With the seperate conversation of my wanting a .30 Gibbs fireforming brass is a hot topic on my mind. The method I would like to use is chambering .30-06 standard LC brass with the bullet seated out so it engages the rifling and holds the case head firmly against the bolt face. What sort of charge/primer would be in order for such and operation? I know this is one of many methods and could use the false shoulder method anyone use this method?
Fireforming through seating bullet into lands
- Thread starter Visionz45
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lilquiz
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I have been fire forming my but off with expanding neck sizes.I use cream of wheat with a light powder charge. I may be misunderstanding, but with a projectile seated with any kind of low powder charge... would that not produce an uber "squib" situation?
Curator
Member
My standard procedure with all new brass cases is to load the first firing with the bullet seated out to cause some resistance to closing the bolt. The bullet then "headspaces" the case on the rifling leade. This keeps the case head tight against the bolt face and insures all the brass expansion is forward and in the neck/shoulder area, not at the case base. I use this particularly with .303 british, .35 Whelen Improved, 8X57 Muaser, 6.5X55 Swede, and .43 Spanish. Surprisingly I often get the best accuracy this way, I do keep loads in the "start" catagory or even slightly less to keep pressures low. Case life is significantly enhanced when you neck size thereafter. I get 12-15 reloadings with my military .303 rifles using this method rather than the usual 3-4 reloads ending in case head seperation. Most cases are taken out of use from case neck splitting after 15+ loadings.
I necked 30-06 cases to 35 Whelen, left the case lube on and loaded cast bullets with AA5744.
Lubed cases slide to the bolt face with the shoulders folding out to fill the chamber front. I experienced no body or case head stretching which will occur when the case sticks to the chamber walls.
My cases came out perfect. Sized them again and cleaned them up for full power loads.
Lubed cases slide to the bolt face with the shoulders folding out to fill the chamber front. I experienced no body or case head stretching which will occur when the case sticks to the chamber walls.
My cases came out perfect. Sized them again and cleaned them up for full power loads.
Sport45
Member
Seating the bullet out might not be enough. The piston action of the primer is going to push the case into the chamber if it can. When the pressure builds enough for the case walls to grab the chamber the case will stretch fore and aft to fill the chamber. Expanding the neck and forming a false shoulder would be a more sure way of forcing the brass to stretch in the direction you want.
Seat the bullet using good neck tension (we don't want the case moving forward around the bullet from the force of the firing pin) and seat it .020 or so into the lands. Use a 90% load to fireform. Next time shoot load it normally and it should be good to go after that second firing.
You are going to move the shoulder forward .197" and expand the shoulder .140".
One of the methods I have used is to expand the neck out to a larger size, in your case .338 inside neck diameter, then using the die for the .30 Gibbs, size the neck to form a small shoulder so you can just close the bolt with pressure, this will hold the case in place, even when the firing pin strikes the primer.
I fill the case with cream of wheat and a charge of 10 grains of Unique, all held in place with a wad, this doesn't completely form the case, but it fits the chamber well enough to make for some very good target practice and gives you the opportunity to sight in and make the sight adjustments as you finish the forming process.
You can use the expanded neck/small shoulder with a stiff charge, but it will ultimately lead to head separation of some cases because of the flow of brass toward the neck.
Ray
One of the methods I have used is to expand the neck out to a larger size, in your case .338 inside neck diameter, then using the die for the .30 Gibbs, size the neck to form a small shoulder so you can just close the bolt with pressure, this will hold the case in place, even when the firing pin strikes the primer.
I fill the case with cream of wheat and a charge of 10 grains of Unique, all held in place with a wad, this doesn't completely form the case, but it fits the chamber well enough to make for some very good target practice and gives you the opportunity to sight in and make the sight adjustments as you finish the forming process.
You can use the expanded neck/small shoulder with a stiff charge, but it will ultimately lead to head separation of some cases because of the flow of brass toward the neck.
Ray
seating the bullet into/against the lands "....seated out so it engages the rifling and holds the case head firmly against the bolt face...." this does not happen because of advise already given. First there is the primer that accelerates to a sped equal to or greater than the speed of the firing pin strike, I use fire forming primers, my primers are crushed by the firing pin before the primer knows it was struck, that leaves the case, powder and bullet setting still until my primer ignites (time is a factor), when the primer fires up it drives the case forward and igniting the powder (time is a factor), when the powder ignites pressure expands the case against the chamber, but because time is a factor the bullet is in the barrel before pressure is at it's max. Then there is that part where the case locks onto the chamber, if the case is driven forward by the primer the case i8s head is not against the bolt face.
Then there is the measure before and after, necking up a 30/06 to 338 pr 35 will shorten the neck, if necking up the case requires effort, the case could shorten or compress between the head of the case and shoulder when fired the case could shorten even more, when the case body fills the chamber the neck of the case is pulled back to form the neck, sharp shoulder and larger case body, SO, you can expect the fire formed case to shorten as much as .040 thousands, my opinion, the 30 Gibbs neck is short enough at .217 without causing it to get shorter. As an alternate method, I use 280 Remington cases , the 280 Remington is 2.540 long with a shoulder .051 thousands ahead of the 30/06, I neck the 280 up to 338/06 then size the neck up case by forming the second shoulder, in doing so I determine the head space of the 30 Gibbs chamber.
Problem: I chamber the 30/06 to 30 Gibbs, this leaves the length of the chamber unchanged, 2.495 + a little, the 30 Gibbs chamber length is 2.460 + a little, and that is the reason I use 280 Remington cases, by the time I neck up the case, establish a second shoulder and before fire forming I have added .040 thousands to the length of the neck, not as long as a 300 Win Mag neck but if most consider the 300 Win mag neck short they should consider the 30 Gibbs neck too short.
I do not use cereal, wax and or t-paper, I form cases once, the last Gibbs I formed I use the maximum powder load for a 150 grain bullet, instead of a 150 grain bullet I used a 200 grain bullet(do not try this at home), as I said 'time is a factor' and I used the one 30 Gibbs barrel to road test three Mauser receivers, the max load of 4895 for 150 grain bullets worked for fire forming with a 200 grain bullet when fire forming, after the case was formed that load could be the maximum after the case is formed (because time is a factor).
http://www.z-hat.com/Cylinder.htm
The cylinder brass by R-P is 2.650 long, for those that know when to quit forming when the case fits the chamber cylinder brass is the best option, again, this brass came out too late for me, I will never need another piece of brass, for wildcats and case forming the R-P cylinder brass is a bargain at $37.00 for 20.
F. Guffey
Then there is the measure before and after, necking up a 30/06 to 338 pr 35 will shorten the neck, if necking up the case requires effort, the case could shorten or compress between the head of the case and shoulder when fired the case could shorten even more, when the case body fills the chamber the neck of the case is pulled back to form the neck, sharp shoulder and larger case body, SO, you can expect the fire formed case to shorten as much as .040 thousands, my opinion, the 30 Gibbs neck is short enough at .217 without causing it to get shorter. As an alternate method, I use 280 Remington cases , the 280 Remington is 2.540 long with a shoulder .051 thousands ahead of the 30/06, I neck the 280 up to 338/06 then size the neck up case by forming the second shoulder, in doing so I determine the head space of the 30 Gibbs chamber.
Problem: I chamber the 30/06 to 30 Gibbs, this leaves the length of the chamber unchanged, 2.495 + a little, the 30 Gibbs chamber length is 2.460 + a little, and that is the reason I use 280 Remington cases, by the time I neck up the case, establish a second shoulder and before fire forming I have added .040 thousands to the length of the neck, not as long as a 300 Win Mag neck but if most consider the 300 Win mag neck short they should consider the 30 Gibbs neck too short.
I do not use cereal, wax and or t-paper, I form cases once, the last Gibbs I formed I use the maximum powder load for a 150 grain bullet, instead of a 150 grain bullet I used a 200 grain bullet(do not try this at home), as I said 'time is a factor' and I used the one 30 Gibbs barrel to road test three Mauser receivers, the max load of 4895 for 150 grain bullets worked for fire forming with a 200 grain bullet when fire forming, after the case was formed that load could be the maximum after the case is formed (because time is a factor).
http://www.z-hat.com/Cylinder.htm
The cylinder brass by R-P is 2.650 long, for those that know when to quit forming when the case fits the chamber cylinder brass is the best option, again, this brass came out too late for me, I will never need another piece of brass, for wildcats and case forming the R-P cylinder brass is a bargain at $37.00 for 20.
F. Guffey
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