If you are planning to go for the steel bolt, i suggest you not to use replica.
I had a ACM T-1, good quality, worked on we m4, but my scar had killed it.
I read from TW forum the the new specter DR replica, in terms of optical quality, is worse than the old one, and it is also not very adjustable.
I recently bought a RS ML-2, really expensive, but really good quality.
If you do not have the budget, I suggest you to look for a Leapers CQB scope, 1-4x great quality and eye relief, which costs only around 700-800HKD/ 100USD, except that it's kind of hevay, comparing with the aimp
