Question in Reverse - Chamber reamer for 6.5 Creedmoor and 140gr Hunting VLD

[Solid7]

So, I know that there are endless questions posted about what is the "best" load for a 6.5 Creedmoor, etc, etc, etc... Mine is sort of like that, but asked a little different. There is SO MUCH info, and SO MUCH of it may be dated, now that the round is a bit more mature.

I'm about to buy a pre-fit barrel for a Zermatt Origin action. I'll be running 16" on a heavy palma contour. The only thing that I've not quite got nailed down, is the sweet spot for freebore. I have zero bench time on a 6.5 Creedmoor. In fact, full disclosure - I am upgrading to the Creedmoor, because I just love my Grendel so damned much.

I have no doubt about what I want to load in the rifle. I tend to build a gun around exactly one round. For me, I'm choosing the Berger 140 hunting VLD with H4350 powder, Lapua brass, Federal BR primers. I intend to use the brass as fire formed, with only an OAL trim. My research tells me that rifling erosion tends to be fairly high in the Creedmore - somewhere between .005-.006" per hundred rounds fired. I've not seen tons of data on different barrel materials, so I assume that to be 416R, and not Chrome Moly. (where CM would be higher erosion)

I'm trying to implement some of the data from precision rifle blog, to help develop a strategy that would see the barrel shoot into a sweet spot after about 1000 rounds, before beginning its downward spiral. For that reason, I'm half tempted to order a chamber that starts out with the bullet "stuffed", and let it wear in. However, I suspect that this may also not be so straightforward. (maybe accelerated and/or non-linear erosion)

For those of you who have been shooting this round for years, what are your opinions? What freebore would you order for this round?

Oh, also, I plan on using this primarily for long range hunting, with that being defined as < 700 yards, for large game like deer and elk. Everything under 300 yards is an absolute snap for the Grendel.

 

[Solid7]

I should probably also say, that when it's not hunting, this will be my 600 yard range gun. And I do intend to do a fair bit of shooting with it. Which, for me, is < 300 rounds per annum.

 

[Newbie2020]

Not to poop in your thread, but I’ve been reading how F-class benchrest and PRS shooters are seating way longer jump—-70-90 thousandths. Not because they get smaller groups than the sweet spot just off the lands, but to avoid the bad groups that are only 100-200 rounds later due to erosion.

This is one of the articles:

More Bullet Jump Research!

This is the 4th article in a series on some new research on bullet jumps. Here is a recap of the pr...

precisionrifleblog.com

 

[Solid7]

Not to poop in your thread, but I’ve been reading how F-class benchrest and PRS shooters are seating way longer jump—-70-90 thousandths. Not because they get smaller groups than the sweet spot just off the lands, but to avoid the bad groups that are only 100-200 rounds later due to erosion.

This is one of the articles:

More Bullet Jump Research!

This is the 4th article in a series on some new research on bullet jumps. Here is a recap of the pr...

precisionrifleblog.com

I didn't take your reply poorly, at all. That's the kind of feedback that I'm looking for. I've actually read that article - and even a follow-on, which I think was an even better one: https://precisionrifleblog.com/2020/03/29/bullet-jump-load-development/

Thing is, I don't have the time, $$$, or patience to shoot as many rounds as the guy who was commenting on the article. And to be honest, after all that data, I'm still not 100% certain what the conclusion was, or how it applies concretely to what I'm asking. I mean, I get that there is a strong inference that seating .070"-.080" off the lands, was where the minimum spread in measured vertical extreme occurred. I get that 0-.020" was where the best accuracy (although not necessarily consistency) was achieved. But I'm not sure that I was able to extract what the best compromise between accuracy and barrel life, actually came out to be.

 

[Solid7]

Also, I like to shoot, but I'm not interested in "chasing" the bullet jump. I want to develop a load one time, and know that it's good. I do understand what I'm asking. Let's just call it the "best compromise".

 

[Newbie2020]

My take was that the longer jump (0.070-0.90”) doesn’t improve anything except consistency over time and therefore you don’t need to change your seating depth as the throat recedes.

 

[Solid7]

My take was that the longer jump (0.070-0.90”) doesn’t improve anything except consistency over time and therefore you don’t need to change your seating depth as the throat recedes.

Yes, I definitely won't be doing that... One cut for ~2500 rounds would be ideal.

 

[Newbie2020]

(I’m typing this waiting for someone to pounce:....)

Pick a modest OAL (2.70-2.82?) from the 6.5 Creedmoor sticky reloading thread on the hide using your 140 VLDs and have the chamber cut for the ogive to be 0.040” or 0.050” off the lands from the very beginning.

based on the article, you will miss all the sweetest spots, but you’ll also miss all the crappy spots in between all the sweet spots and the gun should shoot consistently well for the accuracy life of the barrel using the same load and seating depth.

(I hope Erik Cortina chimes in here pretty soon or somebody’s gonna kick my butt....)

 

[Solid7]

That is exactly the kind of info that I'm looking for...

 

[Newbie2020]

I’ll ask for input from @Dthomas3523 a true expert

 

[Dthomas3523]

If it were me, I’d mock up a bullet where the bearing surface is just above the neck shoulder. Send it off and have a reamer done very close to that or .020 more.

Then if needed (won’t shoot well), I’d have smith throat it a little at a time.

Or just put a tuner on it.

 

[Solid7]

If it were me, I’d mock up a bullet where the bearing surface is just above the neck shoulder. Send it off and have a reamer done very close to that or .020 more.

If I'm being honest, I was kinda hoping that this was already a thing... (and maybe it is - that's what I'm trying to figure out)