Loading advice required - Adam, please help.

[Brian the Brit]

At the range yesterday I shot my various P14 loads off a sandbag at 50 yards starting with a 5 shot group using 41 grains of VihtaVuori N140 and 174 grain Prvi Partizan bullet as a comparator.

The N140 group was very tight and at point of aim. Superb accuracy.

The AA 'groups' (more like vertical strings) were 3" low at 37 grains rising to 1/2" below poa at 39 grains where a reasonable group was starting to develop.

My gut feeling was that I need to push the rounds just a little faster to get Vit N140 accuracy.

However, the Accurate Arms loading data gives 39 grains as a maximum with the Sierra 174 grain HPBT bullet and 44 grains with the Sierra 180 grain SP.

I note, Adam, that you say your best load with this powder is 40 grains. Have I misunderstood something? Is it safe for me to go to 40 grains with this bullet?

I'd appreciate your advice.

[dromia]

OOOH! this is interesting.

Firstly apologies for taking so long to reply Brian but I have some personal issues at present which is keeping me away from these boards at this time.

I've checked back on my data and found that my load came from the 2004 AA data hand book which specifies 39.6-44 gns 2520 with the SRA 180 gn SP as does the current AA data from the web site. Therefore I worked up my loads within this range.

The interesting thing is the SRA 174 gn BT which has a charge range below the starting point of the 180 gn loads.

The top pressure for the 174 bullet with 39 gns powder is 42,900 CUP against 45,000 CUP for 44 gns powder with the 180 gn bullet.

The 174 gn data is new this year as it is not included in the 2004 and 2005 AA data books I have, therefore when I did my load development I just went with the 180 gn data, ignorance is bliss.

The SAAMI maximum average pressure for the .303" is 45,000 CUP according to AA.

We could speculate as to why this apparent "discrepancy" has occurred but a email to Accurate questioning the data would be prudent.

Anyway back to the load, what I am about to write would be my approach to the issue in my rifles. Therefore I cannot recommend that anyone else tries this as you will be potentially working beyond published data. You are one your own here and I do not recommend that anyone follows this procedure and cannot be held responsible for anyone that might choose to go beyond published data. I hope that I make myself clear.

From your description Brian of vertical stringing it does sound like an ignition issue with the powder not generating enough pressure to fully obdurate the case, were the necks of the cases sooty by any chance?

I would increase my loads by .2 gn increments in 3 rd lots over a chronograph looking for any sign of excessive pressure. Without a pressure barrel judging pressure is a very inexact science and I would be reading a multiplicity of signs.

Chronograph, the best and most financially accessible tool that a hand loader can use. For the .303" 2,300-2,400 fps is the range that I would be looking for, if I am there already with this load I would stop and go back to Viht.

Case head expansion, this about measuring the size of the base of the fired case against a reference round, I measure the base of some PP commercial ammo say five rounds and take an average. I fire these rounds in my rifle and take an average again of the fired cases, this will give me a case expansion figure within pressure limits. Using the same cases for my reloads FLRS I can then use their case expansion figures against the commercial reference ones. When expansion gets near the commercial figure I stop. Not an exact science either still lots of variables at play here but still another indicator.

Primer flattening, again not exact but if it increases ina load series then another indicator I use.

Noise and recoil, if it don't feel right then I stop.

Hard extraction is another indicator, personally I usually stop before this happens as the other indicators will have kicked in.

I never now look for a maximum load, only an accurate one within the pressure envelope, life is too short to push the envelope with reloading.

So in summation if it were me with this situation and the apparent load anomaly between a 174 gn and a 180 gn bullet I would check with Accurate Arms first, then in the light of their response try some cautious load development, however I do not recommend that anyone else does this and write this for information and the curiosity of readers.

[Brian the Brit]

Sincere thanks for your very detailed and erudite reply, Adam.

I fully understand your disclaimer and appreciate why you have included it.

I tried e-mailing AA about a week ago but got an error message, something about my browser not generating a header. It meant nothing to me. Doh!

Perhaps a chrono should go to the top of my Christmas list? (What do you mean, "There ain't no Sanity Clause?)

Thanks again, mate!

[joseyclosey]

Quote Dromia, ".... For the .303" 23,000-24,000 fps is the range ...."

Bit of a pokey load that one Adam

Joe

[dromia]

No Poofs loads for me Joe

Wrong place for the comma correction made.

[sunray]

You may find that your rifle just doesn't like the AA powder. Not unusual either. Mind you, when you're working up a new load, forget about the POI. Get a decent group first then adjust your sights for that load.