ok so i bought a spikes crusader rifle.. love everything about it, except for when i shot it. now i know that we should always wear eye and ear protection, but i haven't ALWAYS needed it. this gun, if you don't know has a 14.5" barrel with a pinned and welded compensator. its a dynacomp 2. the ammo i was shooting was 56 grain MEN 5.56. is it the barrel length, the muzzle device, or the ammo?? any explanation would be much appreciated. or is this just a loud ar15?

In my experience, the number one difference in the noise between different AR15 rifles is the flash hider/compensator. The 1.5 inch barrel length difference would be a distant second, with the ammo probably not making a difference at all.
As far as hearing protection, you always need it. Protect your hearing as if your life depends on it! I can tell you when that ringing in your ears becomes permanent it has a very negative impact on your life.

Probably your compensator. I've been near a short barrel AR15 5.56 and that was extremely uncomfortably loud.

It's both ....comps are loud and short barrels are loud

I concur.

Can the flash hider be removed or does that make the barrel too short to be legal at that point? I you can remove it you can put a thread protector on and it will greatly reduce the sound.

Comp!

It's the comp if you are familiar with AR's and yours seems to be louder. I know a plain Jane AR15 with a plain birdcage flash suppressor is one of the most ear piercing guns I've shot. There's just something about the pitch or volume or both about an AR that just kills my ears.

Amen to that.

I just spent the last 3 days ROing 3-gunners through a stage of fire. I encountered almost every conceivable combination of barrel length and comp known to man. Believe me, there is a HUGE difference in noise and muzzle blast between different combos of barrel lengths and comps. Most of the noise and muzzle blast is comp dependent but when coupled to a short barrel the effect can be BRUTAL.

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You should shoot my 7.5" Spikes Concussion upper. There's a reason they named it the "Concussion".

Exactly why I'm suppressing my SBR.

You have a short barrel and a muzzle brake. That's a loud combination.

Now stop shooting centerfires of any kind without hearing protection. You need it whether you think you do or not.