6.5 PRC Case Capacity

[wp06]

Hi all.

Can you guys please drop your 6.5 PRC case capacities and what brass you are using in the reply's.

I am using Norma LRP 6.5 PRC brass and I seem to be getting significantly higher H2O case capacities than most of the stuff I see online, I measured my cases at 70.70gr H2O after it being fired 1x and full sized.

 

[acourvil]

ADG virgin 67.1
ADG once fired 68.3

 

[straightshooter1]

Hi all.

Can you guys please drop your 6.5 PRC case capacities and what brass you are using in the reply's.

I am using Norma LRP 6.5 PRC brass and I seem to be getting significantly higher H2O case capacities than most of the stuff I see online, I measured my cases at 70.70gr H2O after it being fired 1x and full sized.

Be aware that "case capacity is not the same as cases volume. Case capacity is the amount of available space for powder in the case with a seated bullet, which of course, varies accordingly. Case volume is measured to the case mouth rim and what is typically published. You'll want to know what that volume is for a fired case, like acourvil above shows for his ADG fired brass. ADG brass typically as less volume than other brass. I would expect your Norma brass to have a volume of something like 68.8 gr. H2O. Over 70 grs sounds way too high and makes me suspect something going on with the scale you're using.

 

[HerCoStarNTheBeaverPictur]

I just tried a quick measurement on once fired (and sized) lapua. I got 65.7gr

*that’s with an old beam scale

 

[straightshooter1]

Reply

I just tried a quick measurement on once fired (and sized) lapua. I got 65.7gr

*that’s with an old beam scale

This chart from Peterson Cartridge company illustrates quite well how much variance there can be from one lot to another:

 

[Holliday]

Hornady 1x fired: 70.1 grns H20, case length 2.026” 3 case avg

ADG 1x fired: 69.43 grns H20 case length 2.02” - 3 case avg.

Fired in Seekins PH2

 

[straightshooter1]

Just as a comparison . . .

Case volume for my Hornady brass with a case length of 2.024, 2X fired, is 68.8 grs H2O (10 case average with the high being 68.9 and the low at 68.6).

Those who have 70 grs of H2O, I wonder what the case diameters are, as I can see where a chamber with more space can enlarge a case to produce more case volume.

 

[Holliday]

Just as a comparison . . .

Case volume for my Hornady brass with a case length of 2.024, 2X fired, is 68.8 grs H2O (10 case average with the high being 68.9 and the low at 68.6).

Those who have 70 grs of H2O, I wonder what the case diameters are, as I can see where a chamber with more space can enlarge a case to produce more case volume.

I would say that is the likely answer. I did not see what you are shooting them in?

 

[straightshooter1]

I would say that is the likely answer. I did not see what you are shooting them in?

It was a Preferred Barrel Blanks barrel on my RPR. The factory barrel was used to fire form the Hornady cases then used the PBB barrel for subsequent firings and there were no difference in case dimensions that I could determine.

 

[Holliday]

It was a Preferred Barrel Blanks barrel on my RPR. The factory barrel was used to fire form the Hornady cases the used the PBB barrel for subsequent firings and there were no difference in case dimensions that I could determine.

What I can glean on this topic from reading multiple threads on other forums goes as follows.

Apparently the PRC cartridges have a known issue of becoming oversized at the base by the 3rd or 4th firing. This in turn, resulting in the infamous “clickers”. This issue is noted to be most common with heavy/hard brass like ADG.

Apparently, the best fix for this was an oversized reamer that people started using and then some barrel manufacturers(most?) at some point started using as well. Since my Seekins is a hunting rifle, in production for a while, I’m leaning towards them using the larger reamer.

I have not yet definitively determined if my Seekins used an oversized reamer, but I will say I bought a reloading block from joffer.com and had to send it back for them to enlarge the holes. My 1x fired brass simply would not fit. They seemed as baffled by this as me.

Perhaps yours is a match chamber, either older or simply not oversized.

This might explain the discrepancy.

 

[wp06]

Be aware that "case capacity is not the same as cases volume. Case capacity is the amount of available space for powder in the case with a seated bullet, which of course, varies accordingly. Case volume is measured to the case mouth rim and what is typically published. You'll want to know what that volume is for a fired case, like acourvil above shows for his ADG fired brass. ADG brass typically as less volume than other brass. I would expect your Norma brass to have a volume of something like 68.8 gr. H2O. Over 70 grs sounds way too high and makes me suspect something going on with the scale you're using.

Oooohh ok, yes I meant "Case Volume".
And I used a RCBS Chargemaster Link scale that is leveled and calibrated.

 

[wp06]

Just as a comparison . . .

Case volume for my Hornady brass with a case length of 2.024, 2X fired, is 68.8 grs H2O (10 case average with the high being 68.9 and the low at 68.6).

Those who have 70 grs of H2O, I wonder what the case diameters are, as I can see where a chamber with more space can enlarge a case to produce more case volume.

I just measured my 3x fired Norma LRP brass at .532'' at the base, which is exactly the same as saami specs.

 

[wp06]

I just re-measured my cases now with it being 3x fired, and this is what I got:

1. 71.3gr
2. 71.6gr
3. 71.5gr
4. 71.2gr
5. 71.4gr

avg - 71.4gr

 

[straightshooter1]

I just measured my 3x fired Norma LRP brass at .532'' at the base, which is exactly the same as saami specs.

My fired Lapua brass measures .533, and .5325 after being sized. Just at the shoulder-body junction, the fired cases measure .518 and .515 after being sized.

What's your case trim length? And what is the measurement from base to shoulder datum?

 

[wp06]

My fired Lapua brass measures .533, and .5325 after being sized. Just at the shoulder-body junction, the fired cases measure .518 and .515 after being sized.

What's your case trim length? And what is the measurement from base to shoulder datum?

My case trim length is 2.020''.

3x Fired Brass Base to Shoulder Datum: 1.643''

This was measured with the hornady .420 collet.

 

[straightshooter1]

My case trim length is 2.020''.

3x Fired Brass Base to Shoulder Datum: 1.643''

This was measured with the hornady .420 collet.

Measuring my fired Lapua brass (fired 14 times so far) with the Hornady .420 collet, I get 1.639" and my trim length is also at 2.020" and when sized it's 1.638. Assuming your caliper is measuring as accurate as mine, that difference seems to account for a significant amount of difference in our case volumes???

Measuring some of my Lapua virgin brass (never fired), they measure 1.635.

 

[wp06]

Measuring my fired Lapua brass (fired 14 times so far) with the Hornady .420 collet, I get 1.639" and my trim length is also at 2.020" and when sized it's 1.638. Assuming your caliper is measuring as accurate as mine, that difference seems to account for a significant amount of difference in our case volumes???

Measuring some of my Lapua virgin brass (never fired), they measure 1.635.

I got another question for you.

When I reloaded my brass for the 3rd time I noticed that the primer pockets are also not as tight as I'd like to see for x3 brass compared to my 6.5 CM and 22-250REM that I also reload for.( I don't think I'm gonna get x10 firings out of them)

Have you had any experiences similar to this??

I don't think my load is that hot, here is my load that I have used for the entire time:

147gr ELD-M - 3.003"
VV N560 - 56.0gr
Norma LRP Brass
Federal 215M
Velocity - 2900FPS


this is with a 24" barrel.

 

[straightshooter1]

I got another question for you.

When I reloaded my brass for the 3rd time I noticed that the primer pockets are also not as tight as I'd like to see for x3 brass compared to my 6.5 CM and 22-250REM that I also reload for.( I don't think I'm gonna get x10 firings out of them)

Have you had any experiences similar to this??

I don't think my load is that hot, here is my load that I have used for the entire time:

147gr ELD-M - 3.003"
VV N560 - 56.0gr
Norma LRP Brass
Federal 215M
Velocity - 2900FPS


this is with a 24" barrel.

I have not used Norma brass, but I have read and heard many reports suggesting the brass being softer that others, leading to primer pockets opening up relatively soon. 3x firings seems to me a lot sooner than I'd expects. Certainly, Norma's case walls are a bit thinner than than other's, which contributes to you having more case volume that've we've been discussing. Likewise, I don't think 56.0 grs of N560 is hot nor producing an unusual amount pf pressure that should be of any concern. My Lapua case pockets are looser than in the first few firings, but as long as there's no leakage from around the primer and they don't fall out, I don't worry about they feeling looser than before.

Here's some info you might find of interest regarding your brass and your load:

Interesting to me is the difference between to two Norma brass examples (BR with thin wall and the Dasher with thick case all) making me curious about their construction for the 6.5 PRC's:

 

[wp06]

I have not used Norma brass, but I have read and heard many reports suggesting the brass being softer that others, leading to primer pockets opening up relatively soon. 3x firings seems to me a lot sooner than I'd expects. Certainly, Norma's case walls are a bit thinner than than other's, which contributes to you having more case volume that've we've been discussing. Likewise, I don't think 56.0 grs of N560 is hot nor producing an unusual amount pf pressure that should be of any concern. My Lapua case pockets are looser than in the first few firings, but as long as there's no leakage from around the primer and they don't fall out, I don't worry about they feeling looser than before.

Here's some info you might find of interest regarding your brass and your load:

View attachment 8343920

View attachment 8343707

Interesting to me is the difference between to two Norma brass examples (BR with thin wall and the Dasher with thick case all) making me curious about their construction for the 6.5 PRC's:
View attachment 8343708

Thanks for the input.

I’m also curious about the Norma 6.5 PRC’s case construction now.

I also agree that after a few firings on brass the primer pocket will be looser than viegij brass but I have had Lapua 6.5CM brass that’s been fired 15x without the primer pockets being as loose as my current 6.5 PRC Norma x3 brass.

I will keep on shooting and see when what happens, if they don’t last atleast x10 then I’ll invest in some Lapua brass next time.

I might also add that I do in fact anneal all my brass every time after being fired.

 

[Overclok79]

My once fired ADG brass measured 68.7 gr of H2O with a 2.019” trim length.

 

[straightshooter1]

Thanks for the input.

I’m also curious about the Norma 6.5 PRC’s case construction now.

I also agree that after a few firings on brass the primer pocket will be looser than viegij brass but I have had Lapua 6.5CM brass that’s been fired 15x without the primer pockets being as loose as my current 6.5 PRC Norma x3 brass.

I will keep on shooting and see when what happens, if they don’t last atleast x10 then I’ll invest in some Lapua brass next time.

I might also add that I do in fact anneal all my brass every time after being fired.

Did you see the recent video about case brass? Norma brass is part of the testing data presented, though not for a 6.5 PRC. It might give you a little insight as to how Norma brass compares to others. At 1:02:20, he's talking about primer pocket widths: