Fluctuating pellet speeds after service

brouwpa

brouwpa

Super member
Joined
Jul 7, 2022
Messages
1,139
Reaction score
2,096
Location
Stratford upon Avon
Having just fitted a kit and given my 77 a good clean and relube, whilst doing power checks I noticed quite a lot of variations in speed, both up and down.
Is it just a case of getting some lead through it and it will settle down or have made cocked up somewhere?
 
As above . When I cleaned out my HW80 I bought degreaser instead of brake cleaner and used it . I did flush it with brake cleaner also but some of the degreaser was sill in the compression tube.

It dieseled and the first few shots were up and down.

It was stripped again and fully flushed out and rebuilt and did not do it again.
 
It's got a TBT kit in it, no visible sign of dieseling (I have no sense of smell), the shot cycle is much improved (i think). The variations are 3-4 metres per second.
I am probably being impatient as I have put less than 20 pellets through it!!
Will put the scope back on, check it for accuracy then re-chrono. This should also tell me if my chrono is playing up. I have a few guns that have always been very consistent so will check one of them.
Thanks for the suggestions (y)
 
brouwpa said:
It's got a TBT kit in it, no visible sign of dieseling (I have no sense of smell), the shot cycle is much improved (i think). The variations are 3-4 metres per second.
I am probably being impatient as I have put less than 20 pellets through it!!
Will put the scope back on, check it for accuracy then re-chrono. This should also tell me if my chrono is playing up. I have a few guns that have always been very consistent so will check one of them.
Thanks for the suggestions (y)
Click to expand...
10-13 FPS is not a large variation (don't do metric), so I wouldn't be worried. Do an initial chrono check and see what happens over time ... as long as the accuracy is there - IIABDFI 👍
 
brouwpa said:
It's got a TBT kit in it, no visible sign of dieseling (I have no sense of smell), the shot cycle is much improved (i think). The variations are 3-4 metres per second.
I am probably being impatient as I have put less than 20 pellets through it!!
Will put the scope back on, check it for accuracy then re-chrono. This should also tell me if my chrono is playing up. I have a few guns that have always been very consistent so will check one of them.
Thanks for the suggestions (y)
Click to expand...
In my case it was a ftlb or more but as my rifle is FAC it was not much of an issue but it would be is it was still sub12.
 
brouwpa said:
It's got a TBT kit in it, no visible sign of dieseling (I have no sense of smell), the shot cycle is much improved (i think). The variations are 3-4 metres per second.
I am probably being impatient as I have put less than 20 pellets through it!!
Will put the scope back on, check it for accuracy then re-chrono. This should also tell me if my chrono is playing up. I have a few guns that have always been very consistent so will check one of them.
Thanks for the suggestions (y)
Click to expand...
For us " metrically challenged" that 3-4 meters/second is 9 - 12 fps... Not bad numbers, especially immediately after a rebuild...not bad numbers after a full tin, in reality - could be chalked up to pellet variances. No worries.
 
brouwpa said:
Having just fitted a kit and given my 77 a good clean and relube, whilst doing power checks I noticed quite a lot of variations in speed, both up and down.
Is it just a case of getting some lead through it and it will settle down or have made cocked up somewhere?
Click to expand...
There’s usually a bit of leading in plus the lubrication getting evened out and the spring settling. Also if it was a new one in a kit theres the chance it’s grabbing on the guides sometimes until settled
 
To me, grouping is more important than speed.
See how you get on with it before looking for something that may not be there.
 
You have a chrono measuring in mps, that’s the first issue. It’s fine for indicative results eg comfortably below 12ft/lb for a rifle, but its unit of measurement is over 3.28 times larger than the accepted and widely used fps, and that’s before you consider how it handles rounding. Let’s assume logically you shoot a two pellets, one at 3.49mps and the next at 3.51mps, one of those should be displayed as ‘3’ and the other ‘4’, which looks like 3.28 feet per second difference, but in reality is actually insignificant.

Some of the Chinese chrono’s of recent years have options to change this, check if yours is one of them before going any further. If not, borrow or arrange to use a more suitable chrono.

Next up, other than ‘is it comfortably legal’ I wouldn’t normally test a springer till I had run it in post rebuild. For me (not that I do much with springers) I would want an absolute minimum of 50 shots through it, usually more.

Finally 4mps (rounded) is 13fps, 3mps is 10fps, is it the single digit spread some people spend hours upon hours polishing to get? No, but for pellets straight out of the tin on a freshly rebuilt gun, it’s going to be about right. With a RS or Exact in .177 for example, 13fps is 0.05ft/lb or politely put, bugger all.
 
Last edited:
You are literally your own worst enemy here, you have the ability to measure in significantly more detailed units and have chosen not to 🤣
 
Does it just give reading in whole units? Or is there a another figure after a decimal point? Each .3 is roughly a foot.
Either way those aren't terrible numbers. Even on a PCP I'd live with a 10 FPS spread although I'd prefer single digits if possible
 
wuggis72 said:
Does it just give reading in whole units? Or is there a another figure after a decimal point? Each .3 is roughly a foot.
Either way those aren't terrible numbers. Even on a PCP I'd live with a 10 FPS spread although I'd prefer single digits if possible
Click to expand...
Yes it has a decimal point!
 
You must log in or register to reply here.
Back
Top