CP1-M pistol first impressions

[cobalt327]

Kevin, I haven't seen much at all re shot counts, especially for unmodded guns. If I run across anything good I'll post it. And thanks!

[nervoustrigger]

Stan, adjusting the hammer spring preload can definitely be used to tune an O-ring buffer.  The effect isn't quite as dramatic as without an O-ring buffer but still a very useful approach.  I've done it a number of times with good results.
 
For the sake of completeness, an adjustable nose on the hammer is a more versatile way of tuning.  Picture a set screw that you can run in or out to change how far the hammer reaches into the O-ring stack to hit the valve stem.  It's more or less the same effect as fine tuning the height of the O-ring stack by either adding shims or abrading the O-rings.  However that's not really in the cards unless you can make your own hammer because factory hammers are typically heat treated (can't simply drill and tap for a set screw).

So back to adjusting the hammer spring, I'll usually look for a way to make it externally adjustable.  The fact the end cap is drilled and tapped for the stock attachment screw makes it less convenient to do, and since I lucked out with the O-ring buffer, I didn't devote a lot of thought on how to do it.  Before doing anything fancy, you might want to try just adding a couple of flat washers at the end of the spring and see if it has the desired result.  It shouldn't take very many iterations.  Just takes 2 or 3 shots check the velocity, then add or remove washers until you get the speed you want.  They you can move on to running a full cartridge to see how much the shot count has improved compared to stock form.

[nervoustrigger]

Regarding the .22 caliber versus .177, attempting to get the velocity up to anywhere near the .177 will burn through CO2.  Consider this comparison, 450fps for an 8gr .177 represents 3.6fpe.  450fps for a 14.3gr .22 represents 6.4fpe, which is almost 80% more energy.  Think of a 12gr CO2 cartridge as having a finite amount of energy contained inside.  We can't expect 80 shots at 3.6fpe (288fpe total) and the same count at 6.4fpe (512fpe total).
 
With a more modest tune, you can expect a somewhat higher energy total in .22 cal.  It's been a while since I've looked at the numbers but I want to say something like 25% more energy is typical.  So maybe 80 shots at 4.5fpe in .22 cal is feasible, which is a 14.3gr at 375fps.  Again, just a ballpark number.

[WhatUPSbox?]

yes, definitely try the washer/spacer test first, also measure how much the spring is compressed.

I saw this out of the UK, http://www.trrobb.com/SMK_CP1_Co2_target_pistol_Stainless_Steel_Adjustable_Hammer/p1449438_15674579.aspx not sure how just lengthening the nose of hammer without an o-ring buffer does much unless they changed the spring compression.

Your set screw approach makes more sense.

I'd end up making a new end cap

[USAFANG6799]

Instead I accidentally got this one

Interesting because I made the same mistake when I ordered mine for my 2240 way back when.

[cobalt327]

In case anyone's needing them, 50 duro buna O-rings. I haven't found these in silicone but the bunas shouldn't be too far off.

[rrdstarr]

yes, definitely try the washer/spacer test first, also measure how much the spring is compressed.

I saw this out of the UK, http://www.trrobb.com/SMK_CP1_Co2_target_pistol_Stainless_Steel_Adjustable_Hammer/p1449438_15674579.aspx not sure how just lengthening the nose of hammer without an o-ring buffer does much unless they changed the spring compression.

Your set screw approach makes more sense.

I'd end up making a new end cap

TR Robb has a whole buncha parts for the CP1.  Two SS hammer options, Oversize trigger guard, oversize bolt handle, Exhaust valve, transfer ports, Valve body, mainspring guide, and O-ring seal set!  Since I have two guns I am going to try a few parts!

[cobalt327]

TR Robb has a whole buncha parts for the CP1.  Two SS hammer options, Oversize trigger guard, oversize bolt handle, Exhaust valve, transfer ports, Valve body, mainspring guide, and O-ring seal set!  Since I have two guns I am going to try a few parts!

Please post the results-I'd like to hear about these parts, especially the adjustable hammer, valve and TP! BTW, I couldn't find all the parts you mentioned. Is there a link on his site I'm missing?

[rrdstarr]

He has no "search" feature, so I have just these too pages that I found all the CP1 parts on.
http://www.trrobb.com/category/precision%20parts

[cobalt327]

Thanks!

[650cent]

I received this set of springs from Brownells http://www.brownells.com/search/index.htm?k=16070+KIT+1607%2c+50+MINIATURE+SPRINGS&ksubmit=y and found several that work great for trigger sear springs. One was the same size as the original but light gage wire, ended up being too light for my taste although I couldn't cause it to release by itself. The one I ended up using was about an 1' long that I cut down to the factory length, very nice light, crisp release.

Bill

[WhatUPSbox?]

I happen to be in Hobby Lobby today. They have .015" music wire (4, 12" lengths for a buck). The stock sear spring is .020" so I though I'd try winding one. I used a .072" (15  gauge?) finishing nail as a mandrel, cross drilled a small hole to hold the wire, and spun it very slowly with my cordless. I stretched it looser than stock to keep it softer.
The trigger dropped from 2 lbs to about 15 oz, which was what I was looking for for paper punching.

Sometimes you get lucky on the first try.

[cobalt327]

Good job!

[Bob Pratl]

The sear spring is not an easy one to find because of it's small size. If you don't or can't wind one yourself you can use a small spring from a tire valve stem which is about the correct size and lighter. That's what I did and I was able to adjust the trigger pull down to less than 16 oz..

[nervoustrigger]

Due to some renewed chatter about the CP1-M, I decided to do a quick video shooting a Gamo reactive target at 10 meters.  I'm still learning how to shoot a pistol consistently so I'm not trying to say I'm a great shot.  Actually I didn't expect to be able to do this well with a red dot regardless of how good the gun is.  The small paddle looks like nothing even at this distance. 

The sight is a Hammers red dot with 3 dots.  The multiple aim points are nice for longer distances.
http://www.ebay.com/itm/Hammers-Reflex-3-Dot-Crossbow-Red-Dot-Sight-1X30CB-with-Weaver-Rings/171255026935

[Ribbonstone]

Will make more sense once you see it apart.

The large thick brass transfer port sits down into a recess in the VALVE.  It also sits up into a recess in the reciever.  So basicaly, solid brass crosses from inside the valve to inside the reciever, crossing the shear line between valve and air tube.

So long as that chunk of brass is clamped down by the breech, it blocks the valve from any rearward movement (at least until the point that large thick chunk of brass  is sheared/compressed and the breech fails).

[cobalt327]

I clamp the breech to the valve/tube with a padded vise before tightening the small screw that holds the breech on. I haven't heard of failures like on Crosmans but not taking any chances, especially if the TP O-rings are changed or shimmed for a tighter fit.

From Another Airgun Blog:

[Ribbonstone]

My poor old Gamo Knock-Down target.

Old...way before they had interchangeable plates.

But one day, walking though the back parking lot at work, I spotted a big-aze washer.  TUrned out to be a metric big-aze washer, with a 10mm center hold.


So I spot weled it to the face of the old Gamo target and used it at what I thought was a reasonable 20-25 yards for a hole that size.


Mounted to a solid base, doesn't take much to flip the gamo target.  The softer the stake-down/mount, the more energy it takes to flip it, but 6" spiked to hard earth ("splay foot" pattern better than parallel) it will fall from a 4 foot pound hit....not from a 4 foot pound "split".


Yes...I have abused this one over the years (can tell by its cratered nature), even smcaking it with 12ga. loads of #7 1/2 shot on occasion.  Odd thing about that is that it often doesn't fall....think it depends on where the 1st's lead 7 1/2's land...if the fastest 7 1/2's land on the face of the targget, then it kind of "locks-up" the trip system, so the later center hits don't flip it.



Any way, rather than paper, tried my cut down, 5 foot pound, CP1 pistol against this old-dog for a single full 12gr.

Range: 20 yards (by steel tape).
Open sights: (removed the red dot)
Rest: single bag at the front.
59 shots ( you kind of blank-fire one or two off to be sure the 12gr. is popped..only counting the shots with a pellet,)

3 shot check sight-in on the squirrel's head.

56 shots at the center 10mm circle (painted contrasting colors...white and gold in this case, but I'll use any paint I happen to have at hand that contrasts).

I missed flipping the target 5 times/ 51 flips.



I'm not going to worry about the stuby nature of the little critter....it will do what I need doing....in fact, I will refer to it as "Stumpy" in my notes from here on.

[WesBob]

That's great shooting!

[nervoustrigger]

That's just nuts.  Averaging 9 out of 10 shots through a 0.4" hole at 20 yards with open sights.  Wow, well done!

As an aside, I do like that style knockdown target.  But it always bothered me that the kill zone is a gut shot so a while back I fixed it by adding a paddle behind the brain.