New 2100

[Grampy ray]

Man I love that brass probe I wonder how much it adds itself.

[Tack Driver 10]

Ran 2 of my guns over the chrony using 14.3 grain CPHPs.

#1. "1993" 2100 with 10 pumps=638 FPS 12.92 FPE.

#2  "1980"   766 with 10 pumps=704 FPS 15.73 FPE (+2.81).

Both guns are stock, in near new condition and both have the two piece metal/plastic piston.
The plastic pistons are different between the two.
The 766 plastic piston is .020" longer than the 2100 piston.

Perhaps there is credence to the old myth that the early models had more power?
Maybe we should call the MythBusters.

Yep, I found out the hard way. I tried to stick a first generation 766 metal rod with piston into my AM77. Guess what!? I couldn't close the forearm. 

The small .020" difference in the piston length shouldn't prevent the pump arm from closing with the rubber cup seal.
I believe the reason you couldn't close the pump arm was because of the difference in stroke between the versions.

A 766 pump tube has a much shorter stroke by about 3/8" or about 4 5/8".
It has a longer valve body, different pump tube and pump link to match.

The AM77/2100 has a stroke of about 5" so you can't mix and match between the two.
It's all or nothing.

The entire tube including the 766 valve and pump link needs to be swapped.

I'm thinking you swapped the pump tube but used the AM77 pump link?

[DanD]

Ran 2 of my guns over the chrony using 14.3 grain CPHPs.

#1. "1993" 2100 with 10 pumps=638 FPS 12.92 FPE.

#2  "1980"   766 with 10 pumps=704 FPS 15.73 FPE (+2.81).

Do you mean 7.9 gr CPHP @ 7.1 and 8.7 FPE?
Either way, those are good velocities.

On another note, I cleaned the barrel on my new 2100, mounted a scope, and put 10 JSB 8.44 into .309 ctc at 10 yards with 6 pumps. Only other pellet I tried for accuracy so far was CPHP, and they didn't do as well.  Trigger pull measures 4lb 12oz. Although it's long and heavy,  I can feel a notch at the very end of the pull which makes the beak predictable almost like a two stage.  For sure,  this little gun is worth some tinkering.  That stock,  though...

[GreenDragon]

I was feeling frisky the other day after trying out my updated 2100, so I decided to break open my MK-177 and see if there were any opportunities for improvement.

First think I noticed is you can tell it is a modern design.  Much fewer pieces than the 2100, and easier to reassemble etc.  The bolt is one piece, and the barrel is thicker than the 2100 and is tightly attached to the breach / barrel support.  So no need for the old tape mod at that location.  The front of the barrel is pretty firmly gripped by the "flash suppressor", so no need to tape there either.  After a thorough once over, I decided there were only two east mods that would make any improvement.  I added a second washer between the valve and barrel as it seemed to be a loose fit.  Then I routed out a seat for the spare O-ring Tack Driver 10 sent me into the (plastic) breach with my new Dremmel tool to make a seal when the bolt is inserted.  Pics below!

Steve

[Tack Driver 10]

Ran 2 of my guns over the chrony using 14.3 grain CPHPs.

#1. "1993" 2100 with 10 pumps=638 FPS 12.92 FPE.

#2  "1980"   766 with 10 pumps=704 FPS 15.73 FPE (+2.81).

Do you mean 7.9 gr CPHP @ 7.1 and 8.7 FPE?
Either way, those are good velocities.

On another note, I cleaned the barrel on my new 2100, mounted a scope, and put 10 JSB 8.44 into .309 ctc at 10 yards with 6 pumps. Only other pellet I tried for accuracy so far was CPHP, and they didn't do as well.  Trigger pull measures 4lb 12oz. Although it's long and heavy,  I can feel a notch at the very end of the pull which makes the beak predictable almost like a two stage.  For sure,  this little gun is worth some tinkering.  That stock,  though...

Duh yes, I've been testing my 2200 and it bled over into that test.
Too much eggnog!
Thanks for catching that and letting me know. I'll edit it.

My 2100 likes H&N Barracuda Match or FTTs, Barracuda Hunter Extremes are also good
in my other 17 cal guns but haven't tried them in my 2100.

[mav72]

Ran 2 of my guns over the chrony using 14.3 grain CPHPs.

#1. "1993" 2100 with 10 pumps=638 FPS 12.92 FPE.

#2  "1980"   766 with 10 pumps=704 FPS 15.73 FPE (+2.81).

Both guns are stock, in near new condition and both have the two piece metal/plastic piston.
The plastic pistons are different between the two.
The 766 plastic piston is .020" longer than the 2100 piston.

Perhaps there is credence to the old myth that the early models had more power?
Maybe we should call the MythBusters.

Yep, I found out the hard way. I tried to stick a first generation 766 metal rod with piston into my AM77. Guess what!? I couldn't close the forearm. 

The small .020" difference in the piston length shouldn't prevent the pump arm from closing with the rubber cup seal.
I believe the reason you couldn't close the pump arm was because of the difference in stroke between the versions.

A 766 pump tube has a much shorter stroke by about 3/8" or about 4 5/8".
It has a longer valve body, different pump tube and pump link to match.

The AM77/2100 has a stroke of about 5" so you can't mix and match between the two.
It's all or nothing.

The entire tube including the 766 valve and pump link needs to be swapped.

I'm thinking you swapped the pump tube but used the AM77 pump link?

Ahhhh ok I see. I think I remember something to the fact but it was so long ago.

During that time I had mixed 766 parts everywhere. I also had to replace the model "A" 766 pump tube assembly with a "C" version because the original combined valve/transfer port was too fouled up to repair.

[avator]

The 766 has a longer rivet in the pump arm linkage protruding out of either side. The pump tube has been cut out to allow clearance so the pump arm can be fully closed. My 2200 magnum tube (for instance) does not have these clearance notches cut into it. The pump arm linkage will not interchange unless you make the clearance notches or , as I did when putting the black stock and forearm (pump handle) from the 766 on the 2200, just swap the pump handle on the 2200 hardware.

[GreenDragon]

Well, I went ahead and bought a Caldwell chrony and it arrived yesterday. Went to shoot a couple strings to compare my #s to the stock 2100, and I can't get it to read any of my shots. Keep getting a #3 error. Back she goes to Amazon. 

[DanD]

Well, I went ahead and bought a Caldwell chrony and it arrived yesterday. Went to shoot a couple strings to compare my #s to the stock 2100, and I can't get it to read any of my shots. Keep getting a #3 error. Back she goes to Amazon. 

Iirc, a #3 error means the rear sensor isn't reading. It might be worth trying another Caldwell.  Mine is super reliable under the sky and indoors with the light kit.
Good luck!

[avator]

I did a bit of research before I bought my chrono and ended up buying the ProChrono Digital with the usb connection for the laptop. I put a couple Harbor Freight led lights on it and the $2 AA battery adaptor. I'm real happy with it. Had if for about 3 years now.