Crosman 392 difficult to pump/terrible accuracy=help!

[OntarioGunner]

Hey guys-not a regular on this forum anymore and have mostly moved away from airguns. However, I do find them to be a very useful tool busting barn pigeons when I'm out visiting friends. I started years ago with a QB-79, had it tuned, then "upgraded" to air from CO2 and everything that entailed. Thought I wanted something simpler, so I sold that and moved to a Diana 24C. Than a Diana 24 in 22. Didn't love the hold sensitivity with the springers and tried a QB-78 Deluxe that would bleed-out CO2 periodically for no apparent reason. (that I could find)

Decided to go back to my roots with a pumper, I put a million miles on a stock 1377 back in the day (with a 1399 stock) so I considered buying one of the new Crosman 362s when I saw this PAL rated 392 come up for sale. Assumed it would be a "better 362" with a wood stock so I bought it. Condition is basically new.

Did my first test-shoot on the weekend, and not only is the pumping effort incredibly difficult-the accuracy was terrible. As in, 8" group @ 20 yards.

Turned to Google instead of making a tomato stake out of this gun, and found reference to poor maintenance (seals needing lube?) causing excessive pumping effort and in some cases, pins shearing from owners just given'r. lol I'm a middle aged guy, but work with my hands for a living and might be slightly stronger than an office worker of the same age. Anyhow, like a few things in life-I should have stayed where I started and kept the CO2-powered '79 but here I am. One air rifle, and the rifle doesn't work right.

Open to ideas, and have very little experience with servicing air guns. It's not leaking air once pumped, but I can realistically pump it about 3X before things get out of hand. I had to pass the rifle to my nephew to pump it up to 5. (8 is capacity)

Hoping someone reading this has a good sense of what might be happening. I'm back to considering a life without an air rifle. lol

Thanks for chiming in, much appreciated.

[Ace]

quick question, I take it you don't own a chrony ?

[OntarioGunner]

I don't own a chronograph.

[Atlas_cn]

1. How old is the rifle, did you maintain it and did you cleaned the barrel. How did you store your gun--I always put all guns inside gun sock, with Ballistol Lube before long time storage or after couple months use, then put into a case or safe. And if I noticed it is wet and moisture I will put extra Ballistol after use that day.

2. How is the pellets, some pellet just not good and in-consistent by itself, and your gun may just not like it. I have JSB 13.43gr works great with PCPs however all my springers and pumpers seems not like it --the spread is not bad but not as good as crosman HP 14.3gr and it is actually about 20fps slower. I guess the larger pellet diameter may cause more contact with the bore so lower power rifles may not handling it very well.

3. You need oil the pump hinge and seal--it is easy to do--with silicon lube time to time, I oiled it before put to long-time storage and oil again after took out to use, as well as every 250 pellets with Seneca Dragonfly--BTW they are much better than 362 as the design you don't need extra force to pump with the building up pressures. All other pumpers are harder to pump once the tube pressure exceed certain level, even my 880 need some effort to pumping from 8th to 10th stoke , so I usually just put 4-6.

4. Are you steady when shooting (from rest or mono/tri pod or at least lean on something), one of my buddy shoots great on bench with support but he will have 2" spread with same gun at 25 yards while unsupported.

5. How is your cheek welding--you need hold the same spot to get a consistent result. And it does matter a lot with the PEEP sign--optics you may have parallax adjust to compensate but with peep sight if you didn't aligned properly, the pellet will flying everywhere.

And finally, keep in mind that pumper may be less accuracy compare to other rifles, as once you pumped, not rest/adjusted yet and you need to take fast shot right away, you will have errors as your mussel, your heart beat and your body is not claim down from pumping to shooting.

Anyway 8" spread at that range is too big. So I will day try clean/oil first and see.

[OntarioGunner]

Thanks for chiming in. I don't think technique is the issue, I have a proper shooting bench leveled, front heavy bag, rear support bag, custom comb riser on the stock as you have to mount scopes high to clear this mini bolt.

I bought the gun used, but it was (at least outwardly) in brand new condition. Doesn't show any signs of wear. Just insanely high pumping effort required past 3 pumps, and terrible accuracy of a rest.

The scope is one intended for rimfire, but low magnification and a 50 yard parallax setting. I was shooting at about 1/2 the distance, but that alone couldn't explain away the ridiculous accuracy. On at least 3 occasions, the pellet essentially went through the same hole which suggests hold wasn't the issue. I'm thinking the scope is a possibly an issue but more likely, wonky velocity differences.

Still confused about what I could do to possibly remedy/lube, and what product use. Would this require a tear-down?

[Ace]

I'm thinking the scope is a possibly an issue but more likely, wonky velocity differences.

this is why a crony would be very helpful to rule out +/- velocity changes

[OntarioGunner]

I'm thinking the scope is a possibly an issue but more likely, wonky velocity differences.

this is why a crony would be very helpful to rule out +/- velocity changes

I understand, but in my limited reading...it sounds like the pumping effort should not be this heavy-duty. Wouldn't lubing it (still don't have any direction there) be a less expensive place to start than buying a pc. of equipment I've never needed in 40 years of shooting? Not simply after a quick fix, but say I bought one and YES...velocity varies too much, what THEN would be the suggested fix, and why don't we start there? In other words, could there be multiple reasons for why the accuracy could be so poor? I don't want to even own gun that requires so much force to use, seems like addressing that might be the place to start?

[Atlas_cn]

How is the spread looks like? Is it everywhere or more tends to be vertical or horizont? Actually if you have a spread more in horizontal, up and down a lot whicheans fps not stable, so it could be the value/spring/compress tube or simply pellet it self not consistent. If it is tend more vertical, like more to left or right, mostly it could be scope or the crown of barrel.
Also did you tried with different pellets? As too little info to actually judge it.

[Ace]

your correct in that it should not be that much more difficult to pump past 4
yes it gets harder with each pump the second one being the more difficult but not as you describe it to be,
sounds like there might be something going on with the valve because your saying its holding air so your seals must be ok,
it might need a tear down lube and reassemble
Pump stroke…………..Effort in lbs.
1………………………………….11
2………………………………….16
3………………………………….13
4………………………………….15
5………………………………….15
6………………………………….15
7………………………………….15
8………………………………….14

have a read here part one and two....https://www.pyramydair.com/blog/2016/12 ... 92-part-1/

[OntarioGunner]

your correct in that it should not be that much more difficult to pump past 4
yes it gets harder with each pump the second one being the more difficult but not as you describe it to be,
sounds like there might be something going on with the valve because your saying its holding air so your seals must be ok,
it might need a tear down lube and reassemble
Pump stroke…………..Effort in lbs.
1………………………………….11
2………………………………….16
3………………………………….13
4………………………………….15
5………………………………….15
6………………………………….15
7………………………………….15
8………………………………….14

have a read here part one and two....https://www.pyramydair.com/blog/2016/12 ... 92-part-1/

^thanks, that's shocking to see. I'd say by the time it gets to 5 pumps it's probably closer to 30lbs. than 15.

Any GTA airgun mechanics want to take a look?

[Ace]

id be more then happy to look at it for you but unfortunately i just moved
and very busy at the moment and have a lot of backed up work on my bench lol...so I wouldn't
be able to get to it for some time...good luck with it cheers

[Dr Nick]

With regards to accuracy...

Crosman 392/397 had(have) issues with paint overspray on the muzzle, causing inaccuracy. Try swabbing some acetone on the end of the muzzle with a q tip.

I had a 392 years ago and went from ho hum to respectable with after doing this.Accurate with JSB Stratons at 6 pumps

As far as the "hard to pump",have you oiled it ?

[ricksplace]

I use 30wt non detergent motor oil for lubricant in all of my pumpers. (2100, 2200x2, 880, 761xl). In particular, keep the pump cup well oiled. Excess oil will blow out of the barrel. The 2100 and 2200s need a drop or two of oil regularly (about every 50-100 shots) on the pump cup. Velocities will start to drop and pumping effort will increase without it. The motor oil is a better lubricant than silicon oil regarding metal to metal contact. One litre will last you forever.

With regard to chronographs, I concur that a chronograph is an essential tool for airgunners. In my opinion, much moreso than powder burners. When my Chrony quit, I bought a little self-contained unit suitable for airguns only. Check out aliexpress. The unit I bought cost under $50 delivered. I have not missed the use of a chronograph to the same extent with my powder burners.

[Doc Sharptail]

I use 30wt non detergent motor oil for lubricant in all of my pumpers. (2100, 2200x2, 880, 761xl). In particular, keep the pump cup well oiled. Excess oil will blow out of the barrel. The 2100 and 2200s need a drop or two of oil regularly (about every 50-100 shots) on the pump cup. Velocities will start to drop and pumping effort will increase without it. The motor oil is a better lubricant than silicon oil regarding metal to metal contact. One litre will last you forever.

With regard to chronographs, I concur that a chronograph is an essential tool for airgunners. In my opinion, much moreso than powder burners. When my Chrony quit, I bought a little self-contained unit suitable for airguns only. Check out aliexpress. The unit I bought cost under $50 delivered. I have not missed the use of a chronograph to the same extent with my powder burners.

I use the Wally equivalent "air tool oil" which makes perfect sense, and is very likely simply non-detergent oil. After about 15 years use, I'm a little past the halfway mark on the one litre bottle.

Those old cup-piston guns often need the piston cup replaced, especially after un-maintained long-term storage.
I've seen some fairly bad samples that were treated with other things than non-detergent oil.
My normal route is to by-pass the cup piston thing entirely, and go to a flat top piston system. They can be ordered on-line, or self-made.

I would recommend at a minimum inspecting and lubing the piston cup, and more importantly cleaning the internals of the pump tube as simply a start...
The bit on a chronograph is very good advice- it will help you determine how the gun is behaving.

-D.S.