NS,
As long as you can close the bolt on a safe load, or factory ammunition it's almost certain to be safe. It is more dangerous firing hot loads in a normal chamber than firing a normal loads in a too-long chamber.
The worse thing that can happen is the case splits around the middle. This has happened twice to me and apart from a slightly louder noise the bullet exists the barrel and the blast is contained in the chamber which is in battery. Maybe a bit more smoke leaks out of the receiver from the split and there will be a permanent circular mark on the inside wall of the chamber where the case split and the heat was concentrated. Apart from that it doesn't affect accuracy or barrel life.
That said, I recommend firing the first round out of any new barrel from the hip and look away.
SAAMI permits the reaming of Grendel chambers to be within a .01" range - min to max. Add to that the range permitted for ammunition headspace and theoretically with the longest permitted chamber, firing the shortest permitted ammunition you have 0.017" of difference or in other words, case stretch. Any more than that and there is a risk cases will rupture on the first firing. If your first firing was .017" or less, but from then on you bumped that case only .003" it will last the normal life for that brand of case.
If you wanted to be really certain you can cut a disk of sticky tape and attach it to the base of that NO GO gauge to mimic a FIELD gauge. The difference between a NO GO and FIELD is about .004" - .005" or the thickness of sticky tape. In your shoes I would take to the range and fire the first round from the hip.
As Montana said, NO GO is only an arbitrary line in the sand between Min and Max to let people know their chamber its getting towards being too long, but is still within spec and OK to shoot. It is only when a FIELD gauge closes that you start to worry and send it back.
As for putting too much leverage on the bolt handle and it incorrectly closed; the solid metal of a headspace gauge makes that impossible. It's not like a hollow cartridge with a soft brass shell that you can squash into a chamber by leaning on the bolt handle. If you had to put a bit of pressure on the handle to close then it's telling you it is right on the NO GO chamber length, which is less than FIELD so it is a longish chamber but still fine.
As long as you can close the bolt on a safe load, or factory ammunition it's almost certain to be safe. It is more dangerous firing hot loads in a normal chamber than firing a normal loads in a too-long chamber.
The worse thing that can happen is the case splits around the middle. This has happened twice to me and apart from a slightly louder noise the bullet exists the barrel and the blast is contained in the chamber which is in battery. Maybe a bit more smoke leaks out of the receiver from the split and there will be a permanent circular mark on the inside wall of the chamber where the case split and the heat was concentrated. Apart from that it doesn't affect accuracy or barrel life.
That said, I recommend firing the first round out of any new barrel from the hip and look away.
SAAMI permits the reaming of Grendel chambers to be within a .01" range - min to max. Add to that the range permitted for ammunition headspace and theoretically with the longest permitted chamber, firing the shortest permitted ammunition you have 0.017" of difference or in other words, case stretch. Any more than that and there is a risk cases will rupture on the first firing. If your first firing was .017" or less, but from then on you bumped that case only .003" it will last the normal life for that brand of case.
If you wanted to be really certain you can cut a disk of sticky tape and attach it to the base of that NO GO gauge to mimic a FIELD gauge. The difference between a NO GO and FIELD is about .004" - .005" or the thickness of sticky tape. In your shoes I would take to the range and fire the first round from the hip.
As Montana said, NO GO is only an arbitrary line in the sand between Min and Max to let people know their chamber its getting towards being too long, but is still within spec and OK to shoot. It is only when a FIELD gauge closes that you start to worry and send it back.
As for putting too much leverage on the bolt handle and it incorrectly closed; the solid metal of a headspace gauge makes that impossible. It's not like a hollow cartridge with a soft brass shell that you can squash into a chamber by leaning on the bolt handle. If you had to put a bit of pressure on the handle to close then it's telling you it is right on the NO GO chamber length, which is less than FIELD so it is a longish chamber but still fine.