Question on seating depth with jacketed

[Jeffery8mm]

I have a bit of a personal delima going on here.;-)

I still load jacketed bullets for my Win mod 70 270. I bought several hundred of the midway blems a year or so back that turned out to be Hornady bullets. These are 130gr WITH a canalure.
If seated at the canalure, the COAL is 3.14. Most manuals state the 130's should be seated at 3.34. Now at 3.34 that canalure sticks out like a sore thumb, but the gun does shoot better. Is there any harm in seating at 3.34 and the canalure sticking out of the case? Other than asthetics??
Thanks
Jeff

[AZ-Stew]

Two conflicting effects.

1.) You get a tiny bit more case capacity, theoretically lowering chamber pressure.

2.) You seat the bullet a tad closer to the lands, leaving less room for the bullet to move before it slams into the lands, theoretically raising chamber pressure.

In practical terms, however, unless the bullets are pressed into the lands at that seating depth, pressures won't be increased that much. Think about it. the .020 difference in seating depth is only the thickness of 4-6 pieces of paper (depending on paper thickness). It's not that much.

Unless you're seeing blatant pressure signs, such as cratered primers or shiny spots on the case head where the brass has been extruded into the ejector pin hole in the bolt face, I wouldn't worry about it. If the rifle shoots better this way, I'd go with what works.

Regards,

Stew

[HORNET]

What's your jam length with that bullet? Or how far off the rifling is the bullet at the 3.34 length? Lots of target shooters run an OAL that gives about .010" travel before contact. Barnes recommends .030" IIRC. As long as you have some free travel, it'll help hold down pressures a little. As long as it feeds at that length, go for it.

[MT Gianni]

Can you compare your blems to a Hornaday 130? I suspect the blem is a misplaced cannelure. I would seat to the specs recommended for the original bullet.

[felix]

Seating depth is a component of ignition in making up the proper pressure curve for the best barrel vibe. Seating depth must be such that perfect alignment is maintained throughout the ignition phase. For the most part, adjust seating depth as you would change primers, while assuring alignment throughout any modification. ... felix

The best barrel vibe is indicated by the best overall accuracy with the powder used when intentionally altered by one percent at random. The very best powder speed is the one which exhibits the lowest ES when altered about that accuracy point. ... felix

[Jeffery8mm]

Can you compare your blems to a Hornaday 130? I suspect the blem is a misplaced cannelure. I would seat to the specs recommended for the original bullet.

Good thought, I will do that!
Jeff