GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Jzizzle on January 17, 2020, 03:23:46 PM
-
I have Bullboss in .25 wood that I want to both increase power and shot count for plinking and hunting. I want to eventually shoot slugs with this platform. Pellet wise, only the JSB 25.39gr did well for me out past 50 yards.
Bone stock with hammer adjustments my baseline string is here.
01. 899
02. ER
03. 895
04. 890
05. 894
06. 891
07. 885
08. 888
09. 887
10. 891
11. 886
12. 888
13. 884
14. 882
15. 880
16. 880
17. 873
18. 874
-
Thanks to Rsterne, a well know member here on GTA, I have reviewed his modifications for a while and finally performed very similar mods.
After much testing I am right where I want to be in terms of fps and am surprised how consistent this has become. This is unregulated!
New shot string is here.
JSB 25.39
01. 928
02. 931
03. 930
04. 933
05. 932
06. 932
07. 938
08. 940
09. 936
10. 918
11. 935
12. 935
13. 933
14. 931
15. 932
16. 930
17. 931
18. 930
-
Testing results from yesterday with various slugs at 22 yards.
28gr and 30gr that appear to be replicas or similar to fx hybrid.
28gr with deep hollow base
30gr dish base
initially dialed strings over the chrony. I was trying to achieve 950+ fps but that wasnt happening. 910 was max but shot count was only 12 with 3% spread. To get 2 mags ave velocity is 875fps with 3% spread. At these speeds the only one grouping well is the 28gr hollow base slug. Whats interesting is I will get a few hole in hole and then a flier. I think this may be due to how the slug is loaded in magazine and what the probe does while loading into breech. They are a tad too long for the magazine.
I will order these hollow base slugs in 25gr to have a better fit in magazine and to sling at higher fps.
to be continued...
-
Some more testing today. Concluded that the magazine fitment is not the issue.
Today is 17mph sustained winds with over 25mph gusts. Accuracy testing at 22 yards off a bipod and cheap walmart table.
5 shot groups
30gr Dish Slugs (.250) Avg 829 fps 1.02"
28gr Hybrid Slugs (.249) Avg 863 fps .85"
30 gr Hybrid Slugs (.249) Avg 834 fps 1.09"
28 gr Deep Hollow Base (.250) Avg 873 1.57"
All not acceptable at 22 yards! Oh and 25.34 JSB 955 fps .47"
I just got in Varmint knockers 32.8gr Flat Base Slugs.
(.250) Avg 855 fps .39"
This is good news and will test further out on less windy day. Best slug out of the Bullboss so far.
Also on the way is the Hades pellets, AVS slugs, NSA slugs and lighter weight Deep hollow base slugs.
More to come...
-
Thanks to Rsterne, a well know member here on GTA, I have reviewed his modifications for a while and finally performed very similar mods.
After much testing I am right where I want to be in terms of fps and am surprised how consistent this has become. This is unregulated!
New shot string is here.
JSB 25.39
01. 928
02. 931
03. 930
04. 933
05. 932
06. 932
07. 938
08. 940
09. 936
10. 918
11. 935
12. 935
13. 933
14. 931
15. 932
16. 930
17. 931
18. 930
Great string! In some guns, this may be a bit hot for good accuracy with diabolo pellets, or so I have read. Care to outline your specific mods and what problems you may have encountered along the way?
-
Thanks to Rsterne, I have reviewed his modifications for a while and finally performed very similar mods.
Care to share, in details, what mod you did?
-
All ports and valve seat were enlarged to .180"
5 of the valve ports being plugged and epoxied.
Barrel shrouded with carbon fiber tube and tensioned by Ronin LDC.
No issues encountered with the modifications.
With my particular gun, I have 7 turns of usable preload. What I found is once I go to 6 or 7 turns out shot count suffers with 12-14 shots within 3%. Sweet spot for JSB 25gr is 4 turns out and now I'm running 5.5 turns out with the slugs.
-
Also to note the trigger was super heavy out of the box. Hatsan triggers have good adjustability though and its now much lighter with a crisp 2nd stage.
-
Has anyone swapped hammer springs for one that is stiffer? Id like to get another 75+ fps with these varmint knockers 32.8 gr slugs. Possibly a lighter valve spring would give some more power too.
I'm a bit disappointed velocities are not higher with the slugs. Goes to show you how much bearing surface impacts the speed. JSB pellet can go over 1000 fps if you wanted it to.
-
Donny aka Rally Shark should be chiming in on this. He's done a lot of mods to his Bullboss.
I'm paying close attention to these threads because I'm looking to make it more efficient. I'm green in regards to airgun modding, but I am mechanically inclined.
-
All ports and valve seat were enlarged to .180"
5 of the valve ports being plugged and epoxied.
Barrel shrouded with carbon fiber tube and tensioned by Ronin LDC.
No issues encountered with the modifications.
With my particular gun, I have 7 turns of usable preload. What I found is once I go to 6 or 7 turns out shot count suffers with 12-14 shots within 3%. Sweet spot for JSB 25gr is 4 turns out and now I'm running 5.5 turns out with the slugs.
By "turns out" do you mean that you begin from all the way tight and then back off "X" turns?
-
Yes that is correct
-
John, you're still leaving a lot of fps on the table with your BB, and the speed is definitely there if ya want to get it ;) It just needs some more elbow grease and a couple of minor parts. A stiffer hammer spring will help, but your bigger issue is porting at the moment. Below is a list that will get your power up by a good bit, and just ignore me if I mention something you have already done :D :
- Open up the cylinder carrier hole to .180-.185(brass piece that the valve/cylinder screw into, and transfer port sits)
- Open up the transfer port to .180-.185( hard to do, but worth it).
- Open up the barrel port to .180-.185
- Open up remaining hole in the valve to .200
- *Most important on the top end of power, replace the factory derlin valve seat with one made of PEEK, and
open that up to .210. That factory seat is just too squishy to open up much more than it is without failing. You'll
have to make the PEEK valve seat yourself. Another benefit of the PEEK is that it is easier to crack the valve open
since it is harder.
- Install a stiffer hammer spring(I found one at Ace).
- Open up the holes on the valve spring retainer on the back of the valve as much as possible, without making it too
weak. I'm assuming yours has the newer style that screws in with multiple little holes around it?
Or to put all of that into simpler terms... Make sure all the porting past the valve to the barrel is .180-.185, install a PEEK valve seat at .210, stiffer HS. If you do all of that stuff, that Bullboss will really wake up! I think 75-100 fps improvement is entirely possible. I hope that helps :)
-
I pretty much have done all the above with the following exceptions:
-The 1 remaining valve port is .180, so I can bring this up to .20
-Im still using factory valve seat opened to .180, so this can be improved.
-Valve spring retainer is the newer style with multiple holes in it. So I can slightly enlarge all holes? Would this negatively impact efficiency?
- Hammer spring is stock, will source a heavier spring.
-
I pretty much have done all the above with the following exceptions:
-The 1 remaining valve port is .180, so I can bring this up to .20
-Im still using factory valve seat opened to .180, so this can be improved.
-Valve spring retainer is the newer style with multiple holes in it. So I can slightly enlarge all holes? Would this negatively impact efficiency?
- Hammer spring is stock, will source a heavier spring.
Okay, so you did the cylinder carrier, transfer, and barrel then? If so, then all you need to do is tackle the valve seat and spring retainer. I don't recommend opening up that factory valve seat much more, because it will fail if you do. You can take it to .190 safely, but I wouldn't recommend any more than that. PEEK can be opened up quite a bit more safely though, and it will also just work better all around. None of this stuff will hurt the efficiency at all. The larger valve seat opening may actually help a little, since the larger opening will result in the valve closing a little faster. The PEEK valve seat is one of the best mods you can do to almost any Hatsan! Let me know if you need any tips on that.
-
Donny aka Rally Shark should be chiming in on this. He's done a lot of mods to his Bullboss.
I'm paying close attention to these threads because I'm looking to make it more efficient. I'm green in regards to airgun modding, but I am mechanically inclined.
Your biggest determining factor will be what power level do you want it to be efficient at? I sold my Bullboss to VaporTrail, but he tells me he's putting it to good use ;) I think he said he's shooting 28 grain slugs around 960 fps with it currently(.22).
-
Yes, this RallyBoss is mine. There aren't many like it, and it is my own. ;D (FMJ reference)
Slight correction: 28gr at 974 and they're literal hole in hole at 30yds. This Boss can hit with authority. 8)
Zizzle, you should be getting a little more zing from your Boss. I bought bear air's .25 version, and that was slinging 28.5gr Benji domes at 925-917FPS with the HS maxed out. No mods done to it at all; stock ports and valves.
My stock Boss (.22) before I goofed it was slinging 25gr JSBs at 947. After the goof it went down to 927. 28gr EJs were traveling at 840.
I agree with Donny...there's more power available. Especially with your mods.
-
I pretty much have done all the above with the following exceptions:
-The 1 remaining valve port is .180, so I can bring this up to .20
-Im still using factory valve seat opened to .180, so this can be improved.
-Valve spring retainer is the newer style with multiple holes in it. So I can slightly enlarge all holes? Would this negatively impact efficiency?
- Hammer spring is stock, will source a heavier spring.
Okay, so you did the cylinder carrier, transfer, and barrel then? If so, then all you need to do is tackle the valve seat and spring retainer. I don't recommend opening up that factory valve seat much more, because it will fail if you do. You can take it to .190 safely, but I wouldn't recommend any more than that. PEEK can be opened up quite a bit more safely though, and it will also just work better all around. None of this stuff will hurt the efficiency at all. The larger valve seat opening may actually help a little, since the larger opening will result in the valve closing a little faster. The PEEK valve seat is one of the best mods you can do to almost any Hatsan! Let me know if you need any tips on that.
Yes the cylinder carrier, transfer port and barrel have been ported already.
I have reached out to Hatsan for a Nova star hammer spring.
What size should I enlarge the holes in the newer version valve spring retainer cap? Currently I have left this alone.
My valve hole is currently .18" I will enlarge this to .2"
If I attempt to enlarge the delrin valve seat from .18 to .19, is this even worth my time?
Anybody sell the Peek valve seats?
-
I went back in my notes and I actually used a 3/16 drill bit.
I apologize for previous inaccuracies.
Here is what I have written down as far as completed modifications.
-5 valve holes tapped and plugged with 4-40 set screws that I cut down to length.
- Valve top port drilled to .1875". Then epoxied the space over the set screws.
- Cylinder carrier port drilled to .1875"
-Transfer port drilled to .1875"
- Barrel port drilled to .1875"
- Valve seat drilled to .1875"
Next I will enlarge the Valve spring retainer holes a bit. There isn't much material available without thinning the walls too much. Perhaps only enlarge 3 of the 7 holes.
Do you feel it's worthy to further enlarge the Valve port from .1875" to .203"?
Perhaps do the same to the delrin valve seat or is that too much material removed?
-
I went back in my notes and I actually used a 3/16 drill bit.
I apologize for previous inaccuracies.
Here is what I have written down as far as completed modifications.
-5 valve holes tapped and plugged with 4-40 set screws that I cut down to length.
- Valve top port drilled to .1875". Then epoxied the space over the set screws.
- Cylinder carrier port drilled to .1875"
-Transfer port drilled to .1875"
- Barrel port drilled to .1875"
- Valve seat drilled to .1875"
Next I will enlarge the Valve spring retainer holes a bit. There isn't much material available without thinning the walls too much. Perhaps only enlarge 3 of the 7 holes.
Do you feel it's worthy to further enlarge the Valve port from .1875" to .203"?
Perhaps do the same to the delrin valve seat or is that too much material removed?
Looks like all your porting is spot on! The biggest reason I suggested opening the remaining hole in the valve is to give you more room for alignment, since it won't really negatively affect anything. It will also help, if you get a valve seat that can flow more air. The alignment on that valve to the cylinder carrier/transfer area is KEY. If it is off even a little, your top end will suffer. You can loosen that stock screw on the bottom of the trigger tube and shift that carrier fore or aft if needed to adjust the alignment a little. The slightest difference in where that carrier sits can make or break that valve hole alignment. The same goes for the barrel port/transfer alignment. Oh, did you open up the hole in the breech above the transfer? That could be choking it down too, if you didn't. I forgot to mention that one...
I don't know that opening up the factory valve seat anymore is going to make much difference at this point. Another issue with that factory seat is that is has so much of the valve pin in contact with the surface, combined with it being a little soft, makes it require a lot of hammer force to knock it open. You can order some 3/8" PEEK rod from Amazon for not much money. If you have a lathe, they are easy to turn down a little and make, if not they are a bear. I made the first few I did without a lathe. I chucked that PEEK rod into a drill and used sand paper to get the OD the same as the factory seat. Drilling the hole dead center is another matter of ingenuity,lol. Then I used a coping saw blade to make the o-ring groove while spinning it in the drill. It is a good job for an octopus,lol. I'm shooting you a PM on that seat ;)
-
Yes, hole in breech above the transfer also opened up. I pretty much drilled thru the breech into the cylinder carrier port. Then obviously drilled transfer port, barrel port and valve port separately. Every thing is .1875"
Prior to reassembly, I lined ports up perfectly and then used a small blade to mark it on the outside so when I remove the cylinder I know exactly where it needs to be.
-
Hades pellets arrived today.
NSA, AVS, and Griffin slugs coming next week.
Hopefully I hear back from Hatsan by Monday to order the Nova Star hammer spring.
In the meantime I'll work on the valve seat and valve spring retainer.
-
Using Griffin 28gr deep hollow base as the test slug here are comparisons for hammer preload and listed additional changes. All 2900psi fill pressures.
TEST 1
Ports .1875
oem valve seat .1875
OEM Valve Spring Retainer
0 - 619 fps
-1 - 714 fps
-2 - 764 fps
-3 - 816 fps
-4 - 850 fps
-5 - 887 fps
-6 - 890 fps
-7 - 905 fps
TEST 2
Ports .1875
Enlarged Valve Spring Retainer holes
PEEK valve seat .212
0 - 759 fps
-1 - 800 fps
-2 - 850 fps
-3 - 895 fps
-4 - 922 fps
-5 - 894 fps
-6 - 838 fps
TEST 3
Ports .1875
OEM Valve Spring Retainer
PEEK valve seat .212
0 - 736 fps
-1 - 787 fps
-2 - 844 fps
-3 - 877 fps
-4 - 914 fps
-5 - 935 fps
-6 - 878 fps
TEST 4
Ports .1875
OEM Valve Spring Retainer
PEEK valve seat .212
Stiffer Hammer Spring from NovaStar
0 - 897 fps
-1 - 953 fps
-2 - 868 fps
-3 - 801 fps
Any idea as to why Test 4 hammer adjustments reduce fps after 1 turn preload? The spring is same length, only stiffer.
Only combo I didn't try was the enlarged valve spring retainer holes with the stiffer hammer spring.
-
Did more accuracy testing with various weights with Griffin, NSA, AVS and Varmint knockers.
Only ones that work well in this bullboss are NSA 29gr and 36.2gr. AVS 28gr. Varmint Knockers 32.8gr.
Everything else is poor at 22 yards.
-
Accuracy results at 22 yards continued.
AVS 28 gr - .338"
AVS 30 gr - .814"
AVS 32 gr - .480"
Griffin Deep Hollow Base 24 gr - .811"
Griffin Deep Hollow Base 25 gr - .753"
Griffin Deep Hollow Base 26 gr - .643"
Varmint Knockers 32.8 gr - .379"
NSA 38 gr - .903"
NSA 36.2 gr - .459"
NSA 33.5 gr - .743"
NSA 29.5 gr - 2.051"
NSA 29 gr - .660"
NSA 26.8 gr - Off paper >1.5"
-
Using Griffin 28gr deep hollow base as the test slug here are comparisons for hammer preload and listed additional changes. All 2900psi fill pressures.
TEST 1
Ports .1875
oem valve seat .1875
OEM Valve Spring Retainer
0 - 619 fps
-1 - 714 fps
-2 - 764 fps
-3 - 816 fps
-4 - 850 fps
-5 - 887 fps
-6 - 890 fps
-7 - 905 fps
TEST 2
Ports .1875
Enlarged Valve Spring Retainer holes
PEEK valve seat .212
0 - 759 fps
-1 - 800 fps
-2 - 850 fps
-3 - 895 fps
-4 - 922 fps
-5 - 894 fps
-6 - 838 fps
TEST 3
Ports .1875
OEM Valve Spring Retainer
PEEK valve seat .212
0 - 736 fps
-1 - 787 fps
-2 - 844 fps
-3 - 877 fps
-4 - 914 fps
-5 - 935 fps
-6 - 878 fps
TEST 4
Ports .1875
OEM Valve Spring Retainer
PEEK valve seat .212
Stiffer Hammer Spring from NovaStar
0 - 897 fps
-1 - 953 fps
-2 - 868 fps
-3 - 801 fps
Any idea as to why Test 4 hammer adjustments reduce fps after 1 turn preload? The spring is same length, only stiffer.
Only combo I didn't try was the enlarged valve spring retainer holes with the stiffer hammer spring.
On the plus side, it looks like that PEEK seat gave it a bit more oomph! I would go with the opened up valve spring retainer and the stiffer spring for sure.
Now, the odd part is the speed decreasing after adding more preload? My theory is that the de-bounce is sticking and causing excessive hammer bounce, and that the hammer is coming back and hitting the valve. Did you notice the gun sounding "funny" when you added more preload and the fps decreased? It could also be the de-bounce(wishbone) is sticking worse when there is more hammer force causing excessive drag on the hammer... Basically, all my theories are centered around the de-bounce malfunctioning at this point... The only other theory I have right now is there could be a cut o-ring somewhere that only leaks when the pressure during the shot cycle is high enough. All guesses right now though?
-
Yes next I will swap the valve retainer for the one with bigger holes to see what effects it has with the heavier hammer spring.
When I swapped the springs I also replaced the 3 barrel orings. Inspected the transfer port orings and valve orings.... everything looks good.
My debouncer is not riveted, the arms are 2 separate pieces. If I order this part from Hatsan, is it the newer 1 price design?
As to the slugs.
AVS 28gr did really well but they fit loose in magazine and tend to fall backwards and jam the magazine. So because of this I won't run them.
Varmint Knockers 32.8gr are awesome out of the bullboss.
NSA 36.2gr did great too. These are also half the price at the Varmints so I will tune BB and dial.in the scope for these. I have these on order. I'd like to sling these around 950fps.
We'll see what we can make happen.
-
That de-bounce in there now is definitely not going to help. I shot you a PM, but it you may or may not get the good design from Hatsan if you order one. Order the one for an AT44, that is the only chance you'll get the good one. Don't bother mentioning why to Hatsan, they will argue that the two piece is better and they will be wrong. I've fixed 3 separate guns with that two piece design, and there have been many others on here that it caused problems for. I would LOVE to talk to who or whom at Hatsan that decided to make that change >:(
36.2 grain at 950 may be a tall ask out of a Bullboss. I'm not saying it can't do it, but I don't think it can with any usable shot string. If it was a 250 bar gun, it would be no problem. Unfortunately you only have 200 bar to work with. You could probably go to a 3100 psi fill safely, but I wouldn't recommend any higher than that. I know people that have, but that's up to them if they want to play with fire. Besides, you could find they aren't as accurate at 950 fps anyway. Slugs tend to be kind of picky about the speeds they work well at in many guns. I think 900 fps would be closer to realistic, and still very devastating!
I'm hoping some of the other folks on here will chime in on your odd decreasing fps when you add more that one turn preload with that HS. That is rather weird. I have theories, but without the gun in my hands I'm just guessing :) Let us know what you find out after you get to do some more testing! You've already made good progress! Also, go ahead and shoot a string with it at the higher fps setting. The speed should increase down the string a bit I think. If you get a steady declining string, you're likely at the highest setting that will work(prior to decreasing with more turns). I doubt that's the case given the numbers you posted.
-
It looks like you found the “magic” bullet for that gun. Concentrate on playing with that one at different speeds and surely the groups will shrink. Once that’s all figured out and you have the speed and bullet it prefers. Order a but load of them. Good job on the tuning.
-
I can't recall if I saw mention of the valve spring being replaced. Have you checked your valve pin for any deformity?
I still think you should be slinging lead much harder than that. Those 900ish spikes and then massive drops may be the start of a breadcrumb trail that might lead to more power.
Just an observation, but a stock .25 Boss slinging 28.5gr Benjis at 925 vs. an almost modded-to-the-hilt Boss slinging the same weight slugs at 953 peak doesn't add up.
My two .22 Bosses have a major difference with the same scenario. My stocker will sling 28gr EJs at 840. The RallyBoss will absolutely launch 28gr slugs at 974, and that's not even max HS adjustment; at full tilt she'll send the 28s at over 1000FPS.
There's a monster lurking in your Boss...we just have to try and figure out how to release it.
-
It looks like you found the “magic” bullet for that gun. Concentrate on playing with that one at different speeds and surely the groups will shrink. Once that’s all figured out and you have the speed and bullet it prefers. Order a but load of them. Good job on the tuning.
Denis, do you have any ideas on the fps decreasing after more than one turn using the heavier spring?? It is a Nova spring, and the exact same diameter of the stock spring. It is slightly shorter, but that decreasing fps has me a bit stumped...
-
I can't recall if I saw mention of the valve spring being replaced. Have you checked your valve pin for any deformity?
I still think you should be slinging lead much harder than that. Those 900ish spikes and then massive drops may be the start of a breadcrumb trail that might lead to more power.
Just an observation, but a stock .25 Boss slinging 28.5gr Benjis at 925 vs. an almost modded-to-the-hilt Boss slinging the same weight slugs at 953 peak doesn't add up.
My two .22 Bosses have a major difference with the same scenario. My stocker will sling 28gr EJs at 840. The RallyBoss will absolutely launch 28gr slugs at 974, and that's not even max HS adjustment; at full tilt she'll send the 28s at over 1000FPS.
There's a monster lurking in your Boss...we just have to try and figure out how to release it.
Valve spring is original, only with the spring retainer holes slightly enlarged.
The valve pin is in good shape.
I don't think we can compare fps of equal weight pellets to slugs. Lots of variables that will effect that. For instance at same preload 25gr Jsb is 990fps vs 25gr slug at 940fps.
-
I've swapped back to OEM spring and the declining power at more preload has been remedied. The debouncer was not the issue. Spring may be kinking, who knows. Just ain't working right. As a side note with the heavy hammer spring, the trigger weight has also increased and if I try to lighten it up the sear won't catch.
I will see if I can find some shims to use with the OEM spring to increase the tension a bit.
Current power is 60fpe with 36.2gr NSA slugs.
-
I can't recall if I saw mention of the valve spring being replaced. Have you checked your valve pin for any deformity?
I still think you should be slinging lead much harder than that. Those 900ish spikes and then massive drops may be the start of a breadcrumb trail that might lead to more power.
Just an observation, but a stock .25 Boss slinging 28.5gr Benjis at 925 vs. an almost modded-to-the-hilt Boss slinging the same weight slugs at 953 peak doesn't add up.
My two .22 Bosses have a major difference with the same scenario. My stocker will sling 28gr EJs at 840. The RallyBoss will absolutely launch 28gr slugs at 974, and that's not even max HS adjustment; at full tilt she'll send the 28s at over 1000FPS.
There's a monster lurking in your Boss...we just have to try and figure out how to release it.
Valve spring is original, only with the spring retainer holes slightly enlarged.
The valve pin is in good shape.
I don't think we can compare fps of equal weight pellets to slugs. Lots of variables that will effect that. For instance at same preload 25gr Jsb is 990fps vs 25gr slug at 940fps.
possibly, yes. But that lower FPS with the slugs could be an indicator that the slugs are either too large and suffering friction in the barrel, or they are too small and air is being wasted. Is that the stock barrel? Are there perhaps tight spots or a shoddy choke that's robbing you of precious FPE?
-
I can't recall if I saw mention of the valve spring being replaced. Have you checked your valve pin for any deformity?
I still think you should be slinging lead much harder than that. Those 900ish spikes and then massive drops may be the start of a breadcrumb trail that might lead to more power.
Just an observation, but a stock .25 Boss slinging 28.5gr Benjis at 925 vs. an almost modded-to-the-hilt Boss slinging the same weight slugs at 953 peak doesn't add up.
My two .22 Bosses have a major difference with the same scenario. My stocker will sling 28gr EJs at 840. The RallyBoss will absolutely launch 28gr slugs at 974, and that's not even max HS adjustment; at full tilt she'll send the 28s at over 1000FPS.
There's a monster lurking in your Boss...we just have to try and figure out how to release it.
Valve spring is original, only with the spring retainer holes slightly enlarged.
The valve pin is in good shape.
I don't think we can compare fps of equal weight pellets to slugs. Lots of variables that will effect that. For instance at same preload 25gr Jsb is 990fps vs 25gr slug at 940fps.
possibly, yes. But that lower FPS with the slugs could be an indicator that the slugs are either too large and suffering friction in the barrel, or they are too small and air is being wasted. Is that the stock barrel? Are there perhaps tight spots or a shoddy choke that's robbing you of precious FPE?
Paul, his numbers are far enough off that I doubt it comes down to the barrel or ammo. Pellets of the same weight pretty much always make more fps than slugs. I do would recommend a good barrel cleaning at this point though :D I PM'd him a couple of other stuff to check out too. Hopefully, he'll get this BB singing soon! By the mods, it should be a beast.
-
hopefully he gets his beast unleashed. I'm excited for him! Almost makes me want to buy a .25 Boss again. :o
Lol...my wife is gonna clobber me pretty soon. ;D
-
Thanks everyone for your help and input. I do greatly appreciate it.
I will be sure to update everyone on the continued path on my bullboss.
-
I took apart the bullboss once again and added shims for a total of 3mm to be used with OEM spring.
Unfortunately it's too late in the day and the chrony doesn't have enough daylight to register the shots.
More to follow. Eagerly awaiting results!
-
I took apart the bullboss once again and added shims for a total of 3mm to be used with OEM spring.
Unfortunately it's too late in the day and the chrony doesn't have enough daylight to register the shots.
More to follow. Eagerly awaiting results!
We look forward to seeing the results as well :D
-
I'm all out of the 28gr slugs I was using previously so from here on out tests are with the ammo I plan to run.. NSA 36.2gr.
I ran two tests using stock hammer spring.
1mm shim
Preloads
0. 410
-1. 490
-2. 575
-3. 641
-4. 696
-5. 733
-6. 777
-7. 811
-8. 846
-9. 771
3mm shim
Preloads
0. 595
-1 664
-2. 716
-3. 763
-4. 796
-5. 828
-6. 846
-7. 756
Strings with 3mm shims at pretty much max of 840fps avg yields only 6 consistent shots before rapid drop.
In order to get 18 shots within 2% I have to drop to an avg of 790fps.
One thing to note when I swapped from 3mm shim to 1mm shim, I broke my debouncer spring upon reinstall, got kinked and is no longer usable. I replaced with a firmer spring that I cut down. Not sure what impact that has though.
Do you guys think it's worth it to try with maybe 5mm shim? It appears that the shims change power at different preloads but thus far has no impact on max fps.
Trying to achieve 880fps avg with NSA 36.2gr for 18 shots.
-
just FWIW, when I stretched my hammer debounce spring a little too much, it went too low and actually prevented the hammer from sliding back to the cocking position. You may experience something similar.
As for the shims, I've never tried using them, but when I put in a fresh AT44 HS in the Boss, it caused a failure to cock. After the spring got squeezed and settled, it was able to cock again. Seems like the auto-indexing doesn't work as good as it used to as well; the cover can't be too tight otherwise the mag can only be advanced manually.
60FPE should be doable.
-
I'm all out of the 28gr slugs I was using previously so from here on out tests are with the ammo I plan to run.. NSA 36.2gr.
I ran two tests using stock hammer spring.
1mm shim
Preloads
0. 410
-1. 490
-2. 575
-3. 641
-4. 696
-5. 733
-6. 777
-7. 811
-8. 846
-9. 771
3mm shim
Preloads
0. 595
-1 664
-2. 716
-3. 763
-4. 796
-5. 828
-6. 846
-7. 756
Strings with 3mm shims at pretty much max of 840fps avg yields only 6 consistent shots before rapid drop.
In order to get 18 shots within 2% I have to drop to an avg of 790fps.
One thing to note when I swapped from 3mm shim to 1mm shim, I broke my debouncer spring upon reinstall, got kinked and is no longer usable. I replaced with a firmer spring that I cut down. Not sure what impact that has though.
Do you guys think it's worth it to try with maybe 5mm shim? It appears that the shims change power at different preloads but thus far has no impact on max fps.
Trying to achieve 880fps avg with NSA 36.2gr for 18 shots.
You flat out don't have the spring to get to that speed you want. You aren't gonna gain a whole lot with the 5mm shim I don't think. I still think you need to figure out why that heavier spring won't work right, and I think it has something to do with the how the spring is sitting over the trigger. The gun should be able to make more power than it is for sure. I don't know if 18 shots at 62 fpe is going to be achievable. That will be pushing it in the efficiency department, but it may be possible. It is hard to say, given that you can hardly even get to that power for one shot.
-
I switched back to the Nova Spring and used shims so it would not come out of the rear seat. Peak was 834 fps with NSA 36.2gr. Although I didn't gain any fps, the trigger wasn't very stiff/heavy as it was before so the previous test definitely had some interference with the trigger/sear.
Still have to do some more tweaking or may just get a different spring. I know there is more power there...
Next I decided to use .22 peek seat. I also switched back to oem hammer spring with no shims. Using the valve spring retainer with enlarged holes. At max preload ( I think it was 10 turns) I have a high of 898fps. The bigger valve seat gave me about 60fps gain over previous tests. While testing with different preloads each turn gave an increase in fps until the sear would no longer catch.
A string at max NSA 36.2gr
1 879
2 884
3 898
4 887
5 885
6 878
7 882
8 874
9 871
I only have 1 mag with decent es at these speeds.
Next I will switch back to a heavier hammer spring and continue the testing.
-
Now it is starting to look better!
-
agreed. If you can get into the quarter 9s with 36gr slugs, that's going to be quite the thumper.
-
What I can't seem to figure out is why each different configuration has a certain point of preload where the velocity begins to drop.
Now with the most recent test it continues to gain fps all the way to the point where the spring is fully compressed. If I can get a heavier spring to act in this manner I don't see why I couldn't get ~950fps max and tuned down to ~900fps for strings.
-
What I can't seem to figure out is why each different configuration has a certain point of preload where the velocity begins to drop.
Now with the most recent test it continues to gain fps all the way to the point where the spring is fully compressed. If I can get a heavier spring to act in this manner I don't see why I couldn't get ~950fps max and tuned down to ~900fps for strings.
Hopefully, you can get the stiffer spring to work, because it may not have to lean on the valve as much. That would increase your shot count most likely.
-
I went to 4 hardware stores and left empty handed at each one. I will have to source the spring online.
-
That's a bummer :( The only one I've found the spring that works at is Ace. I've found it at a few different Ace stores fwiw. You could probably find one online at McMaster Carr or some other spring store. Just measure the OD/length of the factory spring and start looking. I still think that Nova spring should work, and don't understand why it won't. I've used springs that where a 1/2" shorter, some that were longer with no ill effects. There be some weirdness going on there :(
-
I have a spring on order to test out.
Also, will run all the different types of ammo again at some point once I settle on final tune.
Have some grizzlys on order too.
-
I was thinking about opening my ports further...from .187 to .203. what's the thoughts on this. I don't want to loose too much efficiency as I want 18 shots per fill within 3%.
-
I was thinking about opening my ports further...from .187 to .203. what's the thoughts on this. I don't want to loose too much efficiency as I want 18 shots per fill within 3%.
Correct me if I'm wrong, but I don't think there is enough material in the transfer to handle opening it up that much. That is, if Hatsan hasn't changed the design, and they haven't on any I've seen at least. If you can't open the transfer any more than it is, then opening the other stuff is a waste of time and can actually cause a loss of efficiency and power. I pretty sure 3/16" is gonna be the limit on that transfer, unless you want to try and make one that will handle it.
I know I keep beating a dead horse, but any mods you make at this point to increase power is a dead end, UNTIL you figure out why the gun won't make more power than it is already. I feel like the numbers are low, and something just isn't right with the gun. I don't know what it is, or what is causing it, but something is just a little bit off somewhere. It seems like it is 5-10 fpe below where it should be able to be on the top end. It could be transfer port leak, or hammer sticking/binding, or even spring catching, but I don't know which it is. You're going to be hard pressed to get the string you're looking for with the gun working perfectly, especially on a 200 bar gun that isn't quite happy. I wish I could think of what is going on with it, but I'm at a loss myself :-[
-
I hear ya buddy, and I welcome all ideas and recommendarions.
When I swap the spring I will inspect the orings #2402 at transfer port.
-
Subscribing.... fellow bb owner here.. got to ask.. have you checked valve lift?
-
Hmm...tejon might be on to something. I've gone through 6 Boss cylinders and 4 have given me different readings. The other two were modded and were fairly close to each other in terms of performance.
I tried replacing a valve spring in one of the cylinders, and it was fart city. :( I thought I'd compress it a little, so I put the degas tool on and cranked it all the way down. Left it for several days.
Now the spring is pretty darn loose. There's no pressure in the cylinder, but I can compress the valve pin with my thumb. I think I left it compressed for a little too long.
Anyways, I found out that different cylinders will yield different FPS numbers. Perhaps that is what's going on here?
Just something to further obfuscate an already obfuscated situation. ??? ;D
-
Not so much the cylinder that makes the difference but yes the valve assembly does. I have 2 valve assemblys and they both acted very differently over the chrony before I modded the current one. The valve stem was the only difference I could find between them.
How do I check the valve lift?
I think Donny is on to something though...will disassemble tomorrow.
-
How do I check the valve lift?
[/quote]
look at the hammer, from the right side.... unscrew the cylinder almost all the way, then slowly screw it in watching the hammer, when the hammer start to move stop. then back off slightly and try again, when the hammer starts to move stop. then look at the gap between the valve assembly and the hammer tube... should give you an idea... .
I suspect there is a bump stop inside the hammer tube, to adjust lift, I think on mine it moved, and I have a 5mminch of available lift (my rifle is bottoming out on the valve body, so about 2.5mm actual lift) .,, suffice to say, loud as c//p and only a few innacurate shots,,
-
Tow other areas to look at that HobbyMan2007 and I tried.
First He, and I shortened a very stiff spring, and added a smaller dia spring in side of it. the shorter length prevents hammer bounce, and the small dia spring give it an even higher rate.
My self, on several guns, I added a piece of brass rod turned down to fit inside the hammer where the spring sits to increase the weight of the hammer. This helps greatly to open the valve fully at higher pressurizers. the short dual springs will increase shot count and give higher fps at the same time.
Knife
-
Tow other areas to look at that HobbyMan2007 and I tried.
First He, and I shortened a very stiff spring, and added a smaller dia spring in side of it. the shorter length prevents hammer bounce, and the small dia spring give it an even higher rate.
My self, on several guns, I added a piece of brass rod turned down to fit inside the hammer where the spring sits to increase the weight of the hammer. This helps greatly to open the valve fully at higher pressurizers. the short dual springs will increase shot count and give higher fps at the same time.
Knife
That does work, and I've done that on a couple of guns. Unfortunately, the HS adjustment on this gun requires using a 4mm allen that goes through the spring. The spring OD on the BB is so small, that adding a smaller spring inside it would make it so you couldn't adjust the tension :( There's no easy way to pull the spring, adjust, re-install it either. They don't leave a lot of wiggle room inside the Bullboss for changing the way it works. To make it worse, the spring runs right over the top of the trigger assembly, so a bow in the spring will cause all kinds of crazy stuff to happen too. This is a lot of the reason I modified the Bullboss I had so I could adjust it without the 4mm allen :D I used dual springs on that one. Not everyone is willing to go quite that for down the rabbit hole though,lol.
-
I have been having an issue with a slight air leak at the transfer port. Trying various size o-rings with no success. It would seal for a few shots before it would give. I used gasket maker along with o-rings and this is holding up so far.
I was also having an issue with my valve seat. I damaged my peek seat on removal. (should have just left it alone in there) I then was using an oem delrin seat drilled out to .210 and this failed on me and began to leak after a few hundred shots. I then used an oem delrin drilled out to .203 for a few hundred and no issues......that is until my valve stem broke right at the o-ring groove. Luckily I have an extra valve stem.
I have no clue when these stiffer hammer springs are getting here from china, so that is on hold.
Now with all the issues addressed above..
Here is a 18 shot tune with NSA 36.2gr
OEM Valve Seat .203
All ports .1875
Enlarged Valve Spring Retainer Holes
Stock Hammer Spring
1. 832
2. 841
3. 838
4. 842
5. 842
6. 846
7. 849
8. 848
9. 848
10. 854
11. 848
12. 847
13. 847
14. 846
15. 843
16. 839
17. 828
18. 827
HI- 854
LO- 827
AVG- 842
ES- 27
SD- 7
Efficiency- 1.32
3000psi-2200psi
From previous testing with a peek seat vs delrin, I know speeds would be increased from current to anywhere from 30-60 fps.
-
I recently sourced some 8mm OD Die Springs from Amazon ($7.50 for 10 springs 80mm length):
https://www.amazon.com/gp/product/B013G5H98G/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1 (https://www.amazon.com/gp/product/B013G5H98G/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1)
The cut down yellow die springs is slightly stiffer than the Ace Hardware one I've used in a FlashPup, 4 turns from bottom nets the same FPS as 6 turns out. There is also stiffer blue, then red, green is super stiff. So a lot to work with and a smaller diameter that matches OEM spring and the 4mm hex still fits.
The die springs are not wire springs, so over compression damage is not an issue. Over tightening a wire spring commonly damages it.
Still experimenting with the stiffer ones... stiff short spring can be a good thing.
-
these are the springs I have on order, blue and red with 55mm length. I got the green ones already but they are way too stiff.
thanks
-
I've seen die springs many times, and ignored them, because I assumed they would be too short :-[ Obviously, I need to re-evaluate that thought!
-
The Yellow springs linked above allow a 4mm hex to pass the ID. The blue, red and green 8MM die springs had a smaller ID just enough to block the 4mm hex.
Chucked up the blue spring in the lath and used a cobalt drill bit to open the inside a bit, very fine cut. Surprisingly the spring held up well in the 3 jaw chuck.
Another way to fine tune a die spring, length and section.
-
I was just thinking a short-ish blue spring would probably be a nice setup. I've got my guns dialed in right now, but I may have to try a die spring at some point in the future...
-
A bit of an update here with 36.2 NSA slugs. These slugs stack at 70 yards!
Testing with yellow die spring didn't net me any positive gain.
I went back to the Nova spring with the oem spacer removed. This gave me 9 shots 900-930 fps. Seems like the spacer was the culprit from previous tests. Only downside here is I cant get 2 mags consistently at these speeds, cocking is much stiffer and noise has increased.
I am satisfied here. I feel I have reached the upper limits here. There is more power to be had if shot count wasn't to be considered. I need to reduce speeds to mid 850s for 2 consistent mags. If a bigger reservoir or higher fill was available that would be a different story.
I appreciate everyones input and help through out this build.
Thanks!
-
Awesome... congrats on finishing your project.
And thank you for the tip on the 36.2 nsa... will try them in the future...
-
Awesome... congrats on finishing your project.
And thank you for the tip on the 36.2 nsa... will try them in the future...
Yes, NSA 36.2 did the best for me. NSA 29 were also accurate but I prefer the heavier slug. The Varmint knocker 32.8 were also accurate but a much higher cost then NSA. You can look back at all the slugs and weights I tested. These 3 slugs performed the best for me with NSA 36.2 being #1.
-
The 29gr nsa grouped so-so from my bullboss... i want to try again now that my bullboss is tuned and regulated...
Those 36grainers will have to wait though... till all this disruption ( covid ) ends
-
Hi guys, wonderful post full of experienced gurus suggestions (in fact one of the best I got chance to read) for any Bullboss owner.
As a matter to be fair and give you a brief intro about me, the fact is that my background is about centerfire and reloading, I have several airguns also (Gamo) but never awake too much my interest. Some weeks ago, due the COVID mess I tried with my first PCP, a Hatsan Bullboss .22... well, I just got so impressed that I fully reconsidered my wrong opinion about the airguns.
I like to tweak my practical guns to improve it and get the maximum in any sense (any gun with a fair engineering might be improved).
There comes this thread and enlighten me about the key points to tune up this little marvel.
Although everything seems quite clear, I have a doubt about the so called PEEK seat, I do not know if there is any schematics where explained.
I have a question that you might know. Living in Barcelona (Europe) I'm getting disappointed about the spare parts for the Hatsan line, in the European stores do not seem to be a single one with the whole line of spares, so even is difficult to id the parts, my specific questions are:
Is if the AT or BT line compatible parts with the bullboss or what models share parts.
Is feasible to swap the caliber from .22 to .25, the changes involved (apart of barrel and magazine) if any and if worth it in the output sense (discarded to sell this and get a 6,35 as here the prices are around 600USD for any bullboss and is not easy to sell used ones even with only few shots), despite that, I'm so hooked that I'm wondering already to some other models when this one is set with a satisfactory results.
Are the mods exposed here the best options to get the most long range shots?
Sorry for so long thread but I think this one is too useful to let it down without complete some other details.
Artur
-
You can order spare parts directly from Hatsan website. Bullboss does not share components with the BT line, although it does with the AT44. I can not comment on caliber changes as I have no experience there.
-
Artur...
For your modifications, be sure to take a look at RallyShark's modification thread. There is a link in the beginning of this thread. Jzizzle very closely followed what was done in that thread. As for your questions on the PEEK valve seat, RallyShark's thread has measurements that he used to fabricate the valve seat.
As for your spare parts, you should be able to order from Hatsan's site. Another option is the Chambers website...they have parts there as well. Speaking of parts, the Bullboss is the bullpup version of the AT44, so most the parts are interchangeable. Don't order BT parts...that's a different platform.
As for changing calibers, it's a fairly straightforward procedure. You'd need a barrel, probe, magazine and if I remember correctly an upper block. Your best option would probably be to find a .25 Bullboss that is in need of repair; it'll be much cheaper that way.
I'm a huge fan of the Bullboss, despite some of its quirks. It was my first and second PCP. Then I sold the .25 version and later on picked up RallyShark's .22 Bullboss.
Sometimes they might need a little extra attention to perform properly, but when the problems are addressed, they are an absolutely wonderful rifle.
Good luck and may she bring you much joy!
-
Thanks for your replies :)
Jzizzle: Yes, I've check but Hatsan in Europe is not selling direct so you need to go through dealers and unfortunately they just have between a 5 to 15% of some model parts (or none at all, just selling complete units). As far I'm aware, HAtsan USA is not selling abroad, so I need to stick to EU.
VaporTrail: Thanks for your kind reply, after to recheck and read much more to id the parts, I think I have clear what need to be done, already bought this die springs (yellow and blue as suggested for Rallyshark), about the peek to the seat valve, will get a so small bar as I can find (got to be very expensive to be a media like that).
Sorry for my lack of knowledge as I never had any PCP (It will change very soon as I find super interesting the fact that I can improve the performance in this devices and is fascinating the fact that I might be rather auto sustainable). Need to study more the technical insights of the PCP world in order to have better criteria.
About what I comment to change the caliber, I guess the smarter is to let it as is as best as possible, learn with this superb platform and get anything already in the selected caliber more suitable to awake more power keeping precision.
The fact is that I find the look of this rifle very nice among the most PCP's. Anyway I do not discard to ask you something when I'm dealing with the BB.
I hope any time I can be of any help here. Many thanks.
Artur
-
You just need some 3/8" PEEK rod to make the valve seat, and it isn't that expensive. It goes for about $12-15 here from Amazon. Just measure the factory one, and match it for the most part. The biggest difference will be the size of the hole in the seat(.210" max). I think you're going to have a lot of fun, especially since you have all the tools to do it with :D
-
Bit of a update here.
For whatever the reason the action noise seems to be louder then what I remember. This could also just be my ears since I've been shooting many different pcps lately.
None the less, I added a PEEK striker to the hammer. Drilled and tapped with some thread lock. This has considerably reduced the noise of the action! Well worth it!
-
The extra length of the hammer should reduce your lock time too, since the distance the hammer has to travel to the valve pin is reduced. That could help the accuracy as well. Nice work!
-
HMMM......
that's something that would make my already quiet stock Boss even more quiet.
-
Shots in the dark here, I cant find any info on the air cylinder O-rings needed to reseal. I have a leak and want to reseal the entire cylinder. Hatsan is perennially out of stock.