Hello and thank you all in advance for your help.

I recently acquired a 360SC which I have quickly grown to love. It's a handful with hot magnum loads but a lot of fun with mild stuff.

I'm not new to handloading, been doing it for over 20 years now. I haven't done a lot with a chrono as that's a new addition.

My question is about load data variances with VV N310 powder. I have three different sets of load data from the powder manufacturer ... 1996, 2002, and current load data from VV's website.

1996 data shows me 5.1 - 5.9 grains, 1097 - 1213 fps
2002 data shows me 5.5 - 6.1 grains, 1134 - 1234 fps
2015 data shows me 6.0 - 6.4 grains, 1217 - 1284 fps

Bullet used is 125gr Hornady XTP.

My intent is to build a load that is 'in between' .38spl +P and hot .357 Mag loads with complete, or nearly so, powder burn in a 2" barrel, no flash, and super clean burn.

After a LOT of consideration, I decided to use current load data for my development and am now up to 6.2 grains powder. My velocities average 1086 from a 6.5" model 28 and 1078 from my 2" model 360.

I guess I expected more velocity based on load data but real world results show me that I have the load I'm looking for. No pressure signs have been noted on any cases so far.

Anybody willing to enlighten me on the manufacturer's HUGE variances in data? Is my real world velocity what is to be expected? Since ammo manufacturers publish velocity on the box, should I chrono some store bought personal defense ammunition for comparison?

Sorry about the long story and thank you again for any advice.

I think that Vihtavouri either uses a chronograph that reads fast or they have hand selected a barrel that is abnormally fast, possibly as a result of being extremely worn. Because the velocities they list in all of their load tables for 38 special or 357 Magnum are much much higher than what I've clocked with my Shooting Chrony. I would advise that you completely ignore the published velocities and simply work your loads up by keeping a close eye on indicators for excess pressure.

BTW, as another data point and example of the extent of the velocity hyping they do here are my results for a 6.7 grain charge of 3N37 combined with a 125 grain Ranier plated bullet. According to Vihtavouri this mid range load should be clocking 1050 fps. Out of a 6 inch Dan Wesson 15-2 this 38 special loading produces 800 fps. Out of the 20 inch barrel of my Winchester 1892 this load clocks just 1150 fps. Doing a bit of math reveals that in order for my 38 special load to hit the 1050 fps velocity projected by the Vihtavouri data indicates that a barrel length of 16 inches would be needed.

So, why do powder manufacturers hype their velocity data? It's because the buying public tends to be driven by tow things, low prices and "higher performance". So, being the idiots we are if it's not a bargain special we want the most bang for out buck we can get and with gun powders that means we want the powder that produces the highest published velocity.

The latest data was generated using a 7 inch barrel without the pressure loss from a cylinder gap that one will see with a revolver. While it may not generate 1200 FPS it is a really nice shooting and accurate load. I have loaded up a lot of these and really like them in both my model 27 and my model 66 snub.

Thank you Scooter and NRA doc. Makes perfect sense and goes along with my results.

NRA DOC, how long have you been using N310 in your .357 Magnum? Seems there is quite a diverse gap between the few who use N310 and the many who will NEVER use it.

I use quite a bit of N310 in 45acp Bullseye competition loads . IMHO N340 , N350 , N105 & N110 work much better & have higher loading density in 357mag . For the loads you're looking for N340 or 350 would be a better choice . If you want more power then N105 or N110 , 2400 & W296/H110 are the tickets .