6.5-7 PRC vs 6.5-300 PRC

[SteveBurton]

I've been kicking around ideas for my next build and I wanted to build a 6.5-7 PRC with a shorter barrel, around 20-22", and shoot Berger 156 EOLs. Then I was thinking, why not add some more displacement and do a 6.5 300 PRC? I already know that the more powder you burn down a barrel the shorter it's life will be so there is no need to rehash that argument. I grabbed some info from the 'internets' about approximate case capacity which I've listed below.

6.5 PRC - 68 grs
7 PRC - 73 grs
300 PRC - 77 grs
264 Win Mag - 82 grs
26 Nosler - 93 grs

I've read were Scottw2119 was getting 3200-3300 fps with the 156 EOL out of a 6.5-7 PRC and I think I remember elkaholic saying a customer was getting 3500 fps + out of a 30SM necked down to 6.5. I'm assuming they were using 24"+ barrels. Both of those cases are well below the 264 Win Mag and 26 Nosler in the amount of powder burned and are outperforming them as well. I guess my biggest question is, at what point do you reach diminishing returns in case capacity in relation to speed? Will I be able to find a suitable powder to use in a 20-22" barrel without having a flame thrower? I'm just thinking of ways to add more speed to overcome the shorter barrel length.
Does anyone have any experience with either or both? TIA

 

[wasskeet]

FWIW, for starters I'd say there is more than 5gr difference between 6.5 PRC and 7 PRC case.

 

[stazmania]

I will build a 6.5-7prc next. I think the 7 prc is the ultimate case capacity and design for the 6.5 caliber. At the barrel length you mention I think the 300prc case extra powder volume would have very diminished returns compared to the 7 prc case. But if you want more go for it and enjoy. My 6.5-7prc will have a 26" minimum length barrel. I haven't decided if I will improve the shoulder for brass life not powder capacity yet or not but if you use the 7 case power capacity/horse power would be increased.

 

[Rodbolt]

The 264 Win Mag won't perform with even a 24" barrel, needs 26" plus imo. .284 barrels do a little better short but 30 cal and up does much better at 20-22"

I have no experience with PRC's but a lot with the 6.5x284. It has a 66-68gr water capacity so close to a 6.5PRC. 6.5X284 with a 20" or 22" barrel the fps is so close to a 260R or Creedmoor that that I wouldn't bother.

 

[wasskeet]

Here's the 6.5 PRC and 7 PRC capacities

 

[Justice1327]

Some more case capacity measurements

The Year of the 7mm…at least for me.

I have been a fan of the 7mm since my first 7mm-08 1981 Rem HV, BDL. Over the last two years I have sold many rifles and handguns; both to clean out the safe queens and make room for my custom rifles that use prefits. I finally got all but one of the 7mm cartridges I have wanted. (Still waiting...

www.longrangehunting.com

 

[7.62 Gunner]

I've been kicking around ideas for my next build and I wanted to build a 6.5-7 PRC with a shorter barrel, around 20-22", and shoot Berger 156 EOLs. Then I was thinking, why not add some more displacement and do a 6.5 300 PRC? I already know that the more powder you burn down a barrel the shorter it's life will be so there is no need to rehash that argument. I grabbed some info from the 'internets' about approximate case capacity which I've listed below.

6.5 PRC - 68 grs
7 PRC - 73 grs
300 PRC - 77 grs
264 Win Mag - 82 grs
26 Nosler - 93 grs

I've read were Scottw2119 was getting 3200-3300 fps with the 156 EOL out of a 6.5-7 PRC and I think I remember elkaholic saying a customer was getting 3500 fps + out of a 30SM necked down to 6.5. I'm assuming they were using 24"+ barrels. Both of those cases are well below the 264 Win Mag and 26 Nosler in the amount of powder burned and are outperforming them as well. I guess my biggest question is, at what point do you reach diminishing returns in case capacity in relation to speed? Will I be able to find a suitable powder to use in a 20-22" barrel without having a flame thrower? I'm just thinking of ways to add more speed to overcome the shorter barrel length.
Does anyone have any experience with either or both? TIA

Your capacity numbers are off
6.5 saum capacity is 72-73 grains
6.5-7prc will be close to 80
300 prc is 95 grains
Go 6.5 saum, I'm at 2780 with 147 eldms from a 16" barrel

 

[6.5x300 WBY]

Go over bore or go home . This speaking from a new owner of a 6.5x300 weatherby. I love it so far and just working up to pressure to see where it's at. I got 153.5 Bergers going 3135 so far with zero pressure signs. I made my next rounds for it but my Stock is at the beauty parlor getting a make over. It's stupid accurate so far

 

[MagnumManiac]

If it were me, I would go 300WSM case and never consider any PRC case.
This, and 25 cal, is what I built back in 2000/1 and was very successful, the PRC has no advantage over this case…none.

Cheers.

 

[Phil Rizzo]

Go over bore or go home . This speaking from a new owner of a 6.5x300 weatherby. I love it so far and just working up to pressure to see where it's at. I got 153.5 Bergers going 3135 so far with zero pressure signs. I made my next rounds for it but my Stock is at the beauty parlor getting a make over. It's stupid accurate so far

With a 90+ grain case there is upside to the velocity fo sho.
What I'm curious about is accuracy with that bullet at higher speeds, like 3200+
Keep us posted!
I'm tossing around a few ideas.

 

[6.5x300 WBY]

If it were me, I would go 300WSM case and never consider any PRC case.
This, and 25 cal, is what I built back in 2000/1 and was very successful, the PRC has no advantage over this case…none.

Cheers.

After I learned things from here about things I didn't know, that I didn't know.
I looked at the WSM cases and they seem to of been built perfectly decade's ago. Just the the 284 case.

 

[MagnumManiac]

With a 90+ grain case there is upside to the velocity fo sho.
What I'm curious about is accuracy with that bullet at higher speeds, like 3200+
Keep us posted!
I'm tossing around a few ideas.

I had the same trepidation when I was building my 416Rigby Improved wildcats, but I found it was unfounded as accuracy is just a manifestation of barrel harmonics and unless spun too fast, most bullets will handle far more velocity than you would think.
However, terminal ballistics is a different story, some bullets just shouldn't be pushed fast…

Cheers.

 

[Huntnful]

If it were me, I would go 300WSM case and never consider any PRC case.
This, and 25 cal, is what I built back in 2000/1 and was very successful, the PRC has no advantage over this case…none.

Cheers.

The new release of Lapua WSM brass has me wanting to make a bunch of 300 WSM parent case cartridges lol. But a 6.5-300 WSM sounds ideal.

 

[Bang4theBuck]

I've been kicking around ideas for my next build and I wanted to build a 6.5-7 PRC with a shorter barrel, around 20-22", and shoot Berger 156 EOLs. Then I was thinking, why not add some more displacement and do a 6.5 300 PRC? I already know that the more powder you burn down a barrel the shorter it's life will be so there is no need to rehash that argument. I grabbed some info from the 'internets' about approximate case capacity which I've listed below.

6.5 PRC - 68 grs
7 PRC - 73 grs
300 PRC - 77 grs
264 Win Mag - 82 grs
26 Nosler - 93 grs

I've read were Scottw2119 was getting 3200-3300 fps with the 156 EOL out of a 6.5-7 PRC and I think I remember elkaholic saying a customer was getting 3500 fps + out of a 30SM necked down to 6.5. I'm assuming they were using 24"+ barrels. Both of those cases are well below the 264 Win Mag and 26 Nosler in the amount of powder burned and are outperforming them as well. I guess my biggest question is, at what point do you reach diminishing returns in case capacity in relation to speed? Will I be able to find a suitable powder to use in a 20-22" barrel without having a flame thrower? I'm just thinking of ways to add more speed to overcome the shorter barrel length.
Does anyone have any experience with either or both? TIA

I have shortened the barrel on numerous rifles recently and have gained back most if not all of the velocity losses by switching those rifles to copper monos. Three things contribute:
1. Less engraving pressure makes more velocity.
2. Less weight needed in good quality monos that perform as designed.
3. Because there is less engraving pressure, you can typically use a faster burning powder without as steep of an initial pressure curve. Faster burning cuts down the flame-thrower and accelerates the bullet in a shorter tube.

Its worked for me in numerous cartridges