Heavier the bullet, the longer the bullet since diameter is fixed.
Heavier bullets require faster twist rate rifling.
Overspinning is a way to try and fix the diameter to length issues of really heavy bullets, but it creates a 'One Bullet' rifle since it's NOT going to shoot much lighter/faster bullets well, no matter how much you try to 'Trick Load' the rounds.
When that long/heavy bullet hits 'Trans-sonic' (or 'Transonic') it's going to do REALLY stupid things.
Stroking 'Long Range' out of a .223 takes time & effort.
If you have the time, and the education to stroke that rifle/round, its not a big deal, but I don't recommend it for common shooters that mostly stick to intermediate or short ranges that will want to switch up bullet weights as different opertunity arises.
The entire idea flies in the face of a 'Common Chambering' or 'Multi-Use' rifle.
'Varmint' rifles usually don't get really stupid on barrel rifling twist, they are commonly 1:10" or 1:9" twist rate and do well with 50 to 65 grain 'Common' varmint & hunting bullets.
Keep in mind that 'Varmint' bullets have THIN jackets, easy for rifling to cut, easy for overspinning to sling off...
In some cases, the jacket can be stripped off the core by super fast rifling.
(Which is why factory 'Varmint' barrels don't overspin the factory 'Varmint' bullets)
As to 'Heavy' weight barrels, I'm a fan.
Some of the 'Hunting' weight barrels have harmonic issues that can be frustrating to solve.
It's a weight (mass) vs harmonic oscillation issue that can be a HUGE pain to solve.
If it's NOT a walking Hunter, then I don't see an issue with a heavy barrel other than it excludes some fine factory rifles.
Glass can be tricky...
The new, 'Whiz-Bang' & 'Latest-Greatest' optics companies either won't be here in 10 years, or won't be standing behind their products in 10 years...
They will be bought up by larger companies, they will have moved 'Off Shore', they will require as much to fix you optic as the next 'Whiz-Bang' company wants for a new optic.
NO BATTERIES!
Doesn't matter who you are, or how attentive you are, sooner or later you will get a battery that leaks.
You will forget to turn the optic off and discharge the battery and it will leak.
You will forget to replace the battery & it will leak.
Burris & Leupold are the ONLY companies that warranty against battery leaks I know about.
That's leaks, not discharged & ignored. That's abuse.
I went round & round with NiteForce about a leaking battery they sent installed in the optic, corroded when it arrived here. I finally got a refund from the retailer...
The customer was NOT amused!
Keep in mind the more SIMPLE the optic, the longer it will live.
Without a dozen adjustments, the seals don't get ground and give up letting (anti-fogging) gasses out & moisture in.
Without a zoom (variable magnification) the very small, delicate internal parts are reduced by half, much less to come loose or wear out.
A scalable vairable magnification optic (range estimation marks stay in scale with magnification), the focal plane will change as much as a dozen times, and that's a CRAP LOAD of really small parts that all have to work together for decades PERFECTLY.
Target shooters like 'Clicks', that's detent stops in adjustment.
That means no 'Hair Fine' adjustments you can make on friction adjusters, and more parts that can fail, keep in mind that springs/detent plungers usually ARE NOT internal, they are external exposed to elements.
'Long Fixed' ranges you can use any tube size and adjust the mount angle.
If you intend to shoot vairable ranges, the tube has to be larger diameter for more adjustment room, lower quality optics often use the same wall thickness of tube in all diameters, and that leads to weaker tubes that can deform when rings are tightened.
Oval or outright crushed tubes aren't accurate or repeatable.
Objective lense size over 40mm does you no good at all.
Your eye only has a 6mm pupal fully open.
Objective lenses do NOT 'Collect' more light, they don't jump out and run around gathering up more light, they only TRANSMIT REFLECTED light from the target.
Over 6x magnification, anything larger than 40mm doesn't do you a bit of good since the ocular lense output is going to be 6mm no matter what. Your eye can't use any more than 6mm maximum, so why pay for more?
Light transmission is a big deal, the more REFLECTED LIGHT from the target that gets through the lenses, the brighter & sharper the image will appear to you.
Super clear, high transmission glass is a big deal, and lesser optics companies don't use the best glass, just too expensive & hard to work with.
You won't see much of a difference in store lighting, you will be fine at short ranges in full daylight,but you most certainly notice a difference in twilight or heavy cloud cover!
Keeping coatings to a minimum will help a bunch in light transmission, and unless you spend all day every day on optics, UV coatings are pretty much a waste of money & darken the light transmitted.
Parallax adjustment markings are NEVER exactly correct, the lesser optics aren't even close.
Lay your optic on something sold at a 100 yard range, adjust the parallax for the 100 yard graduation and weave your head slightly behind the ocular lense, prove it to yourself.
If the reticle seems to move on the target, or the target seems to move under the reticle, the parallax graduation is off.
When it's exactly adjusted (sans graduations) the reticle will be dead still on the target.
This would be a good time to scribe/scratch a hash mark on the adjuster so you can find 100 yards again... (Yup! Scratching or painting a brand new optic...)
Focus the ocular for YOUR eye, sharpest sight picture @ 100 yards, lock the focus in place.
Cut a round piece of paper that fits as close into the objective lense, lays on the objective lense as you can, excluding as much light around the edges as possible, then cut a star out of the center getting as close to the edges as possible.
Nothing beats the old paper star dropped on the objective lense, then shinning a flash light through the optic... Move ocular lense/tube/flashlight up/down over a FLAT WHITE sheet of paper.
When the star shape is perfectly crisp, measure the distance from paper to ocular lense.
This is your EXACT focal distance for your eye to stand off from ocular lense. ('Eye Relief')
This will not only tell you the EXACT stand off distance, but you will see the point in the center are sharper, while the points out in the margins are 'Fuzzier'...
This is how well the lenses were ground (curvature) to work with one another.
Any lense in the series MUST be ground on it's exact OPTICAL center or the star will appear 'Warped' or one side 'Fuzzier' than the other.
If the center points are all sharp & crisp, then the lense OPTICAL CENTERS are correct.
If the outer points are sharp & crisp all the way around, then the curvature is correctly ground.
Most lower quality optics will have only the center 10-15% sharp & clear, that means you can ONLY rely on the centered 10-15% of the adjustment to be accurate.
With a set of lenses like this, the ONLY way to be accurate is to grind/lap the rings to center the reticle on the target, if you use the adjustment knobs outside of that 10-15% the optic is going to lie to you...
This plays hell with different range shooting since you have to get out of that 10-15% that's accurate & true if for no other reason elevation at greater ranges.
Just some facts, not by a long shot what you need to know to make an educated selection, just some rough ideas and ways to check an optic before it drives you up a wall!
Footnote,
Etched reticles never break a reticle wire,
Bulllet drop compensators & range estimation graduations are 'Normally' only accurate at the lowest magnification setting since most lower end vairable magnification optics aren't scaleable with magnification, but there are more & more scaleable optics on the market now than there used to be...
Many are poorly done, so keep that in mind.
Nobody but Windy would I write all this for...