Daisy 880, Possible goals?

[DavidS]

I see your logic in the hammer.   I thought it made sense that if the valve begins opening sooner on the spring throw it would take less time to go from closed to open (it does take time to move).   That is that the amount of time between the initial cracking and full open would be less.   Just my understanding of what is supposed to happen.   Though it does make sense that Daisy would not do the extra step with out good reason.

  Again, does not make sense to me. The amount of time between initial crack and full open can not change by adding a shim to the hammer. Crack to open is the same amount of throw with or without a shim on the hammer. This does not change. Open further, yes, open quicker. No. Only a heavier hammer spring or a lighter valve spring can do that.

   So the ONLY thing that can make sense is it restricts flow less. I'll over the winter try, in the same 880 or 35 with a modded hammer and a stock hammer and see if there is any difference at all in FPS.

Thank you for pointing that out.   I guess the amount of preload on the spring when the hammer begins to open would not make a difference with the way the Daisy 880 works, and definitely do see your point.   Thank you.   I am very interested to see what the difference is.

I guess that means that I will have to separate the two hammer mods (the washer shim and weakening the valve spring while putting in a stronger hammer/trigger spring).   Also means that I will have to save the hammer washer shim until after I have a chrony, so I can also see the difference.   I will still be pushing ahead with the other modifications on this newest 880.

Once I have a chrony I will be interested in getting a few new 880's to mod one step at a time in different orders to see what has the most effect, and what has no effect.

Once again your input makes perfect sense.   I look forward to seeing what the results are.   I also look forward to seeing what your next power mod to add to the list will be, as you have come up with more than I have.


To make sure that I am aware of the current complete list:
Does the following cover all the power mods, that are so far known?

• Install Stronger Hammer Spring.
• Weaken Valve Spring.
• Fill limiter slot in piiston with epoxy.
• Cut piston to true flat, and use aluminum tape to make correct length (with aluminum tape coming back to the start of O-Ring slot).
• Bore out transfer port to 0.125 inches.
• Cut piston rod and forward fore stock to allow greater travel (by about 0.1875 inches).
• Shim pump tube forward by about 0.25 inch (give or take depending on particular 880).
• Fill most of gap between the metal check seal cap and pump tube wall ahead of cup seal, with appropriate material (lead works with great care, so does delrin though more work, PLA seems to work well also).
• Shim magnet in bolt forward a bit.
• Epoxy horshue cut washer into hammer slot.

And does the following cover all the known accuracy modifications, that are easy?

• Tape the barrel to fit snug in shroud.
• Debur the barrel lead.
• Shim the magnet on the bolt forward.
• Bore the transfer port to about 0.125 inches.
• Remove the flat spring.
• Polish the contact points.
• Add an over travel adjustment screw for the trigger.
• Add a better sighting device.

[DavidS]

I don't have a chrony, but use penetration through various media at different distances to indicate power levels.
Gives me a good idea at what distance I believe an airgun might be effective against critters of varying toughness.

For my personal knowledge of the ability and improvement of an Air Rifle I do the same.   Though for sharing the improvement in a way that is easy to communicate the difference a chrony helps a lot.

[DavidS]

To make sure that I am aware of the current complete list:
Does the following cover all the power mods, that are so far known?

• Install Stronger Hammer Spring.
• Weaken Valve Spring.
• Fill limiter slot in piiston with epoxy.
• Cut piston to true flat, and use aluminum tape to make correct length (with aluminum tape coming back to the start of O-Ring slot).
• Bore out transfer port to 0.125 inches.
• Cut piston rod and forward fore stock to allow greater travel (by about 0.1875 inches).
• Shim pump tube forward by about 0.25 inch (give or take depending on particular 880).
• Fill most of gap between the metal check seal cap and pump tube wall ahead of cup seal, with appropriate material (lead works with great care, so does delrin though more work, PLA seems to work well also).
• Shim magnet in bolt forward a bit.
• Epoxy horshue cut washer into hammer slot.

As to number 4 (the flat topping piston and using aluminum tape to compensate):

I realize that it may be easier to use PLA to go from the front of the O-Ring to the true flat portion of the piston head.   This would make it possible to get rid of almost all of the head space created between the area in front of the O-Ring on the piston and behind the piston face, as between the piston and pump tube in this area.   Could use an extra pump tube to mold the PLA to perfection, giving only the width of the layer of oil used to prevent the PLA from sticking to the pump tube during molding.

I would think that just barely starting into the O-Ring slot would be enough to hold the new perfect molded PLA shim in place permanently.    Maybe ABS would be a better option, though PLA should do the job.

Just a thought.   I would like to get the head space as close to 0% of the pump volume as possible.   Also why I wish to see how far the total piston stroke can be increased with out custom parts, as the longer the piston stroke the lower the percentage of the pump volume is lost to head space and thus the higher possible pressure, and the less air wasted to head space.

So get rid of all possible head space, and increase the pump stroke as far as possible with out custom parts, the pump should end up as efficient as is possible with out making complete custom parts.

[Methuselah]

Power, I don't ponder for reasons more suitable to another thread, but accuracy I do think can be improved and I'd bet there will continue to be new ideas presented.

I've been wanting to look at making pumping more consistent by adding oiled bushings at pivot points.  Just a thought, haven't checked to see if it practical.

Also perhaps put pump head and abutment inside a 1" tube and polish them against each other so when they hit they will always do it consistently?  No clue if there would be practical results to either, just know I am rarely pumping it the same way each time.

[DavidS]

Power, I don't ponder for reasons more suitable to another thread, but accuracy I do think can be improved and I'd bet there will continue to be new ideas presented.

I've been wanting to look at making pumping more consistent by adding oiled bushings at pivot points.  Just a thought, haven't checked to see if it practical.

Also perhaps put pump head and abutment inside a 1" tube and polish them against each other so when they hit they will always do it consistently?  No clue if there would be practical results to either, just know I am rarely pumping it the same way each time.

For consistency on the 880 there are two primary issues.   One is the small slot through which air is drawn into the pump tube, requiring a longer pause at the top of the stroke to maintain consistancy.  The other is the under sized transfer port.   Though the Daisy 880 is already way way more consistent than most other Air Rifles of a reasonable price, so long as you are careful to pause at the top of each pump stroke.

The transfer port issue is easy to correct with the mentioned modification of boring out the transfer port to 0.125 inches.   As to the air inlet slot in the tube, I guess someone could attempt drilling extra holes to allow air in at the same distance from end of tube as the end of the existing slot, and then deburr well.


A complete list of all of the accuracy modifications that I am aware of for the Daisy 880/Daisy 901 is (including some not so easy mods, that I do not otherwise mention):

• Polish the trigger/sear contact points.
• Taper the hammer contact points as described by Stonykill.
• Remove the flat spring.
• Install a trigger overtravel limiting screw.
• Tape the barrel to fit snug in the shroud.
• Shim the magnet in the bolt further forward to seat the pellet further past the transfer port.
• Lead lap the barrel.
• Weight the stock (only helps for shooting unsupported positions).
• Find the best pellet for the particular 880.
• Epoxy around outside of where barrel meets the valve body (there is a small gap there).
• Weaken the valve spring.
• Do the washer shim in hammer mod (questionable).
• UNTESTED/NOT SURE: Drill extra holes to draw in air, same distance from end of pump tube as the end of existing slot, then debur.