The reason that I don't like 155 gr projectiles because of high velocities over 3,000 fps will make your barrel life shorter.
Ah, now that's an interesting view, one well worth looking at in greater depth.
Barrel life killers are:
1.) absolute maximum pressure / flame temperature loads - a mixture of powder choice and actual charge weight used. A double-base powder load running at 60,000 psi in 308W will kill a barrel's accuracy potential much quicker than a single-base powder load running at 55,000 psi. Less certain, but likely is that if both powder types are producing the same 60,000 psi PMax, the D-B load will wear the barrel out faster than the S-B type, but there are all sorts of potentially mitigating factors at play here.
2.) rapid fire causing serious barrel heating in the leade / throat area resulting in rapid erosion and firecracking of the surfaces. US style string shooting therefore wears barrels out a lot quicker than the paired shooting we do in the UK and I believe Canadians use too. Powders that produce more heat will add to that.
3.) bullet weight, heavy bullets normally wearing throats out significantly quicker than equivalent loads with lighter bullets.
Taking point 3.), first, what's an equivalent load? One that produces the same ME and uses the same type, not necessarily grade of powder. So your 185gn combination at 2,590 produces 2,756 ft/lb ME; the same energy with the 155.5gn Berger is produced at 2,825 fps which will be a very modest performer if you're running a 30" or longer barrel. So, if you you used H. VarGet to produce both loads, they'd both be well below the allowed SAAMI / CIP PMax values. Let's see what QuickLOAD says using a 56.0gn water capacity case (around what you see with Lapua) and assuming you are using a 30-inch barrel with chambers that require the same COAL of 2.900-inch to be just off the rifling
155.5 Berger BT at 2,825 fps MV = 44.4gn Varget / 50,193 psi PMax
185gn Berger LRBT at 2,590 fps MV = 41.5gn Varget / 50,713 psi Pmax
Since they're producing equivalent energies, not too surprisingly they're calculated to use pressures that aren't too far apart, so sheer pressure won't affect barrel life unduly in this case.
However, even though they are equivalent loads in terms of
internal ballistics, the 185gn Berger will likely give a better
external ballistics result in a crosswind at long ranges despite their having almost identical 'form factors' or numerical efficiency values, the 155.5 rated at 0.988, the 185 at 0.985. That's because with two similarly efficient bullet designs at equivalent MVs, the heavier bullet always moves less in any given wind condition.
So uUsing Bryan Litz's range-test acquired G7 BCs, and his PM Ballistics Solver 2 external ballistics software, 10 mph 90-deg crosswind drift at the 800 yards you say you're interested in will be:
155.5 (G7 BC 0.237) / 2,825 fps MV: 58.4-inches (6.97-MOA)
185 (G7 BC 0.283) / 2,590 fps MV: 52.93-inches (6.3-MOA)
Both combinations produce similar terminal velocities at ~1,470 fps, so transonic flight worries aren't a factor.
To get the 155.5gn to the same 800yd wind drift figures, MV has to be raised to 3,000 fps and that needs a maximum load of VarGet, so we're running at 60,000 psi in Lapua brass maybe a shade more.
So, on the face of it, your view is clearly right as we have to run our loads at markedly higher chamber pressures to get equivalent wind performance at long ranges.
On the other hand ....... ! Heavier bullets wear the barrel throat out faster all other being equal because they have substantially greater inertia and therefore require considerably more time and pressure to get them moving down the barrel. Because they accelerate much more slowly than a light bullet, whatever maximum pressure and temperature is produced is applied to the barrel metal for a considerably longer period, so it heats faster.
How these two competing factors balance out in your case and which 'wins out' is an interesting question - one I've no answer to. Using Mikecr's barrel life spreadsheet says your solution wins handsomely at 4,311 rounds barrel life to 2,841 with the 155.5s at a much higher pressure, but the formula takes no account of bullet weight.
The other factor is of course, real-life results on the range. I've done a lot of analysis of my (corrected) wind plots from competitions at various distances up to 1,000 yards over the UK's three main long-distance ranges, Diggle, Blair Atholl and Bisley looking at the
actual shot-to-shot changes in corrected wind and then using an external ballistics program to convert that back to the
equivalent 90-deg wind speed change. It's the shot to shot change that's important, so a day with light but very variable winds can be much harder to cope with than one where the wind averages 25 mph, but sees pretty well constant angles and speeds. I've been surprised at the relatively small shot-to-shot wind speed changes seen in most matches when looked at this way, but you don't have to be much out in your wind-reading to drop points on the F-Class target of course. The point here is what bullet weight suits your rifle set-up, shooting style etc and which gives the smallest groups. The shorter the distance, and the better the conditions, the more important the need for the load combination to shoot as small groups as possible, and for the shooter to find that he or she can hold that load really tight.
Well ... that's the conclusion I've come to over time, others will very likely disagree and in their circumstances, an alternative approach will be better. What I have seen on the GB national scene where all rounds are shot over 800-1,200yd except one short-range season opener, and where 1,000yd is by far the dominant distance in terms of shots fired / points on offer is that over a season with two long-range matches on each of the three UK long distance ranges over a wide variety of weather conditions, is that the bullet weight benefits / disbenefits even themselves out - we get wins with people shooting 155/155.5s and with others shooting 210-230s, and our top two 2012 league placeholders, nothing between them points wise over the season was a 210gn Berger VLD shooter followed by a 155.5gn BT user. The European Championship six match contest went to a 155.5gn user in 2012 and a 185gn LRBT user the previous year, in each case by a convincing winning margin. Bear in mind too that we shoot alternatively in pairs with a 45-second rule. That is after the target reappears from your partner's shot, you have a mere 45 seconds to note and agree his/her score, read the conditions for your shot and take it. With two shooting together, it'll be around 2 minutes from your previous shot - more than enough time for a significant wind change to occur.
So far as the barrel life question goes, I'm intrigued by my own analysis and Mikercr's barrel life spreadsheet results for the two alternative bullet weight / MV options. I'll be honest and say I'm not convinced that it works out like that in real life as I know many people getting very good barrel life indeed with the lighter bullets running at over 3,000 fps, some well over - but it makes you think alright!
