I finally had a chance to pour some pellets today.... Al surprised me by sending everyone a fourth set of pins to make a flat base, 73 gr. pellet as well.... I cast all four versions, and here is what they look like.... Virtually all of the solid base pellets were great, but about half the skirted pellets got tossed back into the pot because the back edge of the skirt had a slight notch from improper fill-out (regardless of the skirt depth).... This was despite running the pot at over 800*F, preheating the mold, and using a fast tempo while casting.... It looks like these pellets will take a while to learn the best technique.... but I'm sure I can reduce the reject rate with practice....
I used 40:1 lead/tin (2.5% tin) and got the following weights....
Deep base pin = 59.3 gr.
Medium base pin = 62.9 gr.
Shallow base pin = 65.7 gr.
Flat base pin = 73.3 gr.
I tethered my .30 cal BRod at 2900 psi, and adjusted the velocity so that the 59 gr. pellet was just under 1000 fps, and got the following for a 5 shot average.... I shot some 50.2 gr. JSBs for comparison.... The chambering effort for the 59 gr. was no different than the JSB, but as the weight increased and the bolt probe pushed the pellet deeper into the throat of the chamber, the effort went up a bit.... However, even the 73 gr. solid chambered in my TJ's barrel just fine, and at 0.301" groove it is tighter than most .30 cal airgun barrels.... so I don't anticipate anyone having chambering issues....
59 gr. = 987 fps (128 FPE)
63 gr. = 944 fps (124 FPE)
66 gr. = 955 fps (133 FPE)
73 gr. = 881 fps (126 FPE)
50 gr. JSB = 1039 fps (120 FPE)
For some reason the 63 gr. (medium base pin) pellets were a bit down on velocity compared to the 66 gr.... The bolt probe in this gun is 0.109", so smaller than the bottom of the recess in the deepest skirt, so the loading depths should progress in a logical order, with the flat base loading the deepest and the lightest pellet the shallowest, so I don't think that is the reason.... This leaves me to conclude that the shallowest base (the 66 gr. pellet), and of course the solid, flat base (73 gr.) are not obturating in the same way, and have less friction as they travel down the bore.... I'm sure the are sealing fine, because the back of the skirt is 0.308", and the head is 0.301".... but it is likely that the deep and medium base pellet skirts are blowing out a bit from the air pressure (as is normal for pellets) which is adding some bore drag.... I can't think of any other reason that the 66 gr. pellet should shoot faster than the 63 gr.... but it did so consistently in this gun....
My backstop inside my shop is only 20 ft. away, but I can usually spot pellets that aren't promising because groups don't just leave one ragged hole at that distance.... In this case, all 5 pellets tested, the JSB and all 4 weights of the NOE pellets, left just one ragged hole about 1/2" OD, with no consistent variation between the different weights.... I am hopeful they will provide good accuracy at range.... but is it very likely that others will get a chance to find out long before I do.... The nice thing is that by tethering my BRod at 2900 psi I have enough power to drive any of these weights into the mid 900s, even the 73 gr. solid....
Bob
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