Hornady manual mistake?

[Bronsonburner]

I have the Hornady 10th edition on my Kindle and I'm seeing some weird data. For the 6.5 mm 120-123 grain pills they list a max of 31.2 grains CFE 223. For the 129-130 grain they list a max with the same powder of 31.7. This doesn't seem right to me. Anyone seeing the same thing? I'm going to work up some loads with the 129 Interlocks using CFE and I don't need my face blown off lol.

[LR1955]

I have the Hornady 10th edition on my Kindle and I'm seeing some weird data. For the 6.5 mm 120-123 grain pills they list a max of 31.2 grains CFE 223. For the 129-130 grain they list a max with the same powder of 31.7. This doesn't seem right to me. Anyone seeing the same thing? I'm going to work up some loads with the 129 Interlocks using CFE and I don't need my face blown off lol.

BB:

The best thing you can do is write or call Hornady and ask. Anything else would be taking someones opinion instead of finding out from the source.

I doubt it will take you more than five minutes to call them.

LR55

[Bronsonburner]

You're right. Sending off an email this AM. I'll report back what they say.

[grayfox]

Same thing in Hornady #9 that I have, so doubtful that it would be a mistake. Lrrpf52 explained it in a couple of threads, it is due to the 120-123 class having to account for the 120 gmx. His take is that it's the that gmx can't go above the 31.2 whereas the cup/core bullets (esp in 129's) don't have that much of a limit. So presumably (but this is obviously not hornady's recommendation!) the 120-123 cup/cores could go higher as well.

edit to add: part of the issue is that monolithic bullets are more resistant to engraving so build up pressure more right out of the gate.

[lazyengineer]

Sometimes I suspect that has to do with different design bullets having differing baring surface or other aspects that affect its frictional or other resistance in the barrel. Mass is the most important factor, but maybe isn't the only factor. That said, whenever you see what you describe, that always should indeed cause pause, and I'm glad you are writing them for confirmation. Please post what they say.

[Bfglowkee]

Boat tail vs flat base. I think I recall reading in few different manuals similar observations when talking about a flat base bullet and the sleeker boat tails. Your already on the horn with Hornady so will be curious to hear the outcome.

[Bronsonburner]

Boat tail vs flat base. I think I recall reading in few different manuals similar observations when talking about a flat base bullet and the sleeker boat tails. Your already on the horn with Hornady so will be curious to hear the outcome.

They group all the same bullet weights in with the same data, boat tail 130s included. So far no response by email. I'll try to give them a call tomorrow if I don't hear back by then.

[204 AR]

They did make a mistake in the 9th edition with cfe and 95-100 grain bullets. The correct data in on their website, but no mention of the 123 gr stuff.

[Bronsonburner]

Response from Hornady this AM:

Question Reference Ticket Number: TT33066
Recently you requested assistance from our customer support center. The following is a summary of your request and our response.

Hornady Support commented at: 03-12-2019 08:04
Mr. ———

Thank you for the email. I checked with our ballistic engineers and the data is correct in the manual.

Thank you
commented at: 03-11-2019 09:00

Inquiring regarding 6.5 Grendel data in the 10th Edition manual. 120-123 grain bullets list 31.2 grains CFE 223 as max. The 129-130 grain bullets list 31.7 grains of the same powder as max. This is from my Kindle edition manual. These numbers do not seem right
to me and I would like some clarification. I am planning to work up some loads using CFE and the 129 grain Interlocks and don't want to have any problems. Thanks!

Date Created: 03-11-2019 09:00 AM
Date Last Updated: 03-12-2019 08:04 AM
Status: Open

[LRRPF52]

I asked them about it years ago, and it's because of the 120gr GMX, which is as long as a lot of 140gr class 6.5 cup and core bullets at 1.400".

It takes up a lot of case capacity, reducing the case volume, and also is more difficult to drive into the lands since it's a monolithic bullet.

Instead of placing it in its own class of bullets, they bundled it in with the 120gr and 123gr A-MAX in the 8th and 9th Editions, as well as the 120gr and 123gr ELD-Ms and 123gr SST in the 10th Edition, because the manuals would get very large with scaling to account for the GMXs. Nosler does the same thing with the Ballistic Tips, Partitions, and E-Tips all included within weight classes, when they really deserve their own data. Partitions and E-Tips resist engraving force into the lands differently than Cup and Core Ballistic Tips.

In independent pressure testing, we found that the 123gr A-MAX hit 50,000psi at 31.9gr in a mid-range SAAMI chamber cut with a Manson reamer designed to simulate mid reamer life. That was with Hornady brass, CCI 450s, and 2.260" COL, once-fired cases.

When dealing with CFE223, these were the max loads for 50,000psi in that chamber with those components:

31.9gr for the Hornady 123gr cup and core bullets
31.7gr for the Hornady 129gr Spire Point (work up and be prepared to stop at a lower charge weight with the 129gr SST or Interbond)
30.4gr for the Nosler 129gr ABLR

The 129gr Spire Point allows more case volume since it's flat-based, but doesn't retain its velocity as well as the 129gr SST with its long boat tail and aerodynamic ogive (Litz BC at .495 G1, which is higher than Hornady's .485 G1).

So the Hornady data is spot-on since they include the 120gr GMX.