Reloading: inconsistent measurments

The Butcher

I have been reloading for 20 years, and I have a problem I can't figure out. Once I find the desired loading length, after setting the dies, and checking the length, with a Stoney Point comparitor, I find that sometimes the OAL is sometimes different by .0010-.0030. What causes this? Is it a difference in the case? Or a difference in the bullet. I figured since I was using a comparitor, the measurment would be the same, since I was taking it off of the ogive. Does not the seating die also touch the bullet at the same point (width of the bullet)? Or is the taper of the ogive different in the bullets, thus causing point of contact different inside the seating die? That would change the measurment on OAL? Help me understand, and correct. Thank you

spclark

I've noticed the same inconsistency when loading .308 Winchester, using several brands of 168g hp's. Much less variance loading pistol ammo with flat point or round nose bullets.Asked a tech guy at Speer who commented that yes, bullets do vary a bit in overall length, hence the variations noted. As long as your die contacts the ogive the same on each round, the imprtant thing - seating depth, or case volume AFTER bullet seating - the OAL can vary quite a bit. He also mentioned that he'd heard of people FILING the tips of their bullets to make 'em flat so the OAL comes out more consistent but didn't think that was too good an idea, ballistic performance-wise.

buddyb

I had the same problem loading .45ACP. Found out I had bullet lube from cast bullets in the seating die.Cleaned the dies ,fixed the problem.

32wsl

spitzer bullets can be made in many different ogives: each brand, or even each lot can be, and often is, different. But, in seating any one lot of bullets into any one lot of brass the OAL can be different by a few thousands due to the varrying aneal of each of the cartridge brass and or the "spring" in the press ram. Also, when you talk of a difference of .0001 or so, there can be a measuring error caused by either the tool or the technique. Benchrest shooters must go nuts trying to track down the specific problem.

Iconoclast

Reference buddyb's comment above, in my experience, often OAL variations come when some foreign material sticks in the cup of the seating stem, not just w/ cast bullets.

The Butcher

Glad to see I'm not alone. Dies are clean, and have done "Benchrest" case prep. I'm leaning towards the ogive being different. More comments are welcome.

v35

The dimension from ogive to tip is probably not that consistent with soft points.The seating punch should have a clearance hole to clear the point of the bullet and that should not be clogged up. A fixture could be made using a nose punch and dial indicator to measure the height of the ogive from the base. You could then segregate by dimension and weight and be unconcerned about where the tips fall.

v35

Also check for variation in case lengths. Differences in length of crimp because of case length differences can give you ctg OAL differences.

JustC

happens all the time, the most consisitent bullet I have found is the balistic tip due to the fact that it will not deform and has a uniform shape even after production. You may consider that if your loading bench is on carpet or the slightest bit flexible, this can easily cause the variances you are talking about.