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Optimum deadspace removal in the bolt for pusher breeches?

breech brass deadspace retaliator springers

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#1 TriggerWarning



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Posted 17 June 2017 - 04:20 AM

I couldnt find this answer anywhere, so I thought I might ask if anyone has documented data on the optimum diameter to let air through in the bolts of pusher breeches. I have a brass retaliator with a simple breech, and I noticed that adding a few layers of tape to fill into the space before the dart (i.e. the bolt) to kill some of that unused deadspace increased my ranges very marginally. Obviously adding too much, and you constrict your airflow leading to your chamber like a coffee straw. It therefore follows that there must be an optimum amount of deadspace to fill in. Can anyone comment on what they've done with their builds?

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#2 jwasko



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Posted 18 June 2017 - 06:36 AM

I don't know that anyone has done extensive testing, but I believe I have read suggestions that it should be kept to at least 3/8inch inner diameter. A chronometer would probably give more reliable data than range testing, but you could try experimenting in the range of 1/4" to 3/8" diameter.

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#3 IAmAPenguin



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Posted 20 June 2017 - 12:41 AM

I would probably go with the ID of 1/2 in or 15/32 in brass for something with a lot of volume such as a longshot/caliburn just for the increased airflow as dead space isnt really an issue. You could probably go smaller on a retaliator though. From what i have concluded there is really no such thing as this so called "Magical Balance" of airflow and dead space reduction as it depends greatly on the volume and speed at wich air is displaced in your blaster. But id say you should get optimum perfrmance for a retaliator with the standard 8kg spring (as i assume that is what most of you are using) with the inside of the bolt lined with something with a 14/32 - 13/32 in inner dimension. Just a tip with the tubing, if you are cutting it with rotary pipe cutters then make sure that the ends of the tube aren't at all bent inwards from the cutting process as this will restrict airflow and not remove dead space in the process. You can avoud this by getting some scissors, shoving them inside the ends of the tube and twisting until the end of the tube looks as close to what it should have when it came out of production. But dont over-do it, or the tube might not fit inside the barrel material anymore. Just go slow and keep testing the fit.
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Also tagged with one or more of these keywords: breech, brass, deadspace, retaliator, springers

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