Today i got a good look at a 8.5 twist 7mm IBI barrel to be used in Fclass as a 284 Win 0.317" no turn chamber.
Looking from both ends in i saw no tooling marks anywhere. No chatter marks from the button or reamer in either of the grooves or lands which is a good indicator that those two processes are under control. This was a 5R button barrel where you could see a uniform radius on each land and each land was uniform for width along its length.
Looking down a barrel is not a science and no one can determine if a barrel is going to shoot or not.
Everything looks great with just the one comment i would make. After looking down virtually every brand of barrel at some point, the lapping in this barrel was done with maybe one grade too course lapping paste. The common belief is courser can be better as opposed highly polished. A finer grit of around 1000 or finer can lead to copper streaking that can be nighe on impossible to remove. Course will burnish, or that is the hope, but this barrel looks just a little too course where the sharp edge on the lands on the trailing side was rounded slightly. These should be sharp in a new barrel and not look like buttressed rifling when this barrel is meant to be a 5R. Dont get me wrong, a buttressed land is very strong and doesn't break off the edge easily, but this was not machined, it was worn to that shape.
My opinion only where shooting will tell.
Cheetah Barrels
Re: Cheetah Barrels
An update on the 284 IBI barrel.
It's been a few weeks since it was chambered where the owner has done a little sorting to settle on Lapua cases, BR2s, 180 Inbreds and 50.9 grains of 2209 for a labrador reading of 2820 fps which is right about on the money for the upper node of this cartridge..
I have not seen any of the initial groups but have been told of the group sizes at 300 and 500 meters and scores at 700, 800 and 900 meters. It reinforces the statement that peering down a barrel with a borescope tells you nothing about the way a barrel will perform.
For a budget barrel they do seem to perform very well with another in 308 at the club touted as a virtual laser to 900 meters.
It's been a few weeks since it was chambered where the owner has done a little sorting to settle on Lapua cases, BR2s, 180 Inbreds and 50.9 grains of 2209 for a labrador reading of 2820 fps which is right about on the money for the upper node of this cartridge..
I have not seen any of the initial groups but have been told of the group sizes at 300 and 500 meters and scores at 700, 800 and 900 meters. It reinforces the statement that peering down a barrel with a borescope tells you nothing about the way a barrel will perform.
For a budget barrel they do seem to perform very well with another in 308 at the club touted as a virtual laser to 900 meters.
-
dashooter
- .338 Lapua Magnum
- Posts: 2797
- Joined: Tue Oct 15, 2013 4:08 pm
- Favourite Cartridge: Wby Magnum's :)
- Location: Deep South Canberra
Re: Cheetah Barrels
I need a Labrador that can do speed readings, my GSP struggles. LolTony Z wrote:An update on the 284 IBI barrel.
It's been a few weeks since it was chambered where the owner has done a little sorting to settle on Lapua cases, BR2s, 180 Inbreds and 50.9 grains of 2209 for a labrador reading of 2820 fps which is right about on the money for the upper node of this cartridge..
I have not seen any of the initial groups but have been told of the group sizes at 300 and 500 meters and scores at 700, 800 and 900 meters. It reinforces the statement that peering down a barrel with a borescope tells you nothing about the way a barrel will perform.
For a budget barrel they do seem to perform very well with another in 308 at the club touted as a virtual laser to 900 meters.
What were the group sizes Tony?
Sent from my iPhone using Tapatalk
Re: Cheetah Barrels
The initial groups were 30 mm at 300 meters for the Inbreds. The 195 vlds were 33mm. At 500 meters the Inbreds were under 50mm
All the groups since then have been bettered. Weekend just gone the owner shot 60.8 and 60.9 with the Inbreds then the 180 vlds at the clubs 300 meter event. During these 10 shot strings, two primers BR2s and S&Bs were used with the edge going to the S&Bs. So the 60.xs were two lots of 5 shots to test elevation with the primer changes. No change of POI, but a noticeable vertical reduction with the S&Bs as many are finding up here with their 6.5 CMs(LRPs) and SAUMs.
The Inbreds were at 50 thou jump, the vlds were at 10 thou jam. Both loads were upped point one grain to a neat 51 grains of a fairly older batch of 2209.
Having just said all that, there has been a considerable accuracy gain with Re23 with around a quarter of a minutes elevation at 3, 7, 8 and 900 meters. This does not represent a bell curve, but shows a linear deviation which is impossible to get in the real world. So some form of compensation must be happening here. Either that or the electronic targets tell lies. They tell me they're good for plus or minus a mm,
I was told on Tuesday that this barrel will be pulled and set aside for the Brisbane and NQRA Queens as it is outperforming the Bartlein and ???? barrels.
All the groups since then have been bettered. Weekend just gone the owner shot 60.8 and 60.9 with the Inbreds then the 180 vlds at the clubs 300 meter event. During these 10 shot strings, two primers BR2s and S&Bs were used with the edge going to the S&Bs. So the 60.xs were two lots of 5 shots to test elevation with the primer changes. No change of POI, but a noticeable vertical reduction with the S&Bs as many are finding up here with their 6.5 CMs(LRPs) and SAUMs.
The Inbreds were at 50 thou jump, the vlds were at 10 thou jam. Both loads were upped point one grain to a neat 51 grains of a fairly older batch of 2209.
Having just said all that, there has been a considerable accuracy gain with Re23 with around a quarter of a minutes elevation at 3, 7, 8 and 900 meters. This does not represent a bell curve, but shows a linear deviation which is impossible to get in the real world. So some form of compensation must be happening here. Either that or the electronic targets tell lies. They tell me they're good for plus or minus a mm,
I was told on Tuesday that this barrel will be pulled and set aside for the Brisbane and NQRA Queens as it is outperforming the Bartlein and ???? barrels.