Impact pin probe distorting pellets?

[madeintheuk]

I remember seeing a post here (didn’t know what to search for) about the impact pin probe causing problems with shooting pellets. My speeds are good with the chrony, and it’s very consistent with spread, but I’m getting horrible groups at 40yds. I’m shooting hades and 35 grain jsbs out of a 500mm superior liner with carbon sleeve and dual transfer port

 

[qball]

You most likely have to adjust the seating depth so the pellet can be seated properly. Remember most pellets have very deep skirt compared to flat or dish base of a slug. In fact you supposed to adjust seating depth for each ammo you shoot, even slugs have major variation on the base.





It’s better to just switch to pellet probe when shooting pellets, very quick and easy. I have dual TP and other upgrades but I prefer the normal tube based probe. 

 

[madeintheuk]

I totally know how probe depth effects speeds, I just didn’t know if it effected accuracy. When I put my wildcat back together, I messed up probe depth, and went from shooting at 915 to 768 with just the slightest miscalculation. I didn’t have accuracy issues with it though, just a serious poi drop. Lol

 

[dizzums]

you have to actually get a barrel and your projectile and see physically whats going on sometimes .. push it through from the breech end ... ideally imo the bolt pushes it freely right up to the point it starts to engage the rifling 'and' the projectile is sized correctly for the barrel .. depending on barrel and some other factors im not an expert at with airguns, more or less, hand ramming the projectile through with a brass rod etc, it should tap through firmly but not loose or tight ... if it falls through withvjust a minimal push for example theres your problem right there, its not sized suitably for the barrel ...

 

[biohazardman]

If there is anything distorting the pellets when you have a pin probe installed I would say it would be the blast of air it gets on the skirt when you pull the trigger. The pin probe does not push the pellets into the chamber as far as it pushes a slug in and you cannot adjust it to do so and still use the magazine. So I would guess that the skirt of the pellet is exposed to the full force of the air from the shot.

Edit;

So, I chambered a pellet with the pellet probe and then pulled the barrel and checked to see where it was. I was very close to the port but I am not sure that a pin probe would make a pellet partially block the port.

 

[Storm13191]

What do y'all use to push pellets through a breech properly

 

[madeintheuk]

Now THAT totally makes sense. Never thought of that before. I’m sure the dual transfer port doesn’t help either. I have the Ernest port, so tomorrow, I’m going to try and flip the barrel to the small port first. Then I’ll do the probe depth test. Anyone wanna trade a pin probe for a pellet probe in .25???

 

[Airgun-hobbyist]

That pin probe should work well with the dual tranfter port, though I use a modified version of the original round pellet probe instead for maximum seating depth. I adjust the probe rod so the tip of the pellet probe is just flush with the edges of the magazine well (when the cocking lever is pulled back to cycle). This gives the furthest distance it can travel forward to seat the pellet, and is pulled back far enough to not effect the loading the magazine.

 

[2L8]

If there is anything distorting the pellets when you have a pin probe installed I would say it would be the blast of air it gets on the skirt when you pull the trigger. The pin probe does not push the pellets into the chamber as far as it pushes a slug in and you cannot adjust it to do so and still use the magazine. So I would guess that the skirt of the pellet is exposed to the full force of the air from the shot. I have not chambered a pellet then pulled the barrel to check this yet but I expect it is so.

This is good advice and worthy of further investigation.

 

[biohazardman]

I looks possible but now that I actually looked it would probly only be really close with lighter pellets with the deep cavity in them. 

 

[madeintheuk]

That pin probe should work well with the dual tranfter port, though I use a modified version of the original round pellet probe instead for maximum seating depth. I adjust the probe rod so the tip of the pellet probe is just flush with the edges of the magazine well (when the cocking lever is pulled back to cycle). This gives the furthest distance it can travel forward to seat the pellet, and is pulled back far enough to not effect the loading the magazine.

While I like your logic, doesn’t this effect how it lines up with the hole in the transfer port? Isn’t that the most critical measurement? If it doesn’t line up perfect, then velocities would suffer due to lack of flow through the transfer port, and into the probe. 

 

[corny]

Now THAT totally makes sense. Never thought of that before. I’m sure the dual transfer port doesn’t help either. I have the Ernest port, so tomorrow, I’m going to try and flip the barrel to the small port first. Then I’ll do the probe depth test. Anyone wanna trade a pin probe for a pellet probe in .25???

FX pin probe? I would, if ur srs? 

 

[madeintheuk]

So, I chambered a pellet with the pellet probe and then pulled the barrel and checked to see where it was. I was very close to the port but I am not sure that a pin probe would make a pellet partially block the port.

what pellet did you chamber? The 35 grain jsb mk2 has a very shallow skirt, but the hades I’ve been using are fairly deep. I’m going to do some testing myself to see if this holds true. Thanks for the advice. This is a good test!

 

[Acruz]

Don't forget the pin probe is for slugs that have a flat or a shallow concave base.

 

[madeintheuk]

Don't forget the pin probe is for slugs that have a flat or a shallow concave base.

I bought the fun setup like this, and while I like the idea of shooting slugs, the majority of what I do is suited more for pellets. I do however want to shoot slugs from time to time. I have knockouts, nsa, and I’m picking up some Vermont knockers to test, but I shoot hades, polymags and a king heavies the most out of both my .25 guns. It seems the way to go is to get the high flow probe from huma. 


on another note, I may be jumping the gun here. The hades were on test when I noticed the issues, but it was shooting them at 960fps. It may just be too fast for the pellets to stabilize. I might tinker with slowing the speed a little, and seeing if it helps any before buying new parts!

 

[qball]

Don't forget the pin probe is for slugs that have a flat or a shallow concave base.

I bought the fun setup like this, and while I like the idea of shooting slugs, the majority of what I do is suited more for pellets. I do however want to shoot slugs from time to time. I have knockouts, nsa, and I’m picking up some Vermont knockers to test, but I shoot hades, polymags and a king heavies the most out of both my .25 guns. It seems the way to go is to get the high flow probe from huma. 


on another note, I may be jumping the gun here. The hades were on test when I noticed the issues, but it was shooting them at 960fps. It may just be too fast for the pellets to stabilize. I might tinker with slowing the speed a little, and seeing if it helps any before buying new parts!

You don't need the pin probe for slugs, even compared to unmodified factory tube probe you only gain 15 fps or something like that. Only reason to have pin probe is to fine tune slug seating depth for shorter slugs to engage the rifling as much as possible but with newer superior liners the rifling started almost at the tip of the barrel so you don't really need it even with short slugs. Then you have test different seating depth but what if you got the right seating depth but then the mag wont work because pin sticking out too much? Simply too much work for me for 15 FPS, the impact has plenty of power to need that 15FPS. Get a huma tube probe or just spend 5 minutes with a Dremel and the difference will be maybe 3-5FPS. 

 

[madeintheuk]

So I did some testing. Put a hades pellet in the chamber, and removed the barrel to check for depth. 

sorry for the blurry pic, but as you can see, the skirt is only half way clear of the transfer port. 
I’m out of adjustment on the probe without interfering with the magazine, so I guess I will need a standard pellet probe to shoot these. 


I did try the king heavy mk2, and due to the shallower skirt, as I thought, it cleared the port just fine, and when I pushed it out, there were clear rifling marks on the entire head to prove it made contact, but the hades did not. 


food for thought for all you pellet/slug shooters thinking of using a pin probe.