The quality of build and components will vary greatly depending on make and when it was made. Not all makes declined at the same time it may also be said that some then improved. Certain makes have been in steady decline for many years with production being constantly cheapened.
As mentioned in a other post in this thread Tikka took a dive when Berretta got control and the T3 is the result. It was designed to be cheap to make. As the same company also own Sako this is also the case in point that their production has also been cheapened. Sadly the 75 is not up to the same standards of build as earlier models.
This cheapening of production is not a new thing. BSA suffered very badly at the hands of the accountants and if the information in Knibbs book is correct the Gun division was actually propping up the loss making Motor cycle division. Parker-Hale suffered several periods of dropped quality which funnily enough coincided with take over of ownership.
Winchester (USRAC) did a ghastly job of cheapening their rifles in the 1960's and then had to steadily improve the new design to make it acceptable to all by the dye hard fans of the marque. However mostly the sales folks spin the cheapskate measures to make them desirable features so we have bead blasted finishes instead of proper polishing ............................. the spin is that it makes it anti glare and some even charged more for this finish and fools bought into the idea

. Plastic stocks were hyped up butt ehr eal reason behind them is cost. The cost a fraction to make compared to reasonable wood........................................ plus of course it appeases the oil companies. The life time of such plastics of course is not known.
before someone starts about military rifles and plastics lets make it clear the post was asking about our sporting or hunting guns

and I very much doubt that the same type of plastic or even manufacture is used for the normal hunting rifle stock to those fitted to battle rifles but even then rifles like the SA80 were cheapened to the point of being virtually useless. With cheap imported steel being used for some parts like the sight rail. The trigger on the SA80 had to go through about 5 types to improve it's strength as they kept breaking off. Oh and yes I have first had experience of these parts having made thousand of them along with other parts for this awful bull pup. The steels for the "D" shaped tube piece that is the safety retainer was bought in from South Africa for instance................................ as if it could not have been made here in the UK

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When comparing build quality one must also take into account other changes for example the American institution SAAMI periodically reviews things and has changed specs for things. Later some seize upon this to claim that soem rifles are not built to specifications. So one needs to check what specs were in force at the time of build and also remember that CIP specs are not always the same as SAAMI.
Many times and mostly in American media I see it claimed that Stery Mannlicher made its barrels with over sized grooves especially in 6.5mm calibre. Of course to the Americans rifles grooves are only made at 0.004" depth and they completely forget that even their famous maker Remington used other depths for their rifling at periods in their history. During the paper patched era they cut their grooves at only 0.0015" deep once again it was to save money. Many European cartridges design specs call for deeper grooves and in Steyr's case their grooves often are nearly double what the Americans would consider normal. Stery was not the only one to cut deep rifling grooves. Husqvarna did so as well and not only for the 6.5mm calibre

although I only own one example of theirs it being a 1935 vintage Model 46 in 9.3mm calibre the rifling grooves best i can measure are 0.007" deep. The two 6.5mm Steyrs I own also have this depth of groove. The bore is correct for calibre at 0.256" but groove diameter is 0.268". Funnily enough the Swedish Mauser of about 1905 Vintage I own also has the same bore and groove size as the Steyr's yet time and time again one reads about their over size bores!
So when considering build quality one must also factor in these changes in specs and also peoples perceptions. There are some very fine quality rifles being made today of course just as there are some truely horrible ones but again one must also consider that not every views quality in the same way. What some on these very forums rave about leave me dead cold and even move me to say I would not give the rifles they are raving about house room. Others no doubt feel similar about the very rifles that I like and cherish.
It does bring the comment:-
There is nowt queer as folk
to mind 
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