Finding the rifling on .270 Winchester

[Sooge]

Hi all
New member here. Hoping to get some answers about .270 win.
Just purchased Hornady OAL gauge and find that using it on a Weatherby mark V in .270 is very inconsistent. Light pressure on the bullet plunger gives readings where bullet looks to deep in the case compared to factory ammo. Bullet is Sierra 110g spritzer. Applying a bit more pressure sees bullet jump suddenly forward to a new stop. Now values are more consistent but not enough bullet in case and COAL bigger than SAAMI spec. Had a good look at SAAMI chamber drawing and noted there is a considerable taper from case mouth to start of bore. Am I hitting start of taper in first instance and then reaching start of bore in second? Have used gauge on different rifle (.223) with good results. Is there something about the .270 chambering that’s giving me issues. I have read that Weatherby rifles in Weatherby cartridges tend to have some freebore but that doesn’t apply to those rifles chambered for standard calibers. Hope the info is not to confusing.
Regards

 

[Bfh_auto]

You're using a short for caliber bullet.
With a 270, you must at least have .277 in the case. This is more important for accuracy than getting close to the lands.
I played this game using 90 gr Sierra's. Accuracy was terrible until I let them jump.

 

[FROGO207]

Agreed the golden rule is at least one caliber of bullet in the case. That means contact with the case. The base of a boattail that does not contact the case is not counted. Otherwise you do not get enough neck tension to get a complete powder burn. As far as I can tell this applies to all bullets in all calibers.