You can't open it up very well because of the way the extractor is located. Every case diameter in a Savage uses the same extractor. The extractor is held in place by spring tension on a ball detent underneath the extractor. The spring and ball are parallel with the bolt in a hole drilled into the locking lug. The varying sizes of bolt heads vary the location of this hole further or nearer from the bolt centerline to keep the extractor aligned with the rim of the case. You COULD conceivably modify an extractor to make it work on the larger bolt face in it's old location but I've never seen it done. I've bought factory bolt heads from Numrich Gun Parts shipped to Canada. Very affordable.