Making Extended probe bolts

[dan_house]

Just read, and reread Carls most excellent posts on the probe experiments. Great work on his part, and very informative.
From Carl's efforts, I'm taking away that an extended probe that pushes the pellet _past_ the TP will gain some speed for the shot. But that gets me back to reailty, and that is "How do I extend the probe?"
Grind off the factory probe section of the bolt and then (hope you get it square) into the drill press?
Suppose I could just order one...... then have to wait

[quickster47 †]

Just read, and reread Carls most excellent posts on the probe experiments. Great work on his part, and very informative.
From Carl's efforts, I'm taking away that an extended probe that pushes the pellet _past_ the TP will gain some speed for the shot. But that gets me back to reailty, and that is "How do I extend the probe?"
Grind off the factory probe section of the bolt and then (hope you get it square) into the drill press?
Suppose I could just order one...... then have to wait

Dan it really helps to have a lathe when doing this operation.

What I do is chuck up the bolt and cut off the OEM probe tip in front of the o-ring.  Then, depending on what I am using for the probe tip, drill a hole into the bolt the same diameter or maybe 0.001" under size.  Next I cut a small piece of the probe material and then using some CA glue insert the new probe tip.  After that I trim the probe tip to my desired length and also cut off the rear end of the bolt so when you pull the bolt back you can load your pellet.  Don't cut too much of the rear cause if you do the gun will not cock.

Carl

[JEBert]

Dan,
I do a lot of stuff on the drill press that I would rather do on a lathe except I don't' have a lathe.  You do need a drill press vice and Harbor Freight has them pretty reasonable.  That's where I got mine so it is not of the best quality but it works for my purposes.
Here are some tips if you (or anyone else) can use them:
Cut the probe off as close to square as you can get it with a hacksaw.  To do this, I use two wooden blocks to help me keep the hacksaw blades pretty square.  Cut two pieces of 2X2's off about 4" long.  Clamp them together and hold them together and flat on the drill press table.  Small bar clamps or large C clamps work equally well.  Drill a hole right in the joint between the blocks.  Below is a pic of me cutting off a barrel and the hole is 13/32" which is 1/32" smaller than the 7/16" barrel.  If using soft wood and need to have a lot of gripping power, you can use a drill 1/16" smaller than what you plan to hold in the blocks rather than 1/32" smaller.
Then chuck the bolt into the drill press, turn it on, and bring it down on a flat section of the table with a piece of 220 grit sandpaper on the table.  Hold the paper from turning and bring the bolt down slowly and carefully so as to not make it want to walk around.  Repeat as necessary moving the sandpaper around to expose a new section to the bolt as needed.  This will get the end awfully square.
Use a drill press vice with some similar blocks in it to hold the bolt straight enough to get a centerpunch mark in it.  An automatic centerpunch works best for this.
Put the drill you plan to use in a pin vice (larger drills can be held in the same types of blocks as above that you make yourself.) and use two blocks like the above example to hold the pin vice and drill vertically in your drill press vice.
Put the bolt in the chuck of the drill press.  This should hold them in alignment to drill out the bolt to epoxy a new probe into it.  The bolt turning in the chuck and the drill bit held in the vice should drill the bolt similar to drilling it in a lathe.
Hope this helps.
Cheers,

[Brent]

WOW Jerry!! Very cool write up and pics!! 

[Cwlongshot]

I just made one on my drill press. I have three more to make this week end. I did not find it hard at all.

I used a hack saw blade and a file as well as a 1/16'' drill bit and some same sized stock. I chose to epoxy my probe in, but lock tite or even super glue as suggested should do the trick.

Good luck,
CW

[agninja]

Question. What if you loaded the pellet normally with the stock bolt, then opened the bolt again and took an allen wrench and stuck it in behind the pellet and pushed the pellet down the barrel a little further? Would that be a way you could manually simulate what the extended bolt probe does?

I guess I might as well just try it and chrony my results to see if it actually increases velocity.

[breakfastchef]

That procedure would produce similar results, but 1) you would not be able to seat the pellet in the same position reliably, and 2) you might create a deformation in the pellet which could affect it's flight.

Question. What if you loaded the pellet normally with the stock bolt, then opened the bolt again and took an allen wrench and stuck it in behind the pellet and pushed the pellet down the barrel a little further? Would that be a way you could manually simulate what the extended bolt probe does?

I guess I might as well just try it and chrony my results to see if it actually increases velocity.

[ettolo]

That procedure would produce similar results, but 1) you would not be able to seat the pellet in the same position reliably, and 2) you might create a deformation in the pellet which could affect it's flight.

I was thinking the same as agninja but planned to do with a "ad hoc" tool, made with pvc or derlin: this way the pellet will not be deformed and his position will always be the same

[Cwlongshot]

Here is a excellent post showing the differences.

http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,10694.msg130489.html#msg130489


Here is a post on the procedure I used to make them.

http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,11232.msg140583.html#msg140583

CW

[agninja]

That procedure would produce similar results, but 1) you would not be able to seat the pellet in the same position reliably, and 2) you might create a deformation in the pellet which could affect it's flight.

I would think that you could push it in to the same spot each time, especially given the curved 90 degree anble of the Allen tool. You might have to snip and bevel the end of it to make for optimal length and fit in the skirt of the pellet. And being that it is inside the skirt, I wouldn't think that it would deform the pellet.

I still need to test and chrony this method. Will try to work on that soon.

[ped]

I would think that you could push it in to the same spot each time, especially given the curved 90 degree anble of the Allen tool. You might have to snip and bevel the end of it to make for optimal length and fit in the skirt of the pellet. And being that it is inside the skirt, I wouldn't think that it would deform the pellet.

I still need to test and chrony this method. Will try to work on that soon.

thats what i used to do when i first read about extended probes ,i cut the short arm down to the length i wanted and it seemed to work well just a bit of a faff doing it but it does work
ped

[DaveB50]

If you extend your bolt, you need to check how far it pushes the pellet into the barrel. You want to push the pellet just far enough for the skirt to clear the transfer port hole. If you push the pellet any farther than that, it will hurt performance, because of the extra air space created.

[WyoMan]

^^^^What DaveB said 

[quickster47 †]

If you push the pellet any farther than that, it will hurt performance, because of the extra air space created.

Excellent point Dave.         Many times we think bigger is better and farther is the best but that ain't always true.

Carl

[Cwlongshot]

If you extend your bolt, you need to check how far it pushes the pellet into the barrel. You want to push the pellet just far enough for the skirt to clear the transfer port hole. If you push the pellet any farther than that, it will hurt performance, because of the extra air space created.

AAH, but if you read my post... It's not as easy as all that. All pellets are just a little different! Deeper skirts require longer probes and shallower skirts shorter ones... SO when making you own ext probes you need to take this into consideration.

Sure too long can be detrimental to optimal velocitys, but what are you loosing by doing nothing nothing?  Just something to ponder..

CW