures but that assumes the same chamber temp, the same internal volume of the brass and the same operation of the primer, all of which can vary in the same way the bullets do. It's an interesting problem to consider all of the variables and try to make the best choice among them and then adjust over time. Next thing you know you'll be buying one of these: http://appliedballisticsllc.com/Pointingdie.htm [if you do, can I borrow it? ]

 

[Sundazes]

You don't have kids, do you?

 

[IndispensableDestiny]

It seems to me that when I load 25 bullets at 5 different charge weights, the only thing that should vary is the charge. I expect the optimal charge for the "longer" (.660) bullets will be the same as for the "shorter" (.655) ones. That they may shoot differently is immaterial right now.

Speaking of consistency, I am amazed at how uniform the new Lapua brass is. You do get what you pay for. I felt compelled to do something to them. I noticed a few necks were slightly out of round from handling. So I neck sized them all with a .335 bushing. I thought of trimming them from 2.007 to 2.005, but let that be. They slipped in and out of a body die, so re-sizing them was pointless. The shoulders on the new cases are set back about .005 when compared to a fired case.

 

[IndispensableDestiny]

You don't have kids, do you?

No, and the wife was away this weekend.

 

[IndispensableDestiny]

Anyway, I'm taking Friday off to test my rounds.

It may have paid off. My loads with 44.0 and 44.2 grains of Varget produced .30 inch groups at 100 yards. Consistent velocities. I felt so good, I ordered 2 more boxes of 175 SMKs.

My loads ended up being .017 off the lands.