Too short pellet probes = inaccuracy

[skorec]

If the pellet/slug tail hole is to deep the pellet probe may be too short.

If pellet/slug tail deform because   hangs over the Transfer port.

You need overlong the probe. 
https://www.gatewaytoairguns.org/GTA/index.php?action=dlattach;topic=133591.0;attach=204979;image

[CraigH]

This is why I prefer the flow-through probe design which seats all pellets by the skirt OD.

[nervoustrigger]

I too have a slight preference for a flow-through type.  Partly because of the consistent seating depth as described but also because pin probes make some pellets want to tip which may lead to either chambering issues or accuracy issues.  Even in cases where there isn’t an obvious hitch when chambering, the pellet may still be seated slightly canted.  It’s less of a concern if the leading edge of the rifling has been eased so the pellet can neatly ride up into place without getting snagged / cut / scored.  Unfortunately the barrels of most low cost AGs have not been properly prepared…they just run in a reamer and back it out, leaving a sharp step where the rifling begins.  In my experience if you take care of that, the preference for a flow-through just goes back to the consistent seating depth.

[Ribbonstone]

Not all that easy to self-convert a probe to a flow though probe. Do prefer it, but not enough to not just extend a too short probe and try that first (although try not to go too skinny on the probe).

[anti-squirrel]

The Crosman 13xx and 22xx are kinda notorious for this issue.

I have the elongated probes - gotta keep some on-hand.  I need to check out those hollow probes though!

[Motorhead]

Then we have the Drawn back probes that seat with full diameter then are drawn back to the edge of transfer path.  AKA ... WAR guns for instance.

Personally with so many guns these days being side lever cocking and not able to be a drawn back design, using a replaceable PIN probe for the pellet used makes the most sense.
Shooting slugs and there snugger fit in chambering can be troublesome and need beefier probe which hurts performance ... gains or losses as usual 

[CraigH]

The Crosman 13xx and 22xx are kinda notorious for this issue.

I have the elongated probes - gotta keep some on-hand.  I need to check out those hollow probes though!

A thin pin probe of proper length will give a few additional fps - given a selected pellet and probe that seats the pellet just forward of the TP.   And the mentioned quality lead work.

MellonAir has stainless steel flow-through probe/bolts for these Crosman guns - $18.

[K.O.]

On my 13xxs and my Maximus a simple L shaped seating tool does the job without blocking the port...

[anti-squirrel]

On my 13xxs and my Maximus a simple L shaped seating tool does the job without blocking the port...

While a great idea, we still should not have to deal with bass-ackwards-engineering.  "Hey, we designed something wrong so now we'll design something else to get around it".

If Crosman designed these airguns so the probe:
A: pushed the pellet far enough forward to not SIT over the PT
B: did not push a pellet over a mounting hole for the breech assembly (on some models)
C: did not clearly cause an airflow obstruction
D: did not cock/tilt a pellet during loading

...  However, the lack of proper planning at Crosman has prompted an entire cottage industry around tweaking and tuning these Lego for better performance.

[skorec]

For now I prefer the idea of tube plug-in probe at full caliber OD whit TP.  Plug in pellet/slug  deeper may avoid/reduce also starting turbulences/nutations/deformations.

[rsterne]

At the power limit, a flat, retractable bolt face is the best, IMO.... Flow-through probes are limited in the amount of air they can flow, and although they do seat the pellet or slug square with the bore, they will not produce as much FPE as a thin probe can.... On rifles where I am not going for full bore-area porting (then I use a retracting bolt), but I want good power, I use a thin probe (but not so thin it damages the slug).... If I want to shoot both pellets and slugs, I make that probe replaceable (threaded into the nose of the bolt), and use a shorter one for slugs....

I would agree that having the skirt of a pellet (which is easy to bend) hanging over the barrel port is asking for accuracy problems....

Bob

[Hobbyman2007]

Anyone who’s used a BNM breach has the pellet over the transfer port problem. I tested both hollow probe and pin type on an FX Impact , it now has the pin type installed and will be staying that way.

[skorec]

At the power limit, a flat, retractable bolt face is the best, IMO.... Flow-through probes are limited in the amount of air they can flow, and although they do seat the pellet or slug square with the bore, they will not produce as much FPE as a thin probe can.... On rifles where I am not going for full bore-area porting (then I use a retracting bolt), but I want good power, I use a thin probe (but not so thin it damages the slug).... If I want to shoot both pellets and slugs, I make that probe replaceable (threaded into the nose of the bolt), and use a shorter one for slugs....

I would agree that having the skirt of a pellet (which is easy to bend) hanging over the barrel port is asking for accuracy problems....

Bob

Bob, You have true as always. I will be thinking haw :
1.   to adjust Kral Puncher breeches  for retractable bolt face system
2.   to add sealing O-ring on it

Peter