Tell me what happened - Ladder Test

[Klem]

KEY,
I'm not seeing any evidence of the headspace growing as you conducted that work-up. There are similar measurements at the start and the end, and regardless of load.

The range of up to .005 could be because some cases spring back more than others in a situation of overstrech.

Where did you get the Bartlein from?

Bobke,
The difference in Lapua cases between new and fire-formed in my gun is 0.78gns of water and is simulated to be a difference of 25fps (QL). Whether that is enough to mess up an OCW is a fair concern. I don't know but surely it would.

[keystone183]

KEY,
I'm not seeing any evidence of the headspace growing as you conducted that work-up. There are similar measurements at the start and the end, and regardless of load.

The range of up to .005 could be because some cases spring back more than others in a situation of overstrech.

Where did you get the Bartlein from?

Bobke,
The difference in Lapua cases between new and fire-formed in my gun is 0.78gns of water and is simulated to be a difference of 25fps (QL). Whether that is enough to mess up an OCW is a fair concern. I don't know but surely it would.

It just seemed odd to me that they were very consistent lengths until 27.5 gr, and then even going back to 26, they were still longer? If they were just longer on the higher charges i would understand it as you explained. Just seemed curios.

I purchased the barrel from someone who purchased it from Precision Firearms. Was sold to me as new never fired, and seemed that way when i put it together.

[teppou]

I'm late to the party here, and trying to catch up and gain more insight.... Similar to keystone, I've tried to read a lot of the forum, and my impression was that 8208 was great with the 123gr bullets. I had copied a quote from stokesrj's opening post in the Preferred Loads thread, which said "123 A-Max, 2.250", 28.5 grains of IMR8208XBR, any case, any primer." Also, my Lyman book and Hodgdon's website list 28.5gr 8208 as max load, so that's what I've been trying. I've kind of settled on 27.9g.

But if QL shows that to be over pressure, maybe I should try something else. What powder do you recommend using if 8208 is too fast?

Also, keystone, did you ever get the stuck case out of the chamber? One thing that worked for me when an oversized chamber brush didn't work was to use Cerrosafe.

[Klem]

I'm late to the party here, and trying to catch up and gain more insight.... Similar to keystone, I've tried to read a lot of the forum, and my impression was that 8208 was great with the 123gr bullets. I had copied a quote from stokesrj's opening post in the Preferred Loads thread, which said "123 A-Max, 2.250", 28.5 grains of IMR8208XBR, any case, any primer." Also, my Lyman book and Hodgdon's website list 28.5gr 8208 as max load, so that's what I've been trying. I've kind of settled on 27.9g.

But if QL shows that to be over pressure, maybe I should try something else. What powder do you recommend using if 8208 is too fast?

Also, keystone, did you ever get the stuck case out of the chamber? One thing that worked for me when an oversized chamber brush didn't work was to use Cerrosafe.

Tepp,

The123ELD and 123AMax are different shapes/length. When pushed into a case so they fit in a mag their bases displace different case volumes. That means different max charges but as they are the same weight it's pretty close. The QL max for a 123AMax is 26.3gns/8208. For a 123ELD it's 26.4gn; 2.283"OAL with a case that is 35.13gns water.

ADI/Hodgdens loading charts recommend 28.5gn/8208 as the max for a 123SMK. This max load is quite a different to QL which recommends no more than 26gns. Which one is truer? The pressure curve is much steeper with faster powders so getting it wrong by 2.5gns is bolt breaking territory. I have loaded 28.5/8208 with the 123AMax and the bolt is still in one piece. QL has a reputation for being conservative so going hotter than it recommends is normally pretty safe. The trouble with Keystone is that it was headspace, and not a hot load that split his cases.

Your question as to what is the most efficient powder for a 123gn depends also on the length of barrel.

What barrel length do you have?

[teppou]

Tepp,

The123ELD and 123AMax are different shapes/length. When pushed into a case so they fit in a mag their bases displace different case volumes. That means different max charges but as they are the same weight it's pretty close. The QL max for a 123AMax is 26.3gns/8208. For a 123ELD it's 26.4gn; 2.283"OAL with a case that is 35.13gns water.

ADI/Hodgdens loading charts recommend 28.5gn/8208 as the max for a 123SMK. This max load is quite a different to QL which recommends no more than 26gns. Which one is truer? The pressure curve is much steeper with faster powders so getting it wrong by 2.5gns is bolt breaking territory. I have loaded 28.5/8208 with the 123AMax and the bolt is still in one piece. QL has a reputation for being conservative so going hotter than it recommends is normally pretty safe. The trouble with Keystone is that it was headspace, and not a hot load that split his cases.

Your question as to what is the most efficient powder for a 123gn depends also on the length of barrel. You want the max velocity at the max safe powder load.

What barrel length do you have?

Thanks for the info. I knew the bullet shapes were different, and could result in different pressures, but it's hard to know how much those pressures differ. Start low and work up and all that.... I have an 18" Criterion barrel. In a test session in April I averaged 2475fps with 27.9gr 8208, and on a cold day in January I got 2483fps. But I also saw 2545fps in September with the same load, all across a Magnetospeed.

[Klem]

Tepp,

Such a range of velocity for a single-based powder is unusual. 8208 is single based so more temp stable than double based powders. There must have been quite a difference in temp, or something else was wrong.

With an 18" barrel a slower powder will be more efficient. Relative to 8208, H4895 will get you an extra 30fps at the max SAAMI limit. It will also be a less severe work up.

[Growler]

[teppou]

Thanks, Klem. And sorry to hijack the thread a bit. I'll see if I can find some H4895, but it's interesting that I don't see it listed as a suggested powder for 123gr bullets in the Grendel. I've looked at the Lyman and Hornady manuals, as well as the Hodgdon website.

It's interesting, too, that according to several powder burn rate charts, H4895 is only slightly slower than 8208. So just enough to get into the sweet spot for the bullet weight?

[EigerWand]

@keystone183 Sorry to hear about your rifle and damage. Pleased to hear you are OK.
It looks as if you've got some photo posting working now.
Could you show us a pic of the broken bolt and the case ?

[Devildog6.5G]