Recently I barreled a 500 S&W with a custom 10" stainless barrel. It was my intention to shorten it 1" at a time and chronograph it with a variety of loads at each length.
Benchrest gunsmith Art Freund did the work. Gap was set at .004" Forcing cone duplicated factory dimensions as nearly as possible.
I ran a clean patch down the bore, checked to see that it was clear, loaded the gun, and aimed through the skyscreens.
The first shot was a load that should have given about 1700 fps with a 450 longnose slug out of the 10" barrel. The gun sounded a bit different than normal and the velocity was 1385. Hmmm...
I tried to open the gun to check the case and it wouldn't open at first. Then I see that the left and right sides of the forcing cone are GONE, and the top and bottom of the cone are splayed up and down, respectively. With a little more effort (hands only) I get the cylinder open. It is undamaged, but the back end of the custom barrel is mostly gone. At home I take pictures, then put the frame in a vise and knock off the pieces of the FC with a brass drift so I can unscrew the barrel. It is split the entire length of the threads.
Comments:
1. This was NOT misalignment. The forcing cone went outward everywhere, stopped only by the topstrap and cylinder nose. The firing pin dent was in the center of the primer, so the round was not grossly misaligned. Further, go to
http://www.john-ross.net/images/450BR500.jpg
for a photo of the cast bullet in question. It is obviously a somewhat self-centering design.
2. Load was NOT an overload. I have shot hundreds and the cases fall out of the cylinder.
3. Art Freund's workmanship was without fault. He did NOT reduce the diameter of the shank where it stuck through the frame--it was factory diameter.
4. Barrel blank was stainless, by a maker that Hamilton Bowen uses. Hamilton is baffled. The maker (for now) seems uninterested in pursuing the problem. My bore riding noses drop in the rifling. Groove diameter is no tighter that .499"
This makes no sense to anyone I've talked to. I plan to get the barrel and remaining blank Rockwell tested this week. I put the factory barrel and shroud back on the gun and it shoots as well as ever with the same ammo.
Pics are here: http://www.john-ross.net/images/500blow1.jpg
and http://www.john-ross.net/images/500blow2.jpg
I don't think the steel is brittle as the top and bottom of the cone was bent outward, not shattered. But the full length split down the threads bothers me...
The velocity was low, IMO, because the forcing cone blew out, giving the gun about a .150" barrel-cylinder gap for the rest of the bullet's 10" travel down the bore.
The barrel screwed in and out by hand with no wobble, just as it should for best fit. It was not choked down by the frame as on some factory guns with oversize barrel threads forced into the frame. Even now, the cracked barrel screws on and off by hand. The frame does not appear to be changed as the factory barrel screws in and out the same way it always did, with no more play than before.
S&W engineer Bret Curry suspects a soft blank. He tells me S&W 500 barrels are 410 stainless and Rockwell 42 on the C scale. I'll know more in a few days.
JR
Benchrest gunsmith Art Freund did the work. Gap was set at .004" Forcing cone duplicated factory dimensions as nearly as possible.
I ran a clean patch down the bore, checked to see that it was clear, loaded the gun, and aimed through the skyscreens.
The first shot was a load that should have given about 1700 fps with a 450 longnose slug out of the 10" barrel. The gun sounded a bit different than normal and the velocity was 1385. Hmmm...
I tried to open the gun to check the case and it wouldn't open at first. Then I see that the left and right sides of the forcing cone are GONE, and the top and bottom of the cone are splayed up and down, respectively. With a little more effort (hands only) I get the cylinder open. It is undamaged, but the back end of the custom barrel is mostly gone. At home I take pictures, then put the frame in a vise and knock off the pieces of the FC with a brass drift so I can unscrew the barrel. It is split the entire length of the threads.
Comments:
1. This was NOT misalignment. The forcing cone went outward everywhere, stopped only by the topstrap and cylinder nose. The firing pin dent was in the center of the primer, so the round was not grossly misaligned. Further, go to
http://www.john-ross.net/images/450BR500.jpg
for a photo of the cast bullet in question. It is obviously a somewhat self-centering design.
2. Load was NOT an overload. I have shot hundreds and the cases fall out of the cylinder.
3. Art Freund's workmanship was without fault. He did NOT reduce the diameter of the shank where it stuck through the frame--it was factory diameter.
4. Barrel blank was stainless, by a maker that Hamilton Bowen uses. Hamilton is baffled. The maker (for now) seems uninterested in pursuing the problem. My bore riding noses drop in the rifling. Groove diameter is no tighter that .499"
This makes no sense to anyone I've talked to. I plan to get the barrel and remaining blank Rockwell tested this week. I put the factory barrel and shroud back on the gun and it shoots as well as ever with the same ammo.
Pics are here: http://www.john-ross.net/images/500blow1.jpg
and http://www.john-ross.net/images/500blow2.jpg
I don't think the steel is brittle as the top and bottom of the cone was bent outward, not shattered. But the full length split down the threads bothers me...
The velocity was low, IMO, because the forcing cone blew out, giving the gun about a .150" barrel-cylinder gap for the rest of the bullet's 10" travel down the bore.
The barrel screwed in and out by hand with no wobble, just as it should for best fit. It was not choked down by the frame as on some factory guns with oversize barrel threads forced into the frame. Even now, the cracked barrel screws on and off by hand. The frame does not appear to be changed as the factory barrel screws in and out the same way it always did, with no more play than before.
S&W engineer Bret Curry suspects a soft blank. He tells me S&W 500 barrels are 410 stainless and Rockwell 42 on the C scale. I'll know more in a few days.
JR
