6.5 Creedmoor Shouldered Pre-Fit Lands

[TN Shooter]

I recently purchased a Bighorn TL3 shoulder pre-fit barrel in 6.5 Creedmoor and plan to shoot 140’s. After installing the barrel and taking some measurements, the lands are at 2.188” using the Hornady comparator and a 140 ELD bullet. I also came to the same measurement by removing the firing pin assembly and seating the bullet incrementally until there was no resistance on the bolt. My other custom barrels are around 2.230" - 2.250" to the lands depending on the barrel. I just wanted to check and make sure this seems correct since it is ~.050" shorter than what I am used to. I contacted the supplier who said the specs were .295” neck and .188” freebore.

Out of curiosity I stopped and picked up some factory Hornady match ammo today with the 140 eld. The ogive measurement is 2.190”. Using the method of removing the firing pin from the bolt, there is a click as the handle engages the extraction cam. So factory ammo into the lands? Just wanted to get some opinions if there is anything I should be worried about or if this is normal. Any info is appreciated. Thanks.

 

[spife7980]

Put a layer of sharpie marker on the factory bullet to diagnose the click, can you see the squared imprints of the lands?

 

[CarlM]

I'm no expert but my TL3 with a PVA barrel and a 140 eld I'm hitting the lands at about 2.184. But you measurement on the Hornandy factory ammo sounds incorrect, after measuring several, all mine come in around 2.127 to 2.130.

 

[TN Shooter]

Put a layer of sharpie marker on the factory bullet to diagnose the click, can you see the squared imprints of the lands?

Factory 140 ELD Match Ammo

 

[TN Shooter]

I'm no expert but my TL3 with a PVA barrel and a 140 eld I'm hitting the lands at about 2.184. But you measurement on the Hornandy factory ammo sounds incorrect, after measuring several, all mine come in around 2.127 to 2.130.

Are you using the Hornady 5-26 insert?

 

[CarlM]

Are you using the Hornady 5-26 insert?

I'm using the Sinclair inserts. Not home now but I'll check when I get home. The rest of our numbers seem pretty similar though.

 

[spife7980]

View attachment 7043625

Factory 140 ELD Match Ammo

That looks like them. 5 groove barrel? Are the marks on the other side as well? The transition up of the lands from the clearanced freebore to the full rifling are a coned shape but taken to only one side is a ramped surface. Your ejector could be pushing it over to the one side and forcing the bullet into that ramped surface earlier than it otherwise would.
But wait. You have a mechanical ejector so there’s no force other than gravity so they should be on all sides provided your cartridge doesn’t have an extreme case of runout.
Looks like you could be a bit less freebore.

 

[TN Shooter]

That looks like them. 5 groove barrel? Are the marks on the other side as well? The transition up of the lands from the clearanced freebore to the full rifling are a coned shape but taken to only one side is a ramped surface. Your ejector could be pushing it over to the one side and forcing the bullet into that ramped surface earlier than it otherwise would.
But wait. You have a mechanical ejector so there’s no force other than gravity so they should be on all sides provided your cartridge doesn’t have an extreme case of runout.
Looks like you could be a bit less freebore.

It is a bartlein 5r and yes there are 5 marks around the bullet. Does the less free ore cause any potential problems with pressure, etc.

 

[spife7980]

It can. It’s easier to keep something in motion than to start it in motion. When the bullet is up against the lands all that pressure is stuck behind it and is having to overcome engraving that bullet (obturation) all at once. If there is a bit of jump before the lands there is some pressure reduction by “blow by” but really the bullet got moving easily and has some momentum over time to help when it hits the lands.
Generally the shorter freebores lend them selves to vld style bullets with small bearing surface but long noses or lighter bullets.
If you have a low charge it will be fine. If the charge is up near maximum it could cause enough to go over pressure.

 

[CarlM]

I'm using the Sinclair inserts. Not home now but I'll check when I get home. The rest of our numbers seem pretty similar though.

Sinclair 6.5mm insert which measures .250. I don't have a lot of factory 140eldm ammo around, but none of it come close to 2.190. Maybe I need a new set of calipers!