Velocity inconsistancy

[350mag1]

The pellets you are using should give a decent velocity string. Just curious, how many pellets have you shot out of your Quest?

[link_dc]

The pellets you are using should give a decent velocity string. Just curious, how many pellets have you shot out of your Quest?

i dont know, probably about 4 tins of 250

[TCooper]

Possible things to consider:
- damaged breech seal
- damaged piston seal
- poor grade of pellets
- improper pellet fit
- dirty barrel
- barrel constrictions throughout length
- bad lubricant tune
- excess lubricants
- dry internals
- faulty mainspring
- etc, etc, etc

Things to try:
- clean barrel
- pull patch slowly through barrel to feel for tight spots
- inspect rifling
- try different pellets
- check piston seal
- check breech seal
- change mainspring
- do a proper lubricant tune
- shoot rifle with a single layer of paper tissue over the breech (watch for movement - leakage)

HTH,
Todd

ive never donea lubricant tune, but how could you do a bad one?

Hi link-dc,

It's easy to do a bad lube tune. Here is the recipe to a very bad lube tune for a springer

1- Use the wrong lubes on the piston and in the chamber (i.e. thin combustible oils)
2 - Use thick petroleum grease all over the piston seal (sides and front).
3 - Use huge amounts of petroleum grease on the spring and guide.
4 - Squirt some WD-40 into the chamber to boost velocity.

Don't try the above tune!

HTH,
Todd

[link_dc]

i can use super lube though right?

[TCooper]

I'm not familiar with superlube. My preference is moly paste and Macarri tar. Maybe someone else can comment on superlube and it's application.

Todd

[TCooper]

Hi Airsmith,

Gerald Cardew wrote a popular airgun book that clearly describes what you attempted to describe
http://www.airgunexpress.com/Accessorie ... 2-5000.htm

Over the last 6 years I have read many airgun forum comments about springer dieseling and the desired "controlled burn". Experimenting with springers will verify the results of the various comments and Cardew's book.

It is well known that springer airguns do have a "controlled diesel" burn. This burn, as well as air compression/movement, helps move the pellet. Minute amounts of lubricant are held on the cross hatched walls of the chamber and the compression results in a tiny amount of dieseling that produces consistent velocity. Usually no smoke, or very little smoke, is seen when the lubricant is in the proper amount. The lubricant is almost a vapour. This is not the same as the loud "crack and smoke" we experience when shooting an over-lubricated springer airgun. Excess dieseling can be harmful. A bone dry springer is also bad.

Dry airgun internals will often produce lower than normal or erratic velocities because of excess friction and lack of a "controlled burn". The HW45/P1 pistol is a good example of an airgun that depends on micro amounts of fuel for velocity. With every shot I see a tiny puff of faint smoke. That's a normal occurence for this pistol. Extra thick smoke or excessive smoke or a "sharp crack" noise or a velocity spike is not normal (excessive dieseling).

A springer airgun produces heat from the piston compressing the air. When the heat gets high enough the burn will happen (controlled dieseling). As you said, it happens in a fraction of a second and quickly cools off. If the temp stayed hot we would be melting piston seals on every shot. An airgun that has excessive lube can diesel heavily and melt seals and damage springs. We definitely don't want excessive and uncontrolled dieseling.

A car's oil gets hot because of all the burning atomized gas happening above it. The heat travels down the metal parts and increases the oil pan temperature. There is always at least one car cylinder flashing, unlike an airgun. A car engine runs continuously and heats the oil, unlike an airgun.

I don't think you are "off your rocker". You just have a pile of web info to sort through

I don't think Link_dc is experiencing excess dieseling. His shots are within a 45fps range (450-495fps). I have experienced dieseling before. My HW35 went from 720fps to 1150fps for one shot. My HW45 went from 430fps to 600fps for one shot. These were the first shots after a lube tune and only happened for one shot. An over-lubed springer airgun will continue to experience this high and erratic velocity spikes from a rich burn. Link_dc is not experiencing high erratic spikes.

If link_dc is shooting outdoors he likely won't get a hot compression tube in the winter. With every cocking motion the cold winter air is sucked into the compression chamber to chill the metal. Even when shooting indoors it takes very fast shooting for numerous shots to feel a temp increase. When using the IZH-61 I could not get any velocity change with 5 rapid shots (475fps). Maybe 15 rapid shots from a magnum airgun might do it. I have not tested this idea for results.

A person would be surprised at how long they actually take between shots when using a break-barrel air rifle. I used a stop watch when testing my TAU-7 pistol. With the pistol clamped into a vise I had to move very fast to shoot pellets with 12-15 seconds between shots. Casually shooting a break-barrel while using a chronograph will add time to the duration. Taking time to write numbers will add more time between shots.

I'm not so sure about the "soft pellet" comment. I don't think the barrel will get hot enough to soften a pellet. The controlled dieseling, as described by Cardew, is not going to harm the pellet. Excess dieseling can harm more than just the pellet. The 2 cent pellet is your last worry if you get dieseling with loud "cracks", huge smoke, and erratic velocity spikes.

With respect,
Todd

[RM422]

Hey link_dc I use superlube on almost every springer. It works great. I also use moly lube. Both will work fine. But the good thing about superlube is it isn't as messy.

[airsmith282]

thanks for all the info Tcooper, i dont belive everything i read myself but what you said makes alot of sence to me, iam still going to continue researching the topic as iam just the kinda person that will keep at someting till i have the right answer..

[link_dc]

..... so what should i do? get a new piston seal, and clean the barrel with those special cleaning pellets?

[TCooper]

Hi link_cd,

Start with the simplest procedure and work from there.

1 - Clean barrel with a piece of strong fishing line and cotton patches and some GooGone ($4 at SuperStore). http://my.tbaytel.net/~coopers@tbaytel. ... ng%20Tips/

Inspect rifling and feel for tight spots when pulling patches.

Check velocity for 10 pellets.

2 - Check breech seal for damage. Replace if necessary.

Check velocity for 10 pellets.

3 - Try different pellets.

Check velocity for 10 pellets.

4 - Do internal cleaning and lube tune.

Check velocity for 10 pellets.

5 - Tear-down rifle and check piston seal and mainspring. Replace parts if necessary.

Check velocity for 10 pellets.

HTH,
Todd

[link_dc]

Hi link_cd,

Start with the simplest procedure and work from there.

1 - Clean barrel with a piece of strong fishing line and cotton patches and some GooGone ($4 at SuperStore). http://my.tbaytel.net/~coopers@tbaytel. ... ng%20Tips/

Inspect rifling and feel for tight spots when pulling patches.

Check velocity for 10 pellets.

2 - Check breech seal for damage. Replace if necessary.

Check velocity for 10 pellets.

3 - Try different pellets.

Check velocity for 10 pellets.

4 - Do internal cleaning and lube tune.

Check velocity for 10 pellets.

5 - Tear-down rifle and check piston seal and mainspring. Replace parts if necessary.

Check velocity for 10 pellets.

HTH,
Todd

how do i make the cotton patches stay on the fishing line? also, does a lube tune increase velocity also? and is there any trick to doing an lube tune?

[RM422]

There's not really any trick to doing a lube tune. But I can't see how your Quest could break down that fast. You have only had it since last fall. Well if you are going to do a lube and tune I would suggest ordering a Quest 1000 piston seeing as you will have your 500 apart anyway. Also order a new piston head to be on the safe side. Maybe a new spring too. As for a lube and tune just make sure you clean the compression tube out really well. Then apply either super lube or moly lube to the spring and the piston. A lube and tune does give a little more velocity. Because the grease makes the parts slide a little faster forcing the air out faster and harder.

[link_dc]

There's not really any trick to doing a lube tune. But I can't see how your Quest could break down that fast. You have only had it since last fall. Well if you are going to do a lube and tune I would suggest ordering a Quest 1000 piston seeing as you will have your 500 apart anyway. Also order a new piston head to be on the safe side. Maybe a new spring too. As for a lube and tune just make sure you clean the compression tube out really well. Then apply either super lube or moly lube to the spring and the piston. A lube and tune does give a little more velocity. Because the grease makes the parts slide a little faster forcing the air out faster and harder.

should i put grease around the piston seal

[link_dc]

k i just tested it out with my chrony again

478.7
494.2
478.6
478.6
467.6
481.0
476.1
461.3
463.3
472.4
488.0
479.8
the bold numers are when i tested it without waiting 30 seconds and the normal numbers i waited about 30 seconds.
so does this look normal?

[RM422]

That looks very normal. I don't think that there is anything wrong with your Quest. And if you give it a lube and tune yes put a tiny bit of grease around the piston seal.