68 special uncontrolled fire
Printed From: Tippmann Paintball
Category: Paintball Equipment
Forum Name: Gun Maintenace and Repair
Forum Description: Important info for keeping your marker in top shape
URL: http://www.tippmannsports.com/forum/wwf77a/forum_posts.asp?TID=191941
Printed Date: 10 May 2024 at 3:58pm
Software Version: Web Wiz Forums 12.04 - http://www.webwizforums.com
Topic: 68 special uncontrolled fire
Posted By: mestapho
Subject: 68 special uncontrolled fire
Date Posted: 12 September 2014 at 10:43pm
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My buddy gave me his old 68 special to play around with. I bought a new CO2 tank and some paintballs. It had a gas leak that was easy enough to fix with a couple of new o-rings in the gun valve. At first it had uncontrolled fire, then it seemed to sort itself out and was firing great. Unfortunately it started having uncontrolled firing again. I pull the trigger and it keeps firing until I stop it by the linkage arm. Seems like it's not recoiling enough for the sear to catch the rear bolt. Any ideas of what needs to be done to correct this?
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Replies:
Posted By: Lightningbolt
Date Posted: 12 September 2014 at 10:46pm
| Check to see if the sear is worn out. Additionally if you have a leak somewhere maybe there isn't enough blow back pressure to reset the sear. |
Posted By: mestapho
Date Posted: 12 September 2014 at 10:58pm
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Thx for the quick reply. The rest of the seals looked good and I couldn't hear any hissing, but I'll recheck them and the sear. I read that not using a siphon tank could cause issues as well, is that true? http://www.amazon.com/Empire-Paintball-24oz-CO2-Tank/dp/B007XKFQCM/ref=sr_1_2?ie=UTF8&qid=1410576778&sr=8-2&keywords=paintball+co2" rel="nofollow - This is the tank I purchased. |
Posted By: Lightningbolt
Date Posted: 12 September 2014 at 11:04pm
| Tippmanns are the best in the business for handling liquid co2. Another potential issue could be a bent guide pin that can occur from a runaway gun which could create resistance. I bent one once cycling my rt 98 at insane speeds. |
Posted By: Mack
Date Posted: 13 September 2014 at 12:20pm
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OK, it's been a long time since I messed with one of these, but I thought the 68 Specials were among the last markers that Tippmann made that were designed for liquid CO2 so required a siphon tank. Where's OS when you need him? ------------- 
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Posted By: mestapho
Date Posted: 13 September 2014 at 2:40pm
Yeah, from poking around I believe that is true. Can you still buy siphon tanks? Couldn't find one online.
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Mack wrote:Posted By: Lightningbolt
Date Posted: 13 September 2014 at 10:34pm
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If I remember os seminar he stated that the anti siphon was for consistency problems particularly when it's cold. Another option is to run the tank vertical with a coiled remote. I don't think that this is the problem with a runaway gun but maybe it's possible. |
Posted By: oldsoldier
Date Posted: 13 September 2014 at 11:49pm
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Three options: 1. Worn sear, or bolt recess. File sear to a 'square' where it engages bolt recess. File recess in bolt to square. If these edges become rounded and they do, bolt will 'bounce' over sear and a runaway. 2. Recoil spring. With age it weakens and will not hold enough forward pressure on bolt to secure lock it on sear. 3. Valve spring too weak, not allowing enough blowback to get the bolt to move far enough back in cycle to engages sear. ------------- 
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Posted By: mestapho
Date Posted: 15 September 2014 at 1:59pm
Thanks for the tips. I refilled the CO2 and its working fine again. I just have to keep the velocity adjuster screw nearly all the way in. I think it was runaway firing last time due to the CO2 being low.
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Posted By: Lightningbolt
Date Posted: 15 September 2014 at 7:44pm
| I was laughing thinking that may be the problem. Glad it's working |