How much moly grease on springer piston?

[Bayman]

I recently re lubed my Rx1 (Hw90) piston with moly grease. My first shot after the gun sits 30min or more is short around 30 fps and the rifle prints low and left 3/8" at only 10 yards. Second shot jumps to the lower side of the normal spread and prints on center. By the third shot its single round hole from then on. Ignoring the first 3 shots the ES is around 10-12. I'm thinking I may have wiped on too much moly on the piston. I wiped on a thin semi transparent coat over the entire piston. Behind the seal of course. Could this be too much?
For shooting groups this is not a problem but to have an unreliable first shot is unacceptable for hunting.

[avator]

It's been my experience that each time I tear a gun down and relube it will need another break in period. Maybe not as long as the original but, a break in period none the less.
As for moly paste.... a little goes a very long way. On the other hand, a generous amount of heavy tar is recommended for the spring itself. I apply it so it 'strings' from coil to coil.
One of the most effective thing is to polish the ends of the spring and their contact points. It needs to spin freely at both ends to minimize twang and torque.
A good barrel cleaning after the break in period is a good idea to clean up any migration of lubes into it.
I'm sure others have different methods.

[nced]

I recently re lubed my Rx1 (Hw90) piston with moly grease. My first shot after the gun sits 30min or more is short around 30 fps and the rifle prints low and left 3/8" at only 10 yards. Second shot jumps to the lower side of the normal spread and prints on center. By the third shot its single round hole from then on. Ignoring the first 3 shots the ES is around 10-12. I'm thinking I may have wiped on too much moly on the piston. I wiped on a thin semi transparent coat over the entire piston. Behind the seal of course. Could this be too much?
For shooting groups this is not a problem but to have an unreliable first shot is unacceptable for hunting.

I've never owned a "rammer" so perhaps they're different when it comes to lubing.
When molly lubes were used only a film was burnished into piston and receiver. The only purpose of molly bearing grease is to break metal to metal contact so a thin film is all that's necessary since molly has an affinity for steel surfaces (not so much for rubber seals however). A film of molly paste thick enough to be "squeegeed" in front of the piston seal did cause "dieseling issues" with my springers. When living in West Virginia I often went on squirrel hunts with a .177 R9 and I would take a few "lube clearing shots" when I got to the "squirrel woods" since I had the same "1st shot issue" as you when hunting.

Anywhoo, if the piston seal isn't damaged by dieseling the "petro grease" will burn up leaving only particles of molly on/in the metal surfaces. Molly bearing lubes have been successfully used in piston guns for decades, however proper application is essential! Petroleum based lubes inside a piston gun (including the spring lube) continues to "out gas" as the gun sits between uses. This "out gasing" creates a diesel prone hydrocarbon rich "atmosphere" that needs to be "burned off" with a few shots before normal function returns. When I used "petrol based lubes" in my springers it would take about a dozen shots to stabilize the poi.

My solution for reducing the amount of warm-up shots was to simply stop using petroleum based lubes. For the first couple years after my "breakup with molly paste" I only used non-dieseling dry graphite powder (the kind puffed into locks) for internal lubing of my .177 R9s. After a couple years I read of a piston shooter using a pricy (compared to molly grease) non-dieseling "space station lube" called Dupont Krytox and I decided to try some. I figured that while graphite powder had worked well it did seem that an actual "non-dieseling grease" would be preferable for a piston seal lube. I ordered a half ounce tube of Krytox GPL205, kinda slathered it inside the R9 deliberately getting some on the piston seal face to test the non-dieseling claims, and I've been using that stuff ever since. Here is a target I shot over two days without any warmup shots before the second day using Krytox GPL as a lube............

LOL...certainly "minute of squirrel head accuracy" even shooting while sitting on a bucket resting the gun on cross sticks!

[young_skywalker]

It's been my experience that each time I tear a gun down and relube it will need another break in period. Maybe not as long as the original but, a break in period none the less.
As for moly paste.... a little goes a very long way. On the other hand, a generous amount of heavy tar is recommended for the spring itself. I apply it so it 'strings' from coil to coil.
One of the most effective thing is to polish the ends of the spring and their contact points. It needs to spin freely at both ends to minimize twang and torque.
A good barrel cleaning after the break in period is a good idea to clean up any migration of lubes into it.
I'm sure others have different methods.

+1 - excellent and concise reply.

[Bayman]

I recently re lubed my Rx1 (Hw90) piston with moly grease. My first shot after the gun sits 30min or more is short around 30 fps and the rifle prints low and left 3/8" at only 10 yards. Second shot jumps to the lower side of the normal spread and prints on center. By the third shot its single round hole from then on. Ignoring the first 3 shots the ES is around 10-12. I'm thinking I may have wiped on too much moly on the piston. I wiped on a thin semi transparent coat over the entire piston. Behind the seal of course. Could this be too much?
For shooting groups this is not a problem but to have an unreliable first shot is unacceptable for hunting.

I've never owned a "rammer" so perhaps they're different when it comes to lubing.
When molly lubes were used only a film was burnished into piston and receiver. The only purpose of molly bearing grease is to break metal to metal contact so a thin film is all that's necessary since molly has an affinity for steel surfaces (not so much for rubber seals however). A film of molly paste thick enough to be "squeegeed" in front of the piston seal did cause "dieseling issues" with my springers. When living in West Virginia I often went on squirrel hunts with a .177 R9 and I would take a few "lube clearing shots" when I got to the "squirrel woods" since I had the same "1st shot issue" as you when hunting.

Anywhoo, if the piston seal isn't damaged by dieseling the "petro grease" will burn up leaving only particles of molly on/in the metal surfaces. Molly bearing lubes have been successfully used in piston guns for decades, however proper application is essential! Petroleum based lubes inside a piston gun (including the spring lube) continues to "out gas" as the gun sits between uses. This "out gasing" creates a diesel prone hydrocarbon rich "atmosphere" that needs to be "burned off" with a few shots before normal function returns. When I used "petrol based lubes" in my springers it would take about a dozen shots to stabilize the poi.

My solution for reducing the amount of warm-up shots was to simply stop using petroleum based lubes. For the first couple years after my "breakup with molly paste" I only used non-dieseling dry graphite powder (the kind puffed into locks) for internal lubing of my .177 R9s. After a couple years I read of a piston shooter using a pricy (compared to molly grease) non-dieseling "space station lube" called Dupont Krytox and I decided to try some. I figured that while graphite powder had worked well it did seem that an actual "non-dieseling grease" would be preferable for a piston seal lube. I ordered a half ounce tube of Krytox GPL205, kinda slathered it inside the R9 deliberately getting some on the piston seal face to test the non-dieseling claims, and I've been using that stuff ever since. Here is a target I shot over two days without any warmup shots before the second day using Krytox GPL as a lube............

LOL...certainly "minute of squirrel head accuracy" even shooting while sitting on a bucket resting the gun on cross sticks!

I started my first relube and piston seal replacement with Krytox and the ES was all over the place. In the 40s & 50s. I went to another style seal and it cut it half. I cleaned out the Krytox and lubed the rifle with a more traditional grease and the extreme Spread dropped to single digits. This rifle has been an enigma for me because the extreme Spread opened up again and I put back in the first replacement seal and relubed it with moly grease and its doing well again. I've had this thing apart so many times and changed so many things I don't what actually fixed it temporarily at any time. Now is the best it's been. Now if I can only get that first shot to hit the POA.

[nced]

"ES was all over the place. In the 40s & 50s"
Hummm......I've never had an extreme spread anywhere near that and I'm puzzled why that would be! I'll tolerate a 10fps spread with a .177 cal pellet, however most of my chrony sessions have a single digit spread. Just a couple days ago I chronied both my .177 Beeman R9 and .177 HW95 and this is the result (all pellets selected at random from box and tin)........
R9.......7.9 grain CPL 849,849,844,850   8.4 grain Air Arms domes 839,839,836,833
HW95..7.9 grain CPL 881,881,884,887   8.4 grain Air Arms Domes 856,859,860,862     

I do have to say that along with nixing the molly grease I also nixed the factory HW piston seal of the era with the thin parachute edge due to the large temperature related poi shifts I got during the fall squirrel hunts in West Virginia when the mornings were cold and the afternoon temps were 25 degrees warmer............
When I bought the HW95 I found that HW had changed their piston seal design and found that a proper fitting factory seal gave performance similar to my home rolled oring sealed piston caps. The "fly in the ointment" is the fact that occasionally a HW piston seal will be undersized and fit the receiver too loosely.


After moving to North Carolina about 12 years ago I did a "temp related velocity test" with Krytox GPL205 as a lube and found the velocity to be very stable. For the test I left the .177 R9 over night in my unheated sun room where the temp fell to the low 20s and then shot a few CPLs over the chrony taking note of the velocities. The next morning I chronied the R9 after spending the night in the house at 70ish degrees and found that there was only a 10 fps difference between the two temps. What really surprised me was the fact that the 20 degree temp speed had the higher velocity.

Sorry that you couldn't solve your RX1/HW90 "first shot poi issues, however I'm glad that you solved your RX1/HW90 ES issues and do whatever works best for you!