Volocity change vrs. seating depth.

[400bull]

I'm fairly new to reloading and could use some advice on a new load that I am working up for my Win 270. I bought a couple boxes of Hornadys' 130 SST hoping that these would be my bread and butter bullet for small game and deer. In the past I have tried to load everything so that the bullet is about .015" off the lands and have good results with it that way. But with the SST I have to be at lest .040" of an inch off the lands because of magazine restrictions. So the first loads I put together I backed them off an additional .040" (total .080") off the lands to make sure I had plenty of clearance from the magazine. When I went to the range last weekend I was getting great groupings with the exception of one flier in all loads tested. The problem is I was hopping to get a little more velocity out of them then I was. My charges varied from 56 gr. of H4831SC to 60 gr. with velocities from 2700 ft/sec (56 gr. charge) to 2940 ft/sec (60 gr. charge). I was wondering if I were to redo the 60 gr. charge but very the seating depth in .010" increments how much would this change my velocity? Should I be able to get that up close to 3100 ft/sec or is that unrealistic?

My Max OAL is 3.50.
Magazine is 3.410.
Loads tested were 3.370
Loads in question are 3.380, 3.390. 3.400. and 3.410

400bull

 

[jmason]

In my very limited experience with a 270 and the same powder your using; you will gain very little speed with seating changes. I recently did some seating tests with 140 grain BTs and shot 5 rounds at each depth starting form touching to .025 off. There appeared to be no avg speed change over the over the spectrum of these 25 rounds. I'd also like to think your leaving a little velocity on the table with your 130s. In my particular rifle I was able to reach near 3100 fps safely with a 140 gr bullet. I did not have consistent ES/SDs up there though. I found decent es/sd at an avg mv of 2969fps.