Mcwhorter 7SPRC rifle

[vancewalker007]

Can someone help me with this? After talking with mcwhorter, they are using 58-59 grains of rl26 to get 3k fps from a 180 grain 7mm. The max load from hornady of rl26 is 55.6 grains pushing a 140. 58-59 grains seems like it would generate serious pressure. Thoughts?

I would like to see some pressure data on this. Maybe the extra .5mm of bore relieves some of the pressure, but I know from experience with a 7mm LRM (like a stretched PRC) that +3000fps can be reached but with heck of lot more powder. Maybe they are using a +P chamber ...? I'm shooting 71.7gr of H1000 and barely reaching 3000fps. Maybe I have a slow barrel.

 

[fish2keel]

I haven't been provided pressure data. I can request it.

It might be best to wait until the real 7mm prc comes out, if ever.

 

[hicountry1]

7 SAUM ish....

 

[LVJ76]

I would like to see some pressure data on this. Maybe the extra .5mm of bore relieves some of the pressure, but I know from experience with a 7mm LRM (like a stretched PRC) that +3000fps can be reached but with heck of lot more powder. Maybe they are using a +P chamber ...? I'm shooting 71.7gr of H1000 and barely reaching 3000fps. Maybe I have a slow barrel.

You should talk to @elkaholic a little more about his 7 SS

 

[elkaholic]

You should talk to @elkaholic a little more about his 7 SS

Somewhere between 80,000-100,000 depending on which detractor you listen too!
So if you use the common argument of straight capacity, with the ss being 73+ grs
and the prc being 69+, that would likely be 85,000-105,000 for the prc, but then it isn't even an improved case so
it could be slightly higher!
I think McWhorter knows enough about what he's doing that I wouldn't worry about it,
is the non sarcastic answer. Just work up slowly in your rifle and decide for yourself, or get an experienced reloader to help you
if you're not comfortable.

 

[vancewalker007]

Somewhere between 80,000-100,000 depending on which detractor you listen too!
So if you use the common argument of straight capacity, with the ss being 73+ grs
and the prc being 69+, that would likely be 85,000-105,000 for the prc, but then it isn't even an improved case so
it could be slightly higher!
I think McWhorter knows enough about what he's doing that I wouldn't worry about it,
is the non sarcastic answer. Just work up slowly in your rifle and decide for yourself, or get an experienced reloader to help you
if you're not comfortable.

Oh I'm not worried, hahaha. I think what we see here is 1. The efficiency of a short fat case and 2. The limit of diminishing returns of a hair more powder. The 180 VLD H in the 3 7mm LRMs I have loaded for only get 50-70fps more velocity out of 10-11gr more powder using a 180 VLD H over the numbers McWhorter is showing. So if you can reliably and safely get 3000fps or better out of a 180 VLD from 10-15% less powder than it takes to get 3080ish fps I say that's a win. I think a lot of people under estimate the value of that short fat case structure.

I never used RL26 in the LRMs so maybe that powder would jump the fps some but I still think 70-71grs is in that diminishing returns region where you need maybe 5-8 more grs for a more meaningful velocity jump.

 

[BoomFlop]

@elkaholic is the king of efficient case designs that actually function in the appropriate action (SA/LA). Also, using case design and brass that handle pressure well will also provide an increase in pressure and still be safe. Most of your BR cases are being pushed much higher pressures that many cases are in competition and still providing numerous reloads. Common sense in reloading applies to all cartridges. I see a lot of velocities in SAAMI cartridges that are probably far more dangerous than some of the wildcat cartridges.

The 7 SPRC (not sure what the S means?) would still probably benefit or be better suited for a long action. If they are putting it in a short action, and still getting 3000 fps from a 180, pressure is going to be pretty high. Obviously, it is working for them.

Steve

 

[fish2keel]

Steve, the S stands for short, short PRC. It is in short action technically.

 

[Browning460]

Hey guys just ordered on today can wait till I get it in.

 

[Roughrice]

Hey guys just ordered on today can wait till I get it in.

The McWhorter in 7 PRC?

 

[Browning460]

Mcwhorter in 7mmsprc yes sir

 

[Roughrice]

Great! Keep us updated!

 

[Browning460]

Will do

 

[Jzeblaz]

Any updates or still waiting?