How to compensate for a differant bullet length

[Jarhead66]

I've been using a 9mm 115gn RN poly coated bullet from Acme bullets. Been seating to 1.10 col using 6.1gn HS-6 and 6.1 Unique with good results. The company changed the shape of their 115gn RN bullet, so I had to go to 1.060 col to just pass my plunk test on my barrel. The original bullet was .560 oal and their new one is .530 oal. How would I make the adjustment, in seating the bullet, with using the above powders powders and not creating excessive pressure. With the new one being shorter but seating deeper is it basically a wash.

 

[Steve C]

The new bullet is shorter by .03" and you reduced the OAL by .04" so you've effectively shorted the aol by .01". 6.1 grs of HS-6 is below Hodgdon's data for a 115 gr lead RN bullet which is 6.4 gr so there's no reason to worry about your HS-6 load.

6.1gr of Unique is a bit hotter than start load on most data for 115gr bullets which is calculated at 5.7 gr using Alliants 6.3 maximum. I would drop it down to a 10% reduction of that 6.3 maximum at 5.7gr and work back up though I doubt if you'd run into any excessive pressure using 6.1. You may simply want to try a few rounds at the 6.1gr load with the new bullet and OAL to see if there are any pressure signs or the accuracy is satisfactory.

 

[Jarhead66]

Thanks Steve, I'll work it up like you stated and see what happens.

 

[AnselHazen]

Is this that 9mm lipstick stuff?