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I know I have said this before on other post's but try the OCW (google it) method first. I have done this before and gives you good indication of the accuracy nodes in your rifle and which charge weights to try different seating depths plus its a great read as well.

Thanks Christel - noted.

why has the thankyou face I posted above turned into a ranting face?!? - Sorry Christel - shoulda been a sign92

forbie wrote:I know I have said this before on other post's but try the OCW (google it) method first. I have done this before and gives you good indication of the accuracy nodes in your rifle and which charge weights to try different seating depths plus its a great read as well.

I've read the instructions for OCW on the link below
http://optimalchargeweight.embarqspace. ... 4529817134

Hmm - not sure if I'm ready to start test loading with powder weights above recommended maximums, I get nervous when I'm within 1 grain below that figure! Interesting theory though, I'll try it some day sign92

It's taken me a while to get everything in place, however on Saturday I finally managed to get down to the range to start recording some .308 test shots.

This first visit was to test out the chrono I'd borrowed (thank you Whoopwhoop!) and to get a base line for all future tests. It was shot over 100M which I know isn't ideal for this kind of thing but I didn't have a choice of range for Saturdays shoot, it was 100M or nothing.

I was using PPU brass which had already been shot about 5 times through this rifle, Federal 210 LR primers and SMK .168g bullet heads. The powder was TR140.
I was using a Remington .308 SPS varmint 26" barrel 1:12 twist in an AX stock.

Conditions:-
Wind: 0-1.8mph
Hum: 80.2%
Temp:57F
Baro: 30.31hg

10 shots using 41g TR140 and a COL 2.82"
2346 2314
2335 2334
2300 2306
2324 2329
2316 2338
Average: 2324fps




10 shots using 41g TR140 and a COL of 2.80"
I pulled the last 2 shots right to see if I was still hitting the target!
2359 2361
2363 2334
2343 2325
2346 2321
2319 2381
Average: 2345fps




10 shots using 41.5g TR140 at COL 2.82”
2327 2349
2316 2336
2325 2340
2310 2350
2330 2357
Average: 2334fps




8 shots using 42g TR140at COL 2.82” ( I shot 8 times at this target then had the lunchtime hooter go before I could shoot 9 and 10). I shot 9 & 10 after lunch at a new target and recorded the FPS scores.
2370 2386
2394 2423
2381 2402
2407 2428
2423 2418
Average: 2403fps


Results
This was really just a run through of process and equipment for me, however I was suprised at how much the group seemed to close up when the COL was reduced to 2.80". The fps scores seemed a little on the low side, I was getting averages of 2550fps using N150, so I think I need to up the powder levels.Others seem to find good results around the 43.5 to 44g level using TR140 however I will continue to work up to these figures slowly.

Tomo wrote:however I was suprised at how much the group seemed to close up when the COL was reduced to 2.80"

...and yet the velocity ES and SD indicate the opposite:

SD at 2.800: 19.6
SD at 2.820: 14.1, 14.5, 19.0

ES at 2.800: 62
ES at 2.820: 46, 47, 58

Not that velocity is the be-all and end-all (especially since you presumably won't be using these at long range) but it does have the human factor removed. What kind of jump do the two lengths correspond to?

Series 4 looks to be an odd-one-out, since the velocity spread is larger (like the 2.800 load), however, it exhibits a fairly significant increase over the course of the string (seen to a lesser extent in series 3). Could this have been caused by not allowing enough time between shots for the barrel to cool to a consistent temperature? If you compensate for the increasing velocity the stats are much closer to the 14/45 of the others at 2.820 length. Of course there are many other possible explanations and causes.

Last time I ran TR140 loads over a chrono the sweet spot gave an SD of 7.8, with about 10.0 outside of that point.



..

Thanks Rox - very interesting read.

The last group I shot was a bit rushed as it was getting close to lunch time, so I didn't allow much time between shots.

My Remi has a very long throat (I think it measured something like 2.94") so there's no way I'll get close to the lands. I've experimented with different cols of between 2.80 and 2.83 and had settled on 2.82"

The next time I go up to Bisley I'll book time on both the 100M and 200M ranges. I can use the chrono to measure speeds in the morning @100M then do some further testing in the afternoon at 200M (I don't think there's room to set up a chrono @ the 200M firing point on SS).

I can load up six rounds each of various weights and lengths then stick 3 of them through the chrono in the morning and then the other 3 @ 200M in the afternoon.

I think I'll start at 41g again and load up 6 @ 2.80 and another 6 @ 2.82". I'll work up in .5g increments until I get to 43.5g.

I spent a frustrating day down at Bisley on Wednesday trying to gather more data for my .308 loads. The weather wasn't the best, okay in the morning with just a swirling lightish breeze and some sun shine, but by lunchtime the wind had picked up and the clouds had well and truely set in. It became too dark for the chrono to work properly and I lost a lot of data :(

At least it didn't rain :)

In the morning I shot at 200M and produced these results (no chrono in use).
I was using PPU brass which had already been shot about 6 times through this rifle, Federal 210 LR primers and SMK .168g bullet heads. The powder was TR140.
I was using a Remington .308 SPS varmint 26" barrel 1:12 twist in an AX stock.


8:30AM
Hum: 85.5%
Bar: 30.25
Temp: 57.7
Wind 2.4-13.5mph! it was all over the place!






In the afternoon I shot at 100M and collected some fps scores (below) with some photo's thrown in.

All shot @ 100M


41g – 2.82”
2434
2450
2418

41g – 2.80”
2437
2418
2449

42g – 2.82”
2471
2463
2472

42g – 2.80”
2518
2497
2512

42.50g – 2.82”
2538
2522
2500



43.5g - 2.80"
ERROR
ERROR
ERROR
(not enough light)

42.80g – 2.82”
2498
2503
2480

42.80g @ 2.80"
ERROR
ERROR
1168??


43g @ 2.82"
1192??
1200??
1195??

43g @ 2.80"
ERROR
ERROR
ERROR



43.2g @ 2.80"
ERROR
ERROR
ERROR

in fact all of this targets data was lost as it really was too dark by this time.

Next time out I think I'll explore between 41-42g a bit more closely (.2g jumps) as well as 43.8g and above (there were no zero pressure signs from the rounds fired - IN THIS RIFLE). Will creep up in .1g jumps I think......VERY carefully!