New brass VS zero headspace chamber
- Thread starter PEI Rob
- Start date
jackie schmidt
New member
Fire it once, then set your die accordingly.
Maybe I am missing something, but I fail to see the problem.........jackie
Maybe I am missing something, but I fail to see the problem.........jackie
Jeff Walker
Member
Headspacing on shoulder or is it a belted case ? I've done belted magnums at zero headspace and had measurements all over the place with different makes of brass, which is why I like to know what brass is planned on being used. Non belted cases, trust your go gauge and fire form.
Boyd Allen
Active member
Yesterday, I fire formed some new Norma 6PPC brass. At first I made the mistake of going too light on the load, and it did not come up to the case "headspace" that I was looking for. I increased the load, and it came closer, but no cigar. Then I raised the load one more time, and got there, at jam. At that point, I decided to do a little seating depth testing as I finished up my forming chores, backed off to light marks on the double ogive 68 grain bullets that I was using, and fired two with the same volume of powder. The difference in pressure, from the seating depth change, was enough that I was again short of my goal, so I upped the charge about .4, and the case dimensions, and test group looked fine. In the future, on cases that are not being blown out to a different body shape, I will simply load 'em like I would normally shoot them and fire them. BTW, the Norma brass measures a full .001 smaller at the top of the extractor groove than Lapua .220 Russian, so assuming what I have been told about the hardness of the heads of these new double struck cases is true, you guys that have tight chambers and click issues may want to try some. On the down side, there seemed to be some variability in neck tension, so I may end up doing some sorting.
M
mike in co
Guest
well guess what...its suppose to be that way
there is a clearance between chamber and cartridge specs...so the brass always fits...( except for 30'06 which for some ungawdly reason has an interference between the two)
mike in co
there is a clearance between chamber and cartridge specs...so the brass always fits...( except for 30'06 which for some ungawdly reason has an interference between the two)
mike in co
K
kansasvet
Guest
On .300 Win Mag brass I have typically found the shoulder to be .006 or .007 shorter than fired brass. Apparently they are counting on the belt to control headspace. When I reload a belted cartridge I headspace off the shoulder making the belt a rather outdated add on to the cartridge.
.006" is more than I want to stretch my brass. This isn't a hunting rifle, it's an F Class competition rifle requiring at least 500 brass. Why are we accepting the fact that brass needs to be fireformed so much? My new brass fits my chamber very well except for the length and I can fix that. Honestly, I would have thought some guys here set headspace negative on purpose for this reason.
J
Jkob
Guest
Anyone ever measure the difference in the belt dimension? It can vary a bunch.
It's not that we haven't done it, It's just that the next lot of brass might come in a little longer. There are pitfalls to trying to set up a previously fitted barrel and skim a tiny bit of shoulder material to adjust headspace. If you fitted it yourself and you want to adjust it it will probably be ok, it would be riskier to try to chase someone else's work and it would be best to have the reamer on hand. For my own purposes, I have no problem with setting chamber length to match the brass I'm using.
Stretching .006 while fire forming is just not that significant.
Scott
Last edited:
This thread is funny.....
Incidentally, the difference between 'GO' and 'NO-GO" is generally .004 while the older military gage known a "Field" adds another 2 thou for .006
IMO (since this is an ACCURACY forum not SporterizingtheMexicanSmallRingMouser.com) there are other things to consider than "this is most'en likely safe to fire...."
opinionsby
al
Incidentally, the difference between 'GO' and 'NO-GO" is generally .004 while the older military gage known a "Field" adds another 2 thou for .006
IMO (since this is an ACCURACY forum not SporterizingtheMexicanSmallRingMouser.com) there are other things to consider than "this is most'en likely safe to fire...."
opinionsby
al
Negative Headspace?
To just answer your question, sure it's OK to set your chamber length to match the brass you plan to use. I do it all the time. Sometimes I don't use gages at all, just set it using sample cases.
There are some professional smiths that don't do things like that out of concerns that someone will later find reason to criticize their work. I have even heard one claim that his insurance required him to fit barrels using the appropriate SAAMI spec gages.
The beauty of using the gunsmith named "self" is that you can try things the way you want to. We wouldn't be where we are without all the shooters that came before us in search of smaller groups.
Scott
To just answer your question, sure it's OK to set your chamber length to match the brass you plan to use. I do it all the time. Sometimes I don't use gages at all, just set it using sample cases.
There are some professional smiths that don't do things like that out of concerns that someone will later find reason to criticize their work. I have even heard one claim that his insurance required him to fit barrels using the appropriate SAAMI spec gages.
The beauty of using the gunsmith named "self" is that you can try things the way you want to. We wouldn't be where we are without all the shooters that came before us in search of smaller groups.
Scott