7mm PRC reloading advise

[SalmonSam]

Hi I'm hoping to get some advise on next steps for my 7prc load development, I'm a fairly new reloader and just started to work up a load after shooting through a case of factory ammo and keeping the brass. The rifle has a suppressed 22" proof barrel with 250 rounds fired. I have been experimenting with H4831sc and 175 eld-x but am ending up a ways off of the load data velocities, which I'm sure is in part due to my 22" barrel however I'm ending up more than 130 fps below the published numbers which is more than I would think. Even when working up above published max from 63.9 to 66.2 I only just break over 2900 and have some pretty pronounced ejector marks on the Hornady brass. Are there other powders that you would recommend for the 22" barrels and 175s or am i going astray somewhere else? Thanks in advance!

 

[bonepoint]

I wish I could get 2900 with my 20" 7 PRC. Also with 175 eldx and 175 Berger and I have tried several different powders. I settled at 2,770 FPS. 2800+ left strong ejector marks and 2,850 was very imprinted ejector marks and a stiff bolt.

 

[Shooter Mike]

Like you, I'm new to reloading as well- maybe 4 years in, and up until this year I've been focused on semi-auto ammo. I have had a similar experience with velocities and what I have learned so far is that the barrels used for book published load velocities are premium barrels that are extremely well maintained so as to provide a level of consistency that you and I may not experience, but will provide the manufactures of ammunition and their components wit the ability to publish safe data.

Coincidentally, I am also working with a 7PRC, and have used both H4831SC and N560. I've used H4831SC with Berger 175gr Elite Hunter, 168gr VLD-Hunter, and Hornady 162gr ELD-X. With the N560, I've used 175gr ELD-X, 175gr Elite Hunter, and 168gr VLD-H.

I get more velocity with the N560 and temp stability is at a 0.5 for me, which is very acceptable. The ELD-X bullets are faster than their equivalent Berger bullets due to a longer bearing surface of the bullets. None of my hand loads, grain-for-grain, have matched book velocities. At 66.3gr of N560 and the 175ELD-X, I was getting 2946fps using Peterson Brass and Rem 9 1/2M primers. I experience some heavier bolt lift with that load as the barrel warms up. With N560 I settled on 63.8gr and Berger 175 Elite Hunter's at 2821fps. I achieved the best accuracy and precision with that load. The 175 ELD-X were okay for me too, but I just seemed to get more fliers than with the Elite Hunter's in this particular gun.

For me personally, when it comes to ejector marks, I've learned that it can be somewhat subjective. Some bolts have double ejector pins with strong springs and will leave a mark of some sorts on nearly every case. I've began to focus more on bolt lift as a measure of sensing over-pressure. That's not to say that your rifle is the same as mine - just something else to consider.

I am currently working on some 168gr VLD-H and 162gr ELD-X with the H4831SC. The ELD-X gives me more in velocity. 65.2gr of H4831SC gives me 2916fps with the ELD-X, whereas with the 168 VLD-H I get 2831fps. Accuracy and precision with both are fine. Since I have velocity to spare with the ELD-X, I'm still tinkering (chasing my tail mostly- I don't leave good enough and well enough alone very often).

 

[SalmonSam]

Thank for the info I’ll see if I can get a hold of some n560 to try out. I would be happy with any accurate load I can work up over 2900, I just wasn’t expecting to have as much velocity loss with the shorter barrel as I seem to be getting. At published max for the h4831sc I’m right at 2800 so some experimentation seems to be in order. I’ll keep the bolt lift in mind, it definitely was getting heavier and the soft Hornady brass was showing some pronounced marks by the time I was seeing decent velocity

 

[Gadjet]

N570 sounds like the powder to use for velocity in the 7PRC.

 

[hunting1]

H1000 and H4831 never broke 2900 in my 22" barrel. 2876 was my top speed, same with the factory.

 

[brianwesson1]

Try Ramshot Grand. I found a good load at 3008 fps , Sd 8.3 with 180 eldm , Peterson brass , 215 M from a 22” C6 barrel.

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[Qholum37]

I compared H1000 and N565 at the beginning of my load development and they had similar velocity but N565 was more accurate. I have a 24” proof barrel and am using the 175 ELD-X. So far I have a good load at 2940 FPS and another that I’m planning on revisiting a bit over 3000. I really like N565. Use it in my 300 PRC and have also used it for 6.5 PRC.

 

[SalmonSam]

Thanks for the suggestions! looks like ive got some work to do haha

 

[Shooter Mike]

H1000 and H4831 never broke 2900 in my 22" barrel. 2876 was my top speed, same with the factory.

Dang. Which bullets are you using? The Berger bullets have a shorter bearing surface and they’re ~80fps slower in my gun than the Hornady ELD-X. I got 2948 with H4831SC and 162gr ELD-X bullets. Accuracy was 1.25” for 4 rounds. So it’s possible with a 22” barrel.

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[hunting1]

Dang. Which bullets are you using? The Berger bullets have a shorter bearing surface and they’re ~80fps slower in my gun than the Hornady ELD-X. I got 2948 with H4831SC and 162gr ELD-X bullets. Accuracy was 1.25” for 4 rounds. So it’s possible with a 22” barrel.

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Hornady 175gr ELDX and factory loads. I am going to bump up the charge and should break 2900. I am pretty sure the factory load is Staball but can't prove it.

 

[Bluefish]

In my recent experience 4831sc won’t make the same velocity as some of the other powders. I think you really need RL-26 to get to 2900

 

[Shooter Mike]

Hornady 175gr ELDX and factory loads. I am going to bump up the charge and should break 2900. I am pretty sure the factory load is Staball but can't prove it.

When I was choosing components while waiting on this gun to arrive, I almost chose the Staball HD, but I was talked out of it because it's a ball powder. In all honestly, I don't really have enough experience with a wide array of powders to say one way or another which type is best for a given situation. I've been very curious about the Staball HD though. I leaned heavily towards H1000, but the logic I applied to not choosing it was the burn rate compared to bullet weight and barrel length. I don't have GRT or QuickLoad, and probably couldn't figure out how to use them anyway, butI'm curious if there's any sort of ratio or formula for choosing powders as they relate to bullet weight and barrel length.

 

[Harvey_NW]

H4831SC has been pretty slow across the board for me in most cartridges except 280AI with a long slender powder column, for whatever reason. I don't have any experience with 7 PRC yet, but I have tested quite a few powders in 6.5, I would definitely suggest testing something slower like N565 or N570 if you want more velocity. VV's load data seems to be extremely conservative, so I would do some research or consult with guys that have experience with their powders in that cartridge when you go to test (or maybe give UM a call). H1000 is usually pretty close in velocity and is worth testing as well.

Also, I agree with what's stated above, Hornady brass is a little softer and will show ejector marks sooner in my experience. I would recommend getting some better brass like ADG or Peterson and it will probably give you better results. Usually get a little more speed with a magnum primer over a large rifle as well, but sometimes the velocity ES is a little higher. I don't get too wrapped up in the numbers if it doesn't seem to show up on targets.

 

[surfcleanlines]

I compared H1000 and N565 at the beginning of my load development and they had similar velocity but N565 was more accurate. I have a 24” proof barrel and am using the 175 ELD-X. So far I have a good load at 2940 FPS and another that I’m planning on revisiting a bit over 3000. I really like N565. Use it in my 300 PRC and have also used it for 6.5 PRC.

How much n565 gave you 2940 out of your 24” proof barrel? Have the same and just started dev with n565. Also, have you noticed your barrel speeding up? If so, what round count?

 

[Qholum37]

68.0 grains early on gave me right around 2940 and I just checked my notes, and I got right at 2960 with the same load at around 80 rounds. I'm now at 140 rounds but have not put it over my chrono to see how much velocity I have picked up. I hit pressure signs at 70.5 and accuracy was going south, so I took it back down to the 68.0 grain load that shot really well and that's where I think I'll stay. Obviously work up as every rifle is different.

 

[surfcleanlines]

68.0 grains early on gave me right around 2940 and I just checked my notes, and I got right at 2960 with the same load at around 80 rounds. I'm now at 140 rounds but have not put it over my chrono to see how much velocity I have picked up. I hit pressure signs at 70.5 and accuracy was going south, so I took it back down to the 68.0 grain load that shot really well and that's where I think I'll stay. Obviously work up as every rifle is different.

Thank you! Appreciate your detailed response. Curious, have you noticed any change in group sizes from your first 50 or so rounds to where you’re at now at 140?

 

[Qholum37]

It has shot pretty good since new I have not noticed anything drastic that's for sure.

 

[Wyoming Shooter]

Here are some Chrono results with 63.0 grains H4831SC and 180s. Next will try 63.5.

 

[Ohiohuntr]

I shot 63, 63.3 and 63.6 today with 4831sc with 175eldx’s. the 63 avg 2844 and shot well 63.3 was ok and not much of a velocity change, 63.6 blew a primer and stiff bolt throw