185-gr SWC, Chap. 7: Crimping is our Style
Posted: Sun Dec 13, 2009 10:11 pm
Part 1
(NOTE: The tests described below were carried out with my bolt rifle (LINK to Bob's bolt rifle). So, what I experienced may be very different than similar trials carried out with other rifles, especially the usual semi-autos. My barrel has a 1:16" twist and .451" grooves, and I don't have to be concerned about port pressures, etc. Do not expect my results to occur with any other rifle. Also, do not forget that this information comes to you on the internet.)
In previous chapters 1-6, I told how I learned that light-for-cartridge bullets, like the 185-grain bullets in a 450B, present a lot of problems. There's a reason Hornady doesn't recommend these. The problem boils down to getting a whole caseful of powder to ignite properly in this cartridge. I finally arrived at the same conclusion as many others on this forum: A crimp (or something like it) was necessary to increase bullet pull and rate of burn.
At the end of October I finally had the crimp die operational (see crimp die construction thread HERE.)
I decided to begin with Lil'Gun, and loaded a series of increasing powder weights. I did not load up a large number of cartridges for this initial exploration. Load procedures were much like those of previous chapters. I used the same Hornady encapsulated 185-grain SWC bullets (#45137). Working with Lil'Gun, I used Winchester SR primers. I began with new cases. Cases were prepped using the FL Hornady sizer and flared a bit with the expander die. Powder was weighed to the nearest 0.05 grains. Bullets were seated so the COAL was 2.000 inches, and then taper crimped with the Hornady die to a mouth dia of 0.476". I applied the Lee factory crimp, so that the center of the crimp was 0.070 below the mouth of the case, with the bullet being distorted as a result.
(See image posted on the crimp die construction thread.) Powder weights were 43-47 grains in increments of 1.0 grains.
At the range, the chronograph was set at 8 feet from the muzzle. With an air, ammo & rifle temperature of 40 degrees F, these were the recorded velocities:
43 grains . . 2441 fps
44 grains . . 2548
45 grains . . 2623
46 grains . . 2663
47 grains . . 2720
A factory load gave 2216 fps. Two of my handloads of the 250 FTX gave 2288 and 2291 fps.
There were no signs of excess pressure with the crimped loads. Case heads showed no expansion when measured immediately in front of the extractor groove. The pressures of firing ironed out the crimp in the cases almost completely.
This sequence was encouraging. The uncrimped loads loads put together with the same amount of powder and fired 4-5 months earlier had given higher velocities at the low end of the series, but were also more erratic. (See Chapter 1).
I decided to proceed with increased powder charges.
(continued in Part 2)
(NOTE: The tests described below were carried out with my bolt rifle (LINK to Bob's bolt rifle). So, what I experienced may be very different than similar trials carried out with other rifles, especially the usual semi-autos. My barrel has a 1:16" twist and .451" grooves, and I don't have to be concerned about port pressures, etc. Do not expect my results to occur with any other rifle. Also, do not forget that this information comes to you on the internet.)
In previous chapters 1-6, I told how I learned that light-for-cartridge bullets, like the 185-grain bullets in a 450B, present a lot of problems. There's a reason Hornady doesn't recommend these. The problem boils down to getting a whole caseful of powder to ignite properly in this cartridge. I finally arrived at the same conclusion as many others on this forum: A crimp (or something like it) was necessary to increase bullet pull and rate of burn.
At the end of October I finally had the crimp die operational (see crimp die construction thread HERE.)
I decided to begin with Lil'Gun, and loaded a series of increasing powder weights. I did not load up a large number of cartridges for this initial exploration. Load procedures were much like those of previous chapters. I used the same Hornady encapsulated 185-grain SWC bullets (#45137). Working with Lil'Gun, I used Winchester SR primers. I began with new cases. Cases were prepped using the FL Hornady sizer and flared a bit with the expander die. Powder was weighed to the nearest 0.05 grains. Bullets were seated so the COAL was 2.000 inches, and then taper crimped with the Hornady die to a mouth dia of 0.476". I applied the Lee factory crimp, so that the center of the crimp was 0.070 below the mouth of the case, with the bullet being distorted as a result.
(See image posted on the crimp die construction thread.) Powder weights were 43-47 grains in increments of 1.0 grains.
At the range, the chronograph was set at 8 feet from the muzzle. With an air, ammo & rifle temperature of 40 degrees F, these were the recorded velocities:
43 grains . . 2441 fps
44 grains . . 2548
45 grains . . 2623
46 grains . . 2663
47 grains . . 2720
A factory load gave 2216 fps. Two of my handloads of the 250 FTX gave 2288 and 2291 fps.
There were no signs of excess pressure with the crimped loads. Case heads showed no expansion when measured immediately in front of the extractor groove. The pressures of firing ironed out the crimp in the cases almost completely.
This sequence was encouraging. The uncrimped loads loads put together with the same amount of powder and fired 4-5 months earlier had given higher velocities at the low end of the series, but were also more erratic. (See Chapter 1).
I decided to proceed with increased powder charges.
(continued in Part 2)