Win 270 COL / distance to lands issue

[Obi Wan Reloadi]

Evening all,

I have worked up a load in Hornady 130gr CX Win 270. RL19. Bergara B14.

My COL touching the lands was 84.8mm (loctite method), so I set the bullet back to 83 mm (approx 75 thou) as it's copper and the recommendation is to start at 50 thou back.

I get reasonable groups, could be tighter but it's a hunting rifle, not a target one so I'm okay with that.

(I will work in mm here, it's easier to visualize). However, the Hornady Manual recommends the COL should be 3.21 inches - which is 81.534 mm.

This would give a 3.3 mm jump to the lands - that's .13 inches.

That seems a lot - what are your thoughts on this please?

Thanks.

 

[Howa 9700]

In theory, yours is the better method, as you are setting COL to your gun's chamber. As long as it feeds from the magazine, chambers and fits, you are good to go.

The Hornady number is a more generic number that should fit in any chamber. If you had not done the work to find the distance to the lands, you could fall back on that.

 

[Obi Wan Reloadi]

In theory, yours is the better method, as you are setting COL to your gun's chamber. As long as it feeds from the magazine, chambers and fits, you are good to go.

The Hornady number is a more generic number that should fit in any chamber. If you had not done the work to find the distance to the lands, you could fall back on that.

Thank you.

 

[41 Mag]

I usually start at mag length, then work up to the velocity range I'm looking for while looking for pressure. Usually somewhere just above around 2800'ish FPS depending upon groups. I'll take a good grouping load over a fast one any day.

That said after I reach the velocity range, I will fine tune by seating deeper in .003 - .005" at a time. I have gone as low as one change to ad much as .110", with the latter actually being the book recommended length.

The jump can also reduce a bit of pressure due to the added distance the bullet travels before reaching the lands as well as having running start verses being up against them to start with. Using the monometal bullets poses a few different criteria when loaded but there is enough being used nowadays that info is readily available.

 

[Chuck R.]

It seems that each bullet and throat are unique individuals!

I just learned this lesson the hard way.. by wasting components, time, shoulder..

READ the manufacture's recommendation!

I'm working up a load using Nolser 168 ABLRs for my 300 Win and went with my usual OCW work-up including stating at .015 off the lands. This worked worked great with some 168 OTMs that I used for fireforming brass. It normally works very well in most of the rifles, with most of the bullets I've worked with.

1st test, accuracy sucked!

1.1-1.75 MOA for 4rds, NOT what I'm used to seeing. So I googled Nolser ABLR "Jump". Found out that Nosler recommends starting at SAAMI OAL as ABLRs like a "jump" of around .050". Numerous forum posts came to the same conclusion, ABLRs like some jump.

So like carpentry, measure twice, cut once, except it's research, research again, then load.