6.5 PRC 20" Barrel Reload Questions

[original_jbond]

Hello,

First post. I have been lurking for awhile and really appreciate all the knowledge and information that gets passed around here. I recently bought a Bergara Crest 6.5 PRC with a 20" barrel and have been working on reloads for it. I am limited to COAL of 2.955 as it is magazine fed. Tried H1000 with 142 ABLR and couldn't seem to get them to work. Moved to Berger 140 VLD-H and settled on 57.0 grains of H1000 with Fed 215M primers. Velocity average was 2836 wth ES of 20, SD around 10. 3 shot 100 yard group of .460" At this point, the rifle has 98 rounds down the barrel.

Took 10 rounds to range to verify 100 yard and 200 yard 5 shot groups.

New Lapua brass that was ran through an expander ball for concentric neck tension - Final neck tension was .002 (2nd/3rd fired brass was at .004 - assumed it was because the brass was new)
57.0 grains H1000
Fed 215M primers
COAL 2.950

Shots were taken 90 seconds apart with a 10 minute cooldown between 100 and 200 yards. I overlayed the 100 yard target on top of the 200 yard target. I am concerned about the amount of drop I have. The first shot on 200 yards is covered by the 100 yard target. I did number the shots in order. Do I need to work my powder charge up further? At this point, needing a direction to do since, as we all know, components are limited.

 

[original_jbond]

Plus, why did the group size get so large?

 

[MtnMann]

Welcome @original_jbond. Just a quick clarification that these 10 rounds were shot with lapua brass that was x3 fired? If that is correct, how many firings were on the brass when you did the initial load work up with H1000 and the 140gr VLDH?

 

[original_jbond]

Thanks! No loads were worked up with hornady brass fired 2/3 times but then received my Lapua brass and wanted to confirm everything. That's when that happened. Lapua brass is new.

 

[MtnMann]

I see potentially two primary variables at play that may be giving you some issues and causing the results on target:

1. Hornady and lapua brass have different case thicknesses/alloy make up which makes the internal case capacity vary between the two brands. This can cause differing pressure spikes between the two brass brands leading to more or less velocity when using the same powder charge.

2. While lapua brass is very consistent and high quality it is still beneficial to have at least 1 firing, and ideally 2 firings, on the brass before settling on a load as the brass is still slightly changing to fit your chamber dimensions. From my experience this typically causing the case to expand creating slightly more internal case capacity and will change the harmonics of the load as well as possibly lower velocity.

 

[original_jbond]

So if I have a believed good load with my multiple use hornady brass, I just need to "deal" with the now same subpar load until my Lapua brass have been fire formed?

I have reloaded for several calibers and never ran into this issue that is why I am so confused about it.

 

[original_jbond]

Side note…I see you're West Slope, Best Slope as well!

 

[Old Rooster]

I learned a good lesson recently.My Lapua brass for 300 win mag came in I did what you did and got horrible groups.A load I have been using for many years with other make's of brass failed to give me the groups I got with Hornady brass!Folks on this forum schooled me on this make of brass.In the future I will NEVER shoot a piece of Lapua brass for groups without fire forming first.
MtnMann hit the nail on the head.Laupa brass is one of the best but very hard and needs to be fire formed to get where you want to be.

 

[MtnMann]

So if I have a believed good load with my multiple use hornady brass, I just need to "deal" with the now same subpar load until my Lapua brass have been fire formed?

I have reloaded for several calibers and never ran into this issue that is why I am so confused about it.

Honestly, I'm still learning and have no personal experience with the 6.5 PRC, but I'm just thinking that the switch to Lapua brass and it being new brass may be adding up the variables to the extent that it is causing a noticeable effect on the performance of the rifle. There could definitely be other causes for the decreased accuracy and slower velocity. Putting the average cartridge and bullet info in Gordon's Reloading Tool is showing approximately 2730 fps based on your charge of 57.0gr of H1000 which would give you about 3.25" drop at 200 yards depending on weather conditions. Note, the simulation is obviously not 100% true to real world findings or pressures and without knowing your actual case volume the data is less accurate. However, I have found it to be very close when comparing real world velocities to the predicted velocities in a lot of my cartridges.

Side note…I see you're West Slope, Best Slope as well!

Hahaha yes it is! I'm kind of close to you and usually hunt over by Maybell. However, due to the winter kill I have been having no luck picking up tags.

 

[BrentM]

Generally you cannot use new brass vs old vs different brands of brass and get equal results. Can you? Yes.

It is more normal to see enough of a difference a person will need to tweak the load a little to get the best results.

Your drop doesn't seem too far off for your velocity. 3" from 100 to 200 for 2800ish fps is fine.

 

[original_jbond]

Mtn Mann do you think I should try for a higher node?

 

[BrentM]

Mtn Mann do you think I should try for a higher node?

Your speed is just slightly above creed speeds. My 20" creed runs a 135 at 2790. My 18" prc is 3000. I have no issue running a 143 at 2925 in that 18". You may need an another 50-100 rounds for the barrel to settle in but right now it's slow.

 

[original_jbond]

I think the part that makes it difficult is component availability. Is there a higher H1000 load you recommend?

 

[MtnMann]

I agree with BrentM, from the other results I've seen posted in this and other forums, the velocities you are seeing seem a little slow which may just be the low round count on your gun.

If you are wanting higher velocity and there are no current pressure concerns I'd probably load 3-shots every 0.5gr and work up maybe 1-2gr as long as pressure isn't a concern. I totally understand the component availability problem though.