Reloading Issue: Why do measurements vary?

[BillLarson]

You got it now. Hammers are the closest being dimensionally equal from one bullet to the next followed by Berger in my opinion.

Match results dont agree......

 

[338 dude]

Thanks all of you who contributed to the confusion. Yes, I recognize all the variations talked about. BUT, the distance between the shell holder and the seating die SHOULD be consistent. If that distance is consistent then cartridge base to bullet orgive should be consistent. UNLESS something happens to shrink or expand that distance AFTER the bullet has been seated. Powder de-compressing, brass somehow pinching bullet outward...might have something to do with it. That exhausts my imagination on the subject.

Annealing will help also

 

[Rick Richard]

Match results dont agree......

Not understanding your comment unless your inferring to rifle competition. If so, my comment has nothing to do with that subject and only directed to bullet dimension consistency. Care to explain?

 

[OldElkHunter1961]

I see that your rifle with your load is shooting half MOA. I also note that no dimensional data depicting the range of variation has been offered. Mean, median and mode might be a useful start.

Three thoughts:

1. What level of repeatable accuracy are you expecting?

2. We live in an imperfect world where myriad variables simultaneously impact every action we take or fail to take.

3. Your intellectual curiosity is laudable as an academic exercise. That is unless you actual expect to see exact, matching numbers repeatedly in all case measurements. I'll cut to the chase; this won't happen. Ever.

 

[lancetkenyon]

If you want exact CBTO, here is what you can do. Back your seating die off by .003". Seat the bullet, measure CBTO, adjust your die however much you need, reseat and remeasure. Then back it back off and repeat. Much easier with a micrometer seater, but can be done with a standard seater too. I usually strive for CBTO within .0005" of target. Meaning no more than .001" variation.

Virgin brass seems to show far more variation, even with an expanding mandrel process. Properly sized fired brass is usually much better.

 

[Harry Knutz]

I use SS rods and Dove soap and tumble. This cleans everything, including primer pockets.

What you probably didn't know is SS pins and tumbling the brass work hardens the necks and increases neck tension, So afterwards you need to anneal, Your response does not make sense in regard to the topic.

In regards to the topic, Bullet Ogives are sometimes not consistent.

 

[KsKevin]

How much variation are you seeing in final CBTO? I measure EVERY final load and always have a range of only 0.001" if not doing a compressed load (Redding press and micrometer seating die).

 

[blackburbot]

How much variance are we talking? You will have some neck tension issues, bullet inconsistency, charging handle pressure inconsistency, inconsistency in your measuring tools and setup. Biggest thing is to go out and shoot these " bad loads". See how much your inconsistency plays down range. I thought my stuff was way off and lots of "advice" from everyone on how to reload and the works. Then you go out and constantly keep stuff around 1/2 MOA out to 900yards. So I started not to listen to all the "experts" and just stick to my usual ways. Take what I said with a grain of salt. But lots of reloading mistakes comes from trying to change too many things without knowing what the real issues to the inconsistency are

 

[CRNA]

I have ran into this before and nearly drove myself nuts. Then I took my seating die apart and cleaned it out thoroughly.
Solved my problem.
Would be worth a shot.

 

[JScanga]

My process is as follows because I use hot salt bath annealing:
-Deprime
-Wet tumble with dawn, lemshine and ss media
-Anneal
-Wash with a little dawn
-Full length bushing die
-Measure and trim as needed
-Chamfer and deburr

Rock Chunker, Redding competition shell holder and a LE Wilson chamber seating die and K&M Arbor press

My loads are constantly +- .002

 

[Koda_]

Does,nt bullet length affect bullet weight...???

Yes.

 

[SSG Graybush]

Reloading any cartridge, when you finish seating the bullet and measure successive fully-loaded cartridges, the measurements should be identical. That is, the distance between the shell holder and the bullet seating die are a constant. So regardless of variations in cartridge case length and carrying bullet lengths, the overall length, Cartridge Base to Orgive should be constant. This assumes no "stretch" or play in the loading machinery. I notice this in all different calibers. What am I missing"

Shape of the ojives are inconsistent so the seating die makes contact at a slightly different point causing a slight change in coal/cbto. Plus the melpates vary. And seating stroke coupled with slightly different neck tension, possibly. Coal is only important for mag length, measure cbto. Its more consistent and a better indication of jump.

 

[BillLarson]

Not understanding your comment unless your inferring to rifle competition. If so, my comment has nothing to do with that subject and only directed to bullet dimension consistency. Care to explain?

your comment was pertaining to Hammer bullets......
if they are more consistent in dimensions..... would,nt you see them used for that quality.... in competitions...???

 

[lancetkenyon]

Does,nt bullet length affect bullet weight...???

Not necessarily.

A mono of the same weight as a cup and core will be much longer.

Shape of the bullet really effects length too. Higher BC bullets will be longer than the same weight lower BC bullets. Like the 7mm 168 Classic Hunter vs the 168 VLD. Or the 200gr SGK vs the 200gr SMK.