260 Base to Ogive Question

[UnitedFan]

GAP built 260 on a Surgeon action with a 26" Bartlein barrel.

I am new to reloading based on Ogive measurements.

Need some thoughts. I attempted to get a measurement with a Sinclair tool. The measurement I came up with is 2.167" BTO.

Does that measurement appear within what may be expected? Not a number that everyone says, an error has been made.

Load:
RL17 41.5 grains
Berger Hybrid 140
BTO 2.222"

I made an error somewhere along the way and loaded some rounds to 2.222" BTO. These rounds shot amazing. Less than an inch at 400 yards. There were however extractor marks indicating pressure. I suspect due to the the rounds being jammed. Sound right?

Does a load jammed .055" even sound plausible?

The reason for all the questions is I have no idea/confidence if my original measurement of 2.167 BTO is accurate.

Thought?

Thanks to everyone in advance.

 

[RyeDaddy]

A 2.167" b/o is within the range of normal, but on the short side. Sounds like it was throated to keep 140's close to the lands at a 2.780" overall length, or throated for light bullets. I would call GAP and ask what freebore specs are on the reamer, and tell them what you're seeing. That would tell you whether you're crazy or not. When you load a 140 Hybrid to 2.167" B/O what is the cartridge overall length?

It would be hard to measure incorrectly with a simple tool like the Sinclair nut, but strange things happen. EDIT TO ADD: What method are you using to get a cartridge seated to measure distance to the lands? Are you using the Hornady tool with a modified case or something else?

About jamming them at 2.222" b/o, if you jam past a certain amount it will just push the bullet further into the case, the neck tension is not enough to engrave a bullet and force it all the way down the barrel. Odds are the pressure signs were real, due to a combination of reduced case capacity from a short length and an extreme amount of jam.