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7-300 PRC Initial Results - Winner

iceng

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7lrm has quite a bit more taper and a longer neck. The 7lrm has 87gr powder capacity, whereas the 7-300prc is closer to 94. The prc will still have a 300" long neck.
Thanks. This excites me. Built a few 300prc, may have to get a 7prc and have an experiment to get some data. Would be nice with 180gr Berger @ 300 zillion fps.
 

TrevK

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Feb 25, 2020
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If I can bump a couple of month old thread, what’s the consensus? Been reading all I can about the 28 Sherman, the 7/300prc, the 7lrm with adg brass, and 28 nos with 400mod bb barrel ideas.. I’m brand new to reloading so I can’t take in 100% of the convo but unless hornady makes the 7prc. This might be the route I go down one day since it seems easier than some others! Almost forget the 7 blaser mag! How do some of you guys feel this 7/300(7prc) stacks up now that you have time under your belt?
 
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Westernhntr

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If I can bump a couple of month old thread, what’s the consensus? Been reading all I can about the 28 Sherman, the 7/300prc, the 7lrm with ash brass, and 28 nos with 400mod bb barrel ideas.. I’m brand new to reloading so I can’t take in 100% of the convo but unless hornady makes the 7prc. This might be the route I go down one day since it seems easier than some others! Almost forget the 7 blaser mag! How do some of you guys feel this 7/300(7prc) stacks up now that you have time under your belt?
I'm with you
I'd love to hear some feedback on this round in 20-22" barrels
 

BruntBronze

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Oct 8, 2019
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Well the point of having available brass and a small case change makes it winner for 7mm-300 PRC. I already have a wildcat better than what's listed, but I don't like the pain of getting brass and fl sizing.

It's an easy do and if criterian or Shilen can be motivated to make prefit barrels. I run 1:8 twist which is no good for the eldm 180gr. My plan of using 197gr SMKs is also not going well (they need jump or get random spikes in pressure).

Once I start playing with it again AND Berger bullets come available, I work the rifle again.
 
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iceng

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I just had a customer bring me a 7-300prc reamer and a barrel to fit up.

Will be interesting to see how it goes, I'm super keen to do a spare barrel for myself, but don't have dies to use with it (no bushing 300prc dies currently).
 

TrevK

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I just had a customer bring me a 7-300prc reamer and a barrel to fit up.

Will be interesting to see how it goes, I'm super keen to do a spare barrel for myself, but don't have dies to use with it (no bushing 300prc dies currently).
Might as well. I’ve been known to have spare engines and transmission that are ready to run, but no project car for them to go in.. yet!
 

bodhisafa

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Bought Lapua brass for my 7-300 prc for my project, it will be a hunting single shot action. I haven’t decided which action to use yet.
 

bodhisafa

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Has anyone tried L E Wilson inline seater dies for their 7/300PRC.

I am wondering if I can just buy their 300 PRC seater to use for this project
 

Westernhntr

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I have lapua 300 PRC brass, which bushing size do I need to step down to 7mm?
I used my 7wsm fl bushing die to size a couple 300 prc cases down with a 315 bushing.
It was just for fun to see how it'd turn out, and it actually worked really well.
One thing I'll say about sizing down with bushings is that the entire neck won't get sized uniformly, you'll end up with a greater neck diameter of approx .005 or more near the shoulder junction.
Also reducing neck diameter more than .006 at a time will cause issues with runout
personally I'd get a cheap FL 7 saum die and use that for your initial sizing.

I'd neck turn after sizing down to take the donut off.
After you've loaded a few rounds measure the neck diameter and subtract .002 for the correct bushing size.
One thing I'd also do is measure the diameter of a fired case and make sure you're getting .004-.006 neck expansion.
If its too tight turn more off the necks

Here's a case I sized down with the 7 wsm die
20210626_092103.jpg
 

Westernhntr

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I'd do it in two steps to prevent a bunch of runout. When I did mine I used a 322 bushing, then ran it into a 7 saum neck sizing die to get it sized down all the way to the shoulder then ran a 282 mandrel to neck it back up for seating. This worked well as there was 2-4k runout after all said and done. Bushings will not size it all the way to base of neck/shoulder junction. And this may prevent chambering depending on how tight the headspace is to normal 300prc dimensions.
Shit I saw your post after writing mine...
Good advice 👍
 

bodhisafa

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I used my 7wsm fl bushing die to size a couple 300 prc cases down with a 315 bushing.
It was just for fun to see how it'd turn out, and it actually worked really well.
One thing I'll say about sizing down with bushings is that the entire neck won't get sized uniformly, you'll end up with a greater neck diameter of approx .005 or more near the shoulder junction.
Also reducing neck diameter more than .006 at a time will cause issues with runout
personally I'd get a cheap FL 7 saum die and use that for your initial sizing.

I'd neck turn after sizing down to take the donut off.
After you've loaded a few rounds measure the neck diameter and subtract .002 for the correct bushing size.
One thing I'd also do is measure the diameter of a fired case and make sure you're getting .004-.006 neck expansion.
If its too tight turn more off the necks

Here's a case I sized down with the 7 wsm die
View attachment 7655453
What’s a good neck turning equipment without going to crazy with the price
 

Westernhntr

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What’s a good neck turning equipment without going to crazy with the price
I use a k&m turner with a power adapter to use with a drill, pretty cheap and easy to use.
You'll want a 7mm pilot mandrel for the turner, and a lee auto-prime magnum shell holder.

Before you neck turn you'll need to run each case through a .284 expander mandrel, then set your cutting depth and get to turning.
Make sure to lube the pilot or case necks with imperial sizing wax

I use 21st century mandrels and die cuz they're available in .001 increments for neck expanding, after sizing down with whichever bushing you end up using you can select an expander that's .001-.002 under bullet diameter.

https://21stcenturyinnovation.com/
https://www.precisionreloading.com/cart.php#!c=188
 
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bodhisafa

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I used my 7wsm fl bushing die to size a couple 300 prc cases down with a 315 bushing.
It was just for fun to see how it'd turn out, and it actually worked really well.
One thing I'll say about sizing down with bushings is that the entire neck won't get sized uniformly, you'll end up with a greater neck diameter of approx .005 or more near the shoulder junction.
Also reducing neck diameter more than .006 at a time will cause issues with runout
personally I'd get a cheap FL 7 saum die and use that for your initial sizing.

I'd neck turn after sizing down to take the donut off.
After you've loaded a few rounds measure the neck diameter and subtract .002 for the correct bushing size.
One thing I'd also do is measure the diameter of a fired case and make sure you're getting .004-.006 neck expansion.
If its too tight turn more off the necks

Here's a case I sized down with the 7 wsm die
View attachment 7655453
After initial neck sizing(7saum), which full length sizer would be good for follow up reloads?
 

bodhisafa

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I'd use a 300 prc fl bushing die with the appropriate bushing that's. 002 less than your loaded neck diameter
I’m going to have Forster hone one of their FL 7 saum sizers, what neck diameter should I specify to neck Lapua 300 prc brass.
This is for initial sizing
 

Westernhntr

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I’m going to have Forster hone one of their FL 7 saum sizers, what neck diameter should I specify to neck Lapua 300 prc brass.
This is for initial sizing
Hmm thats kind of a tough one since the brass will become thicker after sizing down.
I'd think .315 would be a safe bet, that's what my necked down Hornady case measures with a bullet seated.
What you could do is neck a case down then run a .284 expander through it and see what you get for a diameter
 

bodhisafa

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Here is a generic version JGS came up with for my reamer print. I have never made a custom reamer which is why I am posting here. Could you gents critic this reamer version and give me suggestions.

gun info:
Single shot and I will be using the 184 + eight 7mm bullets. 8 twist.

reamer wish list:
1.I would like the bullet to seat appropriately in the neck to avoid donut and still chase lands as needed. it’s fine if it’s a long coal.

2.the body dimensions to remain as parent 300 prc

3. I don’t want a tight neck, something appropriate, I have lapua 300 prc brass to use for this project. While using some calipers I am getting .015 neck thickness reading. I know it’s not the most scientific way but it’s all I have.

F08ADBB7-EE6C-443D-BCCE-FAF4D5E13B16.png
 
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For those of you with the 7 x 300 prc, what freebore for the 190 Berger? Thanks in advance
 

stilts75

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Hello Gentleman,
I have reached out to PTG and JGS. Both have quoted long lead times on a reamer. Anyone willing to sell, rent or loan their reamer? I’ve got my barrel on the way and don’t really care to wait 3 months.
Thanks in advance.
 

Joseph Floerke

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I'll be doing most updates on my FB page so feel free to follow there but I've also copied all the initial data below.


Some of you may know that I had a reamer made to neck down the new 300PRC to 7mm to see what it would do. I.e. A 7-300prc . I got it back from Alamo Precision Rifles on Friday and was able to put about 30 rounds on it so far and the results are impressive. The case shape and length provides some added benefits over the 28 nosler imo. Speed wise it seems to me that it can easily match or beat the 28 nosler with less effort and lower pressure loads. The 28 nosler advertises it can run a 175 around 3125 and but I'm hearing guys say 195s at 3140-3150 with faster powders and in sure this is a warm if not hot load. I'm curently pushing 184 bergers at 3175 with a slow powder and zero pressure and the Barrel isnt even broken in yet. At these speeds it should already run a 195 at 3140-3150 and also no pressure.I played with it a bit over the weekend using retumbo and 8133 and with 82gn 8133 which is a slightly compressed load, Im at 3173 avg with an SD of 4.5 with 184 hybrid. Barrel is a 28" Hawk Hill Custom :) No pressure even with water test. For those that dont know, the water test is pouring water on the case to simulate shooting in rain and if you have a hot load you'll blow primers and get a locked up or hard to open bolt in a heartbeat. I had zero issues and it opened like a normal round. Retumbo is a bit faster still no pressure. This thing is stupid light recoil for the speeds. My original goal with this was to push a 180 pill at a mild 3100-3150 with a powder that gave me almost full case fill and no pressure and it seems to be working spot on for that. Ill post more as I keep testing. brass life test with the same load made it to 7 firings before I had indications of loose primer and thinning case web. I think with something like RL26 or H1000 you could probably push a 180 in the high 3200s to mid 3300s or a 195 around 3200 without being too hot of a load.

Update 1 - 7x firings with 81.4 of 8133 was averaging 3155 with the 184. Everything felt good until the last resize and primer went in pretty easy. Checked the case and saw the faint line of death around the base. Checked the inside and you can feel it getting thin. I wouldnt push it past 5 to be safe depending on your load.

Also realized the Hornady 300 PRC sizing dies are no good. They dont size far enough to the base at all even if you push a piece back to factory dimensions. Hornady you better check your PRC dies or you're going to have a lot of people pissed off they have a sticky bolt on any reloads because your dies arent sizing enough. They arent even changing the dimensions of the case anywhete close to the base from a fired piece to resized . I thought they were sizing way to easy for such a large case and now we know why. They need fixed ASAP.

Update 2 - Between the seating die being a bad design imo which also doesnt work with a Forester Co-AX without chopping down the seating stem, the fact that the sizer doesnt size properly or that the hole diameter for the bushing is massively oversized and causes crazy amounts of neck runout unless you teflon tape the bushing, I'm done with the Hornady "Match Grade" dies. Unfortunately they were the only ones making PRC dies when I needed to get them. I'll probably give them away at some point or maybe do something really silly with them out of frustration. I spoke to Dan Warner today at Warner Tool Company and I'm going to have him make me a set of custom dies. If you havent seen their custom dies, they truly are a work of art with no comparison. I've been considering a set of his dies for a while now and finally going to pull the trigger.
What freebore is your reamer?
With the 195s will they fit in a CIP magazine?