Unusual ballistics.

[Chief Snorkel]

I took my new 4 inch Colt King Cobra to the range today. It's a really sweet shooter, but I encountered some strange results with my hand loads.The loads were 125 grain XTP and 158 grain XTP, both over 17 grains of LilGun. I expected the 158 grain loads to be slower than the 125, but the opposite occurred. The 158 averaged 1355 fps and the 125 averaged 1240 fps.Both loads were quite accurate. I speculate that the heavier bullet causes the powder to build pressure faster, but this is a new one for me. Any ideas?

 

[Drycreek]

I took my new 4 inch Colt King Cobra to the range today. It's a really sweet shooter, but I encountered some strange results with my hand loads.The loads were 125 grain XTP and 158 grain XTP, both over 17 grains of LilGun. I expected the 158 grain loads to be slower than the 125, but the opposite occurred. The 158 averaged 1355 fps and the 125 averaged 1240 fps.Both loads were quite accurate. I speculate that the heavier bullet causes the powder to build pressure faster, but this is a new one for me. Any ideas?

Makes sense to me.

 

[LDB]

I don't reload and am clueless but that never stops me from specking on things. Maybe the heavier bullet is slower to launch as it were, like a heavier car on the starting line, and that, as you said, lets it build more pressure which then squirts it out at a higher speed? That's my best scientifical thinkin' anyway.

 

[dennyntx]

I don't reload and am clueless but that never stops me from specking on things. Maybe the heavier bullet is slower to launch as it were, like a heavier car on the starting line, and that, as you said, lets it build more pressure which then squirts it out at a higher speed? That's my best scientifical thinkin' anyway.

I took my new 4 inch Colt King Cobra to the range today. It's a really sweet shooter, but I encountered some strange results with my hand loads.The loads were 125 grain XTP and 158 grain XTP, both over 17 grains of LilGun. I expected the 158 grain loads to be slower than the 125, but the opposite occurred. The 158 averaged 1355 fps and the 125 averaged 1240 fps.Both loads were quite accurate. I speculate that the heavier bullet causes the powder to build pressure faster, but this is a new one for me. Any ideas?

I took my new 4 inch Colt King Cobra to the range today. It's a really sweet shooter, but I encountered some strange results with my hand loads.The loads were 125 grain XTP and 158 grain XTP, both over 17 grains of LilGun. I expected the 158 grain loads to be slower than the 125, but the opposite occurred. The 158 averaged 1355 fps and the 125 averaged 1240 fps.Both loads were quite accurate. I speculate that the heavier bullet causes the powder to build pressure faster, but this is a new one for me. Any ideas?

A heavier bullet has greater mass creates more resistance to acceleration, leading to higher pressures and a faster build-up of pressure within the cartridge and barrel that's why usually a heavier bullet will have less powder in same caliber.

 

[LDB]

I have the 11th edition Hornady Handbook on my Kindle. I see that now, looking at the .327 Magnum, my current round of interest. Using Titegroup powder the lowest entry for an 85gr XTP is 5.1gr for 1300fps and the 100gr XTP is 5.0gr for 1250fps. Switching to Accurate No. 5 powder the base charge is 7.4gr and 6.7gr again for 1300 and 1250 fps. This reloading stuff is really fascinating.

 

[dennyntx]

I have the 11th edition Hornady Handbook on my Kindle. I see that now, looking at the .327 Magnum, my current round of interest. Using Titegroup powder the lowest entry for an 85gr XTP is 5.1gr for 1300fps and the 100gr XTP is 5.0gr for 1250fps. Switching to Accurate No. 5 powder the base charge is 7.4gr and 6.7gr again for 1300 and 1250 fps. This reloading stuff is really fascinating.

Yup it is definitely interesting amazing how much a small change in any one component affects pressure so much and velocity been reloading for a several years and still learn new stuff everyday