I’m shooting these loads out of the No.4 T that I just rebarrelled with a Lothar Walther 4 groove RH twist barrel. Now at 155 total rounds after these tests. 

Basic Load Data:

PPU Case Annealed and Neck Sized

WLR Primer

VV N140, 40.0, 40.5, 41.0, and 41.5 gr. 

174 gr Sierra MatchKing

3.070” OAL

It was evident after the first group of 40.0 gr N140 that I would not shoot the 41.0 and 41.5 loads as velocities were higher than I expected. Also, the 40.5 gr N140 load, the group blew out. 

Data is for 10 shot groups fired at 600 yards off the bench. 

Also showing is the control group, my standard Varget Match Load.  

I’m going to drop the N140 loads back and try 39.0 and 39.5 gr. Would like to get the velocities about the same as my Varget load, that way the rifle will regulate to the No. 32 scope elevation settings and accuracy will probably be very good as well. N140 is a slightly slower burning powder and giving higher velocities than Varget at the same charge weight. 

I’ll provide an update here on the results of 39.0 and 39.5 gr. 

I think I've mentioned on here before that 41.8grs of N140 has a long held belief here in the UK that it replicates the MkVII load of 2440fps ?? 

I wonder if that is popular (UK) shooting myth, or are your results possibly temperature related? 

  

  

I neglected to give the weather conditions. It was not all that hot, 85 deg F at the time of shooting the N140 loads.  N140 is supposed to be quite temperature stable.  

Vihtavuori website gives the following for N140 with 174 SMK seated to 3.070”:

Min  38.4 gr at 2379 fps

Max 41.7 gr at 2566 fps

Based on my tests, I suspect that is about right. 

 I’m rather suspect of the claim that 41.8 gr duplicates Mk 7 ball muzzle velocities. Or, Vihtavuori has changed their powder formulation since then.  I’m thinking it’s more like 39.8 gr. 

I wonder if I need to re-look at my loads which did at the time include a 900 yard shoot which I am now (slowly) experimenting with a 190gr bullet and N150.

The forecast for tomorrows shoot at Bisley is 93f, assuming I manage to shoot my three details in that heat! 

That’s 10 deg hotter than the forecast for NE Georgia tomorrow.  But it’s the 70-80% RH for tomorrow’s match that I’m more worried about.   

Shooting a 80 round Service Rifle match, four stages of 20 rounds each + 2 sighter shots per stage. 

Geoff, I've had this temperature stability chart saved on my hard drive which shows the expected velocity gain per degree rise in temperature.  Unfortunately the baseline isn't shown nor the low and high temps that the chart can be expected to be reliable but it is useful as a tool to know which powders are the least affected by heat.  I have no idea who developed this chart nor can I speak to its accuracy.

Geoff we're in the middle of a heat wave after the wettest winter I can recall; drove back from Bisley today and the car recorded 32.5c or 90.5f in old money as call it over here. 

Hot weather is not conducive to good shooting!

We're having a bit of a cool down here in Texas Mick, it's only going to be 93 f. today.  ;>)  The only way we can shoot on a really hot day when it's north of 100 is shoot in the shade and have large fans blowing.

I’ve done my own tests with Varget, and found it very stable, as others have.  I’ve not noticed any appreciable change in MV with Varget from 40 deg to 85 deg F which encompasses about 80% of the conditions I shoot in. 

Speaking of heat, I shot in a match yesterday, as did Mick on the other side of the pond, and it was miserable on both sides!  By the time of the last stage of the match at 600 yards in slow fire prone it was around 1230 with full sun right above us.  We had just had a light shower and that sun drove the humidity up to around 80% RH.

Yesterday I was shooting a 80 shot Service Rifle Match with the AR.  My 600 yd stage load is 23.5 gr N140 with the 80 gr SMK. I did not see any change in elevation setting from my last match when it was quite a bit cooler. 

From winter to summer, I’ve not detected more than 1/2 MOA difference at 600 yards with N140 from 40 to 85 deg F.  I get much more change in elevation (and measured velocity) after I clean the bore with JB and completely remove the carbon ring that builds up right in front of the case, as much as 100 fps difference. 

I think I have the newer formulation, I will check when I get home tonight.  

Next step is to test 38.5, 39.0 and 39.5 and that will complete the range of loads from 38.5 to 40.5 gr at which I should be able to interpolate on 2370-2400 MV that I'm looking for; providing it also gives good accuracy at 600 yds.  

I rarely ever go back to the hardcopy book data, unless I know that the power I have is from that time period; otherwise I pull up the current data from the power manufacturer.  

Wx was warm and humid again today, similar to last weeks tests (40.0 and 40.5 gr N140).  Getting tired of this, looking forward to fall.  Winds were switchy today, so shot these at 300 yds, last weeks were at 600 yds.

Again, basic load data is:

PPU Case neck sized

WLR Primer

Vihtavuori N140 Powder, all charges weighed

174 gr Sierra MatchKing

3.07” Cartridge Overall Length

These are all 10 shot groups fired off the bench. Garmin XERO Chrono. Group size is center to center extreme spread in minutes of angle. Temp: 85 deg F. 

To duplicate Mk VII velocity specification (2440 fps),  40.3 to 40.4 gr N140 with 174 SMK

To duplicate my 40.3 gr Varget Match Load, 39.2 to 39.3 gr N140. 

Velocity spreads today were larger than last weeks loads, this may indicate that spreads tighten up with N140 at the higher velocities. 

I'm supposedly "off to the range" tomorrow.

Fingers crossed.

A new store is opening near where in our closest "big town" Easton, Md, down here in the flatlands of the Eastern Shore. It will be only one of two in the entire area with reloading supplies.

Not just yet, we drove past today doing other things & its Under Construction where they're re fronting an existing store.

They're claiming a "soft open" this month & a "Grand Opening" in August.

https://www.mymollys.com/pages/mollys-easton" rel="nofollow - https://www.mymollys.com/pages/mollys-easton

Last weekend I visited a family owned gun shop in Dreux ( France ), it's been there since 1920.

Father to son. It has so much stock, plus very helpful service.

I hope to get the chance to visit a gun shop and shooting range during my visit to the USA next month.

It will be interesting to compare with the European market.

This is interesting Geoff and a lesson in having to rethink historical data, some 30 years ago it was accepted here that it required 41.8grs on N140 to replicate the MkVII rounds ballistic capabilities.  

Either N140 has got hotter or the chrono's have become more accurate over the years, or possibly a case of both? 

I will now have to rethink my loading data...no bad thing given the cost of propellant! 

Zed:

check your PM's! 

You raise a valid point SB regarding chrono's possibly becoming more accurate over the years.  I have an Oehler which I've owned for years and a recently purchased Garmin Xero.  I was interested in doing a side-by-side comparison to see if there was a difference of any significance between the two and found two small differences:  The Garmin recorded slightly higher velocities which is no surprise as the Garmin is recording actual muzzle velocity whereas the sky screens on the Oehler are recording velocities 10 to 12 feet down range but there was one interesting difference: the Oehler reported a slightly higher extreme spread than the Garmin.  I put that down to differing light levels as clouds scudded overhead affecting when the glint of the bullet was picked up.  Are the readings off enough to make a difference in the real world?  Probably not as the average velocity readings were only 4 fps different and the ES was only 3 fps higher with the Oehler.  One last point, the Garmin is many times easier to set up and use than the Oehler which now sits unused in my shop.

These little Garmin chrono's have really made collecting velocity data easy.  Don't leave home without it. 

 

I've been meaning to use mine during the sniper match to keep from making scope elevation adjustments from a high or low velocity shot (error chase); and in that way, it seems it would be contrary to the spirit of the rules.  

Looking at the current rules I would say Garmin's are allowed at Bisley but I've never actually seen one being used in a competition.

 

Electronic Devices 309 

Cellular or mobile telephones, or similar devices, may not at any time be used on or in the vicinity of the firing point, unless their communication functions are disabled eg by placing in ‘flight mode’. Personal electronic devices may be taken to the firing point, provided they are NOT able to receive wireless transmissions. Hardware or software for shot or score recording or assisting with the process of the competition is forbidden, unless issued or explicitly permitted by the competition organisers. Electronic equipment provided by the organisers, or explicitly permitted by them, for the purposes of electronic targetry or spectator information systems are permitted. Where wireless personal devices are explicitly permitted for the receipt and display of electronic target information, the screens of such devices are liable to view by the Register Keeper or a Range Officer on demand and at any time. The wearing of implanted medical devices or hearing aids in everyday use is not prevented by this rule. The only means of communication between the butts and the firing point will be that formally used by the Range and Butt Officers. While firing is actually taking place no person in the butts is permitted to use any other means of communication that could be contacted by any person in sight of the firing point. 

How about things like anemometer hygrometer  or combination units with wind-speed rH & temp?

Nothing RF generating just pen & pencil.

I've occasionally seen shooters pull out a wind meter.  Also, many service/match rifle shooters will use a spotting scope to read the mirage (at about mid range to the target). I've never been successful at doing this so I watch the flags closest to the firing line (typically); for example, I'll watch the 200 yd flag when shooting at 600 yds.   The wind has to be pretty strong and full value to make much difference at 200x, in those cases I might dial in a minute correction.    

 

Same over Geoff but you only ever see tactical shooters use them; most of us usually work off a printed card.  

I've actually attached a 3' length of tree marking tape to the wrist strap.

I use it to get a true wind angle with the meter.

Mostly I use it for background information for my logbooks.

 "Hardware or software for shot or score recording or assisting with the process of the competition is forbidden."

Ironically we had an incident during the winter months when some new people to service rifle events were marking in the butts and phoned their mate on the firing point to tell him all his shots were going left!

I believe those involved have been told to either read the rules or find another discipline to shoot!