The Firearms Forum banner
Status
Not open for further replies.

Explaining Headspace

75K views 90 replies 50 participants last post by  gdmoody 
#1 ·
I have seen this term in a number of manuals, Headspace of a .45 ACP cartridge, which headspaces off the case mouth but have never understood what it meant.

Can someone explain it to me, in understandable terms, what it means and specifically its relevance to reloading .45ACP.

Thanks in advance.
 
#82 ·
Old thread but I'm new here. Let me throw some corn starch into the mix. I load for five M1 rifles (among others). USGI spec ammo is 0.006" longer then the shortest chamber and is 0.006" shorter then the longest chamber.

So a M1 will force size any long rounds. When I reload I never set the shoulder back. I set the sizing die, standard RCBS, so that the case is sized to want is referred to as "partial resizing." I place a dime between the shell holder and the sizing die. The shoulder is fire formed to the chamber (less spring back) but the body of the case is sized to within 0.0001" of where it would be if full length sized. You get basically zero headspace. Your cases last longer the they do if you set the shoulder back.

Some one asked about weather or not cases require trimming to length. If you have any headspace your cases will grow. If you let the case grow too long in length without trimming back to length the end of the brass can grow enough that the case extends beyond the lead and can be pinched between the bullet and the bore of the barrel. This will ruin a day and gun in quick order.
 
#84 ·
Yea I know old! But only read the first few post's and the OP did a great job. Something I read down a few post's was by a 63 yr old guy that didn't know about the hear, or what was called the head. I see a lot of people asking question's about rifles and especially cartridges that don't know what things are called they are talking about. Seem's what most do is assume what they are talking about, normally correctly and just move along. I think that a dis service to them. Problem being they aear ignorant, and they are, and another person with the same problem get's lost till he/she figure's out what is being talked about. I recall one guy talking about his new reloads saying, "the bullet won't load". He was talking about his case's but refereed to them as bullet's. Amazing how many people actually do refer to ammunition as bullet's. With the first guy calling loaded ammo, bullet's, I have to think he never read directions in a manual! Another guy mentioned reading the manual and he was right on. I've got several different manuals and haven't read them in years but as I recall they all say pretty much the same thing about reloading but in different ways! Buying several different manuals would have to be confusing to someone new and I always recommend buying a manual for the brand bullet someone will use and stay with it till they are good to go, takes a while sometimes. But learn one way and once's you have it you can learn to experiment! I can use any manual I have for anyone's bullet by simply starting low and working up watching for pressure sign's as I go, just like using the manufacturer's manual. Lot of people don't understand that even some of the long time loader's. I think it's necessary to reach this point by learning what things are properly called.
 
#90 ·
Headspace is the distance from the head of the cartridge to the face of the bolt
The distance between the bolt face and case head is called 'clearance'. The distance between the datum and the bolt face is 'head space'; most reloaders have trouble with datums. They cannot see a datum, in the very old days it was called a line, it took me years to convince a very few reloaders the datum was not a line, it is a round hole. The 30/06 datum is .375" in diameter.

I see "headspace" was brilliantly explained in the 2nd post back in 2010 - yet, here we are!!!
Back then they just made it up.

F. Guffey
 
Status
Not open for further replies.
You have insufficient privileges to reply here.
Top