This virtually brand-new Hatsan AT-P1 pistol came to me with a few outstanding issues.
Unfortunately, in the course of repairing the known issues, a few other concerns became obvious.
The known issues were as follows:
The gun was difficult to charge from empty - it required six to seven "blasts" of air from the SCUBA tank to seat the valve and begin filling. Once filled, it seemed to hold the charge just fine, sitting overnight with no noticeable pressure loss. If however, the gun was shot at all after filling, the reservoir would slowly bleed down to empty in a matter of three to four hours.
As I was handling the gun, another thing that I noticed was that the breech is sprung - the front is sitting up off the main tube, which in turn is causing the barrel to have an uphill attitude as it extends forward over the reservoir. It appears that the screw that is in the bottom of the magazine cutout is pulling that section of the breech down, but something, which I had presumed to be the transfer port bushing, is holding the front of the breech up, and away from the main tube. I was able to get 0.022" worth of shim in between the breech and the main tube, with no problem, so the gap is substantial. The owner also noted that the magazines were binding at times, which is probably attributable to the sprung breech. When checked, the slot for the mags is about 0.006" narrower at the top of the breech, than at the bottom - which corresponds with the direction in which the breech is sprung.
The gun also had a completely inoperable safety - the gun would fire with or without the safety on. This issue was dealt with separately in another post: http://www.canadiangunnutz.com/forum/showthread.php?887679-Safety-warning-to-owners-of-Hatsan-AT-P1-pistols
The upward angle of the barrel is difficult to photograph, but the difference in the gap between the two yellow arrows, and the two red arrows is quite noticeable with the gun in hand.
This pic shows a stack of feeler gauges totaling 0.022" easily placed between the main tube and the underside of the breech. The rear of the breech sits snug against the main tube.
After eliminating the problem with the inoperable safety, the next item that I addressed was the reservoir/valve assembly. Upon removing the reservoir assembly from the gun, and beginning the dis-assembly process, it became obvious very quickly that the ID of the reservoir tube had some razor sharp burrs to be dealt with, as can be seen by the way it is cutting the o-ring to ribbons as the tube is unscrewed.
Upon removing the valve unit from the reservoir tube, some minute traces of metal filings, and rubber debris are stuck to the inside of the valve and reservoir, by an oily substance throughout the inside of the reservoir.
As well, what has become typical of all the Hatsan guns that I have worked on, the heavy chatter on the threads that hold the valve body to the reservoir is painfully evident. The crest of the threads on this particular example are razor sharp, which no doubt contributed to the o-ring at the valve body to reservoir joint being shredded as badly as it is, as seen here. It was a miracle that this o-ring held pressure at all. When re-assembling, the only way to get a new o-ring past these razor sharp threads, was to wrap the threads with masking tape, install the o-ring, and then remove the masking tape.
While removing the valve body from the reservoir, I noticed that once the reservoir tube cleared the o-ring, that the threads were incredibly loose. I decided to try to somehow illustrate just how ill fitting these threads are, so I fixed a magnetic "V" block, and a dial indicator magnetic base to a one inch thick steel plate. The reservoir tube was held firmly into the "V" of the "V" block, and the valve body was screwed into the reservoir to a point of at least 95% thread engagement. The lateral (side to side) movement was then checked, which resulted in a reading of just under 0.012" at the valve body shoulder. This equates to something around 0.060" to 0.070" lateral movement at the exhaust port end of the valve ! What this means is that you don't even have to turn the valve body for the last few threads to remove it from the reservoir, you can just wiggle it from side to side, and "walk" the valve out !
Next, the linear (forward and back) movement was checked. This resulted in a reading of approximately 0.006". While this does not sound like much, remember - there is at least 95% thread engagement, so for that degree of slop to be present, those threads are holding by only a fraction of what they should be.
As I was cleaning the inside of the reservoir, the next issue presented itself. There is a score in the entire circumference of the reservoir tube ID, located about 85mm down from the valve body end of the tube. Due to where it is, there is no way to properly examine, or measure this score for depth. It is deep enough to be easily felt by inserting a blunt ended rod into the bore, and in my opinion, would seriously degrade the integrity of the tube. Again, due to the location, it was very difficult to get a picture of. The red arrows point to the score.
I am not an engineer specializing in pressure vessels, however, I have had plenty of experience in high pressure hydraulics and pneumatics, and am fully aware of what constitutes unacceptable practice at such pressures. The fact that these threads are so ill fitting at 95% engagement is shoddy by any standard, but when one considers that these mating threads are in brass and aluminum, and expected to withstand 3000 PSI of pressure, it becomes not only absurd, but dangerous. These poorly formed threads cannot possibly be representative of their engineered parameters.
Now, adding the reduced integrity of the scored aluminum reservoir tube into the equation, and you have a recipe for potential disaster.
In my opinion, this reservoir should never have left the factory - it should have been scrapped, not sold to some unsuspecting consumer to pressurize to 3000 PSI, and hope for the best.
Moving on to the valve stem, it was a mess. There were minute chatter marks, as well as radial gouges throughout the sealing face. Again, difficult to get a proper pic of, but when viewed through a 10x loupe, the reason for the valve stem not seating properly, and leaking, is obvious. The valve sealing face had to be cut back to clean up the mess, and then polished to provide a clean, smooth sealing surface. The seat also had to be changed, as it had been damaged by the uneven sealing face of the stem.
Next up, the breech. On the underside, a couple of heavy "bruises" with raised edges had to be cleaned up, as well as the burr around the circumference of the transfer port counterbore. I had believed this to be the cause of the sprung breech, but it only partially cured that issue. The breech was removed, and then both the breech, and the main tube were checked with a precision straightedge, and found to be OK. Next, I measured the height of the transfer port bushing above the main tube, and then the depth of the counterbore in the breech, which was also fine. Yet when the two assemblies are bolted together, the breech is still sprung to some degree. The space between the main tube and the front of the breech is only about half of what it was prior to cleaning up the underside of the breech, so it was left at that.
I decided that I'd take a quick look at the muzzle crown, just in case that might need attention, and while the crown proved to be clean on this particular gun, the same could not be said for the threads for attachment of the air stripper. The pic of these threads speaks for itself. Note as well that the o-ring just ahead of the front sight, is only 3/4 there - yup - a good size piece of the o-ring is just plain missing. The bottom of the o-ring groove has some light chatter, and the usual burrs on either side of the groove, but not as bad as on some other Hatsan guns I have worked on.
So there you have it.
If I never see another Hatsan airgun in my shop for resolution of manufacturing defects, it will be too soon.
Unfortunately, in the course of repairing the known issues, a few other concerns became obvious.
The known issues were as follows:
The gun was difficult to charge from empty - it required six to seven "blasts" of air from the SCUBA tank to seat the valve and begin filling. Once filled, it seemed to hold the charge just fine, sitting overnight with no noticeable pressure loss. If however, the gun was shot at all after filling, the reservoir would slowly bleed down to empty in a matter of three to four hours.
As I was handling the gun, another thing that I noticed was that the breech is sprung - the front is sitting up off the main tube, which in turn is causing the barrel to have an uphill attitude as it extends forward over the reservoir. It appears that the screw that is in the bottom of the magazine cutout is pulling that section of the breech down, but something, which I had presumed to be the transfer port bushing, is holding the front of the breech up, and away from the main tube. I was able to get 0.022" worth of shim in between the breech and the main tube, with no problem, so the gap is substantial. The owner also noted that the magazines were binding at times, which is probably attributable to the sprung breech. When checked, the slot for the mags is about 0.006" narrower at the top of the breech, than at the bottom - which corresponds with the direction in which the breech is sprung.
The gun also had a completely inoperable safety - the gun would fire with or without the safety on. This issue was dealt with separately in another post: http://www.canadiangunnutz.com/forum/showthread.php?887679-Safety-warning-to-owners-of-Hatsan-AT-P1-pistols
The upward angle of the barrel is difficult to photograph, but the difference in the gap between the two yellow arrows, and the two red arrows is quite noticeable with the gun in hand.
This pic shows a stack of feeler gauges totaling 0.022" easily placed between the main tube and the underside of the breech. The rear of the breech sits snug against the main tube.
After eliminating the problem with the inoperable safety, the next item that I addressed was the reservoir/valve assembly. Upon removing the reservoir assembly from the gun, and beginning the dis-assembly process, it became obvious very quickly that the ID of the reservoir tube had some razor sharp burrs to be dealt with, as can be seen by the way it is cutting the o-ring to ribbons as the tube is unscrewed.
Upon removing the valve unit from the reservoir tube, some minute traces of metal filings, and rubber debris are stuck to the inside of the valve and reservoir, by an oily substance throughout the inside of the reservoir.
As well, what has become typical of all the Hatsan guns that I have worked on, the heavy chatter on the threads that hold the valve body to the reservoir is painfully evident. The crest of the threads on this particular example are razor sharp, which no doubt contributed to the o-ring at the valve body to reservoir joint being shredded as badly as it is, as seen here. It was a miracle that this o-ring held pressure at all. When re-assembling, the only way to get a new o-ring past these razor sharp threads, was to wrap the threads with masking tape, install the o-ring, and then remove the masking tape.
While removing the valve body from the reservoir, I noticed that once the reservoir tube cleared the o-ring, that the threads were incredibly loose. I decided to try to somehow illustrate just how ill fitting these threads are, so I fixed a magnetic "V" block, and a dial indicator magnetic base to a one inch thick steel plate. The reservoir tube was held firmly into the "V" of the "V" block, and the valve body was screwed into the reservoir to a point of at least 95% thread engagement. The lateral (side to side) movement was then checked, which resulted in a reading of just under 0.012" at the valve body shoulder. This equates to something around 0.060" to 0.070" lateral movement at the exhaust port end of the valve ! What this means is that you don't even have to turn the valve body for the last few threads to remove it from the reservoir, you can just wiggle it from side to side, and "walk" the valve out !
Next, the linear (forward and back) movement was checked. This resulted in a reading of approximately 0.006". While this does not sound like much, remember - there is at least 95% thread engagement, so for that degree of slop to be present, those threads are holding by only a fraction of what they should be.
As I was cleaning the inside of the reservoir, the next issue presented itself. There is a score in the entire circumference of the reservoir tube ID, located about 85mm down from the valve body end of the tube. Due to where it is, there is no way to properly examine, or measure this score for depth. It is deep enough to be easily felt by inserting a blunt ended rod into the bore, and in my opinion, would seriously degrade the integrity of the tube. Again, due to the location, it was very difficult to get a picture of. The red arrows point to the score.
I am not an engineer specializing in pressure vessels, however, I have had plenty of experience in high pressure hydraulics and pneumatics, and am fully aware of what constitutes unacceptable practice at such pressures. The fact that these threads are so ill fitting at 95% engagement is shoddy by any standard, but when one considers that these mating threads are in brass and aluminum, and expected to withstand 3000 PSI of pressure, it becomes not only absurd, but dangerous. These poorly formed threads cannot possibly be representative of their engineered parameters.
Now, adding the reduced integrity of the scored aluminum reservoir tube into the equation, and you have a recipe for potential disaster.
In my opinion, this reservoir should never have left the factory - it should have been scrapped, not sold to some unsuspecting consumer to pressurize to 3000 PSI, and hope for the best.
Moving on to the valve stem, it was a mess. There were minute chatter marks, as well as radial gouges throughout the sealing face. Again, difficult to get a proper pic of, but when viewed through a 10x loupe, the reason for the valve stem not seating properly, and leaking, is obvious. The valve sealing face had to be cut back to clean up the mess, and then polished to provide a clean, smooth sealing surface. The seat also had to be changed, as it had been damaged by the uneven sealing face of the stem.
Next up, the breech. On the underside, a couple of heavy "bruises" with raised edges had to be cleaned up, as well as the burr around the circumference of the transfer port counterbore. I had believed this to be the cause of the sprung breech, but it only partially cured that issue. The breech was removed, and then both the breech, and the main tube were checked with a precision straightedge, and found to be OK. Next, I measured the height of the transfer port bushing above the main tube, and then the depth of the counterbore in the breech, which was also fine. Yet when the two assemblies are bolted together, the breech is still sprung to some degree. The space between the main tube and the front of the breech is only about half of what it was prior to cleaning up the underside of the breech, so it was left at that.
I decided that I'd take a quick look at the muzzle crown, just in case that might need attention, and while the crown proved to be clean on this particular gun, the same could not be said for the threads for attachment of the air stripper. The pic of these threads speaks for itself. Note as well that the o-ring just ahead of the front sight, is only 3/4 there - yup - a good size piece of the o-ring is just plain missing. The bottom of the o-ring groove has some light chatter, and the usual burrs on either side of the groove, but not as bad as on some other Hatsan guns I have worked on.
So there you have it.
If I never see another Hatsan airgun in my shop for resolution of manufacturing defects, it will be too soon.
