I plan on tackling this project in a few weeks, but have a few questions before hand:
1. As I don't have a 9/16 drill bit, would filing and sanding the inner barrel suffice? I imagine it'll take a long time, but I'll be using low grit sandpaper and have the patience. I'm basically just wondering if it's possible (would also wear down the sides with a 5/16 bit too).
2. As I also don't have a dremel, would using a mini hacksaw work for shaping the breeches? I could use sandpaper to smoothen out and finalize the edges. Like I said I have lots of patience for this, and I'm basically wondering if it's possible.
3. I plan on using the stock spring for the reasons I stated in previous posts ( low stress, ease of priming, 100fps), and am wondering how long my 17/32 brass barrel should be. From observing and analyzing other sleeper breeches, I'm guessing around 4-6 inches of brass; however, I have no experience form brass breeches so this is just an estimate.
My Longshot currently is able to hit 100fps with an 8 kg spring. However, I would like to build a sleeper to make the entire system more consistent, and air efficient. I'd rather build a sleeper with a short brass barrel and use the stock spring rather than my current setup. That's because the lower spring load means less internal stress, and I can easily one hand prime without damaging the boltsled.
You do not need a sleeper breech to get 100 fps. That should be more than achievable by just a spring replacement (5-8kg, [k26], etc.) and AR/peg removal.
Off the top of my head, your setup would hit somewhere in the 160+ fps area.
A [k26] gets 100fps?! I thought it was more like 140...
Also, the only reason why I'm considering a sleeper breech is to maximize my Longshot's air efficiency while reducing it to the lowest spring possible. That way, I can get my desired 100 fps with low stress on my internals.
A 5kg sleeper with only 6 inches of brass can get 160fps?! That's very high. Maybe a 5kg with 4 inches of brass would be better... Has anyone tried building a sleeper breech with the stock spring?