throwing a stick in the seating depth chicken yard

did some quick practice drills today. from standing as fast as i could, i went prone and fired one round at the 2.5" head on a reduced IPSC (slightly oblique) at 295 yards, then one round at the 6" head of a full size IPSC at 428 yards, then one round at a 1.75" wide ruler at 352 yards.

my timer battery was dead so I'm just guessing it took about 8 seconds to fire the 3 rounds. it felt slow, though my goal was 6 seconds.

i did this exercise 3 times, so 9 rounds fired total. the first time i aimed at the triangle instead of the ruler so there's one round there (barely, due to bad wind call) and 2 on the ruler , and i missed my first shot on the 428yd head (i assume also due to same bad wind call, but i might have forgotten to hold up the 1 mil i needed).




anyways, the point of this is.... in early October I drove with some friends Elk hunting. my box of ammo rode on a wooden trailer with broken springs through OK, TX, to Albuquerque, then north, and when i got into the mountains of colorado, my box of ammo looked like this: with an obvious lack of neck tension allowing many of the bullets to vibrate down into the case.




so this is the ammo I used for the drills above. I simply pulled the bullets with my finger back into the neck and stuck them in the magazine, then shot them.

so i just think this is funny because earlier this week i spent $149 for a sinclair/wilsonLE seater die with a micrometer that measures to .0005", when obviously my finger-seating probably left a .200 or more variance in depth, and they were still able to hold a sub MOA target and a 1/2 MOA target.

i think in certain circumstances, seating depth matters. but i just don't see the results others seem to when i read all the reports of load development. other than the fact that i'm using lighter neck tension than most people, i'm curious what others are doing that makes one bullet depth shoot different than another.

for all i know, when i slammed the bolt forward, the bullet pushed back into the case again.

Berettaprof that's a good example of the sort of conventional wisdom I'd like to challenge. How would bullet setback cause increased pressure?
If I put the remaining rounds over a chrono and the ES is low would you still think bullet setback causes pressure increase?

Duvel yep pretty much. Though it was kind of a lot of vibration on the trailer. And because i only put about a thou of sizing on anyway I always push on the bullet before putting it in the box to make sure it doesn't move and these didn't under reasonable finger pressure.

Why rcmodel? Accuracy is obviously good. Velocity is consistent enough to match my dope. I've never subjected my ammo to 3 days of vibration and won't do it again.

I don't see it as defective anymore than you'd say a corvette is defective because you can't drive it on BLM trails. You don't say a scope is defective after you drove over it with your truck. It's match ammo and it was abused. Yet it still functioned better than it would have if it had significant neck tension.

Duvel got a link?

I'm not saying it doesn't btw. I really don't know and am honestly not familiar with the documentation he's referencing. If it's really an issue it would be good to share it here. If it's an old wives tale then let's test and show it one way or another. If it increases pressure in one circumstance but not another then what is the critical difference?

thanks for the link Duvel! did you see these graphs in that thread? the first is from a UofM paper and the second is from a lyman manual, according to the poster. it shows pressure decreasing from seated in the lands until about 250 thou off the lands, then gradually rising again. obviously, contrary to popinfresh's test.

so my question again is why is it different for some?

btw, i don't really buy the explanations of more or less volume. I can't prove it, but I believe when the primer detonates, it shoves the bullet forward into the lands before the powder burns enough to build pressure. i could be wrong of course, but seems like as far as powder burning is concerned, the volume is determined by the size of the bullet and case, and how far the lands are from the bolt head. i don't see how seating depth could change it.

snuffy, honestly, i've really only hunted a handful of times in my life, and i'm really horrible at it so i dont' have hunting rounds or a dedicated hunting rifle.
I drive to matches all over the country several times per year. Last year I even drove over 5000 miles round trip to hang out in the salmon wilderness, much of which was very rough driving. i've never had bullets do this before due to vibration. so it was new to me. that's why i posted it. i have of course made batches of ammo that didn't have enough neck tension, which is why i mentioned i test every bullet before putting it in the box. again, when i put them in the box, i was unable to move the bullets by pushing on it with my finger. so it's not like there was no neck tension at all.