When firing at anything, angles of the intended target are important. Or objects in front of the target.  Military and police learned that many years ago. I would think this question is about a side window on a door not the windshield. So, this answer is about that situation.
My guess the window would break, bullet would be deflected slightly but continue. My guess is the muzzle would be backed off the glass before the bullet strikes it due to recoil. If we are talking about most calibers used for self-defense.

BUT, I would never advise pushing the muzzle against any surface and firing the handgun IF it's a semi-auto. It's just too easy to push the slide of any semi-auto handgun out of battery when pushed up against an object. It's also possible to get ONE round off but the slide not working freely as it should, could jam the action. Causing the empty brass to stove pipe or stick in the action. 
When my dept. went from revolver to semi auto service side arm. I was a firearms instructor.  We seen and heard about many tests that gun was put through. Pushing the muzzle against a hard object normally took it out of battery.
And yes, it's damn loud in a vehicle when you fire a gun inside it.                 

That's terrible that someone ruined your rifle. I am an old timer lefty and been looking for Mark V in .257 used for years that is a hunting rifle, not collector. As I read the story, I was hoping that the rifle might be for sale. But if a new barrel and bolt or even possible gunsmith work done on the bolt to make it a usable rifle again. At any cost over a few hundred for just the rifle. After repaired, the owner would be upside down in money spend vs worth.
As a side note: I found a 1980s LH 7mm mark V, 3 years ago at Cabalas for 1500 that had been rebarreled and had same vintage Leupold scope. It was there for around 6 moths that I knew, I offered 1000 and got it. It shot great, bluing was in bad shape. I ungraded the scope, after some shooting at the range the stock split. I replaced the stock with a custom composite and had it reblued. I now have 2400 invested in a rifle worth? Maybe 1,000-1500. It does shoot great.  But is a money pit.
It makes me sick to hear how that .257 was ruined.   
   

It makes a good question. But, I have as many co workers have left ammo in car trunks, plastic boxes, factory cardboard, metal, in magazines, in vehicles such as cars, SUVs pickups and boats. I bet many other cops and military have also.
And when taken to the range or else where they fire.
As for weapons: The departments 12 ga and .308's sat in the gun locks inside the vehicle or in trunks. I had both, all of them were fitted with limb saver recoil pads. Those pads melted from the heat, after a few years they got replaced. Ammo was shot up normally on a yearly qualification.       
Another note not asked: Because motor officers and like me boat operators may have the service guns, ammo and spare ammo exposed to rain all day. How does water affect ammo?
I did a test with 38 spl ammo both factory and handloads. I keep 24 rounds under water for 5 minutes. I wiped them off and shot everyone without any problem.
My grandfather worked on a dredge in the Columbia River many years ago. According to my father a sealed metal box of M1 3006 ammo once was brought up. It was marked 1940 something AP ammo. I used the key to open the box, just like a spam can in 2015. The ammo looked ok, I fired a bunch clips of it in my M1. All fired as should. (AP stands for armor piercing). I gave the opened box and 2 bandoliers to a friend that owned a gun shop to display.             

Just general information.  I have owned 9 and own a RV. Used a 5er and a motorhome. My RVs have been bumper pulls and truck campers. 2 most common mistakes for 1st timers. Truck/TV (tow Vehicle) is too small. How does that happen? Payload. Pickups always list what their MAX amount the vehicle can tow not what it can carry. All pickups since about 1996 list the vehicles payload near the driver's door. Each style and trim in a given line will have a different payload. You need to look and read the vehicle's payload you're looking to buy not a general F350 payload to match up what you're towing.
Then the RV companies don't help much they list dry weights of their RVs not loaded. Those are always low and not real at all. My current ORV is 29ft. company lists tongue weight 695 lbs empty weight at 6600 lbs. Real weight over a scale show tongue weight at 1100 lbs and trailer weight at 7400 lbs. Few salesmen will fit your RV and TV to tow safe and legal.
The 2nd mistake most make, that 1st RV ends up not being the right match for you and what you expect of it. Could be too small, too big, too tall, not enough storage, not enough water or electric power etc, etc.
My advice get a 1 ton pickup truck, buy a used RV. In a year or few trips later you will want another RV.
Or what I read all the time in the RV forums, a couple went out and got a new Toyota pickup because they like Toyota and a mid size 5th wheel because the Toyota can pull it. They dump the TV at a loss after the 1st outing or dump thousands into it to take it carry more than it was ever intended. Bottom line buy enough truck period. Air bags and other add-ons won't make it work out. 

Just a guess on my part. The new (er) scopes used for long range shooting have scopes about as big as a 2 liter pop bottle. Ok, that was an exaggeration. But look at the size of them scopes with 34mm main tubes. The center of the scope is far to high for normal comb height to get a cheek weld. You either need an adjustable comb or just a really tall one.   

I carry an extra piece of conduit in the f350 and SUV as a cheater bar to go over the star. Still changing tires at 66 years old.

I would describe mine as being the same. I only have one mark V. I have handled many others and don't recall flipping the safety on/off on others.
1st is a guess, it has a camming action, it's rotating one direction for on and another for off. So to put it on safe it very well could be more pressure needed to compress the spring or block a part to hold it, then releasing the same part. I don't see mine as a problem.

Advice, if you don't know how to take it apart. Learn how before hand. Make sure you have the tools needed. 

Question: For as long as you have owned the rifle, has this always been doing this or is it new that this is happening. That would tell me if this is a problem or normal. 

The last thing I would ever be worried about is a gun manufacturer replacing a broken/worn/nonfunctioning part. I doubt that any of those 3 things apply to this case. Just saying let them fix it if it needs fixed.