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PostPosted: Thu Jul 25, 2019 7:20 pm 
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Does the extended bolt probe really increase fps in 2289/....1377/22...or is it a sales pitch?


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PostPosted: Thu Jul 25, 2019 7:35 pm 
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You meant from yours to change to something like mine?

Actually I asked the similar question before when I did my mod... But my question was as the extended probe will push the pellet going deeper into the breech... So it means the distance from the pellet to the muzzle is shortened... So the fps decreases.... (We know 14 inches barrel will have faster muzzle speed than 10 inches barrel...)

And the answer is my guessing is wrong as so less than half of a finger nail distance difference won't make any changes at all...

And the advantage for this mod is the pellet will be sit in position better than the short probe, and your shots will be more consistent and increase the accuracy.... Image

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PostPosted: Thu Jul 25, 2019 7:42 pm 
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Seems to me the pellet is sitting TOO far back in the 1377/22/89 guns.....thereby restricting air flow....but hey if a longer bolt only improves accuracy.... thats okay too... :D

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PostPosted: Thu Jul 25, 2019 8:08 pm 
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If using a longer bolt can increase fps, that will only mean the pellet you are using is not for the short probe bolt... I.e, the Crosman pellet's.skirt design is different from the European pellet brands, like JSB, H&N... The Crosman pellet has a flat bottom inside the skirt, so the original bolt can push it in without issue... But the JSB etc pellets have a long skirt which using an extended probe bolt would be better...

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PostPosted: Thu Jul 25, 2019 8:26 pm 
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Oh... And why I did this mod is because I like the stainless steel and the bolt handle... The extended probe is just s bonus ~ [emoji38]


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PostPosted: Thu Jul 25, 2019 10:26 pm 
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If the skirt is obstructing the transfer port after being pushed in by the probe it will decrease the fps. A probe that is longer and just pushes past the transfer port a hair will increase the fps a tad.

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PostPosted: Fri Jul 26, 2019 5:47 am 
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Yes ~ that's the main reason ~

The X-Match is about 2 times deeper inside the skirt than the Crosman...

ImageImageImage

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PostPosted: Fri Jul 26, 2019 9:24 am 
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I just bought 210s of Crossman premier 22's from Amazon for really cheap just for planking was very surprised how different they were from the Jsb's.
I noticed that even though that the same weight as the jsb's I'm using they're about 15 to 20 FPS faster consistently. Quite possibly because they get seated further past my transfer port. For the CR 600 w There is an extended bolt probe available from the UK but it's not cheap.
TRRobbe is the company and has a handful of upgraded parts available for it.

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PostPosted: Fri Jul 26, 2019 9:30 am 
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Maybe while a pellet is sit further from the transfer port, the blow out air pressure can be hold and increase the pressure a little bit (get more air in between the TP and pellet) before really start pushing the pellet to move ??

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PostPosted: Fri Jul 26, 2019 10:16 am 
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walther wrote:
I just bought 210s of Crossman premier 22's from Amazon for really cheap just for planking was very surprised how different they were from the Jsb's.
I noticed that even though that the same weight as the jsb's I'm using they're about 15 to 20 FPS faster consistently. Quite possibly because they get seated further past my transfer port. For the CR 600 w There is an extended bolt probe available from the UK but it's not cheap.
TRRobbe is the company and has a handful of upgraded parts available for it.

It COULD be because of different seating position but it could also be a difference in pellet drag...my chrony shows the 14.3 crosman hollow point shoots slower than the crosman pointed 14.3's in my pal and non pal air rifles...so I'm supposing it's more barrel contact with the hollow points slowing them down.....seating position looks the same...

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PostPosted: Sat Aug 10, 2019 6:35 am 
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Based on my black eagle, if I used the pellet seater to sit the pellet about 1mm deeper into the breech, I get about 10m/s extra muzzle speed, 14gr .22 pellets.

It's about 30fps! Quite a lot for a detuned non PAL rifle....

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PostPosted: Sat Aug 10, 2019 7:56 am 
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YepYep wrote:
Based on my black eagle, if I used the pellet seater to sit the pellet about 1mm deeper into the breech, I get about 10m/s extra muzzle speed, 14gr .22 pellets.

It's about 30fps! Quite a lot for a detuned non PAL rifle....

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Not ALL types of pellets react the same way.....depending on how they initially fit in the breech....loose fit pellets can lose some energy if seated.....and for the pellets that CAN benefit from being seated .....there is a sweet spot of course...as you have found.....because seating them TOO far into the breech and energy is lost due to the extra space now available to "fill" with a charge of air...My initial question about extended probes was not so much the effect they have on fps because of seating depth of a pellet....but moreso how the shape of the probe itself may influence the force of the air...

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PostPosted: Sat Aug 10, 2019 8:48 am 
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There's a thorough study on bolt probes on the CAPOF, made by quickster47 (R.I.P. Carl), where you can find a detailed analysis of five bolt probe design. This was done on the 2240 platform, but the principles apply to 13xx pistols as well. General consensus is that any probe that will push the pellet further than the TP, without restricting the flow like the OEM bolt probe, will yield approximately between 15 and 30 additionnal fps, all others factors being the same. Unfortunately, you can't see the pictures if you're not logged in, but the text by itself is very detailed.

https://www.crosman-air-pistol-owners-f ... 741.0.html

An extended bolt probe WILL give a bit more fps because there's more flow, and more than probably improve the accuracy since the pellet's skirt is no longer deformed by the blast of gas/air from the TP. I personally think the probe should be custom made for the pellet you're using, because as Yep Yep said, the ''depth of skirt'' will vary depending on the brand/model used, thus affecting the depth of pellet insertion. HTH :wink:


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PostPosted: Sat Aug 10, 2019 9:00 am 
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airmec wrote:
There's a thorough study on bolt probes on the CAPOF, made by quickster47 (R.I.P. Carl), where you can find a detailed analysis of five bolt probe design. This was done on the 2240 platform, but the principles apply to 13xx pistols as well. General consensus is that any probe that will push the pellet further than the TP, without restricting the flow like the OEM bolt probe, will yield approximately between 15 and 30 additionnal fps, all others factors being the same. Unfortunately, you can't see the pictures if you're not logged in, but the text by itself is very detailed.

https://www.crosman-air-pistol-owners-f ... 741.0.html

An extended bolt probe WILL give a bit more fps because there's more flow, and more than probably improve the accuracy since the pellet's skirt is no longer deformed by the blast of gas/air from the TP. I personally think the probe should be custom made for the pellet you're using, because as Yep Yep said, the ''depth of skirt'' will vary depending on the brand/model used, thus affecting the depth of pellet insertion. HTH :wink:


Makes you wonder why manufacturers would design guns with a pellet sitting in the breech directly over the blast of air....instead of having the pellet skirt clear of the air blast....makes sense that a powerful charge of air would deform a pellet...especially the softer ones.....

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PostPosted: Sat Aug 10, 2019 10:57 am 
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Quote:
Makes you wonder why manufacturers would design guns with a pellet sitting in the breech directly over the blast of air

Maybe Crosman want to favour their pellets (with a shallow skirt) over their competitors?.... :wink:

Bob

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