zeroing, using the same fps with different wt 30 30 bullets

[Doctor]

I shoot cowboy lever action silohuette. One of our events uses 30 30 rifles and i have good zeros at 2100 fps with sierra 125gr bullets with 26.2 h 322. I would like opinions if i change the bullets to 150 gr and use another powder, 4064 imr loaded at 2100fps,will the zero be fairly close under the same weather conditions?

[Steve RA]

Depends on how you consider "fairly close", big difference would be difference in ballistic coefficient between the two bullets. You didn't mention the distances involved, but, using 30-30s I assume they would not be terribly far. Probably not too much difference, why don't you load some up and see what happens.

[dauntedfuture]

take a look on JBM ballistics and compare the two loads. Provided you are shooting lead bullets, the BC's are both going to be very low. 125 jacket blat base vs 150 jacket BT, the edge will go to the 150 BT. Set the computer up to zero both loads at 100 yds and see what drop you get at 200 or 300 yds with both. At 200 yds I suspect you will be 3" high with the 150's provided all else remains the same.

[Doctor]

thanks

the jbm computer is helpful