Causes? Loaded to hot for bullet type?

[Don357]

I fired some of my .38spl and .357mag reloads today and got a surprise. The .38spl's were loaded with a 158gr LSWC on top of 3.4gr of "Bullseye" and a CCI #500 primer. They shot great. Using a Ruger Blackhawk with a 6 1/2" barrel, I was able to get a 4", 6 shot group at 15 yds on the 2nd cylinder. It took the first to get used to the sights.
The .357mag's were loaded with 158gr LSWC on top of 6.4gr of "Bullseye" and a Federal #200 primer. Again, with the same gun, on the 2nd cylinder I was able to get 5 shots in a 6" group at the same distance, but the bullets seemed to be "key holing".
Could the load be to hot for the bullets or could there be some other cause for the "key holing"?

 

[Pumpkinheaver]

Severe leading of your barrel could cause problems. What size are the bullets you are using? What kind of lead bullet?

 

[lwknight]

Bullseye is a fast powder. You could be skidding the riflings if the bullets are not hard enough. I never liked bullseye for heavier loads. Its too radical under pressure.

 

[rcmodel]

I would bet you money your barrel is leaded so bad you can't see the rifling.

6.4 Bullseye is very close to a max load giving 1,320 FPS & 33,900 CUP.

Dollars to donuts you ain't got store bought bullets that will handle that without severe leading!

rc