7mm 300 PRC

[canezach]

First and foremost, just in case anyone is confused, this thread is about taking a 300 PRC case and necking it down to 7mm. Call it the 7/300 PRC, the 7 PRC long, 7mm 300 PRC, whatever you want to call it.

I didn't see a reloading thread here, and while I may have missed it because of not using the right terms in the search to find it, I figured I would start one as a placeholder. I ordered a barrel from PVA for my Desert Tech during their July 4th sale, so as soon as it comes in, I'll be posting all my load development here. I have ADG brass, 180 ELDM, and a few different powders to try: Reloder 23, Reloder 26, H4831SC, and H1000. If anyone else has loads for the 7/300, let's see them! I'm anticipating 3100+ fps with the 180 ELDMs and 3200+ with RL26

 

[bcrich]

My best load is 66g of Reloder 26 with a 180g Eld & Fed 215 primer = 2,990 fps in a factory 26” Rem 700 long range
5 shot groups a hair under 1/2” @ 100yds & between factory ammo out to 2k yds my hand loads shoot better than factory .

Hornady brass

 

[Bobby Ball]

I have roughly 400 rounds down range this month. I've got chrono and strain gauge chamber pressure measurements for H1000, WinStaBall HD, N570, N565, some with both large primers, and magnum primers. Running ADG, Berger 190 LRHT, high altitude, 30" Krieger. Best group so far (4) .341 several loads with SD ranging from 2.4-4.8 found . 020-.005 and . 080 jump were working for me. Lots of loads in the 3150-3200 fps range. Id really like to get together with whoever else is doing this cartridge. I couldn't find much info at all, so I've been doing a lot of testing and recording to help anyone else who is. I just started putting some info on two other 7-300 posts, (some of it needs editing due to a scale calibration issue) but It would be great to have all the info in one spot. I don't have a long history of experience and I'm definitely not a professional shooter by any means ,but I would be happy to provide the information I have correct or incorrect. And if it's incorrect maybe someone here would be able to help me sort it out so it's more useful to everyone.

 

[canezach]

I am still waiting on my barrel from PVA, so I can't even help my own thread, but as soon as it comes in, I'll be testing Reloder 23, Reloder 26, H1000, maybe H4831SC

 

[Bobby Ball]

H1k does fairly well. I have 2 nodes that I found for mine. And it pushes fairly fast. My very first load I made up was h1k and it had a 4.3 SD. It will also run large rifle and magnum primers fairly similarly. Couple thousand more psi on the pressure with lrp. But SD is fairly similar. Been trying to get a hold of 26 but to no avail. So far the N565 is head and shoulders above everything I have tried so far for accuracy. But on the slower end speed wise. Burn rate wise everything I've tried so far is between reloader 23 and 33. N565 has been the fastest burn rate for me to date. I've been sort of hovering around retumbo range. It's been a bit of a challenge finding charges with a density getting closer to case fill and not running over pressure. 570 made for good case fill. I've been advised that the 568 was rather slow velocity wise but it should be the best case fill volume. Going to shoot more 565 this weekend. I'll post more if any of this helps you.

 

[canezach]

Please do! It's all helpful.

 

[bcrich]

Good thing ADG brass has been showing up , all my loads have been with Hornady brass but now I’m gonna start a work up with ADG .
Edit ….I think I fucked up are you guys talking about necking down 300PRC to 7mm? Because my dyslexic brain assumed 7mm PRC sorry .

 

[Bobby Ball]

I just found more and I need to order it myself. Unknown munitions has like 90 boxes left at $98 a box. The Adg cases take about 10% less charge but they have held up well. I have punished them during my steep learning curve. I'm surprised they will even still talk to me. Hahaha. I was trying to case sort them initially which took about 60 seconds when I found that basically all of them were with like 2 grains or less and I gave up on that in pretty short order. Same with the Berger bullets. I have not used any other 300 PRC brass so I don't have much to go off of, and my chamber was cut for the Adg brass so I probably won't be trying anything else anyway. I'm on my 8th firing so far on one of the boxes. No signs of giving up.

 

[canezach]

Good thing ADG brass has been showing up , all my loads have been with Hornady brass but now I’m gonna start a work up with ADG .
Edit ….I think I fucked up are you guys talking about necking down 300PRC to 7mm? Because my dyslexic brain assumed 7mm PRC sorry .

Yes, it's the 300 PRC case necked down to 7mm, or "7 PRC long", 7/300 PRC, whatever else they want to call it

 

[canezach]

I just found more and I need to order it myself. Unknown munitions has like 90 boxes left at $98 a box. The Adg cases take about 10% less charge but they have held up well. I have punished them during my steep learning curve. I'm surprised they will even still talk to me. Hahaha. I was trying to case sort them initially which took about 60 seconds when I found that basically all of them were with like 2 grains or less and I gave up on that in pretty short order. Same with the Berger bullets. I have not used any other 300 PRC brass so I don't have much to go off of, and my chamber was cut for the Adg brass so I probably won't be trying anything else anyway. I'm on my 8th firing so far on one of the boxes. No signs of giving up.

I have 200 pieces of ADG brass, so that's all I'll be using, unless I can find a good deal on Lapua brass. I've used the ADG brass for my 25 PRC and it's held up fine, and I just saw Powder Valley has Lapua brass for $1.85 apiece.

 

[Bobby Ball]

Didn't get a chance to shoot the fine tune loads this weekend. Aiming for Wednesday morning. And as a bonus windfall for the day, I found and ordered 4lbs of retumbo. So I should have data on that once it arrives.

 

[Weatherbee]

I have roughly 400 rounds down range this month. I've got chrono and strain gauge chamber pressure measurements for H1000, WinStaBall HD, N570, N565, some with both large primers, and magnum primers. Running ADG, Berger 190 LRHT, high altitude, 30" Krieger. Best group so far (4) .341 several loads with SD ranging from 2.4-4.8 found . 020-.005 and . 080 jump were working for me. Lots of loads in the 3150-3200 fps range. Id really like to get together with whoever else is doing this cartridge. I couldn't find much info at all, so I've been doing a lot of testing and recording to help anyone else who is. I just started putting some info on two other 7-300 posts, (some of it needs editing due to a scale calibration issue) but It would be great to have all the info in one spot. I don't have a long history of experience and I'm definitely not a professional shooter by any means ,but I would be happy to provide the information I have correct or incorrect. And if it's incorrect maybe someone here would be able to help me sort it out so it's more useful to everyone.View attachment 8207332View attachment 8207333View attachment 8207334

PM sent

 

[Bobby Ball]

Also if anyone needs the amp info. I'm running a #31 pilot with 031B analyze code and new ADG brass code is 0149. After neck turning I analyzed 3 cases and the new code for the thinner necks is 0146

 

[W54/XM-388]

Which sizing die steps has everyone found the best for necking it down?
I'll probably be using Lapua brass mostly.

 

[Bobby Ball]

If I remember correctly I did . 314,
.312, .311, .310
Probably way overkill, it was a first for me, so I figured what would it hurt to do an extra step or two, now I rum just the . 311 or . 310 in the sizing die. ADG and annealing every time between reloads. I run mostly the short action customs bushings, but I also have Redding. 313, .311 it was very difficult to get the sizes I wanted, so I pieced it along the way. Now I'm playing around with mandrel dimensions and bushings to find what the closest sizes are that I can use to get the neck tension I'm aiming for and work the brass the least.

 

[Weatherbee]

Here are some results for my 7-300 PRC. I actually built two of them. Both are dressed with AG Composite stocks, trigger tech diamond triggers, Nightforce NX8 SCopes. Bartlein had an TBAC Ultra 5 and the Proof had a Cortina Tuner Break. The Bartelin dressed weighs right at 10 LBS, the Proof weighs 8.5 LBS.

-24" Bartlein 1:8 Twist
-Curtis Custom Helix Hybrid Hunter

-22" Proof 1:8.4 Twist
-Defiance Anti

Shooting in Southeast Central Texas. 350 FT of Elevation

24" Bartlein - Berger 195 Grain EOL, 84 Grains of N570, Lapua Brass. 215 Primer. Average of 3180 FPS. 1/4" MOA Groups
Berger - 180 Grain Hybrid. 83.5 Grains of N570, Lapua Brass. 215 Primer. Average of 3290 FPS. 1/4" MOA Groups

22" Proof - Berger 180 Grain Hybrid. 83.5 Grains of N570, Lapua Brass. 215 Primer. Average 3190 FPS. 1/2" MOA Groups (still aint done tuning this one)

Recoil is minimal, 195 GR recoil is much more than 180. One of the easiest to tune rounds ive ever shot. Believe load development was 18 rounds on the Bartlein 24". Used same data for 22" proof. it took 12 shots working up from 81 Grains of N570.

I think you would be hard pressed to find another hunting round that is ballistically superior that doesn't come with proprietary brass. Simple neck down of 300 PRC Lapua Brass.

Brass Prep - Neck down using .311 Bushing, Redding Bushing dies, Forster Press. Chamfer and debur. No annealing, no case trim.

COAL was based on reamer prints. Reamer was based on the 195's. 3.66. Did not measure CBTO.

Load at your own risk, these are only my numbers. not responsible for any accidents for following my load data

 

[Bobby Ball]

Loading up powder ladder for Retumbo and 190 LRHT, also N565 with 184 f-class. Should have velocities and chamber pressure info in the next day or two.

 

[wadebrown]

I have a couple of 7 mm blanks on the shelf and a trued 700 receiver with a PTG bolt and would like to do a 7-300 PRC, does anyone have a reamer they would like to sell me? I did the 300-375 Ruger years before the 300 PRC came out I have 375 Ruger brass from my bear gun and a magnum Hpwa 1500 on the shelf and I thing a 7 mm little brother would a good addition to the stable.

Maybe I should have a small shelf so I would have fewer possibilities,

Thanks
wade

 

[surgeon260]

Just curious - why would someone choose this chamber over a 28 Nosler, which is commercially available and has outstanding brass readily available?

 

[fdkay]

28 nosler is geared to lighter weight bullets.

 

[canezach]

I'm still waiting on my barrel

 

[WB300]

28 nosler is geared to lighter weight bullets.

In what way??? I'm curious because I was thinking of putting a faster twist barrel on so I can run the heavies without pushing pressure and maybe getting a little better barrel life.

Am I missing something?

OP... not trying to derail. Was thinking of a 300/7 PRC or 28 Nos.

 

[fdkay]

In what way??? I'm curious because I was thinking of putting a faster twist barrel on so I can run the heavies without pushing pressure and maybe getting a little better barrel life.

Am I missing something?

OP... not trying to derail. Was thinking of a 300/7 PRC or 28 Nos.

The case is quite long, the bullets are seated deeply into the case. Most of the factory ammo runs around the 160 class bullets, though there are few 175 loads.
If you throat it long to seat the bullets out and run CIP length mags, you should be good to go.

 

[Bobby Ball]

I don't really have any arguments or reasoning as to why I have mine over 28 nosler. It just sounded cool so I figured I'd give it a shot to be totally honest. I'm really enjoying it. I'm happy with the performance. Pushing 190's right around 3200 fps. Really fun to shoot. Almost no recoil. I just did a 30 shot string of rounds I put together yesterday that held an SD of 10fps.
Also, as an update I did get the retumbo load test done and some more N595 this weekend, should have it up by tonight.

 

[Bobby Ball]

Ok got a few days of testing done with the range all to myself with great weather. I did a lot of the strain gauge data logging straight into GR Trace, and I wish I would have just had the data go straight into the Pressure trace software as I just spent the last day and a half figuring out how to calibrate the chamber pressure readings. That's why it took some extra time to get the info up. So I'll just start with the parameters.

6000' Altitude (Mountains of Colorado)
Temp 59f
Baro 29.53
No wind
102 yards

30" Krieger- heavy marksman 1.250-.90 / 8.750 twist rate / roughly 900 rounds through it
Kelbly Atlas Tactical
XLR Element C-6 buttstock (fully weighted)
Triggertech Diamond pro
Hawkins Precision one piece mount
Tract Toric 4.5-30x56
total gun weight in current form 21 lbs/ shooting prone position
Using Magnetospeed V3 for chrono
Pressure Trace2 strain gauge for chamber pressure measurements

ADG brass I think 8-9 firings to date
Trimmed 2.565
Case volume 93.5
Neck turned to .014 thickness
Annealed after every firing
Never case cleaned or tumbled, But always wiped down and primer pockets cleaned
Neck tension 2.5 thou
COAL: 3.685
CBTO: 2.940
Primer seating depth: .002

Bullets: Berger 184gr F-Open Hybrid Target (All other tests have been 190gr LRHT, but I couldn't get any more at the time)
Primers: Remington Magnum Large Rife/ sorted by cup thickness into .001 increments. 6 thousandth's variance in the box of 1k. F-ING 6! All cups used measured .132 (Again, the only magnum primers I've been able to get. With some of the other powders I have done load testing for I have also tried CCI Large Rifle and CCI #34 NATO).
Powder: For this test Retumbo. I have also tested H1000, Win Sta-Ball HD, N570, N565. I did not run up to max pressure on this test, but I did run 75, 75.5, 76, 76.5, 77, 77.5, and 78. No signs of pressure at 78. Each group was 5 shots except the final group of 80gr because I'm a case short.

I think it's important to say also that in a few of the groups I had a strange load where one single bullet would be significantly higher or lower than all of the others. as an example the very first shot of group 1 was 20 fps faster than all of the rest, so it shows an SD of 10.5 and ES of 25 but removing that one odd round makes it an SD of 2.2 and an ES of 5. Same with the last shot in group 2 which shows an SD of 18.8 and an ES of 46. removing that final shot would make the SD 5.8, and the ES 11. The final group of 78 grains shows a ridiculous SD of 35.6 and an ES of 76, but removing the bad round shows an SD of 9.3, and an ES of 17. I'm assuming it has something to do with my reloading, but I haven't pinpointed the problem. I'm not going to make any excuses or apologies, I just thought that with that large of a swing that it was worth letting whoever reads this, know not to misinterpret what might look like a bad load charge weight when despite my human error, its actually great. some charge weights were just totally awful regardless numbers wise, and didn't seem to me that they were worth investigating any further. Those two groups were 76.5 and 77gr.

75gr
max 3035 (3055)
min 3030
avg 3032
SD 2.2 (corrected)
ES 5 (corrected)

75.5gr
max 3068 (3103)
min 3057
avg 3032
SD 5.8 (corrected)
ES 11 (corrected)

76gr
max 3097
min 3075
avg 3085
SD 10.4
ES 22

76.5gr
max 3163
min 3095
avg 3128
SD 32
ES 68


77gr
max 3163
min 3030
avg 3032
SD 2.2 (corrected)
ES 5 (corrected)

77.5gr
max 3035 (3055)
min 3030
avg 3032
SD 2.2 (corrected)
ES 5 (corrected)

78gr
max 3159
min 3142
avg 3148
SD 9.3 (corrected)
ES 17 (corrected)

I'll add more later and if anyone needs detailed info I'm more than happy to share. Hope this helps.

 

[6cmShooter]

I just got my 7-300prc prefit barrel in. I'm wondering if I can use a standard 300 prc headspace gauge to check it when I install it on my action.

 

[Weatherbee]

Yes

 

[canezach]

I'm still waiting on my barrel from PVA that I ordered during the 2023 July 4th sale, so hopefully @bohem Has an update for me

 

[FredHammer]

I just got my 7-300prc prefit barrel in. I'm wondering if I can use a standard 300 prc headspace gauge to check it when I install it on my action.

They are spec'd by the parent case, so it would work. Like the 308 WIN headspace will work for .243, 7mm-08, etc.

 

[FredHammer]

I'm still waiting on my barrel from PVA that I ordered during the 2023 July 4th sale, so hopefully @bohem Has an update for me

Even with their move, this seems like a long delay for them. Call Ben and get a status.

 

[timmyb]

I'm still waiting on my barrel from PVA that I ordered during the 2023 July 4th sale, so hopefully @bohem Has an update for me

I'm in the same boat with you, waiting on two DT barrels from the July 4th sale.

 

[canezach]

I'm in the same boat with you, waiting on two DT barrels from the July 4th sale.

Same. That 7/300 barrel is for my DT