7mm-08 AI Headspace comparator diameter.
- Thread starter 64Rambler
- Start date
HandgunHTR
Gold $$ Contributor
I use the .400.
Guessing you're using the Hornady tool? In standard 7-08 about 1/2 way (per the instructions 
) between the nominal shoulder/neck diameter is closer to the .375 insert than the .400 insert. The larger Ackey shoulder would likely change that relationship to the .400.
In reality, it's a comparator. It only compares. Either one will be fine as long as you use the same insert for measuring the same chamberings. In a pinch, a deprimed 9mm case inverted can also be used as a comparator for 7mm, just make sure to use the same piece for all future comparisons.
If you're setting up the die for fireforming loads, I do that by feel. Just a wee bit of resistance on bolt closure. Keep the locking lugs lubed. If you absolutely must use the tool for this I'd probably use the .330 insert due to the interference point being c.315 at the neck/shoulder junction on standard case in Ackley chamber.
) between the nominal shoulder/neck diameter is closer to the .375 insert than the .400 insert. The larger Ackey shoulder would likely change that relationship to the .400.In reality, it's a comparator. It only compares. Either one will be fine as long as you use the same insert for measuring the same chamberings. In a pinch, a deprimed 9mm case inverted can also be used as a comparator for 7mm, just make sure to use the same piece for all future comparisons.
If you're setting up the die for fireforming loads, I do that by feel. Just a wee bit of resistance on bolt closure. Keep the locking lugs lubed. If you absolutely must use the tool for this I'd probably use the .330 insert due to the interference point being c.315 at the neck/shoulder junction on standard case in Ackley chamber.
64Rambler
Gold $$ Contributor
Thanks for that. My fire forming loads are from turned and necked down .308 cases, necked down to give slight resistance on bolt close; i.e. false shoulder. I was going back and forth between the 0.375 and 0.350 comparators, but you're right; as long as I'm consistent I should be good to go.Guessing you're using the Hornady tool? In standard 7-08 about 1/2 way (per the instructions
In reality, it's a comparator. It only compares. Either one will be fine as long as you use the same insert for measuring the same chamberings. In a pinch, a deprimed 9mm case inverted can also be used as a comparator for 7mm, just make sure to use the same piece for all future comparisons.
If you're setting up the die for fireforming loads, I do that by feel. Just a wee bit of resistance on bolt closure. Keep the locking lugs lubed. If you absolutely must use the tool for this I'd probably use the .330 insert due to the interference point being c.315 at the neck/shoulder junction on standard case in Ackley chamber.
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