Casting / Weight vs. Size

[PoofNoEyeBrows]

Here's the question. I cast 100 .452 RNFP (Lee Die) 255gr bullets. Because of the high antimony content the bullets averaged out at 222gr. What if any considerations should I take into account for the weight difference? My first thought is that I would stick with 255gr load data as the size of the round is the same thus limiting case capacity. I would assume that velocity would more then likely increase since weight is different, unless the bearing surface of the bullet actually has more of an effect then the overall weight. Anyways, let the speculation begin.

Round Details

Caliber: 460 Rowland

Powders: Accurate #7 / #5

Brass: Starline (New)

Primers: Winchester (LP)

 

[Omega]

I would use the data for the weight, since it's the same size, relatively, the weight would be the only difference. Velocity will be different, increase as you speculated, and pressure, probably less, since the bullet will move forward sooner. Bearing surface should start the same since it's the same mold, but hardness may be an issue since the bullet may not obturate as much, leading to less bearing surface.

[Sunfish]

Rowland velocities are pretty fast for lead without a gas check. The pressure will as stated be lower.  #5 with the heavy data would be where I would start. If you get leading you will know its not a good combination

[PoofNoEyeBrows]

Thanks for the replies guys. I am aware of the leading possibilities which is one of the reasons I am experimenting with this specific alloy which is around 30 bhn. I have published load data for aac #7 so I will probably start there as it is a little slower then #5. 

[RED333]

Powder coat your boolits and you will get no leading.

[PoofNoEyeBrows]

I am going to the range tomorrow. I will cook up 3 seperate batches with slowly increased charges. If possible I will take pictures of the bore. Not sure if I can get a good angle since the comp locks the barrel to the slide for the most part. I'll report back after in case anyone else is interested in the results.

[RED333]

12 hours ago, PoofNoEyeBrows said:

I'll report back after in case anyone else is interested in the results.

Please do

[PoofNoEyeBrows]

Ok so went to the range today. Listed data I am using as my base for a new load is 12gr aac #7 with a cast SWC 250gr. I worked all my loads in batches of 5 and went up incrementally from 9.5 to 11.1.

No signs of over pressure

No lead fouling what so ever

Accuracy was amazing. 

I will continue to work this load up and then run it through the crony.

[RED333]

Thanks for the update, nice rig and good shootin!!!

 

[MacGyver]

Neat setup!