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Longshot Sleeper Breech build questions

Sleeper breech Longshot mod

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#1 Bubba Longshot

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Posted 14 January 2018 - 12:15 PM

So I was thinking of ways to improve my Longshot, and decided that I'd like to build a sleeper breech one day (probably during the summer). I only want around 100 fps, so I was wondering if it was possible to use a 5kg spring with roughly 6 inches of 17/32 brass as the barrel.

Thanks
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#2 blitz

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Posted 14 January 2018 - 05:31 PM

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. 


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#3 Bubba Longshot

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Posted 14 January 2018 - 07:01 PM

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?


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#4 blitz

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Posted 14 January 2018 - 07:36 PM

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?

 

Hitting 100 fps is achievable with a AR removed breech with aftermarket springs. With this setup, there is relatively little difference in performance with a 5kg, 8kg, or 12kg spring. The lack of a sealed barrel (with the exception of the stock breech) means that the springload/air is not handled effectively.

Sealed breeches (sleeper or otherwise) require a baseline springload/volume so the dart can just get out of the barrel. The measly 2.5-3kg stock springs just don't cut it with most setups, as the barrels are too long. Sure, you could shorten the barrels so it /could/ fire at 100fps, but then what's the point of making a sleeper? I've made my fair share of them, and it's a lot of work. It would be more efficient however. 

I /really/ don't want to sound non-constructive or demeaning. I just find that 100fps is a bar that is pretty easy to achieve, especially with a LS plunger tube as your platform. 

 

What darts do you plan to use?


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#5 Bubba Longshot

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Posted 14 January 2018 - 07:44 PM

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.

I plan on using full length darts.

Thanks
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#6 Bubba Longshot

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Posted 20 January 2018 - 07:17 PM

Bump


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.


Thank you very much
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#7 blitz

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Posted 21 January 2018 - 02:20 PM

1. Yes, it is possible. Just be careful and go slow. Use files and a drill bit over sanding. 

 

2. Uh... That's going to be really really difficult if not impossible. You need to not bend the brass (at least inward for the 9/16" and outward for the 17/32"), which is far easier with a rotary tool. You could buy a cutting wheel and then attach that to your drill chuck and then cut it that way.

 

3. Start off with 6" and then cut down as you see fit with your choice of spring. Test, cut, repeat until you're happy. If you're using elite darts, you might want to invest in a scar barrel or a ported addition of 9/16" over your 17/32" barrel.

 

The stock 2.5kg may be insufficient for /any/ barrel length and you might want to move up to 5kg. Part of being a modder is testing, messing up, and starting again. 


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#8 Bubba Longshot

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Posted 21 January 2018 - 04:04 PM

Ok, I never realized that you could put a cutting wheel on a drill; I'll try doing that. As for the springs, I have a spare recon spring that I could add if the stock one is not enough.

What would you say is the hardest part in making a sleeper breech?
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#9 blitz

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Posted 21 January 2018 - 06:15 PM

Yeah, adding that second spring might be very necessary. 

The hardest part is cutting the brass so it doesn't bend or burr so that there's friction with the other pipes. Cut outward with your cutting wheel on the 9/16" and inward with the 17/32". The boring out of the stock breech is annoying, but not super difficult. Just go slow and take your time. 


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