I have always wondered if the anality of measuring rim thickness really does make a difference to consistency.
As I was bored and clearly had too much time on my hands I thought I would give it a go.
Rather than drop £60 on two rim gauge it occurred to me that a .243 empty is a perfect comparator for .22WMR and .17HMR rim thickness and a .22 centrefire case would work perfectly for .22lr and .17M2 rim thickness.
Saddler (Jon) on here was kind enough to give me a couple of .223 empties for the smaller of the two case and I have some .243 already.
Easy enough to do, measure case in calipers and zero, drop the rimfire round and read off new measurement
I re-zeroed every 3 rounds and opened and closed calipers a couple of times on each round.
using fairly small sampled of 40-100-
First up .22lr subs
I have a selection of:
Winchester - measured between 0.97mm and 1.03mm (variance of 0.06mm)
Eley - Measured between 0.99mm and 1.02mm (variance of 0.03mm)
RWS - Measured between 0.98 and 1.11mm (variance of 0.13mm! shocking compared to the others and this was the smallest sample of less than 40)
Next the .17M2 (my favourite of the HV rimfire rounds)
pretty much a 25:25:25:25 split between 1.03mm:1.04mm:1.05mm:1.06mm with a couple at 1.02mm(variance of 0.05mm)
Next .22 WMR
Remington 30gr Gamepoint -
amazingly they all measured either 1.17mm or 1.18mm (a variance of only 0.01mm!)
Next up CCI 20gr HMR
measured between 1.14mm and 1.20mm (a variance of 0.06mm)
Will test out the .17M2 tomorrow hope it is not too windy!
I am making the assumption that a batch of sized rounds will group better than a batch of random rounds.
My plan is to test one batch of sized, one batch of sized but with a range from large to small and one batch of random unknown sizes.
I am hoping to join an indoor range next week and test the .22lr subs