Thread: High Pressure signs?

Originally Posted by janleroux

Hi @Cordite, that is interesting comment you made that I did not know - so are you saying that you could run into over pressure if you under load as well? Is it because there is not sufficient pressure to move the projectile out of the barrel and you have pressure peaking somewhere during the process?

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Something to do with a standing wave set up, returning and detonating the unignited portion. It is dangerous to have as it is a detonation, not a combustion, and double base powder is basically the same as gelignite albeit in different proportions, nitrocellulose and nitroglycerin. We are talking blown up guns here.

Anyway roughly how much percent of the case space under the bullet is taken up by your charge? 40 grain does not sound like underfilling.

Someone here may have some calculator software to tell you what pressures to expect from that load.

Originally Posted by janleroux

Apologies - finger trouble. Yes, it is H4350.


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It was 10-ring I was querying about whether he meant H4350 as he was saying H4320 throughout his post, and it was my understanding that 4350 was 2209, and my checks seem to confirm that. That’s why I quoted his post, not yours...

Originally Posted by Cordite

Something to do with a standing wave set up, returning and detonating the unignited portion. It is dangerous to have as it is a detonation, not a combustion, and double base powder is basically the same as gelignite albeit in different proportions, nitrocellulose and nitroglycerin. We are talking blown up guns here.

Anyway roughly how much percent of the case space under the bullet is taken up by your charge? 40 grain does not sound like underfilling.

Someone here may have some calculator software to tell you what pressures to expect from that load.

Difficult to give a persentage, but with 41gr I can still hear movement inside casing when I shake it, after I seated the projectile, so I would estimate that I would be able to go to about 44gr before starting to compress.

If I load the case to the brim is takes just a bit more than 47gr in total.


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Originally Posted by Cigar

It was 10-ring I was querying about whether he meant H4350 as he was saying H4320 throughout his post, and it was my understanding that 4350 was 2209, and my checks seem to confirm that. That’s why I quoted his post, not yours...

No probs. It sounded like a typical mistake I would make.


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Originally Posted by janleroux

No probs. It sounded like a typical mistake I would make.


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"BTW: H4320 is AR2209, exactly the same powder. ADI supply Hodgdon with AR2209 and they repack it under their name. I've used both at different times and had identical velocities. AR2209 is a little less expensive to buy and you also get 500gms vs 1lb for the Hodgdon."

Yes my mistake. Thanks for pointing that out; especially when talking about powder and charge weights. I meant H4350 is AR2209. My apologies.

Originally Posted by janleroux

Difficult to give a persentage, but with 41gr I can still hear movement inside casing when I shake it, after I seated the projectile, so I would estimate that I would be able to go to about 44gr before starting to compress.

If I load the case to the brim is takes just a bit more than 47gr in total.

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That does not sound underfilled. Generally H4350 will have a percentage unburnt powder at the end of it, more used up with heavier bullet loads.

On the face of it it does sound like the earlier advice about something up with the primers.

Here is someone playing with just about your current ingredients:

The face of the primers could also be flat. They still look smooth and rounded.


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@janleroux I have a Howa 6.5CM 24inch heavy barrel

When running 140ELDM It really likes them at about 2770 FPS with a COAL of 2.840"

I find the standard 2.80 Factory COAL too much of a jump to the lands and builds up pressure faster with increasing charge weight.
In my Howa pressure signs start with an increasing ridge (primer cratering) around the primer strike well before I start getting ejector smear or sticky bolt lift.

H4350/2209 is certainly known for accuracy/temp insensitivity in 6.5cm

But don't discount RL16 also very temp stable and can give better MV and accuracy in my rifle

You might not be able to reach 2770 with a Coal of 2.80 before getting significant pressure signs.

Also you need to consider how many rounds have gone down your barrel if it's still new, less than 100 - 200 rounds, you may well find a speed increase as the barrel wears in.

Here's an example from QL for your bullet with H4350 in a 24" barrel note the COAL is 2.865 also note that the cartridge case capacity may not match yours if it's smaller pressures will reach higher.

Do not take any figures like these for gospel always start lower and work up.


Cartridge : 6.5 Creedmoor Hornady
Bullet : .264, 143, Hornady ELD-X 2635 G7
Useable Case Capaci: 46.313 grain H2O = 3.007 cm³
Cartridge O.A.L. L6: 2.865 inch = 72.77 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Hodgdon H4350

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.704% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-07.0 94 39.32 2548 2061 48192 8838 97.3 1.347
-06.3 95 39.62 2566 2090 49240 8897 97.5 1.334
-05.6 96 39.92 2584 2120 50310 8956 97.7 1.321
-04.9 96 40.22 2602 2149 51405 9013 97.9 1.308 ! Near Maximum !
-04.2 97 40.51 2620 2179 52523 9069 98.1 1.296 ! Near Maximum !
-03.5 98 40.81 2638 2209 53665 9123 98.3 1.283 ! Near Maximum !
-02.8 98 41.11 2655 2239 54833 9176 98.5 1.271 ! Near Maximum !
-02.1 99 41.41 2673 2269 56026 9227 98.7 1.259 ! Near Maximum !
-01.4 100 41.70 2691 2299 57245 9277 98.8 1.246 ! Near Maximum !
-00.7 101 42.00 2709 2330 58492 9325 99.0 1.235 ! Near Maximum !
+00.0 101 42.30 2727 2361 59766 9372 99.1 1.223 !DANGEROUS LOAD-DO NOT USE!
+00.7 102 42.60 2744 2391 61069 9417 99.2 1.211 !DANGEROUS LOAD-DO NOT USE!
+01.4 103 42.90 2762 2422 62402 9460 99.3 1.200 !DANGEROUS LOAD-DO NOT USE!
+02.1 103 43.19 2780 2453 63764 9502 99.4 1.188 !DANGEROUS LOAD-DO NOT USE!
+02.8 104 43.49 2797 2484 65157 9543 99.5 1.177 !DANGEROUS LOAD-DO NOT USE!
+03.5 105 43.79 2815 2516 66582 9581 99.6 1.166 !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 101 42.30 2832 2547 70203 9091 100.0 1.144 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 101 42.30 2580 2114 49511 9234 94.4 1.326

Originally Posted by Burb122

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Which brand of primers are these?


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Originally Posted by spada

@janleroux I have a Howa 6.5CM 24inch heavy barrel

When running 140ELDM It really likes them at about 2770 FPS with a COAL of 2.840"

I find the standard 2.80 Factory COAL too much of a jump to the lands and builds up pressure faster with increasing charge weight.
In my Howa pressure signs start with an increasing ridge (primer cratering) around the primer strike well before I start getting ejector smear or sticky bolt lift.

H4350/2209 is certainly known for accuracy/temp insensitivity in 6.5cm

But don't discount RL16 also very temp stable and can give better MV and accuracy in my rifle

You might not be able to reach 2770 with a Coal of 2.80 before getting significant pressure signs.

Also you need to consider how many rounds have gone down your barrel if it's still new, less than 100 - 200 rounds, you may well find a speed increase as the barrel wears in.

Here's an example from QL for your bullet with H4350 in a 24" barrel note the COAL is 2.865 also note that the cartridge case capacity may not match yours if it's smaller pressures will reach higher.

Do not take any figures like these for gospel always start lower and work up.


Cartridge : 6.5 Creedmoor Hornady
Bullet : .264, 143, Hornady ELD-X 2635 G7
Useable Case Capaci: 46.313 grain H2O = 3.007 cm³
Cartridge O.A.L. L6: 2.865 inch = 72.77 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Hodgdon H4350

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.704% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-07.0 94 39.32 2548 2061 48192 8838 97.3 1.347
-06.3 95 39.62 2566 2090 49240 8897 97.5 1.334
-05.6 96 39.92 2584 2120 50310 8956 97.7 1.321
-04.9 96 40.22 2602 2149 51405 9013 97.9 1.308 ! Near Maximum !
-04.2 97 40.51 2620 2179 52523 9069 98.1 1.296 ! Near Maximum !
-03.5 98 40.81 2638 2209 53665 9123 98.3 1.283 ! Near Maximum !
-02.8 98 41.11 2655 2239 54833 9176 98.5 1.271 ! Near Maximum !
-02.1 99 41.41 2673 2269 56026 9227 98.7 1.259 ! Near Maximum !
-01.4 100 41.70 2691 2299 57245 9277 98.8 1.246 ! Near Maximum !
-00.7 101 42.00 2709 2330 58492 9325 99.0 1.235 ! Near Maximum !
+00.0 101 42.30 2727 2361 59766 9372 99.1 1.223 !DANGEROUS LOAD-DO NOT USE!
+00.7 102 42.60 2744 2391 61069 9417 99.2 1.211 !DANGEROUS LOAD-DO NOT USE!
+01.4 103 42.90 2762 2422 62402 9460 99.3 1.200 !DANGEROUS LOAD-DO NOT USE!
+02.1 103 43.19 2780 2453 63764 9502 99.4 1.188 !DANGEROUS LOAD-DO NOT USE!
+02.8 104 43.49 2797 2484 65157 9543 99.5 1.177 !DANGEROUS LOAD-DO NOT USE!
+03.5 105 43.79 2815 2516 66582 9581 99.6 1.166 !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 101 42.30 2832 2547 70203 9091 100.0 1.144 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 101 42.30 2580 2114 49511 9234 94.4 1.326

Wow, thanks! I will digest this a bit. Very good info and comparisons to have. Appreciate it!


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Originally Posted by janleroux

Which brand of primers are these?


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Bet the one on the left was "biffy"

Originally Posted by spada

@janleroux I have a Howa 6.5CM 24inch heavy barrel

When running 140ELDM It really likes them at about 2770 FPS with a COAL of 2.840"

I find the standard 2.80 Factory COAL too much of a jump to the lands and builds up pressure faster with increasing charge weight.
In my Howa pressure signs start with an increasing ridge (primer cratering) around the primer strike well before I start getting ejector smear or sticky bolt lift.

H4350/2209 is certainly known for accuracy/temp insensitivity in 6.5cm

But don't discount RL16 also very temp stable and can give better MV and accuracy in my rifle

You might not be able to reach 2770 with a Coal of 2.80 before getting significant pressure signs.

Also you need to consider how many rounds have gone down your barrel if it's still new, less than 100 - 200 rounds, you may well find a speed increase as the barrel wears in.

Here's an example from QL for your bullet with H4350 in a 24" barrel note the COAL is 2.865 also note that the cartridge case capacity may not match yours if it's smaller pressures will reach higher.

Do not take any figures like these for gospel always start lower and work up.


Cartridge : 6.5 Creedmoor Hornady
Bullet : .264, 143, Hornady ELD-X 2635 G7
Useable Case Capaci: 46.313 grain H2O = 3.007 cm³
Cartridge O.A.L. L6: 2.865 inch = 72.77 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Hodgdon H4350

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.704% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-07.0 94 39.32 2548 2061 48192 8838 97.3 1.347
-06.3 95 39.62 2566 2090 49240 8897 97.5 1.334
-05.6 96 39.92 2584 2120 50310 8956 97.7 1.321
-04.9 96 40.22 2602 2149 51405 9013 97.9 1.308 ! Near Maximum !
-04.2 97 40.51 2620 2179 52523 9069 98.1 1.296 ! Near Maximum !
-03.5 98 40.81 2638 2209 53665 9123 98.3 1.283 ! Near Maximum !
-02.8 98 41.11 2655 2239 54833 9176 98.5 1.271 ! Near Maximum !
-02.1 99 41.41 2673 2269 56026 9227 98.7 1.259 ! Near Maximum !
-01.4 100 41.70 2691 2299 57245 9277 98.8 1.246 ! Near Maximum !
-00.7 101 42.00 2709 2330 58492 9325 99.0 1.235 ! Near Maximum !
+00.0 101 42.30 2727 2361 59766 9372 99.1 1.223 !DANGEROUS LOAD-DO NOT USE!
+00.7 102 42.60 2744 2391 61069 9417 99.2 1.211 !DANGEROUS LOAD-DO NOT USE!
+01.4 103 42.90 2762 2422 62402 9460 99.3 1.200 !DANGEROUS LOAD-DO NOT USE!
+02.1 103 43.19 2780 2453 63764 9502 99.4 1.188 !DANGEROUS LOAD-DO NOT USE!
+02.8 104 43.49 2797 2484 65157 9543 99.5 1.177 !DANGEROUS LOAD-DO NOT USE!
+03.5 105 43.79 2815 2516 66582 9581 99.6 1.166 !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 101 42.30 2832 2547 70203 9091 100.0 1.144 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 101 42.30 2580 2114 49511 9234 94.4 1.326

I am standing at about 150 rounds through this barrel. Very interesting to compare my results with QL output:

CHARGE AVE VEL (fps) ES GRP MOA
Factory 2669 43 0.77
37.5 2460 43 0.66
38.0 2462 61 0.37
38.5 2535 51 0.75
39.0 2527 11 0.65
39.5 2566 9 0.3
40.0 2598 2 0.57
40.5 2602 36 0.69
41.0 2622 7 0.71

My plan was to only go up to 42gr max - so this is inline with my next steps. Thanks!

Originally Posted by Cordite

Something to do with a standing wave set up, returning and detonating the unignited portion. It is dangerous to have as it is a detonation, not a combustion, and double base powder is basically the same as gelignite albeit in different proportions, nitrocellulose and nitroglycerin. We are talking blown up guns here.

I believe this effect is known as a "flashover".

Originally Posted by Burb122

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Yes...when the edges become sharp, you attach a string to the trigger and let the other 5 off from a hole in the ground. I blew a 44 mag back in the 70's.