300PRC - Factory 212gr ELD-X Loaded in the lands?

[Mike Lum]

Picked up a Bergara premiere a while ago in 300 PRC and finally found some bullets to load! The rifle shoots so well with the Hornady ELD-X I figured I would do my best despite components to try and replicate the load as best I could.

Using a comparator to find the jam I did the 220gr bullet test a couple times and got a comparator measure of 2.905. Took a measure of the 212 gr out of the box was 2.910, a decent amount longer than my testing measurement. I decided to use a black sharpie to mark the boxed 212gr and chamber it to inspect for contact marks and indeed there was substantial amount of marker rubbed off on the odrive of the bullet.

The fact that this 212gr. box load is shooting the same hole at 100 yards when I build a stable position, loaded that far into the lands is throwing me off a starting point with my load development procedure of starting at least .002 back of jam.
I clocked the box ammo at 2931fps (26 inch barrel).

In contrast I have a Tikka in .264 that the same ELD-X loaded from the factory and they are VERY far from the magazine length capacity OR the lands.. so its not something the manufacturer is doing intentionally with the loading of that bullet. Also, their Outfitter series 300 PRC with the 190gr CX measures considerably shorter on the comparator and is jumping a long ways.

Should I back off the factory seating depth based on my jam calculation for safety sake when I am doing my powder load development and if I can't get it shooting as well as the box cartridge slowly creep up to Jamming them?
I'd really rather work up a load that doesn't have me chasing barrel erosion...

 

[Gargoyle]

That's what I would do.

 

[Ned Ludd]

Picked up a Bergara premiere a while ago in 300 PRC and finally found some bullets to load! The rifle shoots so well with the Hornady ELD-X I figured I would do my best despite components to try and replicate the load as best I could.

Using a comparator to find the jam I did the 220gr bullet test a couple times and got a comparator measure of 2.905. Took a measure of the 212 gr out of the box was 2.910, a decent amount longer than my testing measurement. I decided to use a black sharpie to mark the boxed 212gr and chamber it to inspect for contact marks and indeed there was substantial amount of marker rubbed off on the odrive of the bullet.

The fact that this 212gr. box load is shooting the same hole at 100 yards when I build a stable position, loaded that far into the lands is throwing me off a starting point with my load development procedure of starting at least .002 back of jam.
I clocked the box ammo at 2931fps (26 inch barrel).

In contrast I have a Tikka in .264 that the same ELD-X loaded from the factory and they are VERY far from the magazine length capacity OR the lands.. so its not something the manufacturer is doing intentionally with the loading of that bullet. Also, their Outfitter series 300 PRC with the 190gr CX measures considerably shorter on the comparator and is jumping a long ways.

Should I back off the factory seating depth based on my jam calculation for safety sake when I am doing my powder load development and if I can't get it shooting as well as the box cartridge slowly creep up to Jamming them?
I'd really rather work up a load that doesn't have me chasing barrel erosion...

The real question is whether the reason the factory ammo shoots so well because the bullet is seated into the rifling. In the past, I have observed that .223 Rem handloads with 90 VLDs will stack them up in one ragged hole at 100 yd when the bullet is seated in a narrow window between approximately .004" to .007" into the lands, or when seated in a slightly wider window of about .018" to .024" off the lands. If you find handloads with the 212 gr ELD-X shoot comparably well at some distance off the lands, you're GTG. If they do not, you may find it necessary to seat them into the lands in order to reproduce the commercial ammunition performance.

Some bullets don't seem to tune in as well when seated into the lands, some can be tuned in both into the lands and off of the lands, and some don't seem to tune in at all unless they are seated into the lands. The exact reason for this seems fairly elusive at this point. However, it doesn't matter in your particular situation because all you need to do is some seating depth testing to determine where the bullet groups optimally in your handloads. In the scenario with the 90 VLDs I mentioned above, I chose to shoot them at ~.021" off the lands for several reasons, including the initial pressure spike sometimes observed with bullets seated into the lands (the load is already pretty hard on brass), not wanting to "chase the lands", and the fact that the optimal seating depth window was noticeably wider in that particular instance with jumped bullets.

If you prefer not to seat bullets into the lands initially, simply carry out a suitable seating depth test to determine how they perform when seated off the lands. If you find something good, problem solved. If not, you can still decide whether you wish to try further load development seating them into the lands. If you're feeding rounds from a magazine, presumably the commercial ammunition with the bullet seated into the lands still feeds properly. But there may be a limit on how far you could chase the lands and still have that be true. If so, knowing the maximum length of loaded rounds that will feed reliably from the magazine would be beneficial, and it would also provide a maximum COAL for the purpose of seating depth testing.

 

[Mike Lum]

Thanks for the thought out replies.
Still at the stage of trying to find a stable powder node with what's available locally here in Canada.
I loaded up to just short of Vitavori's recommended max pressure load for N568 @ 79.7 for a 220 grain, loaded it back 2 thousands off JAM and fired one off to test for pressure signs. No noticeable pressure signs at 2861FPS. Will likely run a ladder test up from here until i start to see pressure signs, as i'm at 96% case capacity. Seating depth will follow.

Currently its -34C outside here, needless to say doing any load development at this temperature and then trying to shoot it after its been sitting on your dashboard on a hot summer day is recipe for disaster. Main reason why my OP was concerned about the safety of Jamming these rounds.. a load that is developed at the first node below pmax @ -20C fired at +40C is bad news, add to that increased pressure of jamming a bullet that's warmed up and expanded in a barrel that's also expanded.

With 50-60 degree temperature swings it's difficult to develop a load that performs the same at either extreme, as a temperature swing like that will knock you out of any node. I've found the need to run 2 loads for my 22-250 varmint rifle, one for +30 degrees and another for -25. Ideally a guy can get enough data that you might be able to find how much deeper you can seat the bullet to compensate for the colder temperatures and seat your loaded warm weather rounds deeper to stay on the same pressure node. BUT and big but.. you can't do this if you need to chase the lands for that load to succeed.

There's a big bonus to anyone that can Identify which powder Hornady has put into this 212gr ELD-X "Precision Hunter". It's cambered in 300PRC, COAL=3.6335, 79.9gr of powder and it whips out of a 26 inch barrel at 2931 @20 degrees Celsius if that helps anyone narrow down the performance range. I looked at pictures in Gordons for the most common ones but couldn't find anyting like this. It almost looks similar to a ball powder..

 

[Kurz]

The fact that this 212gr. box load is shooting the same hole at 100 yards when I build a stable position,

Reality suggests two things:

Keep buying and shooting the factory 212 gr. cartridges. This obviously indicates that your Bergara really likes this load!

Trying to fabricate a new load to simulate the original factory box load can prove to be daunting. Factory loads do not use the same formulation of powder that we as consumers buy at the LGS or online. Excluding the jump/jam discussion, you will still have a bunch of testing trying to replicate your factory load.

Enjoy!

 

[FeMan]

I developed a 300 PRC load with 212 ELDXs for a buddy a while back. I pulled a bullet on a factory round from Hornady and it was a stick powder if I remember correctly. That picture looks like a Vit powder to me. 568 or 570? Either my memory is bad (possible) or they used a different powder in yours.

If it helps, his rifle tuned at 2920 with H1000 and the 212's jumped 0.020". It shoots very tight. I am currently trying 215 Hybrids in it now that they are back on the planet. They show great promise.