Benjamin 347 question



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Offline Rimrock

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Benjamin 347 question
« on: February 18, 2019, 02:50:59 AM »
I have a Benjamin 347, serial #T254340, apparently a 1976 model. It shoots rather well but does not dump all of its air on the first shot. As a matter of fact, it retains quite a bit. Is this because the hammer spring is either too strong or too weak? Help will be appreciated.
  • Manteca, CA
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Offline TooJung2Die

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Re: Benjamin 347 question
« Reply #1 on: February 18, 2019, 07:37:50 AM »
Not dumping all the air can be caused by several things. Hammer spring is too weak, hammer is too light, hammer is sticking, exhaust valve is sticking, are some common causes. If the hammer is original we can eliminate a hammer that is too light. If the hammer lube is sticky or thick it makes the hammer slow down. The hammer should be oiled, not greased. Same goes for the exhaust valve shaft. If all that is good then the hammer spring may have gotten weaker with age.
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Offline RBQChicken

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Re: Benjamin 347 question
« Reply #2 on: February 18, 2019, 08:21:24 AM »
I don't think there should be any lube on the hammer.  Clean any/all lube off the hammer, make sure it is smooth and clean and clean the tube it slides in as well.
Yes, the hammer spring could be weak from being left in the cocked position for a long time.  The last thing to consider (if the gun has been resealed) is too strong an exhaust spring in the valve.  Seems like the replacement springs that you get in some of these kits come with a stronger exhaust spring than original stock.  You definitely don't want that.
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Offline Hoosier Daddy

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Re: Benjamin 347 question
« Reply #3 on: February 18, 2019, 09:21:01 AM »
Just to confirm, you are aware 8 pumps is the max... correct?
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Offline Yng@hrt

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Re: Benjamin 347 question
« Reply #4 on: February 18, 2019, 09:37:27 AM »
Think about it as a car sitting idle for years. Same thing applies here. Oil & everything else that's been feed into the gun has gummed up. If you flush the gun you'll see exactly what I mean. Your gun will cough up all of that crud & free the valve.


  • New Mexico
Benji's;
2-Prewar '42 312's, '68 312, '69 347, '82-'86 342 (checkered), '90 342 (non checkered), 2-'91 S392P's, '93 S397P, '93 397P, '95 S397P, '96 392PA (w/"P" trigger group), & a '53 137 pistol.
Dan's;
Several Vintage Silver & Blue Streaks, H9 & H9A, including a '69 Silver w/factory Williams.
Daisy's;
Most notable- 2-Model 21's, 882 w/factory Williams, 2-Golden Boys & 4 Golden Spikes, Christmas Dream 20,25,30,35, Model 1894's; RME, Win, Spittin Image, Limited Edition, 2-BBS, 2-NRA, Wells Fargo, Sealed Box 1894, 880's; 20th Anniv, Silver Anniv, Eldorado, & '71 model. Red Ryder signed by David Sanders, & 2 Pony Express.
Crosman;
'49 101
Favorite everyday backyard plinker '71 880. Easy to pump & the sweetest modified trigger.

Offline ped

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Re: Benjamin 347 question
« Reply #5 on: February 18, 2019, 04:09:19 PM »
strip and degrease the hammer and spring but I'd say the spring could be soft
hammers are best lubed but very lightly first polish the contacting areas then lightly add some moly paste and burnish it in
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Offline Rimrock

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Re: Benjamin 347 question
« Reply #6 on: February 18, 2019, 11:11:41 PM »
Thanks for all the replies. I will start with degunking and cleaning the hammer and tube. Right, 8 pumps max. I will report back when I get time to get to it.   Thanks again.
  • Manteca, CA
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Offline Rimrock

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Re: Benjamin 347 question
« Reply #7 on: February 19, 2019, 08:56:51 PM »
Well, I played with it today. I gave it the alcohol treatment and cleaned the hammer and hammer tube. It did not have a lot of gunk.

Then I shot in on the chrony. With Benjamin 7.9 hollow points I shot three shot strings. 2 pumps averaged 423 FPS. 4 pumps averaged 586.
6 pumps averaged 688 and retained enough air to shoot 354 FPS. 8 pumps averaged 747 and retained enough air to shoot 535 FPS.
 I think I will try to find a stiffer hammer spring.

I am glad that there is a recommended max of 8 pumps. The last couple are HARD. And doesn't give that much more.
  • Manteca, CA
Sheridan Blue Streak
Benjamon 347
Sheridan Bluestreak
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Benjamin Discovery

Offline Yng@hrt

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Re: Benjamin 347 question
« Reply #8 on: February 19, 2019, 09:12:17 PM »
Those numbers are impressive to say the least.

With regards to the flush; since the gun is holding air with each cycle, cycle the gun with two pumps & on the third pump add quite a bit of alcohol above the cup into the air tube & close the lever. Position the gun muzzle end down in a bucket or whatever overnight . The next morning cycle the gun several times & discharge the air into a white rag. Do this several time to see if crud starts blowing out of the gun.

I have had guns act the same way then all of a sudden all kinds of crud start blowing out.

 
  • New Mexico
Benji's;
2-Prewar '42 312's, '68 312, '69 347, '82-'86 342 (checkered), '90 342 (non checkered), 2-'91 S392P's, '93 S397P, '93 397P, '95 S397P, '96 392PA (w/"P" trigger group), & a '53 137 pistol.
Dan's;
Several Vintage Silver & Blue Streaks, H9 & H9A, including a '69 Silver w/factory Williams.
Daisy's;
Most notable- 2-Model 21's, 882 w/factory Williams, 2-Golden Boys & 4 Golden Spikes, Christmas Dream 20,25,30,35, Model 1894's; RME, Win, Spittin Image, Limited Edition, 2-BBS, 2-NRA, Wells Fargo, Sealed Box 1894, 880's; 20th Anniv, Silver Anniv, Eldorado, & '71 model. Red Ryder signed by David Sanders, & 2 Pony Express.
Crosman;
'49 101
Favorite everyday backyard plinker '71 880. Easy to pump & the sweetest modified trigger.

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