Thanks!!! I tried your example but it turns out there are other forces at play preventing me from escaping the 440x400 rendered size so I decided to just make the thumbnail a clickable link to the full sized image.
I edited my forked copy of templates/oscar/catalogue/partials/gallery.html
{% for image in all_images %}
<div class="carousel-item {% if forloop.first %}active{% endif %}">
{% oscar_thumbnail image.original '440x400' upscale=False as thumb %}
<a href="/media/{{ image.original }}"><img src="{{ thumb.url }}" alt="{{ product.get_title }}" /></a>
</div>
{% endfor %}
HERE IS MY FULL CODE FOR GALLERY.HTML:
{% load i18n %}
{% load image_tags %}
{% with all_images=product.get_all_images %}
{# use length rather then count as the images get queried anyways #}
{% if all_images|length > 1 %}
<div id="product_gallery" class="carousel slide">
<div class="img-thumbnail mb-3">
<div class="carousel-inner">
{% for image in all_images %}
<div class="carousel-item {% if forloop.first %}active{% endif %}">
{% oscar_thumbnail image.original '440x400' upscale=False as thumb %}
<a href="/media/{{ image.original }}"><img src="{{ thumb.url }}" alt="{{ product.get_title }}" /></a>
</div>
{% endfor %}
</div>
<a class="carousel-control-prev" href="#product_gallery" role="button" data-slide="prev">
<span class="carousel-control-prev-icon" aria-hidden="true"></span>
<span class="sr-only">{% trans "Previous" %}</span>
</a>
<a class="carousel-control-next" href="#product_gallery" role="button" data-slide="next">
<span class="carousel-control-next-icon" aria-hidden="true"></span>
<span class="sr-only">{% trans "Next" %}</span>
</a>
</div>
<ol class="carousel-indicators img-thumbnail">
{% for image in all_images %}
<li data-target="#product_gallery" data-slide-to="{{ forloop.counter0 }}" class="{% if forloop.first %}active{% endif %}">
{% oscar_thumbnail image.original "65x55" crop="center" as thumb %}
<img src="{{ thumb.url }}" alt="{{ product.get_title }}" />
</li>
{% endfor %}
</ol>
</div>
{% else %}
{# Only one image to show #}
<div id="product_gallery" class="carousel">
<div class="img-thumbnail">
<div class="carousel-inner">
<div class="carousel-item active">
{% with image=product.primary_image %}
{% oscar_thumbnail image.original "440x400" upscale=False as thumb %}
<a href="/media/{{ image.original }}"><img src="{{ thumb.url }}" alt="{{ product.get_title }}" /></a>
{% endwith %}
</div>
</div>
</div>
</div>
{% endif %}
{% endwith %}