Hatsan Carnivore .30 Cal Modding/Tunning Results

[rjorge]

It started when blackdiesel and I had a conversation about the Carnivore, and his question was whether it could deliver 14 shots at 90 FPE + with JSB 50 gr. pellets. My answer was yes; surely I could get 1.1 FPE/ci out of the Carnivore platform. I have a BT65 in .25 myself and knew the limitations quite well, so I thought...

Norm shipped it my way and told me to be a mad scientist with it... Little did he know the transformation it would undergo. I think every time I sent him update pictures he was like "What the heck is he doing???” I did not shoot any strings prior to disassembling it, as Norm was not satisfied with its stock performance, so I went straight to modding it. My favorite geek word... modify!

I started by making a new bolt to replace the stock brass. The stock pellet probe was too long, thick and loose in the breech, so I made one without the flaws in 304 SS. I also made a new magazine centering probe in 304 SS to replace the wobbly stock piece and tossed the “gold ball” and replaced it with a SS knob. All the other bolt parts were sanded smooth and polished.




 
Next I moved to the valve. I basically modded the valve like I did on my BT with a few twists, which consisted of boring the inside for easier flow past the poppet, new PEEK poppet to replace the soft Delrin (.266” thru hole), thinned valve stem to .120” and turned the sealing head diameter to .240” (.012” of sealing surface), moved the valve stem spring to the front of the valve, allowing for better flow and wider selection of spring rates, and plugging all holes with solder. Once all holes were plugged, I screwed the valve into the bushing while the gun was assembled and step drilled the valve hole to .228” while mounted on the Lathe milling attachment. The TP was changed to 304 SS and drilled to .234”. The 90 degree turn from the valve throat to the TP was smoothed.






 
The barrel came next. I first cleaned it and polished the bore with bore paste, since there was evidence of barrel rust. Next I inspected the crown to make sure no burs were present, finishing with a light polish. I noticed that the barrel port did not line up when the barrel set screws were tightened, so I tightened the barrel to the breech and step drilled the barrel port and breech port to .228”.  The leade was rough with deep gouges, so I re-finished it, added a slight ramp into the grooves and polished it to a mirror finish. The deep gouges are still there, but won’t affect the pellet/bullet loading.

I also modified the trigger for a long 1st stage followed by a 1 lb. pull second stage, as Norm likes it. This consisted of polishing/straightening sear parts, loosening the stock trigger spring and shimming parts where needed.

A new ¾” long hammer adjustment screw in SS replaced the stock. I modified it to accept a 4mm hex, so Norm can use the same one from his AT-44’s.



I moved on to assemble everything to see what the above mods did. Again, the goal is a 14 shot string with low ES. The results weren’t what I wanted. The tightest string was averaging 890 fps for 7 shots and an ES of 8 fps. I could have tuned it further, but decided to stop and get a few measurements…

It turns out that the valve lift potential was a sad max of .102”! There is no way, a stock Carnivore with modest ports will make big power with a decent shot string. In order to extend the shot string, I needed more lift. So onto more modifications… 

The valve bushing was the first limiting factor, so the face was milled .100” in order to extend the lift to a maximum of .200” (more than enough) before the hammer would hit the bushing. Next was the valve. With the hammer spring now on the outside of the valve, I made the necessary changes to allow the valve to open to .210”. I don’t want the valve to be the hammer stop. The hammer pull back lever needs to be modified as well, since the hammer would now hit the wheel that pulls against the hammer. It took a combination of things to allow the hammer enough travel. The tricky part was modding the hammer. I used a carbide flute mill bit to recess the point of contact against the hammer pull back lever wheel. This also required an extension of the back of the hammer in order to reset the trigger sear once the hammer was pulled back. I opened the back part of the hammer and made a bushing out of aluminum. I added a steel button at the point of contact against the trigger sear reset to avoid gouging/wear over time. The bushing was pressed in place with Green Loctite and the hammer weight is now 89g vs 93g stock. So with these mods the maximum potential lift is now .200”.






 
I also changed the hammer spring to a 17 lbs./inch 2 ½” long SS spring. It is ¼” shorter than stock and stiffer. The reason behind this is to minimize the stress on the anti-hammer-bounce lever by using less preload compared to the stock hammer spring. McMaster Carr part # 1986K19.



After everything was lubed and assembled, I was very anxious to see what kind of performance I would get. The max preload is 10 turns, where 1-3 turns the spring is loose and 4-10 turns the spring is in tension. The stock spring is in tension at 0 preload. I filled the tube to 200 BAR and shot the following 2 shot strings, I used the gauge on the airtube to record a rough idea of pressure drop. It matched to my tank @ 200 BAR.

10 turns: 1006 (112 FPE) / 997. (End pressure of ~180 BAR or .68 FPE/ci)
9 turns: 968 /987 (End pressure of ~185 BAR or .97 FPE/ci)
8 turns: 906/923 (End pressure of ~190+ BAR  or 1.2+ FPE/ci)   
 
This gave me all the information I needed to know. I decided to shoot a full string @ 8 turns, or 4 turns past no tension. One thing I did notice was how much quieter the gun was shooting compared to before. A short snap is the best I can describe. The BT has an anti-hammer-bounce device that uses a mechanical stop to keep the hammer from opening the valve twice, which was smoothed and polished were needed.

On to the full shot string starting at 200 BAR @ 8 turns:

906/923/939/934/948/958/957/951/959/960/957/962/949/950/947/952/948/950/934/923/908/905

If shot to within:

4% of max: 20 shots avg. 946 fps or 99.4 FPE, 39 fps ES. Fill to 190 BAR refill @ 105 BAR. 1.3 FPE/ci
2% of max: 14 shots avg. 953 fps or 101 FPE, 15 fps ES. Fill to 175 BAR refill @ 110 BAR. 1.4 FPE/ci!!! 

The chronograph is a F1 chrony, which is in my basement with a 100w halogen light 6ft above it; I get no errors this way. The muzzle was ~3 ft. from the chronograph. 



I believe its a combination of things that are making this beast click...

I have always been a firm believer on using heavy poppet springs along with a hard seat (PEEK in this case), as I have confirmed time after time how the right combination acts to complement each other in providing a nearly flat shot string over a wide range of pressure. Its a dynamic balance of short and an extremely fast closing of the valve at high pressure and a slow and steady dwell increase as the pressure drops. The high volume of air behind the poppet provides a nearly constant force against the poppet during the shot, which is the main acting force on closing and slowly decreases as the pressure drops.

The hammer design plays a huge roll in avoiding excessive air use. The sear engages at the very back of the hammer, providing no drag once released. There are only 2 narrow areas of contact against the tube, which allows the hammer to have very little friction against the tube ID (both are steel). The front of the hammer being mostly open, keeps air from compressing and "pushing" the hammer back after making contact against the stem. To keep the hammer from bouncing, a lever is used to mechanically stop it during return. With a low hammer spring preload force and high closing force against the poppet, in conjunction with the anti-hammer-bounce device, it leaves very low potential for bounce throughout the shot string.

Next step is to test its accuracy. With such a low ES, I am expecting nice groups out to 100 yards... I’ll post pictures when I get it done. I am also testing the BBT 70gr bullets when I get them. Hope you enjoyed the read as much as I enjoyed working on it!

[blackdiesel]

I can't say enough how much I appreciate all the work that you did to this.   

[Bwalton]

Good read I see that you took around .060 off the valve stem... Good power and shot count, The BT65 platform is great to work on. Good job with the modifications.

[SpiralGroove]

Wow Jorge -> just Fantastic Work
Blackdiesel should fly you to the Bahamas for a vacation!
I Love it   Thanks for sharing ............ Kirk

[Bwalton]

I would try to tighten up that shot string a bit. Try to get the the heart of the string right off the top is key for accuracy.  I would tune to make it look like this 948/958/957/951/959/960/957/962/949/950/947/952/948/950....then fall off you should get good long distance accuracy, but it can not start so late in the string.. That is a great regulator string. I will be doing some what the same tune but with a special reg for this set up and dive into the 2-3fps es....Great work can't wait to see the 100yard groups!

[rjorge]

Thanks guys! I agree Kirk!

Baxter, I just confirmed what I mentioned about filling pressures. I filled to 175 BAR and the string started right at 945 fps then 948 fps... so all you have to do is fill to 175 BAR for a 2% of max string or to 190 for a 4% string.

[blackdiesel]

This might make me start back hunting on a regular basis.  Ok Bugs Bunny, you better beware if I'm in your neighborhood.   

[Bwalton]

Thanks guys! I agree Kirk!

Baxter, I just confirmed what I mentioned about filling pressures. I filled to 175 BAR and the string started right at 945 fps then 948 fps... so all you have to do is fill to 175 BAR for a 2% of max string or to 190 for a 4% string.

Sounds good.... I should be up and going this weekend non-Regulated, waiting on the Huma .30cal reg for it. Should have some groups also, but do not have the 50gr as of yet only the 44gr JSB

[hotshot]

I started by making a new bolt to replace the stock brass. The stock pellet probe was too long, thick and loose in the breech, so I made one without the flaws in 304 SS. 

Apologies in advance if this is a stupid question; but will replacing the tapered section of the pellet probe with a square section create any long-term wear and tear problems with the breech O-ring seal?

[blackdiesel]

Thanks guys! I agree Kirk!

Baxter, I just confirmed what I mentioned about filling pressures. I filled to 175 BAR and the string started right at 945 fps then 948 fps... so all you have to do is fill to 175 BAR for a 2% of max string or to 190 for a 4% string.

Sounds good.... I should be up and going this weekend non-Regulated, waiting on the Huma .30cal reg for it. Should have some groups also, but do not have the 50gr as of yet only the 44gr JSB

Trenier seems to have the best deal on the 50 gr.  They're only $12.29 per tin there.

[Bwalton]

Thanks Norm have to get a few tins

[Hobbyman2007]

Nice work, like what u did with increasing clearance on the hammer. I'll have to dig into my .25 to see if it was stoping me from getting to the 100 fpe mark.

[jaraxle1zx]

Nice job
I wonder if you can get hatsan 35cal to shoot the jsb at 950fps? I didn't buy that cal thinking I could not get 950fps.
900fps would be the slowest I would want to shoot 25+ cal pellets.

Hobbieman. The bt65 is from what I can tell the same platform as 30 cal. Only thing keeping it from hitting 100fpe is the size of pellet you can fit in breech. The bt65 25cal will sling jsb 25 grains at 1200fps if you wanted it to. Do RG's mods and you could see over 1200fps.

What I found out modding the 25 cal is mid 1100's with 25 gr takes a lot to get it moving faster.
Heaver grain pellets would have a greater increase in fps with same mods than the lighter 25 grain pellet.
Must be wind drag at a certain fps. So I never got 100fpe out of 25 gr jsb. 

When I got my bt65 30 cal I detuned my 25 cal. But if you had the right slug and you could load it, the 25 cal would do 100fpe

[rjorge]

Apologies in advance if this is a stupid question; but will replacing the tapered section of the pellet probe with a square section create any long-term wear and tear problems with the breech O-ring seal?

You are correct. It is hard to see, but a small radius was added; which I later had to increase. I changed the o ring to 70 Duro as well.

[OleTomCat]

Nice job
I wonder if you can get hatsan 35cal to shoot the jsb at 950fps? I didn't buy that cal thinking I could not get 950fps.
900fps would be the slowest I would want to shoot 25+ cal pellets.

Hobbieman. The bt65 is from what I can tell the same platform as 30 cal. Only thing keeping it from hitting 100fpe is the size of pellet you can fit in breech. The bt65 25cal will sling jsb 25 grains at 1200fps if you wanted it to. Do RG's mods and you could see over 1200fps.

What I found out modding the 25 cal is mid 1100's with 25 gr takes a lot to get it moving faster.
Heaver grain pellets would have a greater increase in fps with same mods than the lighter 25 grain pellet.
Must be wind drag at a certain fps. So I never got 100fpe out of 25 gr jsb. 

When I got my bt65 30 cal I detuned my 25 cal. But if you had the right slug and you could load it, the 25 cal would do 100fpe

I had good luck with the Rat Sniper Slugs in my .25

http://www.ratsniperslugs.com/order-page.html

[rjorge]

After confirming that the barrel had a bad leade and was causing bad accuracy, a new barrel was requested from Hatsan and a swap was made.



The accuracy wasn't good at 950 fps with the 50 gr pellets, so I decided to try to add a regulator to see what kind of numbers I would get (goal of low ES with 44 gr JSB's). I used a Huma reg for a BT65 .25 cal, I just had to make a plenum extension as 19 cc is not enough. The final plenum volume is 75cc and the regulator was set at 120 BAR. There is around 155cc left. The ES seems to be tightening to below 5 fps. 



At 120 BAR with a spring added (double spring) at different preloads (44 gr JSB's):

0-------720
1/2-1--745
1-------810
1-1/2--870
2-------885
2-1/2--920
3-------944
3-1/2--960
4-------970
4-1/2--960

Anything past 3-1/4 to 3-1/2 turns begins to waste air, so I set the spring preload at 2-3/4 turns for 14+ shots @ 930 fps avg. The string extends down to 105 BAR with 3 extra shots past set point in the 930 fps range. Crazy efficiency! Fill pressure is 200 BAR. At ideal conditions sub 3/4" groups are common at 50 yards.

A second air tube was left unregulated and a variety of strings can be achieved, from 14 shots at 100 FPE (as before) to a 4 shot string at 1005-1027-1020-1007 fps (50gr JSB's ) with a 1" group @ 50 yards.

One other modification needed was on the magazine indexing arm, the one that is pushed by the hammer. It had to be extended to fully cycle the magazine.

We are considering this project complete!

[Prouzy]

Wow, great work! There cant possibly be anything left to change/mod 

[Bwalton]

I did not see the shot string and ES of the regulator? Nice work... Yes they can get 100ftlb no problem but can not use it as @ 1000fps accuracy with the 44gr will suffer. I think that a good cast pellet with the right twist and weight, will be a nice hunting machine. Good job with the rifle, I know that was a lot of work though.

[rjorge]

The shot string is 93X from 200 BAR to 120 BAR for 14 shots, ES around 5 fps. Every shot string will be different, what matters is that the ES is low. Past 120 BAR it goes up close to 940 for 1 shot and back down in the 930's for a couple more shots. At 105 BAR the velocity is down in the 920 range.

I have only seen 2-3  Carnivores here on GTA reaching 100 FPE, not an easy task on this platforrm.. 4 shots at 115 FPE (50gr @ 1015 fps avg) can definitely be used for hunting with 1" groups @ 50 yards. 

The micro groove barrel will be a challenge for cast bullets.

[Rocker1]

Great thread thanks for sharing, your work is exemplary to say the least, the time involved in tuning some airguns is beyond imagination sometimes, if tuners got payed  minimum wage the price would far exceed the price of the gun. David