mactavish

This 147gr OCW was shot in virtually no wind (I'd waited nearly two months to shoot this batch that I made up last November, having passed up a number of shooting days due to learning the hard way by twice wasting lead doing OCW in choppy conditions). The real point I made earlier is that with these pretty small groups from a factory rifle on a small tactical bipod, a tiny rear bag and about 10 minutes cooling after each group, I reckon I'm not prepared to believe either rig or I am good enough to resolve POI causes and effects further. We're all fallible (as demonstrated by the big flyer on the last group). If I did try to draw conclusions further from the resulting groups I think I could easily be chasing shadows. (See the pic below where I've just overlaid the whole set in Photoshop. Note that discounting the 2 "flyers" at top & left, that all 16 remaining rounds lie in a 8.5mm x 12mm group. At 100 metres and across a whole grain of powder, you got to be happy with that... ) Anyway... I've just checked back in my Loading/Firing Records and note I actually speed tested 10 of that 46.86gr load last month. They were shot in 5°C conditions (hence slightly lower MVs than indicated by an earlier RS70 and 147gr ELDM speed ladder shot last October) and ranged 2808 - 2823 fps for an ES of 15 and an SD of 4.9. As mentioned, I'm pretty happy with that, especially given the potential for inconsistencies in my batch 2 brass from which this OCW was shot.

You might be right... but then again, from 100 metres out I was more inclined to conclude that I couldn't rule out that what had occurred within the 6mm of 46.8's horizontal aspect and the 6mm of 47.0's vertical aspect, wasn't down to the trigger puller...

Assume that's a typo, VarmLR, but 46.85 grains seems pretty clear to me... Oops! Apologies. That's a typo of my own. I was referring to RS62 throughout. Results for RS60 have been mixed in this rifle. I've found reasonable accuracy, but neither in the same "across the board" manner or specifically excellent nodes as found with RS62 and with RS70.Turns out it's just less forgiving at the higher velocities I was chasing with it and I'll be keeping RS60 for future use in a custom project I'm currently contemplating. And yes, I reckon you're right re bearing length being less on the Scenars v the SSTs. That they're a smidge lighter and I've also found them to be ever so slightly narrower than the SSTs, it's no surprise to see them flying 30-40fps faster for a given charge. I've not done extensive strings on my developed loads to find MV consistency (I've a magnetospeed and I consider every round shot a bit wasted in terms of anything other than for assessing MV), but in the 2 or 3 I speed tested after OCW, I did find ES for both RS62 & 70 to average sub 15 in all the nodes found and that was with no regard to barrel temp controls. I guess for now, these hastily found preliminary ES figures are well within acceptable working limits, but as this season progresses and ranges increase, I might find that revisiting MV consistency and making a few tweaks beneficial. Related to this, I too seem to have found accuracy has incrementally improved over the first 3 firings of this Lapua brass and I reckon ES has probably benefited here too (I'm bumping 2 thou, which is obviously working well also). Unlike you however, I've only ever used Murom S/R Magnum primers (KVB-223M) from the outset, so can't comment on any other primer type, though I do find it odd you're finding any pressure signs with RS62. I wasn't even seeing pressure with Scenars on 44gr of RS60 pushing them at 2915 fps...!! (Though I did see pressure with Berger HTs from 43.7gr+ RS60 at 2850fps+.) Incidently, I have 5 batches of 100 cases ranging from 1x unfired to batches 1& 2 being 4x fired. A problem I considered from early on (and another reason for limiting MV analysis) was because I was running various different powders and bullets (from mild to pretty hot) within batches 1 and 2, I knew load to load consistency within these batches could be affected and I now no longer use them for ultimate precision (as an aside; finding the ES values noted above is something of a bonus). My aim is to anneal, trim and re-batch all batches after 5 firings. Again, as this year progresses and I undertake more longer range precision work with single bullets & charges now identified, I will be able to use case batches 3, 4, 5 and a re-batched 1 & 2 to provide more consistent precision MV analysis and tweaking.

When you found the SST needed more powder than the Scenar, was this to hold the same MV, or did you find 44gr doesn't hold quite so accurately for them? I ask, because I found (without getting down to scientific levels of measurement) that 44gr RS60 proved equally accurate across every 139/140 bullet tried to date. I also found Berger HT & Hornady ELDM & SST all consistently average 2640 fps, while Scenars average 2670. To be fair, however, I have not invested "scientific levels of measurement" into the Scenars, SSTs and 140 ELDMs because my focus for ultimate precision in this rifle turned to the Berger 140gr HT for short/medium range and Hornady 147gr for long range. This is why they were the only bullets afforded full OCW and subsequent seating depth analysis. (The Scenars and 140 ELDMs were acquired early doors while awaiting the arrival of 147 ELDMs to the UK and I'm now running down my last few, while I found some SSTs really cheap a few months ago and couldn't pass up the opportunity... that I found them to hold well under 1 MOA in practice/plinking (with zero time invested) was a great bonus. ) Anyway, good results yesterday... these A1s really ain't too bad... OCW: Hornady 147gr ELDM at 2800fps+ ...

Hi VarmLR, It's great to see your OCW experiences written up in such detail. Very interesting. Given your experiences to date, you might be interested to learn that on doing 140gr Berger Hybrid Target OCW in my own A1 last July... I happened upon the exactly the same figures as you quoted above. The self-same powder, cases & also including Murom S/R magnum primers from the outset. Our respective results appear identical even down to finding that 42.4gr of RS62 is marginally the more accurate, being a remarkably consistent 1 hole maker at 100m. I also found that the same charges of RS62 work exactly the same across a number of 139/140gr bullets I've tried from Hornady & Lapua, with only relatively minor MV shifts between each. Subsequently, I've mucked around with various bullets from 95gr to 147gr and the four RS powders (52, 60, 62 & 70) that lend well across the 6.5mm Creedmoor spectrum. The upshot has been [mostly] positive results and to summarise, I've found the Creedmoor is a fantastically versatile round. That said however, I think I did find a real darling in this rifle... a combination the rifle might have been built for. Finally getting my hands on some 147 gr ELDMs last October, I'm now running them at 2825fps with RS70 and it shoots repeatable 6mm groups at 100 meters. Such a slippery little specimen at over 2800 with this level of precision is proving to be an absolute blast.