Minimum WOP for standard QB78 trigger???

Minimum WOP for standard QB78 trigger???

Joined: July 31st, 2007, 2:59 am

December 8th, 2010, 8:39 pm #1

Okay, first off guys I am not interested in hearing about having a QB78 trigger tuned, or the use of after market or upgrade parts. All I am asking is what is the minimum weight-of-pull that can be achieved with adjustment on a standard, basic .177 caliber QB78?

This model:
http://www.archerairguns.com/QB78-Chine ... p/qb78.htm

This gun is to be a gift for my daughter & son-in-law for the purpose of exterminating Starlings off their back yard bird feeder at no more than 20yds distance. They have been flinging BBs at the varmint birds from my grandson's Daisy Red Ryder with only occasional success. I thought The QB78 might be the ticket for a low cost accurate rifle that will assure hits and with minimal report!

Considering my son-in-law is a hunter/shooter but not an avid airgunner, I think a stock basic QB78 with a low powered inexpensive Leapers added will be all they need.

Thanks for your answers.


Randy
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Joined: January 9th, 2005, 1:46 am

December 8th, 2010, 11:07 pm #2

Randy,

I agree that a basic QB78 with a low-powered, inexpensive Leapers scope such as the 4 x 32 would be ideal for your gift.

As you probably know, the pull weight of the standard QB78 trigger is easily adjusted by rotating the bottom screw (remove action from the stock first). If you rotate that screw out to about flush with the trigger housing, the pull weight will usually be in the 2.5 to 3.0 pound range. This screw can be backed-out further for still lower pull weights, but wood may have to be shaved from the stock to achieve this. I wouldn't go much lower than this...

The lightest pull weight I've seen for a standard QB78 trigger is in the 1.5lbs range. But, as with any trigger adjustment, it's important to ensure that safety is not compromised and that the trigger will not fire as a result of unintended jarring. A little more pull weight is better than a dangerous trigger, at least in my opinion as a card-carrying "live coward"

Stephen Archer
Archer Airguns Inc.
Website http://www.archerairguns.com
Videos http://www.youtube.com/ArcherAirguns
Blog http://www.archerairguns.info
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Joined: June 7th, 2010, 12:14 am

December 9th, 2010, 3:34 am #3

Okay, first off guys I am not interested in hearing about having a QB78 trigger tuned, or the use of after market or upgrade parts. All I am asking is what is the minimum weight-of-pull that can be achieved with adjustment on a standard, basic .177 caliber QB78?

This model:
http://www.archerairguns.com/QB78-Chine ... p/qb78.htm

This gun is to be a gift for my daughter & son-in-law for the purpose of exterminating Starlings off their back yard bird feeder at no more than 20yds distance. They have been flinging BBs at the varmint birds from my grandson's Daisy Red Ryder with only occasional success. I thought The QB78 might be the ticket for a low cost accurate rifle that will assure hits and with minimal report!

Considering my son-in-law is a hunter/shooter but not an avid airgunner, I think a stock basic QB78 with a low powered inexpensive Leapers added will be all they need.

Thanks for your answers.


Randy
Friction at the first sear the only thing stopping a firing event.

I doubt that is an acceptable "adjustment" however.

Having replaced the springs on the 2078 trigger to achieve two stage resistance, I find the qb triggers very friendly to modification if not adjustment.

2 cents
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Joined: October 28th, 2010, 1:21 am

December 9th, 2010, 4:03 am #4

I am interested in what you didl did you follow a particular guide, and where did you get the springs.
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Joined: January 9th, 2005, 1:46 am

December 9th, 2010, 1:37 pm #5

Friction at the first sear the only thing stopping a firing event.

I doubt that is an acceptable "adjustment" however.

Having replaced the springs on the 2078 trigger to achieve two stage resistance, I find the qb triggers very friendly to modification if not adjustment.

2 cents
The QB78 and AR2078 trigger mechanisms are not exactly the same. In particular, the spring and method of adjustment for pull weight are different.

My comments were based on the QB78 trigger. The AR trigger starts out with a much lower pull weight of around 1.5 lbs.

I have to say that I've never tried removing all spring tension from either trigger mechanism...

Stephen Archer
Archer Airguns Inc.
Website http://www.archerairguns.com
Videos http://www.youtube.com/ArcherAirguns
Blog http://www.archerairguns.info
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Joined: July 31st, 2007, 2:59 am

December 9th, 2010, 5:22 pm #6

Okay, first off guys I am not interested in hearing about having a QB78 trigger tuned, or the use of after market or upgrade parts. All I am asking is what is the minimum weight-of-pull that can be achieved with adjustment on a standard, basic .177 caliber QB78?

This model:
http://www.archerairguns.com/QB78-Chine ... p/qb78.htm

This gun is to be a gift for my daughter & son-in-law for the purpose of exterminating Starlings off their back yard bird feeder at no more than 20yds distance. They have been flinging BBs at the varmint birds from my grandson's Daisy Red Ryder with only occasional success. I thought The QB78 might be the ticket for a low cost accurate rifle that will assure hits and with minimal report!

Considering my son-in-law is a hunter/shooter but not an avid airgunner, I think a stock basic QB78 with a low powered inexpensive Leapers added will be all they need.

Thanks for your answers.


Randy
Thanks guys, that answers my question. Cal, I understand your point. Mr. Archer, thanks for the info. regarding the difference in triggers between models, I wondered about that as well.


Randy
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Joined: June 7th, 2010, 12:14 am

December 9th, 2010, 6:43 pm #7

I am interested in what you didl did you follow a particular guide, and where did you get the springs.
P/N 3126A53
At both the trigger over travel stop location, and the original trigger spring location.

The mechanical advantage of the trigger makes for a very sensitive trigger pull weight.

Some machine work required Drill and tap for the 10-32 thread requirement at the Over travel position, and an adapter sleeve in the tension spring location. (Needed for the AR series trigger, drill and tap for the QB series)

A smear of Crane Cams Assembly Lube (moly) at the contact points goes a long way to making for a creep free feeling at let off.
I prefer a generous first stage and associated sear engagement, with the release only a wish beyond the felt second stage resistance.

YMMV

Cal
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Joined: January 25th, 2006, 3:24 am

December 12th, 2010, 5:14 am #8

So, you drilled and tapped both the trigger spring and overtravel holes on a QB to 10-32 then inserted the McMaster Carr part no. 3126A53 in both holes and adjusted from there? It sounds like an easy and inexpensive solution to make the QB trigger more consistent. Thanks for sharing!

Bill Dempsey
bdempsey@swat.coop
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Joined: June 7th, 2010, 12:14 am

December 12th, 2010, 10:37 pm #9

I have modified the AR2078 trigger. This variant differs from the QB series trigger in that the trigger spring is adjusted by means of a "Right angle plunger". The adjusting screw is accessible from the bottom. This plunger is larger than a 10-32 screw, so an internally tapped sleeve was fitted to reduce the plunger bore diameter. (I used a "Rivnut" for this piece only because I had it on hand) The result is equal in effect to taping the QB series housing, 10-32.

With that,

By the incorporation of 10-32 internal threads at both the trigger spring location, and the over travel adjustment screw location, fitting the commercial spring plungers achieves a very easily adjusted two rate trigger. The location of the two plungers results in differences of mechanical advantage that aide sensitivity.

I really need to take some photos......

Cal
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