300WM experiment using McGuire 178 gr Copper Rose bullets

KonoctisWigwam

Well-known member
Joined
Sep 3, 2025
Messages
90
Location
Kelseyville, CA
I'm currently hobbling together this 300WM, and waiting on a trigger. My plan is to move the barreled action into a Long Action Fierce Carbon Rogue stock, but I quickly realized that I need a .400" thick recoil lug, that's a whopper! :oops:

McGuire makes both Mag Fed and Sensitive Single Fed bullet in the same length/weight. On their 168 gr CRs, they offer a long sensitive bullet, but AFAICT, their other bullets are the same length for both. Both are solid tips.

CRs are expanding, not fracturing. In this regard, they are not like Hammer, Cutting Edge, Lehigh Defense, Maker, et al, as those are fracturing bullets. Those use the theory that the petals shed and create a massive EDIT: wound channel. The 8.6 blackout is pretty amazing in that regard, as the fast twist causes Barnes TTSX bullets to shed their petals. It is amazing how massive the subsonic petals are. The fracturing bullets leave a solid slug for pass through, after the petals have been shed, so you end up with a mini-solid, similar to solids used on Dangerous Game in Africa. But we're not talking 8.6 blackout here, we're talking 300WM.

What I am trying to do is have an extended single fed bullet in the chamber of my rifle, with the intention that this is the bullet that will kill the game, and then I have 3 mag fed bullets to followup with.

These are both Copper Rose bullets, and the mag fed rounds are set to 3.430", which is the longest that will fit in the mag. I am still shy a few parts to pull this together, and it requires fastening several components with a torque wrench, and being able to measure, etc.., but that stuff is in transit. I have extended the single fed bullets out to 3.650", based on how it seats to the next cannelure. I like to think of it as giving an extended life to the 300WM. This looks like a modern bullet, and the BC is crazy on these CRs, McGuire Ballistics states these as having a .600, where all the rest of the bullets are much lower, in the 400s, 500s tops.

I am testing a ladder for both H4831SC and Reloader 23. I'm using H4831SC in 6.5 PRC with CX and LRX bullets.

Sam says he thinks the mag fed as having less pressure, but that doesn't seem right to me, since seating the bullet farther should create more pressure, I thought, but I will be testing this with a LabRadar to make certain, maybe Sam is correct, he seems to know his bullets pretty well.

On the left is set to mag length max, 3.430", and on the right is a single fed bullet set out to 3.650". However the powder/pressure works out, I want to use the single fed in the chamber and the mag fed in the mag. An accurate load with the mag fed will get me a hunting round, but my plan is to use my 6.5 PRC as my primary hunting rifle this year. My 300WM is my backup.

300wm-178cr-mf-vs-sf.webp


This shows my loads, I'm moving the last ladder test for H4831SC to be in the range listed on the Hornady app for 176-180 grain bullets.
300wm-load-development.webp


My loads are using Peterson Long Brass, CCI 34 Primers, McGuire 178 Copper Rose bullets, and both H4831SC and Reloader 23 as the powder.
300wm-load-development-178cr.webp


I don't have a trigger on my Remington 700, but do have a scope mounted on it. I have a better, but non-illuminated scope to put on it, but need a picatinny rail. The trigger is in the mail, as-is a magazine. When I convert the 300WM over to the Fierce Carbon Rogue stock, which is an M5 bottom metal, I am going to use a Hawkins Hunter Mag, it will hold 3 Magnum rounds. I will have similar to the DBL which holds 3 also, but will be able to have different rounds I can swap out with a mag. I only plan to have 2 mags. If I can't drop game with that ammo, I need to get another hobby...🤷‍♂️
 
Last edited:
Well, that didn't take too long...I'm pulling all of these bullets and reloading them with H4350, which I only have 1 lb. of, per a McGuire enthusiast on LRH (ButterBean). Lee said not to worry about the COAL, and seat them the same. The only difference is the SF bullets are too sensitive to feed in a mag.

He also uses the 168 CRs.

So, to the shop I go, to dig out my H4350, and pull these. Still misting up here, hope it's dry for you guys. Good day to hunt, IMO. 🤔
 
I’m right there with you on pressure...Seating deeper generally lowers it since it boosts the case volume, but it’s not always straightforward. I've experienced some surprises depending on the bullet design and how the powder burns. LabRadar will reveal the real deal, and I’m eager to find out how H4831SC measures up against Reloader 23 in your setup. Personally, I've had great success with H4831SC in my 6.5 PRC too
 
I’m right there with you on pressure...Seating deeper generally lowers it since it boosts the case volume, but it’s not always straightforward. I've experienced some surprises depending on the bullet design and how the powder burns. LabRadar will reveal the real deal, and I’m eager to find out how H4831SC measures up against Reloader 23 in your setup. Personally, I've had great success with H4831SC in my 6.5 PRC too
I can test that further, but I pulled all of the 300WM loads and ready for round 2 using H4350.

I have more wiggle room on 6.5 PRC, and here's why...I have a combo box of 50 using 125 Copper Rose bullets, and I have an extra 25 Single Feed bullets, where 300 WM, I only have a combo box of 50 (25 MF and 25 SF).

I also have 2 boxes of Peterson Brass for 6.5 PRC, where I only have 1 box of Peterson 300WM brass.

I also have load data from the Hornady app to give me a start, using both H4831SC and Reloader 23.

Ready for round 2 on 300WM, this is what was recommended as XLNT powder for 300WM, by an acquaintance on LRH.

300wm-ready-for-round-2.webp
 

Latest posts

Back
Top