Maximus upgrades

[bowdoc64]

Great group at 50 yards Drew. My Maximus likes 14.3 JSB's.

I'm going to try some others. Some one said their like the 15s so I will give them a shot to. To be honest I shot a 40 yards group and I think they have tighen up now that I ran some jsbs thru the gun and the wind died down.. Going to clean the barrel today and shoot some groups see if it changes anything

[bowdoc64]

Clean barrel JSB 18.3. Sub dime at 40 for 4 with the 5th flying wide.. windy today.. everything is to the left today so maybe that's what opened it up.

[grand-galop]

Clean barrel JSB 18.3. Sub dime at 40 for 4 with the 5th flying wide.. windy today.. everything is to the left today so maybe that's what opened it up.

Do you got the original barrel band setup??   The QB line and Crosman Maximus/Disco have always fascinated me on how cheap they start at and can be very accurate with little help..

[Hoosier Daddy]

Clean barrel JSB 18.3. Sub dime at 40 for 4 with the 5th flying wide.. windy today.. everything is to the left today so maybe that's what opened it up.

The QB line and Crosman Maximus/Disco have always fascinated me on how cheap they start at and can be very accurate with little help..

Dont dismiss the Xisico line. Super under recognized from my experience. 

[grand-galop]

Clean barrel JSB 18.3. Sub dime at 40 for 4 with the 5th flying wide.. windy today.. everything is to the left today so maybe that's what opened it up.

The QB line and Crosman Maximus/Disco have always fascinated me on how cheap they start at and can be very accurate with little help..

Dont dismiss the Xisico line. Super under recognized from my experience

I wont talk about the Xisico because I dont own any and to my understanding is they are hard to get some places..

[bowdoc64]

Clean barrel JSB 18.3. Sub dime at 40 for 4 with the 5th flying wide.. windy today.. everything is to the left today so maybe that's what opened it up.

Do you got the original barrel band setup??   The QB line and Crosman Maximus/Disco have always fascinated me on how cheap they start at and can be very accurate with little help..

Everything is stock except for the changes I made to the valve and the hammer spring.. They  are accurate even out the box

[bowdoc64]

Almost forgot since cleaning the barrel my cphp are getting to be laser accurate again..  Tight 40 yard groups maybe better then the JSB

[Hoosier Daddy]

Well that is GREAT news Drew!!!

[KnifeMaker]

I would like to try the 14 gr. JSB's. Shoots the 15 and 18's well, with the nod going to the 18's. Tried a tin of Field Target from H&N. Good looking pellets, not so good in accuracy in my Maxi. Not even as good as the lowly Crosman domes. GRRRRR!!!

The replacement Huma Reg. form Treiner is doing a fine job. I wanted to shoot the 15 gr JSB's at 880, and it does just that. In stock form, it shot them at 780-790. Re-worked the valve and got them over 900. But not good shot count. Even at 840, I got one mag, and 2-3 more useful shots at 50 yards.

With the valve work, Magnum spring and screws to raise the fill pressure, and the huma set to 1700, she will go 930. Backed the spring down, and can get three mags at 860 fps.  Can go 4 with only a small rise and  drop in fps. 
Will lower the Reg. another 100 fps and see where she is. 

Knife

Knife   

[bowdoc64]

I would like to try the 14 gr. JSB's. Shoots the 15 and 18's well, with the nod going to the 18's. Tried a tin of Field Target from H&N. Good looking pellets, not so good in accuracy in my Maxi. Not even as good as the lowly Crosman domes. GRRRRR!!!

The replacement Huma Reg. form Treiner is doing a fine job. I wanted to shoot the 15 gr JSB's at 880, and it does just that. In stock form, it shot them at 780-790. Re-worked the valve and got them over 900. But not good shot count. Even at 840, I got one mag, and 2-3 more useful shots at 50 yards.

With the valve work, Magnum spring and screws to raise the fill pressure, and the huma set to 1700, she will go 930. Backed the spring down, and can get three mags at 860 fps.  Can go 4 with only a small rise and  drop in fps. 
Will lower the Reg. another 100 fps and see where she is. 

Knife

Knife

Good info.. What mods to the valve and I did the upgraded screws to. I fill to roughly 2200 psi a little over 150 bar. I get a easy 15 to 20 shots. Im thinking if you did the same thing to your Maximus  that I did to mine then I might be getting around the same volocities.

[bowdoc64]

Well that is GREAT news Drew!!!

Did you do the three screw mod to your trigger.. I think I might do that tomorrow but only the two. What size screw I need?

[bowdoc64]

I did the single screw trigger mod. Just to stop the over travel. I have zero over travel now and love it. Trigger is perfect to me
 Even if it's still the plastic one. I have a soft spring on the take up and the bent hairpin spring has it breaking around 2lbs. And now  all the over travel is gone. Trigger breaks and stops solid wall. Should have my HN Hunter exsteem and Terminators tomorrow can't wait to shoot groups with the new trigger

[KnifeMaker]

I would like to try the 14 gr. JSB's. Shoots the 15 and 18's well, with the nod going to the 18's. Tried a tin of Field Target from H&N. Good looking pellets, not so good in accuracy in my Maxi. Not even as good as the lowly Crosman domes. GRRRRR!!!


The replacement Huma Reg. form Treiner is doing a fine job. I wanted to shoot the 15 gr JSB's at 880, and it does just that. In stock form, it shot them at 780-790. Re-worked the valve and got them over 900. But not good shot count. Even at 840, I got one mag, and 2-3 more useful shots at 50 yards.

With the valve work, Magnum spring and screws to raise the fill pressure, and the huma set to 1700, she will go 930. Backed the spring down, and can get three mags at 860 fps.  Can go 4 with only a small rise and  drop in fps. 
Will lower the Reg. another 100 fps and see where she is. 

Knife

Knife

Good info.. What mods to the valve and I did the upgraded screws to. I fill to roughly 2200 psi a little over 150 bar. I get a easy 15 to 20 shots. Im thinking if you did the same thing to your Maximus  that I did to mine then I might be getting around the same volocities.

Drew, I followed a thread by BStern on one of his Discos. I opened up the valve port, transfer port and barrel port to .157"  Angled it forward and slightly oblong for better flow. Put a smaller, (weaker valve poppet-return in, and opened the inlet of the valve as far as I could and still be able to use the return spring.

Once I put the BNM Breach on it, I notice when looking at the transfer port, that the probe was not pushing the pellet far enough forward.  The Pellet skirt covered almost 2 thirds of the port.
I notched the rear of the breach just in front of the bolt where it contacts the back of the breach when pushing forward, but not pulled down into battery, and did the same inside the breach where the cocking screw is located in order to set the pellet fully into the bbl. Oddly, fps only increased by 24-25 fps, but apparently the air blast was deforming the skirt, and accuracy really improved after the mod. 

Knife

[Tater]

Drew, I followed a thread by BStern on one of his Discos. I opened up the valve port, transfer port and barrel port to .157"  Angled it forward and slightly oblong for better flow. Put a smaller, (weaker valve poppet-return in, and opened the inlet of the valve as far as I could and still be able to use the return spring.

Once I put the BNM Breach on it, I notice when looking at the transfer port, that the probe was not pushing the pellet far enough forward.  The Pellet skirt covered almost 2 thirds of the port.
I notched the rear of the breach just in front of the bolt where it contacts the back of the breach when pushing forward, but not pulled down into battery, and did the same inside the breach where the cocking screw is located in order to set the pellet fully into the bbl. Oddly, fps only increased by 24-25 fps, but apparently the air blast was deforming the skirt, and accuracy really improved after the mod. 

Knife

Man, there's no way I'd attempt or even think of stuff like that. The things/ideas/mods/tweaks all you guys come up with always impresses.

[bowdoc64]

I would like to try the 14 gr. JSB's. Shoots the 15 and 18's well, with the nod going to the 18's. Tried a tin of Field Target from H&N. Good looking pellets, not so good in accuracy in my Maxi. Not even as good as the lowly Crosman domes. GRRRRR!!!


The replacement Huma Reg. form Treiner is doing a fine job. I wanted to shoot the 15 gr JSB's at 880, and it does just that. In stock form, it shot them at 780-790. Re-worked the valve and got them over 900. But not good shot count. Even at 840, I got one mag, and 2-3 more useful shots at 50 yards.

With the valve work, Magnum spring and screws to raise the fill pressure, and the huma set to 1700, she will go 930. Backed the spring down, and can get three mags at 860 fps.  Can go 4 with only a small rise and  drop in fps. 
Will lower the Reg. another 100 fps and see where she is. 

Knife

Knife

Good info.. What mods to the valve and I did the upgraded screws to. I fill to roughly 2200 psi a little over 150 bar. I get a easy 15 to 20 shots. Im thinking if you did the same thing to your Maximus  that I did to mine then I might be getting around the same volocities.

Drew, I followed a thread by BStern on one of his Discos. I opened up the valve port, transfer port and barrel port to .157"  Angled it forward and slightly oblong for better flow. Put a smaller, (weaker valve poppet-return in, and opened the inlet of the valve as far as I could and still be able to use the return spring.

Once I put the BNM Breach on it, I notice when looking at the transfer port, that the probe was not pushing the pellet far enough forward.  The Pellet skirt covered almost 2 thirds of the port.
I notched the rear of the breach just in front of the bolt where it contacts the back of the breach when pushing forward, but not pulled down into battery, and did the same inside the breach where the cocking screw is located in order to set the pellet fully into the bbl. Oddly, fps only increased by 24-25 fps, but apparently the air blast was deforming the skirt, and accuracy really improved after the mod. 

Knife

Awesome.. I tried a larger transfer port but everyone said it would make a very peeky shot curve.. The guy from magmun airpower even stated that I would get better results with the stock transfer port.

[bowdoc64]

The one hole in the black is the HN Terminator 5 shot the other is HN Hunter exsteem. 25 yard.. The Terminator spread out past 25. The extreemes stay about the same

[bowdoc64]

I have a few Terminators in my tin if I hunt inside 30 yards really want to see what they do to small game now

[longhunter]

I would like to try the 14 gr. JSB's. Shoots the 15 and 18's well, with the nod going to the 18's. Tried a tin of Field Target from H&N. Good looking pellets, not so good in accuracy in my Maxi. Not even as good as the lowly Crosman domes. GRRRRR!!!


The replacement Huma Reg. form Treiner is doing a fine job. I wanted to shoot the 15 gr JSB's at 880, and it does just that. In stock form, it shot them at 780-790. Re-worked the valve and got them over 900. But not good shot count. Even at 840, I got one mag, and 2-3 more useful shots at 50 yards.

With the valve work, Magnum spring and screws to raise the fill pressure, and the huma set to 1700, she will go 930. Backed the spring down, and can get three mags at 860 fps.  Can go 4 with only a small rise and  drop in fps. 
Will lower the Reg. another 100 fps and see where she is. 

Knife

Knife

Good info.. What mods to the valve and I did the upgraded screws to. I fill to roughly 2200 psi a little over 150 bar. I get a easy 15 to 20 shots. Im thinking if you did the same thing to your Maximus  that I did to mine then I might be getting around the same volocities.

Drew, I followed a thread by BStern on one of his Discos. I opened up the valve port, transfer port and barrel port to .157"  Angled it forward and slightly oblong for better flow. Put a smaller, (weaker valve poppet-return in, and opened the inlet of the valve as far as I could and still be able to use the return spring.

Once I put the BNM Breach on it, I notice when looking at the transfer port, that the probe was not pushing the pellet far enough forward.  The Pellet skirt covered almost 2 thirds of the port.
I notched the rear of the breach just in front of the bolt where it contacts the back of the breach when pushing forward, but not pulled down into battery, and did the same inside the breach where the cocking screw is located in order to set the pellet fully into the bbl. Oddly, fps only increased by 24-25 fps, but apparently the air blast was deforming the skirt, and accuracy really improved after the mod. 

Knife

That's why everyone goes the extended bolt probe route. It seats the pellet deeper, without having to modify the breech.

[bowdoc64]

I would like to try the 14 gr. JSB's. Shoots the 15 and 18's well, with the nod going to the 18's. Tried a tin of Field Target from H&N. Good looking pellets, not so good in accuracy in my Maxi. Not even as good as the lowly Crosman domes. GRRRRR!!!


The replacement Huma Reg. form Treiner is doing a fine job. I wanted to shoot the 15 gr JSB's at 880, and it does just that. In stock form, it shot them at 780-790. Re-worked the valve and got them over 900. But not good shot count. Even at 840, I got one mag, and 2-3 more useful shots at 50 yards.

With the valve work, Magnum spring and screws to raise the fill pressure, and the huma set to 1700, she will go 930. Backed the spring down, and can get three mags at 860 fps.  Can go 4 with only a small rise and  drop in fps. 
Will lower the Reg. another 100 fps and see where she is. 

Knife

Knife

Good info.. What mods to the valve and I did the upgraded screws to. I fill to roughly 2200 psi a little over 150 bar. I get a easy 15 to 20 shots. Im thinking if you did the same thing to your Maximus  that I did to mine then I might be getting around the same volocities.

Drew, I followed a thread by BStern on one of his Discos. I opened up the valve port, transfer port and barrel port to .157"  Angled it forward and slightly oblong for better flow. Put a smaller, (weaker valve poppet-return in, and opened the inlet of the valve as far as I could and still be able to use the return spring.

Once I put the BNM Breach on it, I notice when looking at the transfer port, that the probe was not pushing the pellet far enough forward.  The Pellet skirt covered almost 2 thirds of the port.
I notched the rear of the breach just in front of the bolt where it contacts the back of the breach when pushing forward, but not pulled down into battery, and did the same inside the breach where the cocking screw is located in order to set the pellet fully into the bbl. Oddly, fps only increased by 24-25 fps, but apparently the air blast was deforming the skirt, and accuracy really improved after the mod. 

Knife

That's why everyone goes the extended bolt probe route. It seats the pellet deeper, without having to modify the breech.

Who makes a good extended bolt probe for the Maximus

[KnifeMaker]

Problem with an extended probe, is that it is almost impossible to load a full size pellet. Especially in the dark when pasting.

Top Compound the issue, the extended probe will be over the port when firing. Grrrrr!!!  But the loading issues, with the tiny loading port is the biggest issue. The bolt does not retract as far as a Disco bolt. PITA!!!

The BNM Breech cured that problem!

Knife