AirMaks Arms Katran velocity unstable?

[ericf]

I took delivery of my new katran LB HP from UA a couple weeks ago. I'm having an issue with stabilizing the velocity. The extreme spread is 60fps over 10 shots. I've also experienced the very first 4-5 shots hitting 4 inches low at 50 yards , with the remainder of the days shots being on target. I don't know if I should check the hammer/ spring setup and apply a lube to pivot shaft and spring or look at the regulator possibly needing cleaning and o-rings lubricated. Any experience and advice? Thanks in advance.

 

[bchannell]

Have you talked to UA? That would be the next step after asking here. Obviously it's out of tune, has a reg problem or leaking after the poppet.
My first step would be back the hammer spring way off, shoot over the chrony. Keep increasing the hammer til velocity stops rising and back it down slightly. Then see if velocity has stabilized. It's possible but not likely that the reg is not broke in yet, but even at that you probably wouldn't see 60 fps spreads.

Those are, grrrrreat guns, and I'm sure it's fixable. I never had a more reliable 177 than a Katran L

 

[RoosterCogburn]

Have you talked to UA? That would be the next step after asking here. Obviously it's out of tune, has a reg problem or leaking after the poppet.
My first step would be back the hammer spring way off, shoot over the chrony. Keep increasing the hammer til velocity stops rising and back it down slightly. Then see if velocity has stabilized. It's possible but not likely that the reg is not broke in yet, but even at that you probably wouldn't see 60 fps spreads.

Those are, grrrrreat guns, and I'm sure it's fixable. I never had a more reliable 177 than a Katran L

Yeah the hammer spring setting at any particular pressure is a very very small window.. it makes it very easy to find. Its set perfect or it will let you know either the spread is <5fps or its a very liberal spread. how is the efficiency and what does the shot sound like?

 

[ericf]

shot sound is relatively quiet (compared to my other AA-s410) which isn't moderated) . I just re-chrono'ed and over 14 shots these are the figures.
Hi-971.3
Low-898.4
SD-19.5
CV-2.05%
ES- 72.9
Avg. 947.1

I can shoot 4 magazines through it and pressure drops about 50 bar.
I'm not familiar with increasing hammer spring then back off. What does that tell me? (Sorry for the ignorance). My first thought was the simplest thing first.
I'm going to remove the side plate and add lubricant sparingly around the spring contact areas and hammer pivot. It probably won't accomplish much, but simplest to do.
Thanks

 

[ericf]

I very sparingly lubed up the hammer spring , spring guide, guide strut and hammer pivot pin. I went back to my chrono and started low and fired one shot noting vel. about 1/2 turn increase and fired again. I did this till velocity no longer increased. The velocity for a 18.2 grn. diablo appeared stabilized at around 1045 fps. I then decreased spring pressure till I settled around 975. I fired a 10 shot string/
results,
Hi-1005
low-959
sd-13.8
cv-1.39
ES-45.1
Avg. 991.
Regarding a "break in" , I have fired about 200 shots through it.

Ill give UA a call tomorrow and see what they recommend.

 

[RoosterCogburn]

I took delivery of my new katran LB HP from UA a couple weeks ago. I'm having an issue with stabilizing the velocity. The extreme spread is 60fps over 10 shots. I've also experienced the very first 4-5 shots hitting 4 inches low at 50

I very sparingly lubed up the hammer spring , spring guide, guide strut and hammer pivot pin. I went back to my chrono and started low and fired one shot noting vel. about 1/2 turn increase and fired again. I did this till velocity no longer increased. The velocity for a 18.2 grn. diablo appeared stabilized at around 1045 fps. I then decreased spring pressure till I settled around 975. I fired a 10 shot string/
results,
Hi-1005
low-959
sd-13.8
cv-1.39
ES-45.1
Avg. 991.
Regarding a "break in" , I have fired about 200 shots through it.

Ill give UA a call tomorrow and see what they recommend.

½Turn is too large an adjustment. Do ⅛ turns. Also 1 shot is not enough to know where you are. Adjust. Fire 3-5 shots. Adjust. Eventually you'll hit a peak number. Then the next adjustment it will drop. If the peak you reach isnt high enough for you. More reg pressure needed..

 

[RoosterCogburn]

I owned the SAME EXACT bchannel had. His .177L. The difference between sweet spot and not is about ⅙turn either side of perfect and it goes to hell.

 

[RoosterCogburn]

½Turn is too large an adjustment. Do ⅛ turns. Also 1 shot is not enough to know where you are. Adjust. Fire 3-5 shots. Adjust. Eventually you'll hit a peak number. Then the next adjustment it will drop. If the peak you reach isnt high enough for you. More reg pressure needed..

Also. Give 12-15 seconds between shots to insure the same plenum pressure each shot. Shoot too fast and you'll be off.

 

[ericf]

ok, I'll give it another "shot" (pun intended) in a few days. I'll back down the hammer spring a couple of complete turns. but what am I looking for when increasing and firing a few, (rinse and repeat). Am I watching for the highest vel. achieved using the hammer spring adjustment? Wouldn't the velocity always show an increase as hammer spring tension increases? I must not fully understand how the physics applies.

 

[Bigbaby]

From what I’ve read on correct pellet speed, it seems that you are trying to operate at excessive speed and destabilizing your pellets. Pellet speed should be 900fps +/-20fps. Holdover Ted did a simple tuning video, he recommended reducing your reg pressure, turning hammer spring to max, increase your reg pressure til you reach velocity slightly higher than desired fps, then decreasing hammer spring til you get a drop in velocity. SMALL INCREMENTS.

 

[Ranchibi]

Find the highest velocity for that set reg pressure before velocity starts to drop from increasing the HS then lower speed by 5% that should be the most efficient tune. Good luck and have fun!

 

[RoosterCogburn]

Find the highest velocity for that set reg pressure before velocity starts to drop from increasing the HS then lower speed by 5% that should be the most efficient tune. Good luck and have fun!

Correct. To OP. When you see the highest number before you adjust and the fps drops. Dial back to.thst position and then 1/20-

ok, I'll give it another "shot" (pun intended) in a few days. I'll back down the hammer spring a couple of complete turns. but what am I looking for when increasing and firing a few, (rinse and repeat). Am I watching for the highest vel. achieved using the hammer spring adjustment? Wouldn't the velocity always show an increase as hammer spring tension increases? I must not fully understand how the physics applies.

Yes. You'll adjust. See a number then. Adjust. And youll.get an obvious decrease. The katran is a bit more pronounced with this than most guns.

As to what ranchibi said. Absolutely. At 100 on the .177L i could reach 930 woth 10.03mk3 ko slugs. But it would shoot horrible. Backed to 890-900 shot like a dream. You MAY have a 20ps window you can operate on efficiently, consistently, and accurately with the katran at any given reg pressure. Youre trying to shoot pellets WAY too fast. If that is the velocity
100b gives you (damn) try 20.8,22 or 25.39 pellets.

 

[ericf]

The Beginner’s Guide to Tuning a Regulated PCP Airgun - American Airgunner

The Beginner’s Guide to Tuning a Regulated PCP Airgun By Nicolas Gregoris The airgun market has seen an influx of feature-packed and highly adjustable platforms in recent years. Features like externally adjustable hammer spring tension, regulator pressure, and transfer ports are now commonly...

americanairgunner.com

I found this too. I'll take it all into consideration.

 

[mercado]

I took delivery of my new katran LB HP from UA a couple weeks ago. I'm having an issue with stabilizing the velocity. The extreme spread is 60fps over 10 shots. I've also experienced the very first 4-5 shots hitting 4 inches low at 50 yards , with the remainder of the days shots being on target. I don't know if I should check the hammer/ spring setup and apply a lube to pivot shaft and spring or look at the regulator possibly needing cleaning and o-rings lubricated. Any experience and advice? Thanks in advance.

It happened to me with a .22 krait L with the new huma reg.. spread was sometimes like 80fps , i just sold it.. will never buy something from that brand again .. but that is me there's a lot of member here that got one with a working reg n they really enjoy the platform.

 

[JimD]

My Caiman X was purchased new from UA and the regulator (Huma) failed twice in about the first tin of pellets due to poor assembly. I don't know who assembled it but they put WAY too much silicone grease in the area where the spring washers are (first failure) and apparently none on the O-ring on the adjustment screw (second failure). I fixed these things and it works great. One sign of a failed regulator is the velocity is a function of the pressure in the main air storage area. Usually the velocity is low at full fill pressure, rises as pressure falls, and then it falls again at really low storage pressure. If that is what your gun is doing the regulator is not working. My experience is UA will want to fix it for you. I did it myself but that was not what they wanted. They offered to pay for return shipment for me.

I've never seen that big a variation but I've had a hammer spring mis-matched to the regulator setting double the ES. I had my Bullshark at about 7% under peak velocity and the ES was really high and the first shot velocity was much lower and it would rise quickly over the first 3 shots. Increasing the hammer spring to about 5% under the peak dropped the ES a lot and made the first shot much closer to the rest of the string. To know this you have to know what the peak velocity is for the regulator setting. That means turning the hammer spring up until velocity falls instead of rising. I agree with the others that said the Air Maks pivoting hammer is touchy to adjust with smaller than normal changes advisable but my Caiman needed bigger changes than they suggest. I would try 1/4 turn at a time, at least to start. You should be able to get a ES no higher than 20 fps but only if you have the gun tuned reasonably. My guns like the HS set at 3-5% under the peak. Higher seems to cause less issues than setting it too low (it just wastes air). I choose the final setting based upon keeping the first shot consistent with the string and accuracy. If I had to pick between them it would be accuracy.

I agree that velocity that may be as high as 1000 fps is too fast for pellets. I've had guns shoot well in low 900s but not high 900s. But I would not think that would affect the ES. Still heavier pellets seem indicated. If you want something inexpensive to try I would use H&N Baracudas that weigh 21 grain. They shoot well in my P35-22 but for this you mainly want to drop the velocity to a reasonable range - and you might find the gun likes them. My Caiman likes H&N 18 grain (and shoots them a little over 900 fps accurately). The fact that your first shot velocity is low suggests you gun will push the 18s even faster if you set the hammer spring appropriately.

 

[RoosterCogburn]

My Caiman X was purchased new from UA and the regulator (Huma) failed twice in about the first tin of pellets due to poor assembly. I don't know who assembled it but they put WAY too much silicone grease in the area where the spring washers are (first failure) and apparently none on the O-ring on the adjustment screw (second failure). I fixed these things and it works great. One sign of a failed regulator is the velocity is a function of the pressure in the main air storage area. Usually the velocity is low at full fill pressure, rises as pressure falls, and then it falls again at really low storage pressure. If that is what your gun is doing the regulator is not working. My experience is UA will want to fix it for you. I did it myself but that was not what they wanted. They offered to pay for return shipment for me.

I've never seen that big a variation but I've had a hammer spring mis-matched to the regulator setting double the ES. I had my Bullshark at about 7% under peak velocity and the ES was really high and the first shot velocity was much lower and it would rise quickly over the first 3 shots. Increasing the hammer spring to about 5% under the peak dropped the ES a lot and made the first shot much closer to the rest of the string. To know this you have to know what the peak velocity is for the regulator setting. That means turning the hammer spring up until velocity falls instead of rising. I agree with the others that said the Air Maks pivoting hammer is touchy to adjust with smaller than normal changes advisable but my Caiman needed bigger changes than they suggest. I would try 1/4 turn at a time, at least to start. You should be able to get a ES no higher than 20 fps but only if you have the gun tuned reasonably. My guns like the HS set at 3-5% under the peak. Higher seems to cause less issues than setting it too low (it just wastes air). I choose the final setting based upon keeping the first shot consistent with the string and accuracy. If I had to pick between them it would be accuracy.

I agree that velocity that may be as high as 1000 fps is too fast for pellets. I've had guns shoot well in low 900s but not high 900s. But I would not think that would affect the ES. Still heavier pellets seem indicated. If you want something inexpensive to try I would use H&N Baracudas that weigh 21 grain. They shoot well in my P35-22 but for this you mainly want to drop the velocity to a reasonable range - and you might find the gun likes them. My Caiman likes H&N 18 grain (and shoots them a little over 900 fps accurately). The fact that your first shot velocity is low suggests you gun will push the 18s even faster if you set the hammer spring appropriately.

I tried the huma reg in the katran. Needless to say the stock reg was quickly replaced. The airmaks katran reg is fantastic.

 

[JimD]

I have only had SPA and one Huma regulator apart but I think they both work very well as long as they are assembled correctly. I've had my SPA regulators stop functioning due to too little silicone grease in the spring washer area. That seems to be the touchiest assembly issue. The stem has to slide freely to function but if you totally encase the washers in grease it can mess the up too. The O-rings and the body of the regulator they slide in need grease but the spring washers do not need grease. I now put a screw in the end of the spring washer stem piece (which is functionally a piston) and make sure it slides smoothly before reassembling the gun now.

 

[ericf]

I'll be giving UA a call today. Maybe they will give me a "Deal" on a new regulator. Regarding the tuning. I did more research into the "how and what" and tuning appears easy enough albeit a little time consuming. One thing that's not going to work is that the velocities are all over the place. I am not able to get consistent minimal velocity increases (or decreases) to make such an attempt. It's a frustrating mess. one shot will be 870 and without any adjustment the next will be 930, then a third will be 910. I think actual "Proper" tuning will be impossible till this regulator gets fixed or replaced.
One other Newbie question. Once the rifle is tuned, will it need to be re-tuned for each different pell weight? Logic tells me yes considering needed air volume change to move a heavier/lighter pell down the barrel, but I'm not so sure.
Thanks again for all the input and advice. Its priceless info.
btw. I did purchase a tin of the HN baracudas 21gn pells. The rifle didn't like them, however, that was also before I discovered this current issue which most likely was a contributing factor.

 

[RoosterCogburn]

I'll be giving UA a call today. Maybe they will give me a "Deal" on a new regulator. Regarding the tuning. I did more research into the "how and what" and tuning appears easy enough albeit a little time consuming. One thing that's not going to work is that the velocities are all over the place. I am not able to get consistent minimal velocity increases (or decreases) to make such an attempt. It's a frustrating mess. one shot will be 870 and without any adjustment the next will be 930, then a third will be 910. I think actual "Proper" tuning will be impossible till this regulator gets fixed or replaced.
One other Newbie question. Once the rifle is tuned, will it need to be re-tuned for each different pell weight? Logic tells me yes considering needed air volume change to move a heavier/lighter pell down the barrel, but I'm not so sure.
Thanks again for all the input and advice. Its priceless info.
btw. I did purchase a tin of the HN baracudas 21gn pells. The rifle didn't like them, however, that was also before I discovered this current issue which most likely was a contributing factor.

Thats what tuning does. Were trying to figure if youre over the place BECAUSE of an out of balance tune. Being over or under hammer can cause this. Although this is unusually severe. The katran. Even a superb gun like mine was/is. Will have giant spreads if the hammer is set incorrectly. The katran is very sensitive to this.

 

[ericf]

"The katran. Even a superb gun like mine was/is. Will have giant spreads if the hammer is set incorrectly. The katran is very sensitive to this."

So I can better understand, If the hammer setting is the issue, and I am able to get a decent setting on the hammer, the velocities should stabilize far better than what I'm seeing. Is this a correct interpretation? Then, with the hammer set at this designated point giving me stability in fps, the only way I can reduce velocity (if needed) is to use a heavier pell or disassemble it and adjust the regulator. And adjusting the regulator will cause the whole process to start over. Is my understanding correct? I apologize again for my lack of knowledge in this matter.