atl5029
Well-Known Member
It might be slightly. How would this affect velocity?
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More powder, less velocity - how is this possible?
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It might be slightly. How would this affect velocity?
atl5029
Well-Known Member
Thanks everyone for your replies. I think I am going to retest, and this time make sure the chrony is farther out. As someone said earlier, I need to make sure it is level too, which would make a huge difference. I'll also put in a fresh battery. Testing it with some factory 22 ammo is also a good idea. I don't think it is broken, as I just shot a different rifle though it a week or two ago and got perfectly fine readings. It was farther away that time though, which raised my original suspicion of it being too close.
With a powder increase, high pressure may produce less velocity.
Compressed load - changing the shape of the powder, small, may increase the burn rate. This make more pressure. http://www.firearmsid.com/Feature%20Articles/McCord_gunpowder/
Compressed load - changing the shape of the powder, small, may increase the burn rate. This make more pressure. http://www.firearmsid.com/Feature%20Articles/McCord_gunpowder/
In Richard Lee's book on reloading I remember reading that he done a test on compressed loads. At a certain point in the compression he stated that the vel actually began to drop for a few loads as he increased the charge .5 at a time. He stated that he believed this was due to harder ignition due to the compressed charge. I would imagine that if your load is only slightly compressed this would not be the case.
atl5029
Well-Known Member
I'll have to note if it is compressing the powder when I load some new rounds to retest.
Clark
Well-Known Member
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- Oct 19, 2006
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I know from Lapua 308 Palma brass with small primer pockets necked down to 260 with 120 gr nos bal tip moly bullets, CCI 450 small rifle magnum primers, 40 gr CFE shoots, 42 gr does not fire.
Velocity drops off alot.... to zero with more powder
Velocity drops off alot.... to zero with more powder
atl5029
Well-Known Member
Noted a slight bit of compression when loading 49 grains of H4831SC. I am using Norma 260 Rem brass fire formed to AI and 140 AMAX seated to 2.91"COAL. I am hearing and feeling powder granules crunch a little bit near the end of the press stroke, but when I shake the loaded rounds I can hear the powder rattle around a little in there, so it's not super compressed.
Going to the range tomorrow to retest 49 grains of H4831SC and 46 grains of IMR 4831. I'll be sure to set up my chrono 15' away or more and that it's level. I'll run some factory 120 grain 300 Blackout through it with my AR to make sure it is working correctly before I test my long range ordinance. I'll report back for everyone's future reference.
Going to the range tomorrow to retest 49 grains of H4831SC and 46 grains of IMR 4831. I'll be sure to set up my chrono 15' away or more and that it's level. I'll run some factory 120 grain 300 Blackout through it with my AR to make sure it is working correctly before I test my long range ordinance. I'll report back for everyone's future reference.
atl5029
Well-Known Member
Well I learned a couple of things today...
1. My problem was definitely the fact that my chrony was way too close and possibly not level. I set it up much farther out than last time and shot some Remington UMC 120 grain 300 Blackout though it and was getting expected velocities betweem around 2200 FPS. Shot my 260 AI loads with 49 and 49.5 grains of H4831SC. 5 rounds at 49 grains averaged 2896 FPS and 5 rounds at 49.5 grains averaged 2909. This is what I would expect.
2. IMR4831 must throw a hell of a fireball compared to H4831SC. I also shot 5 rounds loaded with 46 grains of IMR4831, and my first two shots gave me unrealistic values in the mid 1300s. I moved my chrony even farther out and it gave me good readings again. I'm guessing the gasses are getting into the chrony and doing weird things. The 3 rounds that gave good readings averaged 2830 FPS.
All 3 of these loads shot into a nice group, which is always good.
3. The third thing explains a lot of my previous troubles....old IMR4831 is a lot hotter than new IMR4831. When I first started load development for this rifle, I used an old canister of powder I bought from an old timer with some other reloading equipment. It was an old metal canister, probably made in the 70's if not earlier. That same load of 46 grains gave me about 2950 FPS previously, and did again today. With that powder I was also getting really flattened primers and other pressure signs. Who knows if the powder in that canister was even really 4831. Lesson learned...when buying powder from people you really don't know, be 110% sure you know what you're buying.
All in all though it seems load development is back on track. Hope you guys find this experience to be useful knowledge
1. My problem was definitely the fact that my chrony was way too close and possibly not level. I set it up much farther out than last time and shot some Remington UMC 120 grain 300 Blackout though it and was getting expected velocities betweem around 2200 FPS. Shot my 260 AI loads with 49 and 49.5 grains of H4831SC. 5 rounds at 49 grains averaged 2896 FPS and 5 rounds at 49.5 grains averaged 2909. This is what I would expect.
2. IMR4831 must throw a hell of a fireball compared to H4831SC. I also shot 5 rounds loaded with 46 grains of IMR4831, and my first two shots gave me unrealistic values in the mid 1300s. I moved my chrony even farther out and it gave me good readings again. I'm guessing the gasses are getting into the chrony and doing weird things. The 3 rounds that gave good readings averaged 2830 FPS.
All 3 of these loads shot into a nice group, which is always good.
3. The third thing explains a lot of my previous troubles....old IMR4831 is a lot hotter than new IMR4831. When I first started load development for this rifle, I used an old canister of powder I bought from an old timer with some other reloading equipment. It was an old metal canister, probably made in the 70's if not earlier. That same load of 46 grains gave me about 2950 FPS previously, and did again today. With that powder I was also getting really flattened primers and other pressure signs. Who knows if the powder in that canister was even really 4831. Lesson learned...when buying powder from people you really don't know, be 110% sure you know what you're buying.
All in all though it seems load development is back on track. Hope you guys find this experience to be useful knowledge
S
shaughn
Guest
Glad we could help.
Kennibear
Well-Known Member
NRA did some tests in the 60's for their Reloading Digest and they found that when a powder is pushed past its designed peak pressure the velocity drops. 4895 is designed (chemically) to work best at 48kpsi. I would guess 7828 to work at the max of 65kpsi. Most nitrocellulose chemistries run away at 70kpsi. The NRA experts thought the powders might be reaching a detonation threshold.
Something to consider. 4831 is old school technology.
KB
Something to consider. 4831 is old school technology.
KB
