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McGuire Ballistics 6.5 PRC load workup!

KH_Outdoors

KH_Outdoors

Well-Known Member
Joined
May 28, 2022
Messages
538
Location
Iowa
I've been testing some new mono's here recently and thought I would share the next "workup" in line. So far I've tested a couple different projectiles from McGuire Ballistics and just had great luck. Hope you enjoy!

This will be with my TS Customs 6.5 PRC.

Rifle Specs:

TS Built 6.5 PRC
Lone Peak Fuzion ti Med
22" Carbon Sendero light
Triggertech Special
KS1 TS exclusive stock
Hawkins bottom metal & goodies!
AB Raptor 6 +1" reflex


Components:

ADG 1x fired Brass
125 Copper Rose
N560 (to start)
CCI250
 

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Starting out with a quick throat measurement. My chamber is a standard chamber for reference.

COAL @ the lands: 3.0000", I'll start about .030" off the lands (2.970" COAL)

Initial N560 charge ladder: starting 56 gr, up to pressure in .5 gr incremental increases

The goal is to achieve best accuracy & speed. I've had really good luck with N560 in "light for caliber" mono's, as well as "shorter" barrels. My buddy Steve @Huntnful had good luck with N560 in his last 6.5 PRC's too!
 

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Work up in hot temps as 560 will bite you with its temp sensitivity.

I've thought about trying some of the 270 offerings they have. I probably will after I do some more shooting with the CEB Lazers.
 
Idaho Trecker said:
Work up in hot temps as 560 will bite you with its temp sensitivity.

I've thought about trying some of the 270 offerings they have. I probably will after I do some more shooting with the CEB Lazers.
Click to expand...

Looking like 30-50's F for my working temps here. I will definitely be cautious and document as I go. If N560 doesn't pan out I may try N555 also for that reason. N560 is what's on hand, so hey... let's see how it does!
 
Sounds like a good plan! I just started work-up with N555 in my original 300ss with lighter weight bullets (178 eldm). So far I'm liking it through my pressure test. I have some loaded for groups now. Maybe I'll freeze a few and get a baseline temp sensitivity. If 555 pans out I've been thinking of trying it in my 33 nosler too.
 
I've heard it's a great powder and very stable. I'd love to try it in something. That may be one of the powders I try in my next 338 project too
 
Idaho Trecker said:
Sounds like a good plan! I just started work-up with N555 in my original 300ss with lighter weight bullets (178 eldm). So far I'm liking it through my pressure test. I have some loaded for groups now. Maybe I'll freeze a few and get a baseline temp sensitivity. If 555 pans out I've been thinking of trying it in my 33 nosler too.
Click to expand...

If you think of it, let me know how it shoots for you. I've heard N555 works really good in these smaller cases. Didn't Erik Cortina set some F Class records with it?
 
I will. I don't know what you decided for your next 338 build... I won't derail this thread on the 338 stuff.

Some small amount of data I have on n555 isn't at all conclusive but more apples to oranges so far. I think you would do well with n555 in your application here.

300ss 178 eldm virgin brass is the 40 degree but I'm shooting it in the first rifle chambered for it which has a very different chamber than now so I still fireformed it going easy. My fireforming load was 59 grains of h4831sc with a .030" jam gave me 2720 fps. Once fired with a .015" jump of the same 59 grain load of n555 gave me 2864 fps and no perceived pressure signs. Like I said not a direct comparison between powders but I like it so far. Temp testing to come.
 
Idaho Trecker said:
I will. I don't know what you decided for your next 338 build... I won't derail this thread on the 338 stuff.

Some small amount of data I have on n555 isn't at all conclusive but more apples to oranges so far. I think you would do well with n555 in your application here.

300ss 178 eldm virgin brass is the 40 degree but I'm shooting it in the first rifle chambered for it which has a very different chamber than now so I still fireformed it going easy. My fireforming load was 59 grains of h4831sc with a .030" jam gave me 2720 fps. Once fired with a .015" jump of the same 59 grain load of n555 gave me 2864 fps and no perceived pressure signs. Like I said not a direct comparison between powders but I like it so far. Temp testing to come.
Click to expand...

Nice! I'll start another thread on the 338 soon, appreciate that man 🤙🏽
 
Got out and ran my initial charge weight ladder from 56 - Pressure. I'm pretty stoked with the speeds I'm seeing with N560. Also notable, every round landed inside of a 1" square at 100 yards. Most of them under 1/2" untill it got closer to pressure, that's promising!

Velocity- N560/125 CR workup

56 - 3123
56.5 - 3105
57 - 3137
57.5 - 3156
58 - 3194
58.5 - 3205
59 - 3246
59.5 - 3263
60 - 3300
60.5 - 3342 - *heavy bolt lift & click*
61 - DISCONTINUED

From here I'm going to back off 1 full grain from initial pressure signs at 60.5 to 59.5 gr and start shooting groups. Probably 58, 58.5, 59, 59.5 and record velocities, looking at groups etc...

Looking good between that 3200-3300 fps range!
 

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Last edited:
Phil Rizzo said:
That's quite fast for a 22" barrel.
I wish n560 was temp stable, real bad!
Click to expand...

Surprised me! I'm not married to N560 though. Just have a bunch of it... so if it works out, great! If not, lots of other options out there. Giving it a fair chance for now.
 
First groups with the 125 Copper Rose & N560, it's looking like a winner!

20240227_093037.jpg


Velocities & such:

58 gr - .681"

Average - 3182
ES - 22
SD - 11.2

58.5 gr - .430"

Average - 3211
ES - 22
SD - 11.3

59 gr - .166"

Average - 3245
ES - 9
SD - 4.6

59.5 gr - .705"

Average - 3281
ES - 5
SD - 2.6

To be honest, I would feel comfortable hunting with any one of these combinations. 59 gr of N560 seems like a clear choice though, so I'm going to load up the rest of what I have at 59 gr N560 for BC testing and accuracy at distance.

So far 3245 fps and 1.5 gr below pressure drilling small groups AND suppressed with extremely low recoil. Looking better and better with each outing.
 

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