Great thread, here is my tuppence worth. This is a topic about which I have thought long and hard. I often find myself with this same dilemma.
Let me tell you about one rifle that I 'restored' and the epiphany that came with it.
I enjoy tinkering with older Lee Metfords and Enfields. I picked up a nice Enfield made long Lee that had done a tour of duty with a local hunt camp and had been used for hunting and plinking for generations. The bore had been kept clean and oiled and overall, it just needed a little help in the woodwork department.
Around the turn of the last century, if a factory did repair work, on completion, it would be inspected and stamped with a factory inspection marking and a two digit date. Some rifles read like a book where they had been back and forth getting repairs and upgrades.
On this particular rifle, I read all the markings and I found several BR inspector stamps and adjacent dates stamped into the left butt socket. This suggested to me that it had been returned to the Birmingham Repair facility (Sparkbrook) for work. I checked it out and found that the barrel bands, rear volley arm and back sight leaf had been replaced with BSA and Sparkbrook flavoured items. The sights had been updated for Mk.VII ammo and the throat in the barrel's chamber had been updated for the pointy bullet.
I rummaged around in the bins and found Enfield marked parts with acceptance stamps from the era of the rifle. I switched them out and now I had an Enfield rifle with all Enfield parts mounted. Yes, well done I thought, I put it back to how it was when it left the factory.
It then dawned on me as to what I had just done. When I first got the rifle and was reading the markings, I could tell that it had been factory repaired and where they had been working on that rifle. I could tell as to what they had done to it.
What I had just done was to remove this evidence, so now the next owner will take a look at the BR factory markings and wonder why it was there and what had been done. I had just destroyed much evidence of its history. So I put everything back to the way I found it.
RSAF Enfield actually had a parts pool to which all manufacturers would ship batches of parts. Then when there was a shortage, any factory could draw what it needed from the pool to keep production going. Being on site, Enfield was constantly dipping into it to keep their production flowing. I note that many, if not most Enfield made long Lee rifles have BSA marked trigger guards (go take a look). Probably drawn from the pool and factory fitted rather than a later replacement.
So even factory fresh rifles could be a mix match of manufacturers' parts. Long Branch and Savage shared their resources too, so a mix match can be 'correct'.
I get it about switching out parts to put everything into the same livery, I really do. My OCD often kicks in and I have a hard time resisting.
If I build something from parts or restore a cut up sporter, then no problems, whatever fits and works is good for me, it aint a collector piece. But a complete rifle that comes to me in 'as in service' configuration now stays that way. I have learnt to live with it.
You have no way of telling if your parts were switched out in service or by Farmer Brown. So in this case, I would say switch them if it makes you warm and fuzzy when you take the rifle out to play. Otherwise, leave it be. It is quite 'correct' as is.
If I do come across an all one brand of parts rifle, it makes me suspicious and I look closer at it. Having restored and cleaned many antique rifles, I can usually tell if somebody has been 'improving' something.
Read some of the threads about M1 Garrand and M1 Carbine collectors. Oh my goodness!! Some of them are quite anal about having all matching parts on their rifle. Which I find ironic as the factories assembled with mixed parts at the get go.
