fsqridah

09-20-2010, 10:51

I have three different loads for my Kimber Ultra Carry II, and just out of curiousity, I'd like opinions on how you think the 3" affects the external ballistics.

- 160gr Corbon DPX @ 1050fps/392fpe out of 3" test barrel. A test I saw online was getting an avg of 1080fps out of a 3" Colt Defender with 12-12.5" of penetration.

- 185gr +P Black Hills TAC-XP @ 1000fps/411fpe out of 5" test barrel. Not quite as hot as the Corbon DPX loading (1075fps/475fpe), but more controllable. The same test was getting 16-16.5" of penetration from the 185gr DPX loading from a 5" barrel.

- 230gr +P Buffalo Bore Gold Dot @ 950fps/461fpe out of 5" test barrel. I sent an email to a BB rep and he said he hadn't done any testing/chrono'ing from a 3" barrel so he wasn't sure about velocities.

I've used all three loadings on water jugs (clothed/unclothed) and all of them had 100% expansion (at least during my informal testing). I was unable to measure penetration depths, but the 230gr BB load seemed to dig the deepest and expanded to .72-74 inches. The 160gr and 185gr TAC-XPs both expanded to .80-.84 inches, but didn't penetrate as far. The recoil was the least with the 160gr, followed by the 185gr, then the 230gr.

From what I've seen, a 3" barrel cuts the velocity 10-15% from a 5" barrel. However, if you do the math, a 15% loss of velocity yields 850fps/297fpe for the 185gr and 808fps/333fpe for the 230gr. The 160gr makes at least the advertised 1050fps/392fpe from a 3" barrel. If you compare bullet weight, MV, ME, and Mmomentum of the reduced velocities, you get the following:

160gr @ 1050fps/392fpe/24 lbs. ft/sec

185gr @ 850fps/297fpe/22.5 lbs. ft/sec

230gr @ 808fps/333fpe/26.5 lbs. ft/sec

To compare, the 230gr short barrel Gold Dot gets 820fps/343fpe from a 4" barrel. Assuming a 10% loss of velocity (4" down to 3"), you get 738fps/343fpe from a 3" barrel. Gunblast did a test of the standard 230gr Gold dot rated at 890fps/404fpe from a 5" barrel and got an avg of 765fps/299fpe from a 3" Kimber, which provided .73" expansion/15.3" penetration on bare gelatin. The drop from 890fps to 765fps indicates a 14% loss of velocity going from a 5" barrel to a 3" barrel, which is what I used to do my estimated calculations.

Now, adding in the Speer numbers, you get:

160gr @ 1050fps/392fpe/24 lbs. ft/sec (Corbon DPX)

185gr @ 850fps/297fpe/22.5 lbs. ft/sec (+P Black Hills TAC-XP)

230gr @ 808fps/333fpe/26.5 lbs. ft/sec (+P Buffalo Bore GDHP)

230gr @ 738fps/343fpe/24.2 lbs. ft/sec (Speer SB Gold Dot)

230gr @ 765fps/299fpe/25.1 lbs. ft/sec (Speer Gold Dot)

After shooting all five, the 230gr short-barrel Gold Dot has the least amount of recoil. Compared to the 160gr DPX (49fpe less with .2 lbs. ft/sec more), it makes sense. However, the 230gr +P BB loading by far had the most recoil of the five, followed by the 185gr +P Black Hills, then the 230gr Speer, then the 160gr DPX, then the 230gr Speer short-barrel. The momemtum ratings are very close, so the muzzle energy should be the most indicative of how the load will recoil. If you consider the velocity losses, the 160gr DPX has the highest ME, so it should produce the most recoil. Felt recoil cannot be calculated with numbers alone, but for now, I'm comparing numbers to actual shooting. From shooting, the 160gr has very light recoil. Comparing the ME of the 230gr +P BB and Speer SB Gold Dot, the Speer has 10fpe more with slightly less momentum. According to this observation, the 230gr +P BB should have more recoil, but not by much. From shooting both, there is a HUGE difference in recoil. Part of that could be the unburned powder from the +P loading. But consider that a 3" with a +P load will still get higher velocities than a 5" with a non +P load, then the 230gr +P BB out of a 3" barrel should get higher velocity than the 230gr Speer GD out of a 5" barrel, which yields 890fps. Because of the huge difference in recoil (barely any versus very significant), it only makes sense that the 230gr +P BB out of a 3" would be getting more than 890fps, but a 15% loss from the posted 950fps yields 808fps, which is 82fps less than the 890fps. The 160gr DPX uses a fast burning powder charge optimized for short barrels, so its recoil could possibly be discounted when compared to the rest. But sense the SB-GD uses a faster burning powder, it should retain higher MV/ME than I posted (10% loss), meaning it would have even more ME than the 230gr +P BB than it already does. However, it could be that a lot of powder in the 230gr +P BB load fails to burn in the 3" barrel, increasing recoil by a significant amount.

As said, felt recoil can be vastly different from the numbers, but I'm wondering if the 15% loss of velocity is always accurate, or if the posted numbers from the ammo manufacturers is not indicative of the performance one would get from a 5" barrel. Someone needs to let me borrow a chrono so I could do a direct comparison between a 5" 1911 and 3" 1911.

- 160gr Corbon DPX @ 1050fps/392fpe out of 3" test barrel. A test I saw online was getting an avg of 1080fps out of a 3" Colt Defender with 12-12.5" of penetration.

- 185gr +P Black Hills TAC-XP @ 1000fps/411fpe out of 5" test barrel. Not quite as hot as the Corbon DPX loading (1075fps/475fpe), but more controllable. The same test was getting 16-16.5" of penetration from the 185gr DPX loading from a 5" barrel.

- 230gr +P Buffalo Bore Gold Dot @ 950fps/461fpe out of 5" test barrel. I sent an email to a BB rep and he said he hadn't done any testing/chrono'ing from a 3" barrel so he wasn't sure about velocities.

I've used all three loadings on water jugs (clothed/unclothed) and all of them had 100% expansion (at least during my informal testing). I was unable to measure penetration depths, but the 230gr BB load seemed to dig the deepest and expanded to .72-74 inches. The 160gr and 185gr TAC-XPs both expanded to .80-.84 inches, but didn't penetrate as far. The recoil was the least with the 160gr, followed by the 185gr, then the 230gr.

From what I've seen, a 3" barrel cuts the velocity 10-15% from a 5" barrel. However, if you do the math, a 15% loss of velocity yields 850fps/297fpe for the 185gr and 808fps/333fpe for the 230gr. The 160gr makes at least the advertised 1050fps/392fpe from a 3" barrel. If you compare bullet weight, MV, ME, and Mmomentum of the reduced velocities, you get the following:

160gr @ 1050fps/392fpe/24 lbs. ft/sec

185gr @ 850fps/297fpe/22.5 lbs. ft/sec

230gr @ 808fps/333fpe/26.5 lbs. ft/sec

To compare, the 230gr short barrel Gold Dot gets 820fps/343fpe from a 4" barrel. Assuming a 10% loss of velocity (4" down to 3"), you get 738fps/343fpe from a 3" barrel. Gunblast did a test of the standard 230gr Gold dot rated at 890fps/404fpe from a 5" barrel and got an avg of 765fps/299fpe from a 3" Kimber, which provided .73" expansion/15.3" penetration on bare gelatin. The drop from 890fps to 765fps indicates a 14% loss of velocity going from a 5" barrel to a 3" barrel, which is what I used to do my estimated calculations.

Now, adding in the Speer numbers, you get:

160gr @ 1050fps/392fpe/24 lbs. ft/sec (Corbon DPX)

185gr @ 850fps/297fpe/22.5 lbs. ft/sec (+P Black Hills TAC-XP)

230gr @ 808fps/333fpe/26.5 lbs. ft/sec (+P Buffalo Bore GDHP)

230gr @ 738fps/343fpe/24.2 lbs. ft/sec (Speer SB Gold Dot)

230gr @ 765fps/299fpe/25.1 lbs. ft/sec (Speer Gold Dot)

After shooting all five, the 230gr short-barrel Gold Dot has the least amount of recoil. Compared to the 160gr DPX (49fpe less with .2 lbs. ft/sec more), it makes sense. However, the 230gr +P BB loading by far had the most recoil of the five, followed by the 185gr +P Black Hills, then the 230gr Speer, then the 160gr DPX, then the 230gr Speer short-barrel. The momemtum ratings are very close, so the muzzle energy should be the most indicative of how the load will recoil. If you consider the velocity losses, the 160gr DPX has the highest ME, so it should produce the most recoil. Felt recoil cannot be calculated with numbers alone, but for now, I'm comparing numbers to actual shooting. From shooting, the 160gr has very light recoil. Comparing the ME of the 230gr +P BB and Speer SB Gold Dot, the Speer has 10fpe more with slightly less momentum. According to this observation, the 230gr +P BB should have more recoil, but not by much. From shooting both, there is a HUGE difference in recoil. Part of that could be the unburned powder from the +P loading. But consider that a 3" with a +P load will still get higher velocities than a 5" with a non +P load, then the 230gr +P BB out of a 3" barrel should get higher velocity than the 230gr Speer GD out of a 5" barrel, which yields 890fps. Because of the huge difference in recoil (barely any versus very significant), it only makes sense that the 230gr +P BB out of a 3" would be getting more than 890fps, but a 15% loss from the posted 950fps yields 808fps, which is 82fps less than the 890fps. The 160gr DPX uses a fast burning powder charge optimized for short barrels, so its recoil could possibly be discounted when compared to the rest. But sense the SB-GD uses a faster burning powder, it should retain higher MV/ME than I posted (10% loss), meaning it would have even more ME than the 230gr +P BB than it already does. However, it could be that a lot of powder in the 230gr +P BB load fails to burn in the 3" barrel, increasing recoil by a significant amount.

As said, felt recoil can be vastly different from the numbers, but I'm wondering if the 15% loss of velocity is always accurate, or if the posted numbers from the ammo manufacturers is not indicative of the performance one would get from a 5" barrel. Someone needs to let me borrow a chrono so I could do a direct comparison between a 5" 1911 and 3" 1911.