Bulldog bolt probe....

[ShakySarge]

I have been tinkering around with the bulldog.357 and currently have opened up the ports to 9/32” and have been able to achieve a maximum speed of 860 FPS and a slowest of 842 FPS with 153gr cast bullets. This is a substantial improvement from stock but there isn’t a lot more that I can do with the platform without sending it off to a professional. That being said, has anyone tried probing the bolt yet? Using cast bullets it should increase the speed slightly. I was thinking about ordering another bolt just to try and see what is or isn’t gained.

Any suggestions on length and width of such probe?

[Iamscotticus]

Anything new here?
Im interested.

[ShakySarge]

Waiting for the second bolt to arrive but I’ll certainly post the results.

[ShakySarge]

Probe is finished. Below is what it looks like with a 1/8” diameter probe. Hopefully have better weather tomorrow for chronograph testing.

[PCPhack]

Interested the see before and after strings.

[Iamscotticus]

How did you turn that?

[ShakySarge]

I shaved the concaved end off right where it ended and then drilled it out slowly one size at a time, then used epoxy to secure the 1/8” probe.

[ShakySarge]

It seems to have made a slight increase in speed but nothing dramatic. 5 shots from 3k with 150gr .358 went from 868-876-880-872-859. These speeds don’t seem impressive but with a 150gr bullet sized to .358 it’s fair to say that a smaller diameter bullet would greatly increase the numbers. When I first received the gun new the max was around 750 for the 150gr.

[oldpro]

I tried that same mod and lost 10fps from a widened and channeling of stock bolt. I believe the stock bolt redirects the air better than just letting it fill the area with a pin type probe.

[ShakySarge]

It improved slightly but not a huge increase. I will take anything that I can get at this point.

[YEMX]

It improved slightly but not a huge increase. I will take anything that I can get at this point.

Perhaps a new valve? 

[ShakySarge]

It may be necessary in the future. For now it is A Okay.

[ShakySarge]

I went through the bulldog today and discovered the reason as to why a probe that clears the magazine is only a minor, and in some cases, zero improvement. It is apparent that if the probe is able to clear the magazine then the pellet, or bullet isn’t pushed far enough into the chamber and actually blocks a portion of the port on the barrel. After realizing this by using a small mirror and a light I went about ways to make it work. I found that by pulling back on the cocking arm while inserting the magazine it not only cleared the magazine but also seated the bullet far enough forward to clear the port.

After another string I found that the speed increased to 899-886-870-862-849 for a max speed increase of 19fps. It just goes to show that with a little patience and a bit of attention to detail, what one can accomplish!

[Iamscotticus]

Good work. Great info. I wish I understood any of it. LOL.
So the procedure is to pull back on the probe bolt when inserting the magazine? 
CANCEL MY ORDER!

[ShakySarge]

Yes. To insert the magazine you will need to keep the cocking arm pulled all the way rearward so that the probe doesn’t hang on the bottom of the magazine. Once loaded it can be cocked normally unless changing out the mag. This may not be necessary if you have not bored out the transfer ports.