I would suggest purchasing a copy of QuickLoad, or downloading Gordon's Reloading Tool:
www.neconos.com
www.grtools.de
You can inut your specific load data and see where the pressure estimates fall with respect to SAAMI MAX value. In my hands, F-TR loads with heavies predicted by QuickLoad to have pressure slightly in excess of 57K psi would kill the primer pockets in 2-3 firings (i.e. 90 VLDs @2850 fps froma 30" barrel). Loads with 80.5 Bergers at approximately the same velocity (2860 fps) in a 26" barrel were predicted to be close to MAX pressure, maybe 54.5K psi, and the brass was good for at least 4-5 firings. I'm guessing you probably run the 80 SMKs at somewhere in the 2750 to 2800 fps velocity range without trashing the primer pockets too quickly. Predicted pressure would probably be somewhere in the 50-53K psi range, but you'd have to run the program with your specific load data to know for sure.
There are many variables that can affect pressure. Powder and primer choice are obvious ones, as well as internal brass case volume. It may also be possible to increase velocity simply by changing to a different powder. The velocity at which a given load actually tunes in in your specific setup will also be a big part of the equation. However, it is generally not easy to increase velocity with a lighter, lower BC bullet to the point where one can obtain external ballistics comparable to the next higher weight class of bullets. So one alternative might be to consider using an 85-90 gr bullet with a much higher BC. Obviously, the rifle setup itself may be the limiting factor there. But another possibility would be to use an 80 gr bullet with a much higher BC than the 80 SMK. I have recently been using Hornady's 80 gr ELDM to lap in a couple new 28" barrels I had cut for an F-TR rifle. The 80 ELDMs are shooting extremely well in my hands. They have a G7 BC of approximately 0.258 versus 0.221 for the 80 SMK (Litz, Ballistic Performance of Rifle Bullets, 3rd Ed.), which is an increase of almost 17%. A 17% increase in BC at the same bullet weight is HUGE, and would provide a noticeable benefit in terms of wind deflection and drop, even at the same velocity you're currently running the 80 SMKs. Again, the question here would be whether your rifle is set up to shoot the 80 ELDMs. A 7-twist barrel would be necessary, and perhaps a little longer freebore than might be optimal for the 80 SMK as the 80 ELDMs have a fairly long bearing surface. Nonetheless, using a more modern bullet design with a higher BC would something to think about.
The quest for velocity is not a new one. Further, I agree with you that a load pushing the 80 SMK at 2685 fps from a 26" barrel is slightly anemic and could be juiced up a bit without destroying the brass in a single firing. However, as an exercise you might consider running some external ballistics predictions using something like JBM Ballistics (
https://www.jbmballistics.com/cgi-bin/jbmtraj_simp-5.1.cgi) to determine exactly how much difference in drop and wind deflection an additional 50 or 100 fps velocity will buy. It's usually nearly not as much as one would think.
In the past, I have run the high node using 90 VLDs in F-TR rifles with 30" barrels. The primary reason for doing that was not specifically to increase velocity, but rather to hit a really nice fat accuracy node at about 2850 fps. Several years of killing the primer pockets of Lapua brass in 2-3 firings [largely] cured me of doing that. It also led me to my final suggestion, which pertains to the brass itself. Due to the expense of Lapua .223 Rem brass and the high rate at which I went through it running those loads, I am always on the lookout for a brand of brass that shoots with the same precision as Lapua, but that lasts a bit longer and isn't quite so expensive. To date, I have had pretty good luck in terms of the precision aspect with Norma brass. It doesn't last any longer than Lapua, but it shoots just as well in my hands and it costs half as much. Starline is another manufacturer that may be worth consideration, and they have gained a following among F-TR shooters using .223 Rem. I have both the .223 Rem and 5.56 NATO Starline brass, but haven't really used it enough at this point to draw any conclusions regarding precision relative to Lapua. However, Starline's reputation is that the primer pockets seem to outlast many other brands, and again, the cost is significantly lower than Lapua. By using a different brand of brass, it may thus be possible to achieve the same precision under conditions where brass life is less of a concern due to the lower cost of the brass, OR the brass may actually last longer (i.e. Starline).
But damn it shoots good.
