Dies for Bumping Shoulder - Page 6

**Unclenick** · November 6, 2019, 09:10 AM

Well, excess headspace is another one SAAMI's glossary does not have. I think 44 AMP is right that the purpose defines it. Military armorers will likely define it as headspace that allows a chamber to close on a Field Reject gauge, requiring them to change the barrel. But they aren't concerned with reloading. Only handloaders think headspace is excessive if there is enough to have an adverse effect on brass reloading life. Only precision shooters will define it as extra space that adversely impacts group size.

The distinction I see between head clearance and excess headspace is just that the latter can account for chamber space either in front of or behind the cartridge position in the chamber, as Bart suggests. Head clearance is limited by SAAMI's definition to being space behind the case head when the cartridge case is seated fully forward. The reason the difference matters has mostly to do with belted cases. They can have head clearance and shoulder clearance simultaneously when the belt is forward against its seat (and normally do when using commercially loaded ammunition in SAAMI spec chambers). Excess headspace would then be the sum of the two extra spaces (and that may be for brass life and accuracy purposes, both).

Bart B. · November 7, 2019, 11:18 AM

I asked SAAMI about "shoulder clearance" for belted and rimmed bottleneck cases. He said that makes sense and fits into the scheme of their glossary. But doubted it would ever happen.

Military rifle teams shooting 30 caliber belted magnums usually got better accuracy with new cases having both head and shoulder clearance compared to traditional full-length sized cases headspacing on their shoulders.

Metal god · November 8, 2019, 10:01 PM

Hold on a second, did we exhaust this topic with out the thread being closed . It’s been 24+ hours with out a post

. Hmmm how could we go so long without a fight and closer ? I wonder what was so different about this thread then all the other closed ones ?

pwc · November 8, 2019, 10:52 PM

Well, as HiBC said earlier, no other topic has generated as much discussion as headspace. Maybe we're all talked out...by the way, I like "Guffyspace".

jetinteriorguy · November 9, 2019, 08:00 AM

The reason this thread lasted is because it was a good discussion that I for one, have truly learned something from it. At least this is my $.02.

November 6, 2019, 09:10 AM	#126
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	Well, excess headspace is another one SAAMI's glossary does not have. I think 44 AMP is right that the purpose defines it. Military armorers will likely define it as headspace that allows a chamber to close on a Field Reject gauge, requiring them to change the barrel. But they aren't concerned with reloading. Only handloaders think headspace is excessive if there is enough to have an adverse effect on brass reloading life. Only precision shooters will define it as extra space that adversely impacts group size. The distinction I see between head clearance and excess headspace is just that the latter can account for chamber space either in front of or behind the cartridge position in the chamber, as Bart suggests. Head clearance is limited by SAAMI's definition to being space behind the case head when the cartridge case is seated fully forward. The reason the difference matters has mostly to do with belted cases. They can have head clearance and shoulder clearance simultaneously when the belt is forward against its seat (and normally do when using commercially loaded ammunition in SAAMI spec chambers). Excess headspace would then be the sum of the two extra spaces (and that may be for brass life and accuracy purposes, both). __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

November 7, 2019, 11:18 AM	#127
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	I asked SAAMI about "shoulder clearance" for belted and rimmed bottleneck cases. He said that makes sense and fits into the scheme of their glossary. But doubted it would ever happen. Military rifle teams shooting 30 caliber belted magnums usually got better accuracy with new cases having both head and shoulder clearance compared to traditional full-length sized cases headspacing on their shoulders. Last edited by Bart B.; November 7, 2019 at 12:49 PM.

November 8, 2019, 10:01 PM	#128
Metal god Senior Member Join Date: April 10, 2012 Location: San Diego CA Posts: 6,875	Hold on a second, did we exhaust this topic with out the thread being closed . It’s been 24+ hours with out a post . Hmmm how could we go so long without a fight and closer ? I wonder what was so different about this thread then all the other closed ones ? __________________ If Jesus had a gun , he'd probably still be alive ! I almost always write my posts regardless of content in a jovial manor and intent . If that's not how you took it , please try again .

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November 8, 2019, 10:52 PM	#129
pwc Senior Member Join Date: March 21, 2018 Location: AZ Posts: 236	Well, as HiBC said earlier, no other topic has generated as much discussion as headspace. Maybe we're all talked out...by the way, I like "Guffyspace".

November 9, 2019, 08:00 AM	#130
jetinteriorguy Senior Member Join Date: April 28, 2013 Posts: 3,169	The reason this thread lasted is because it was a good discussion that I for one, have truly learned something from it. At least this is my $.02.