BigBore .308 Joe Bontrager Rebuild (picture heavy)
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BigBore .308 Joe Bontrager Rebuild (picture heavy)
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Topic: BigBore .308 Joe Bontrager Rebuild (picture heavy) (Read 3313 times))
MartinDWhite
Plinker
Posts: 182
BigBore .308 Joe Bontrager Rebuild (picture heavy)
«
on:
July 18, 2013, 12:25:43 AM »
A while ago I purchased a Bontrager .308. Joe appears to have disappeared and is no longer in business (We won't talk about why). There are a few issues I want to fix about the rifle. As I do it, I doubt he will mind me posting details of the insides of his design (I assume it is his implementation of a knock open valve bigbore design).
1 - There is only one bolt keeping the loading probe (bolt) in the breech and it takes all the pressure of the shot. When I received the rifle this bolt (top rear bolt holding breech to main tube) was broken. I have heard a rumor, that I can't confirm, about a person getting hurt from this make of rifle and bolt leaving the breech backwards. I suspect that rifle had the same broken bolt this one did and it fell out before the shot. Again that is speculation and rumor. All the other bigbores have two methods of stopping the loading probe from leaving the rifle backwards.
2 - The Breech is mounted at a slight angle causing the barrel to bend ever so slightly. This is because that same rear bolt for the breech is in hole that is slighty off center.
3 - The cocking handle is too long to fit an any reasonable case.
Here are the highlights of a photo log of the take apart. The complete log, higher resolution, can be seen here -->
http://www.martinwhite.name/images/index.php?p=&dir=July_17_2013
This is the bolt in question. This is a replacement I put in after getting the rifle.
The front rail piece bolts are also holding in the barrel. Barrel is also press fit into breech. I can't get it out.
Bolt probe depth as seen from transfer port.
Bolts holding valve in pressure tube are drilled all the way through and tapped all the way through. This means the bolts are seeing the air pressure during a shot.....strange.
Valve body with totally shot orings (punny isn't it). It will get new orings.
The valve stem appears to be made from a counter sunk bolt, still have the allen key hole on the end. It rests on a plastic valve face (appears to be delrin).
The amount the valve can open
Spring, hammer (after being polished), cocking knob (after being shortened), and end cap
Hole for cocking knob allow the spring to rest against the threaded part of the cocking knob
Yes that is a wood dowel as a spring guide inside the main spring.
I always wondered why the trigger is off center.
More to come as I get to work on it. Only a few nights a week do I get to work on my projects. The rest of the time is taken by family and friends.
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GTA
»
All Springer/NP/PCP Air Gun Discussion General
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,
ezman604
,
Tater
) »
BigBore .308 Joe Bontrager Rebuild (picture heavy)