2240 bolt probe mod for velocity

[MichaelM]

LOL Jeff atleast ell us was it a extended prob or a flow through that was your Pick.... no need to say who made them

[quickster47 †]

some were longer some were smaller dia. and one flow thru had oversized hole compared to the specs i have. was surprised to find a 70fps variation over the 6 of them with 5 of them being within 40fps which left me with 1 clear loser. will not go into specifics because what works for me may not work for you but i definately have my two favorites now. this was in no way a comprehensive test and there are way to many variables to be able to draw any concrete conclusions, just saying it pays to experiment.

Your results are not surprising and truthfully what I feel everyone experiences.

As always with some many parts, "Your Mileage May Vary".

Carl

[howie1968]

I have the  origiganl bolt that came with the plastic bolt,  let me ask this if i was to reduce the  diameter of the probe on my steel bolt with  my steel breech kit how would i do this? with a dremel and roll it to make it even. i havent progresed to even tamper with valve work but if i can gain some by going to the 14.5 inch barrel then do a probe mod and increse velovity some, as stated im basically going to shoot paper and cans but like the idea of popping a rabbit. i want as much energy as i can muster without getting into the valves just yet, i feel another 2240 will be ordered soon

[quickster47 †]

^^^ It could be done with a Dremel albeit I am not sure exactly how true it would turn out but the absolute best way would be to use a lathe.  However, being that you may not have a lathe or access to one, there are many here on this forum that have had exceptionally good luck chucking something like the bolt in a variable speed drill and doing something like what you are proposing.  Just take your time and be in no hurry.

BTW, your original brass bolt that came with the plastic breech would have to be taken apart and the cocking handle removed and then the bolt tapped to 8-32 to accept the handle.  The brass bolt and handle are staked together from the factory.

Carl

[BDS]

IMO, the research done by so many folks on this forum, shows modest velocity gains at best. For me, the most important attributes of the extended probe are air-flow (as Carl noted) and a really good o-ring seal on the probe. A good seal, with the pellet pushed past the transfer port makes the "lock time" slightly quicker or more efficient with less chance of pellet damage or scrapes on the head or skirt when loading. All good stuff in the quest for repeatability which adds to overall accuracy and efficiency of the gun.

I believe Charles Mellon agrees with this concept, as his webpage for the extended probes (choose hollow or solid types) basically states (my paraphrase) don't ask me which style is better, buy them both if you are that anal about it.   

[DaveB50]

I remember seeing a video where they cut  the bolt off froward of the o ring, then drilled and inserted a piece of music wire. This way you could also extend the probe.

[agninja]

Yea, I saw some russian dude make a video and he took apart a lighter, I guess just for the o-ring, and put that on the bolt probe. Then he drilled it out and glued some piano wire in there. I had no idea what purpose that served when I was watching it, but now it all makes sense.

[HappyHunter]

I remember seeing a video where they cut  the bolt off froward of the o ring, then drilled and inserted a piece of music wire. This way you could also extend the probe.

Well, I never made a video of mine , but that's how I did it too. Instead of music wire though, I used (are you ready for this?) - S/S finishing nails!  . Before you ask, "Why finishing nails"?... short answer is "Because that's all I had on hand at the time that would work"! Keep in  mind the only tools I had at my disposal was a cheap drill press, a Dremel and some files/sandpaper!   

"Skinny" probe on left is from a 1-1/4" nail. Shank is 1/16" diameter (made for a nice, snug fit in bolt), head of nail was 3/32". The fatter probe on the right is made from the shank of a 2-1/2" nail, which was the same diameter as the "head" of the first one (3/32").


Both probes were cut 5/8" long, 3/8" of which is inserted into a 1/16" hole drilled in end of bolt which gave me a finished bolt length of 1-7/8" - just barely enough room to still load Polymag's  and still have the skirt completely ahead of TP:





Todd

[quickster47 †]

Good job Todd.  As they say, necessity is the mother of invention. 

Carl

[Brent]

Cool Todd!

[Noah]

Yea, I saw some russian dude make a video and he took apart a lighter, I guess just for the o-ring, and put that on the bolt probe. Then he drilled it out and glued some piano wire in there. I had no idea what purpose that served when I was watching it, but now it all makes sense.

I also saw that same video and was pretty impressed with the kid's ability to do this-and-that... 

[DaveB50]

Good looking bolts there Todd.

[cheewee]

LOL Jeff atleast ell us was it a extended prob or a flow through that was your Pick.... no need to say who made them

the probes that performed the best were both extended probes with dia. slightly smaller that what i consider to be the norm.

[WyoMan]

I read but don't remember where that its tough to get the flow-thru to beat
the extended until you get to .22 and above......
tough to pull the breech on a good build just to test stuff ....nice work cheewee 

[MichaelM]

I read but don't remember where that its tough to get the flow-thru to beat
the extended until you get to .22 and above......
tough to pull the breech on a good build just to test stuff ....nice work cheewee 

This is also what I have come to understand from research.... (I personaly have not gotten there yet but my thoughts and experiance with other things would have me tending to lean in this direction as well) the opening is just to restrictive no matter how big you get it in .177(and alot of time have decreases in speed)  and in .22 its really toss up as they both seem to be about equel.... seams the real gains start in the .25 and up as far as power+ consistancy goes.... where there is enough meat on the prob you can open it way up and have plenty of flow.....

think I will try to experiment with both 1/8 and 1/16 drill rod....  and maybe smaller if 1/16 seems to be beefy enough to stand up to the abuse.....

And Thanks Jeff for going through the pain of pulling your girl apart and putting her back together  to test this out for us!!!!