Seating near lands and pressure

[The Oregonian]

at what point does seating near the lands increase pressure?

I have two powder nodes I am testing with BT180's in a 30-06. I am going to test seating next...recipe that came with the gun is .085 off the lands. Going to test several depths down to maybe .020 off but want to be aware of any pressure spikes that this may cause.

The lower powder node has plenty of room above it with no pressure signs. The other node is slightly above book value (57.3 of H4350) but I have shot up to 58.5 as part of a test and only got very slight ejector marks and no other signs - sticky bolt, primers, etc.

I don't believe the BT's are very depth sensitive but I want to tighten up the groups if possible. I am about .75 MOA during powder tests.

Thx

 

[tankgijohn72]

Depends on the bullet and cartridge etc. have done a seating depth test with pressure gauges. Showed slight increase at less than 0.010. Test was repeated an minimal increase was shown. If you are using published load data it shouldn't result in any real danger. Berger published a decent article on it. If you approach the rifling, "in theory" your pressure should get higher. But at the same time when you move the bullet towards the rifling, your effective case volume gets larger so your chamber pressure "in theory" should decrease.

 

[nmbarta]

I haven't seen anything unless I'm right on the lands or jammed a little. I don't even go there anymore. Too many issues with that for a hunting rifle for me.
I'm don't claim to be an expert but I don't think you'll see a diffrence at .020 off
Everything I reload for is between .030 and .080 off.

 

[woods]

at what point does seating near the lands increase pressure?

I have two powder nodes I am testing with BT180's in a 30-06. I am going to test seating next...recipe that came with the gun is .085 off the lands. Going to test several depths down to maybe .020 off but want to be aware of any pressure spikes that this may cause.

The lower powder node has plenty of room above it with no pressure signs. The other node is slightly above book value (57.3 of H4350) but I have shot up to 58.5 as part of a test and only got very slight ejector marks and no other signs - sticky bolt, primers, etc.

I don't believe the BT's are very depth sensitive but I want to tighten up the groups if possible. I am about .75 MOA during powder tests.

Thx

 

[The Oregonian]

Many thanks to all. I will progressively get closer to the lands and watch for any signs of pressure but doesn't look like there should be a huge jump moving 10 thou at a time.