I believe it might barely be possible to load the 80.5s with the boattail/bearing surface junction above the case neck/shoulder junction and keep them to mag length IF you modify the lip of the magazine to accommodate a longer bullet. However, that is only a guess and I have not actually tried to do it. Alternatively, some specific manufacturer might make mags that are long enough, although most are not.
Some time ago, I worked up a load with the 80.5s for a .223 Rem rifle that has zero freebore. As a result, the bullets are seated very deep in the case. I have never actually tried it ( We single feed everything in F-TR competitions), but I believe by eyeballing them that these rounds might just be barely short enough to feed from an AICS mag...but just barely, if at all. Although that load shoots very well, I would not consider it "optimal", as having the bullets seated well below the case neck/shoulder junction means higher pressure and potentially other issues, as compared to a load or a rifle that has sufficient freebore to seat the bullets out in the neck where you'd ideally want them to be. Nonetheless, I was able to get it to it work using H322, which is a very fine-grained powder that occupies less case volume than powders such as Varget or H4895 that have slightly slower burn rates and would generally be considered more suitable for bullets of that weight class.
To achieve the goal I believe you're seeking, you could go the route I did, seating the 80.5s way down in the neck. You may get lucky like I did and come up with something that shoots pretty well. Alternatively, you might consider trying the 80 gr Matchking, which has a slightly shorter BTO dimension, but still has a much higher BC than most 77 gr .224" bullets. They would likely still be seated pretty far down in the neck, but not quite as far as the 80.5s. Another option might be to work up a load with Nosler's new 77 gr RDF bullet. Nosler claims a G7 BC of 0.228, which is comparable to that of Berger's 80.5. I have previously tried some of Nosler's 85 gr RDF bullets, and they seemed to shoot reasonably well. I have been meaning to buy some of the 77 RDFs to see how they shoot and determine whether the reported BC measures up in my hands, but have not yet done so. A final option might be to use something like PTG's Uni-Throater tool to extend the freebore of the rifle to accommodate the longer, heavier bullets. Of course, once done, that modification can only be undone by replacing the barrel.
Any time you try to develop a load for a bullet that is too long for the freebore of the rifle for which it is intended, you will likely run into these issues. Either you go with a long bullet sunk deeper in the case than would be considered optimal, or you go with a lighter, shorter bullet that will usually have a lower BC. As I mentioned, it is certainly possible to go the long/heavy bullet seated deep route and end up with a decent load, but it certainly isn't "optimal". In addition to higher pressures and potentially having to use a faster or finer-grained powder than you might ordinarily choose, you can also encounter seating depth issues (i.e. if the bullet wants to be seated fairly far off the lands, it exacerbates the problem). In the load I worked up with the 80.5s, they are seated at ~.024" off the lands, with a COAL of 2.324". I just measured the opening in an AICS mag with calipers, and it looks as if a COAL of about 2.500" would be very close to touching the mag lip. You might extend that a very small amount by using a round file or Dremel to remove the mag lip. However, it is likely that putting the bullet meplat so close to the inside wall of the mag might create feeding issues during actual use, even if by eye there appears to be sufficient room. So I'd probably want to be fairly conservative with regard to how close the bullet nose was situated to the mag wall to ensure normal feeding.
In any event, you likely have several option that might work, so I wouldn't say it would necessarily be a wast of good reloading components. You could play around with the numbers a bit first to help select the route with the highest chances of success, then load a few dummy rounds to determine the maximum COAL at which the bullet could be seated. Once you know where the bullet is seated in the neck at the maximum possible COAL value, you should ave a pretty good idea of whether you can get enough of a given powder in the case to achieve the approximate velocity you're after (i.e. would it be a heavily compressed load?), and make a determination of whether a different powder with lower bulk density might be necessary. In terms of optimizing seating depth, once you know the maximum possible COAL, there is only one direction you can adjust seating the bullet - deeper in the case. It should be possible to find a seating depth where the groups tighten up by moving the bullet farther and farther off the lands, but the most important factor is how far you actually have to go. In a situation such as this where case volume is already an issue due to having to seat the bullet deeper than is optimal, pressure may also become an issue if you have to move them too far off the lands. In that event, a reduction in charge weight would be necessary. Nonetheless, it is likely possible to achieve what you're asking, but it may take a fair bit of effort and testing on your part. Hope this information is useful to you.
