Thread: High Pressure signs?

Originally Posted by Cordite

He said Hodgdon 4350 at first. Not a powder I'd expect to hear mentioned in connection with overpressure, unless you only half filled the case and had some detonation kind of thing going on. Some recommend magnum primers for slow powders, but go by the book. H4350 "likes" heavier projectiles btw.

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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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 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 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:

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".

Cartridge : 6.5 Creedmoor Hornady
Bullet : .264, 140, Hornady ELD-M 26331
Useable Case Capaci: 47.551 grain H2O = 3.087 cm³
Cartridge O.A.L. L6: 2.800 inch = 71.12 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Hodgdon H4350 *T

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.469% 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

-04.7 95 40.60 2606 2112 49550 9061 97.6 1.321
-04.2 95 40.80 2618 2131 50254 9100 97.7 1.313
-03.8 96 41.00 2630 2151 50968 9138 97.9 1.304
-03.3 96 41.20 2642 2170 51692 9176 98.0 1.296
-02.8 97 41.40 2654 2190 52426 9213 98.1 1.287
-02.3 97 41.60 2666 2210 53171 9249 98.3 1.279
-01.9 97 41.80 2678 2229 53926 9285 98.4 1.271 ! Near Maximum !
-01.4 98 42.00 2690 2249 54692 9320 98.5 1.263 ! Near Maximum !
-00.9 98 42.20 2702 2269 55469 9354 98.6 1.255 ! Near Maximum !
-00.5 99 42.40 2713 2289 56258 9388 98.7 1.247 ! Near Maximum !
+00.0 99 42.60 2725 2309 57057 9421 98.8 1.239 ! Near Maximum !
+00.5 100 42.80 2737 2329 57869 9454 98.9 1.231 ! Near Maximum !
+00.9 100 43.00 2749 2349 58691 9486 99.0 1.224 ! Near Maximum !
+01.4 101 43.20 2761 2369 59526 9517 99.1 1.216 ! Near Maximum !
+01.9 101 43.40 2773 2390 60373 9547 99.2 1.208 ! Near Maximum !
+02.3 102 43.60 2784 2410 61233 9577 99.2 1.201 ! Near Maximum !

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 99 42.60 2834 2497 66997 9178 100.0 1.158 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 99 42.60 2576 2063 47289 9233 93.8 1.345

Originally Posted by spada

Cartridge : 6.5 Creedmoor Hornady
Bullet : .264, 140, Hornady ELD-M 26331
Useable Case Capaci: 47.551 grain H2O = 3.087 cm³
Cartridge O.A.L. L6: 2.800 inch = 71.12 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Hodgdon H4350 *T

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.469% 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

-04.7 95 40.60 2606 2112 49550 9061 97.6 1.321
-04.2 95 40.80 2618 2131 50254 9100 97.7 1.313
-03.8 96 41.00 2630 2151 50968 9138 97.9 1.304
-03.3 96 41.20 2642 2170 51692 9176 98.0 1.296
-02.8 97 41.40 2654 2190 52426 9213 98.1 1.287
-02.3 97 41.60 2666 2210 53171 9249 98.3 1.279
-01.9 97 41.80 2678 2229 53926 9285 98.4 1.271 ! Near Maximum !
-01.4 98 42.00 2690 2249 54692 9320 98.5 1.263 ! Near Maximum !
-00.9 98 42.20 2702 2269 55469 9354 98.6 1.255 ! Near Maximum !
-00.5 99 42.40 2713 2289 56258 9388 98.7 1.247 ! Near Maximum !
+00.0 99 42.60 2725 2309 57057 9421 98.8 1.239 ! Near Maximum !
+00.5 100 42.80 2737 2329 57869 9454 98.9 1.231 ! Near Maximum !
+00.9 100 43.00 2749 2349 58691 9486 99.0 1.224 ! Near Maximum !
+01.4 101 43.20 2761 2369 59526 9517 99.1 1.216 ! Near Maximum !
+01.9 101 43.40 2773 2390 60373 9547 99.2 1.208 ! Near Maximum !
+02.3 102 43.60 2784 2410 61233 9577 99.2 1.201 ! Near Maximum !

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 99 42.60 2834 2497 66997 9178 100.0 1.158 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 99 42.60 2576 2063 47289 9233 93.8 1.345

Thanks a mil @spada!


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