Ok, I'm kind of scratching my head over this, and maybe it's simpler than I'm making it, so hopefully someone else has some insight.
Wife's gun, her shooting.
Gevarm .222 Rem 22"bbl (50's or 60's era?). Firing pin protrusion .065". Firing pin is .075" dia. and the firing pin hole is .077" dia. Bolt locks at the rear of the action.
Lights Winchester and Federal primers no problem. CCI and Rem. 7.5 primers tend to misfire. Factory Federal 50gr ammo gets flattened/cratered primers but shoots decent. Factory Winchester ammo looks/shoots o.k. IIRC.
Tried the following loads (Hornady manual) with both Win Sr and Rem 7.5 primers: 23.0, 23.7, 24.4, 25.1, 25.8 - H-335 powder. Federal brass, full length sized. 5 shots each except as noted. Shot at 100yds.
23.0 - Win - Firing pin marks good, primers backed out .01" - 3014fps*
23.0 - Rem - Slight cratering, primers backed out .01" - 2984fps
23.7 - Win - Firing pin marks good, primers backed out .01" - 3129fps
23.7 - Rem - Increased cratering, primers backed out .005" - 3130fps**
24.4 - Win - Firing pin marks good, primers backed out .003" - 3223fps
24.4 - Rem - Inconsistent cratering, primers backed out .003" - 3191fps***
25.1 - Win - Firing pin marks good, primers flush - 3335fps
25.1 - Rem - Cratering, primers flush - 3299fps****
25.8 - Win - Slight cratering, primers flush - 3442fps
25.8 - Rem - Cratering, primers flush - ?fps*****
* - Chronograph errors, only one round read
** - One Primer would not light
*** - Chronograph error, only three rounds read
**** - One primer hit three times to light
***** - One primer would not light, chronograph errors
I'm not quite sure what to make of it.
The firing pin hole seems nice and snug so I don't think that's the cause of the cratering.
I suspect the firing pin spring might not be strong enough to light the 7.5, but I had always understood that Rem7.5 primers were thicker so it strikes me as odd that the thinner WinSr that lights easily doesn't crater, but the Rem does.
I considered that maybe the headspace was excessive causing the backed out primers, but the backing out goes away at higher loads and I don't have headspace gauges to check the chamber.
I also considered that maybe the lighter loads were too light and that might be the cause of the backed out primers.
The 7.5 primers that wouldn't light have healthy-looking firing pin marks in them.
23.0 and 23.7 loads shoot nice, as do the 25.8.
24.4 and 25.1 aren't as good but still not terrible
It also seems the Win primers are getting slightly higher velocities although the groups are similar between charge weights.
It looks like Winchester is the go-to for reliability/slight edge on velocity in this particular application.
I also considered neck sizing to reduce the primers backing out, but I'm not 100% sure if that's the right solution.
Any insight welcomed.
Wife's gun, her shooting.
Gevarm .222 Rem 22"bbl (50's or 60's era?). Firing pin protrusion .065". Firing pin is .075" dia. and the firing pin hole is .077" dia. Bolt locks at the rear of the action.
Lights Winchester and Federal primers no problem. CCI and Rem. 7.5 primers tend to misfire. Factory Federal 50gr ammo gets flattened/cratered primers but shoots decent. Factory Winchester ammo looks/shoots o.k. IIRC.
Tried the following loads (Hornady manual) with both Win Sr and Rem 7.5 primers: 23.0, 23.7, 24.4, 25.1, 25.8 - H-335 powder. Federal brass, full length sized. 5 shots each except as noted. Shot at 100yds.
23.0 - Win - Firing pin marks good, primers backed out .01" - 3014fps*
23.0 - Rem - Slight cratering, primers backed out .01" - 2984fps
23.7 - Win - Firing pin marks good, primers backed out .01" - 3129fps
23.7 - Rem - Increased cratering, primers backed out .005" - 3130fps**
24.4 - Win - Firing pin marks good, primers backed out .003" - 3223fps
24.4 - Rem - Inconsistent cratering, primers backed out .003" - 3191fps***
25.1 - Win - Firing pin marks good, primers flush - 3335fps
25.1 - Rem - Cratering, primers flush - 3299fps****
25.8 - Win - Slight cratering, primers flush - 3442fps
25.8 - Rem - Cratering, primers flush - ?fps*****
* - Chronograph errors, only one round read
** - One Primer would not light
*** - Chronograph error, only three rounds read
**** - One primer hit three times to light
***** - One primer would not light, chronograph errors
I'm not quite sure what to make of it.
The firing pin hole seems nice and snug so I don't think that's the cause of the cratering.
I suspect the firing pin spring might not be strong enough to light the 7.5, but I had always understood that Rem7.5 primers were thicker so it strikes me as odd that the thinner WinSr that lights easily doesn't crater, but the Rem does.
I considered that maybe the headspace was excessive causing the backed out primers, but the backing out goes away at higher loads and I don't have headspace gauges to check the chamber.
I also considered that maybe the lighter loads were too light and that might be the cause of the backed out primers.
The 7.5 primers that wouldn't light have healthy-looking firing pin marks in them.
23.0 and 23.7 loads shoot nice, as do the 25.8.
24.4 and 25.1 aren't as good but still not terrible
It also seems the Win primers are getting slightly higher velocities although the groups are similar between charge weights.
It looks like Winchester is the go-to for reliability/slight edge on velocity in this particular application.
I also considered neck sizing to reduce the primers backing out, but I'm not 100% sure if that's the right solution.
Any insight welcomed.
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