My 18" X-Caliber Barrel - An ongoing review and discussion

[Deputy819]

I think I’ve got the load for the Sierra 120gr Pro Hunters nailed down. Just shot this 5-shot group this morning at 100 yards and it includes the ‘Cold Bore’ shot. I was lucky enough to have 7 lbs of H-4895 from another project that didn’t come to fruition. That seems to be the ticket with the Sierra 120gr Pro Hunters in THIS barrel….which is what you have as well.

[Okie_Poke]

I think I’ve got the load for the Sierra 120gr Pro Hunters nailed down. Just shot this 5-shot group this morning at 100 yards and it includes the ‘Cold Bore’ shot. I was lucky enough to have 7 lbs of H-4895 from another project that didn’t come to fruition. That seems to be the ticket with the Sierra 120gr Pro Hunters in THIS barrel….which is what you have as well.

That will work!

[Okie_Poke]

I didn't get an opportunity to do any more shooting this weekend. However, I did have a little bit of time this afternoon to take some measurements. One of the things nagging me since I confirmed the factory 123 ELDMs are shooting better than my handloads with the same bullet is whether my reloading process is to blame. While that very well could be it, my measurement excercise this afternoon gives me some confidence that is not the likely culprit. I think I just need to find the powder and charge my barrel likes with this bullet.

To provide some context, I'm reloading for my Grendel on a Dillon XL-750 progessive press. I've modified my loading procedure while I'm doing load workup, however, so that I'm really running it kinda like a single stage press with a case feeder and on-press priming. That is, I'm running the brass through one time to resize and prime but not do anything else. Next, I'm charging with powder off the press, measuring every powder charge. Then, I'm seating on the press, feeding the charged cases into the seater station manually. My resizing die is a Redding Type S FL with a bushing; the seater is a Forster Micrometer. The sizing and seating dies are both set up to "float" in an Armanov toolhead.

Because I'm using a progressive press, I thought that was perhaps introducing more variance into my handloads than I realized, even though I'm measuring ever powder charge instead of throwing them. I have several rounds of factory ammo and several rounds of my handloads left from the last batch I tested. So, I decided to measure 10 rounds of each for a few characteristics. I used a headspace comparator to check the consistency of the brass size. I used a bullet comparator to measure the CBTO to check variance in seating depth. And I used a Sinclair concentricity gauge to measure runout of each loaded round.

I've copied a table below showing the results. In sum, my loaded rounds measured at least as good, or better than, the factory rounds. With respect to brass size, both factory and my handloads varied no more than .002." With respect to seating depth, factory ammo varied .007" from min to max and my handloads varied. .004." With respect to runout, factory ammo averaged .005" in TIR, whereas the handloads averaged .003." The factory ammo had one with .008" of runout and another with .010" of runout, while the largest TIR on my handloads was .005."

image.png

I'm not making any claim that any of this really matters a whole lot in the grand scheme of things. Also, I expect I could probably tighten this up a little bit if I did this on my single stage press. Without digging back through old reloading notes, I don't really know how this compares to my best match ammo I load on my single stage. But that doesn't really matter for present purposes because the point of this excercise was to see whether my handloads were better or worse than factory ammo using these metrics. They are at least as good as the factory ammo. So, that suggests to me the issue is elsewhere and I should try turning other knobs before fiddling with my reloading process. I am hoping a change in powder is the ticket.

[Deputy819]

The change in powder worked for me! I was initially running Benchmark powder, but kept getting a first round “flier” with the other 4 shots stacked on top of each other. I knew from previous testing (with other powders) that my seating depth for the 120gr Pro Hunter was good. Ran a powder ladder with H4895 and ended up going slightly above Sierra’s listed max and “BAM”….no more fliers!! Life is good again. 👍

[Okie_Poke]

I still haven't shot again yet. I probably won't get to until next weekend. But I did load up 10 rounds with each of the following powders this afternoon: (1) CFE 223; (2) SW Match; (3) AR COMP; and (4) Lever. I backed off of max or even near-max loads and am generally shooting for around 2450 fps with 123 ELDMs. I'll report when I do that shooting.

In the meantime, I was curious how the external measurements of my 6.5 Grendel rounds compared to the handloads for my 6.5 Creedmoor that I loaded on my single stage press. So, I measured 10 of my Creedmoor handloads this afternoon using the same metrics as I did for the Grendel factory ammo and handloads previously. Chart below. Unsurprisingly, the ammo loaded on the single stage is more consistent with respect to these exterior metrics (which may or may not actually matter to practical accuracy . . . ). Both the Grendel and the Creedmoor loads used ELDM bullets, so i'm not comparing Hornady bullets in one cartridge to Berger or Sierra bullets in the other. My Creedmoor loads do get Lapual brass instead of Hornady brass, though I don't know how much that would matter to these measurements. In any event, I have no doubt I could tighten up the external consistency of my Grendel loads by switching back to the single stage, but I'm playing with powder first. While I think variations in these external measurements could affect accuracy in some rifle systems, I consider them to be a pretty small "knob" at the moment and likely lost in the noise of other things. I'm just sharing because I was curious to see the data compared and thought others might be as well.

image.png