CP1-M pistol first impressions

[nervoustrigger]

Hi Wayne, you guessed right on the brass screw technique.  The bevel was uniform (just very rough with chatter marks), and the rifling at the muzzle wasn't damaged so I didn't have to do anything more drastic like chop the end.
 
When dressing a crown using this method, the points I like to emphasize are:
1.  Use a light touch.  Applying force to abrade the material more quickly will usually leave a burr.  By light touch I mean when I have the barrel clamped to the bench with the muzzle facing up, I do not press downward with the drill.  Instead I partially support its weight to limit how hard the screw is engaged against the crown.
2.  Orbit the drill in a somewhat random manner.  Attempting to hold the drill stationary will produce an uneven bevel.  Figure 8 movements tend to work well.
3.  Periodically switch the drill between clockwise and counterclockwise rotation.  Not strictly necessary if you finish up with a very fine abrasive but it's easy to do so I see no reason to skip it.
4.  When you think you are done, inspect with a magnifying glass or jeweler's loupe.  I like 5x but as little as 3x will suffice.  You want to see a very crisp cog-like appearance at the end of the bore.
5.  Verify there is no burr when you are done.  For me at least, pushing a couple of pellets through is a far more reliable way to check than using a cotton swab.  There should be absolutely no increase in resistance when the head of the pellet reaches the muzzle.  Naturally, it's a little harder to distinguish when dealing with choked barrels but usually the choke is long enough that I can develop a sense of how hard I was pushing to feed it through the constriction versus how it feels just as the head is about to emerge into the world.
 
I hope this helps!

[flyingmachine]

my .22 cp1-m just arrived today.  It definitely need some tuning as each shot is accompanied by a huge puff of CO2 and I'm only getting about 24 shots before a noticeable drop in POI.  At the current state, the noise level is not garage friendly.  The crown is not quite as mangled as Jason's but I think I will give the brass screw trick a try. 

[imadunatic]

Ok. I am 100% convinced that the CP1M (at least the current batch) suffers miserably from hammer bounce. I just ran this string off of mine with a lightweight (Full MDS Hammer, I'm guessing 15 grams) and a heavy (8lb) spring with about .050" of negative preload. Temp is 53 degrees in the basement right now, and this was shot using 7.3gr CPHP because I'm running low on JSB and AA 8.4gr.



This to me, is concrete proof that we need to figure out a way to fit an internal SSG with the stock spring and hammer and get our shot counts into the hundred-ish range. Mine was getting a little hard to cock and latch towards the end, and I suspect that the MDS hammer is not holding up to the scraping it's most likely taking from the seer on every shot(as predicted). I think the stock hammer would be fine if we can just get an SSG in there....

Oh my.... 

Edit: I usually draw the line at the first shot below 300 with my pistols, which means for this run, even with 11 shots counting for nothing, it made 307 FPE in 127 shots, and shooting it until the last pellet rolled out the barrel it made 316 FPE in 137 shots.

If I extrapolate the shots I didn't count during tuning (which were blasting gas!!) and use the average, that is 342 FPE above 300 FPS and 350 FPE for 137 shots. That is much much closer to what I expect out of CO2 cartridge on a 177 at this power level.

Edit 2: Also, My "plateau" if you will was 467 FPS during my spring tuning, which is what it was before I added the shim to the transfer port to try and seal it up better, so I'm thinking even though the length and diameter of the transfer port/o-rings, it wasn't leaking that much out of the transfer port. I still haven't powdered it to check for leaks, so there could be something else hindering my FPS (besides the 53 degree temps).

[nervoustrigger]

Nice work there, Kevin.  That's looking very promising. 

If I can find a suitable hardware, I'm planning to fashion an SSG and see how it goes.  I'll share pictures and the results.

BTW if you used 7.3gr for your FPE calculations, you shortchanged yourself a bit.  CPHP are 7.9gr.

[dv8eod]

If it'll help, my belief is there was roughly 3/16" of play in the hammer. I didn't have to stretch very much to get the spring to hold the hammer against the valve stem. Bear in mind, I'm just guessing here, but might give you a good starting point. I definitely think it would benefit from an ssg or similar, especially in .22.

[imadunatic]

BTW if you used 7.3gr for your FPE calculations, you shortchanged yourself a bit.  CPHP are 7.9gr.

You're exactly right, I did use 7.3 even in my calculations. So my total FPE above 300 FPS was about 370 FPE and total for the string was ~380 FPE.

If it'll help, my belief is there was roughly 3/16" of play in the hammer. I didn't have to stretch very much to get the spring to hold the hammer against the valve stem. Bear in mind, I'm just guessing here, but might give you a good starting point. I definitely think it would benefit from an ssg or similar, especially in .22.

Thanks Terry. That definitely helps.


I think this may be a candidate for a sort of twin spring system (maybe only internally adjustable though). I noticed last night in my brainstorming that the stock spring is counter-wound to every other spring in my collection, and as luck would have it, a stock Crosman 760 pumpmaster spring fits perfectly inside the stock spring (really any 5/16 OD spring fits perfectly inside) and is about 3/8" shorter. As much as I don't want to cut the stock spring (since you can't get parts...  ) I'm thinking of clipping the stock spring until it has about a negative .050" preload (maybe more?), than use a stock 2240 (shorter, but could easily be stretched) or 760 hammer spring to fine tune the power level to what I want.

Ideally, I'd like this to be at 500 FPS with 8.4gr @ 75 degrees for 70-80 shots (which would be 322-380 FPE)

What kind of FPS are the .22 version making?

[grimeszee]

I used an O-ring behind the hammer spring to add a little tension and gain about 30fps. Dropped my shot count from 90 to about 65 per cart.

[nervoustrigger]

Just a quick update on mine.  No efficiency mods yet but I stripped it down last weekend, deburred and polished up the things that count and recrowned the barrel.  Work and family have been keeping me busy but I had a little time Thursday night to get it reassembled and managed to get some time yesterday after lawn work to sight it in and try it out. 

It took me a little longer than I wanted to get the red dot resighted because the adjustment locking screws tend to shift the POI so I had to creep up on the final adjustment.  Afterwards though, hitting the spoon spinners at 10 yards with my hands braced on my knee quickly became boring.  Offhand went pretty much the same way...missed some but could always call it when the trigger broke. 

So I went back to my table at 25 yards and put a few shots on paper to confirm that yes, the combination of high sight line and 10yd zero has it hitting high at 25yds.   With that in mind, I thought it would be a fun challenge to engage the spoons from this distance.   Definitely more of a challenge even with the advantage of bracing my hands on the table.  I was averaging something like 2 for 5 at first but got it up closer to 3 or 4 after some practice.

So then I eyeballed the rat spinner hanging out at 43 yards.  Oh, what the heck.  I guesstimated the holdover and sent the first shot over it.  Lowered my POA for the second shot but sent it too high as well.  Another adjustment and the 3rd shot sent back a satisfying ding! sound.  Pretty soon I was hitting it well more than missing it.  Granted, it's much larger than the spoons but it put a big smile on my face to ring it 3 times in a row with a pistol and red dot lobbing cheap wadcutters around 500fps. 

I have never done much pistol shooting.  Normally I'm shooting rifles with at least 9x magnification and much flatter trajectory.  To be honest, I was skeptical that could enjoy such an imprecise sight but once I adjusted my expectations, it's actually a lot of fun

[dv8eod]

What's really neat shooting like that, is you learn how to adjust fire with anything that has open sights. When I was 8-9 years old, my only gun was the Daisy 102, and I picked up on the technique pretty quick. It didn't take long to figure out it worked with all types of guns. If you can see the trajectory, corrections can be made on the fly.

[650cent]

Did anyone's else crown look like it was done with a lava rock?  Fortunately the rifling looks pretty good once it is given an opportunity to show itself:

Jason how did you go about doing the recrowning job on that one?  I've never personally done a crown job myself but I see how a lot do it with the brass screw trick.

Newby here, what is the brass screw trick, I understand about recrowning the barrel but not with a brass screw.

Bill

[imadunatic]

Newby here, what is the brass screw trick, I understand about recrowning the barrel but not with a brass screw.

Bill

Bill, up at the top of this page... http://www.gatewaytoairguns.org/GTA/index.php?topic=124266.msg1216506#msg1216506

Also, youtube (for the basics)

[rrdstarr]

Just a quick update on mine.  No efficiency mods yet but I stripped it down last weekend, deburred and polished up the things that count and recrowned the barrel.  Work and family have been keeping me busy but I had a little time Thursday night to get it reassembled and managed to get some time yesterday after lawn work to sight it in and try it out. 

It took me a little longer than I wanted to get the red dot resighted because the adjustment locking screws tend to shift the POI so I had to creep up on the final adjustment.  Afterwards though, hitting the spoon spinners at 10 yards with my hands braced on my knee quickly became boring.  Offhand went pretty much the same way...missed some but could always call it when the trigger broke. 

So I went back to my table at 25 yards and put a few shots on paper to confirm that yes, the combination of high sight line and 10yd zero has it hitting high at 25yds.   With that in mind, I thought it would be a fun challenge to engage the spoons from this distance.   Definitely more of a challenge even with the advantage of bracing my hands on the table.  I was averaging something like 2 for 5 at first but got it up closer to 3 or 4 after some practice.

So then I eyeballed the rat spinner hanging out at 43 yards.  Oh, what the heck.  I guesstimated the holdover and sent the first shot over it.  Lowered my POA for the second shot but sent it too high as well.  Another adjustment and the 3rd shot sent back a satisfying ding! sound.  Pretty soon I was hitting it well more than missing it.  Granted, it's much larger than the spoons but it put a big smile on my face to ring it 3 times in a row with a pistol and red dot lobbing cheap wadcutters around 500fps. 

I have never done much pistol shooting.  Normally I'm shooting rifles with at least 9x magnification and much flatter trajectory.  To be honest, I was skeptical that could enjoy such an imprecise sight but once I adjusted my expectations, it's actually a lot of fun

You might want to see if you can find some old Elmer Keith books on Pistol shooting.  He was person responsible for getting the .357, .41 and .44 S&W Magnum cartridge up and running.  He could shoot as far as 600 yds and hit his target everytime.  Lots of good books written by him.  Worth making the time to read if your a big game hunter or handgun shooter.  I might have a book of his in my gunsmithing library to loan.

[Bob Pratl]

I ordered one last Friday morning, in .22 caliper, and I received it this afternoon. My first impression is that it is extremely well built and the machining is above par. It is the first Chinese piece that I am very pleased with after spending a lot on money on a new Chinese lathe and mill that I had to re-machine 80% of it to get it within specs. My only con is that the trigger needs some polishing and adjustments to get it to my liking which I do not see as a problem. After an initial disassembly, inspection and clean up I shot 20 pellets through it which grouped great and fired smoothly.
Deffently a great fun piece and well worth the $89.00. This weekend I will put it through it's paces. Bob

[650cent]

Got my CP1-M today, pulled the barrel and run a brush and a few patches down the bore, it was kind of dirty. Noticed its shooting about an inch high at 10 yards. What size shim are you guys installing under the front sight to get the groups down? I have the rear sight screwed all the way down. Overall I ready like this pistol, its going to be a lot of fun in the back yard.

Bill

[imadunatic]

Well, I'm giving up on the lightweight hammer. I just can't get what I would call an "acceptable" cocking force with such a lightweight hammer.

I can get it to shoot well, and the shot cycle is smooth (love the MDS hammers) and the shot count is astronomical, but the ergonomics of it are terrible even with the extended bolt handle (2 fingers wide) I made the other day. 

I've tossed around the idea of a steel-MDS hybrid hammer and may pursue that, but in the meantime I've decided to venture down the fully internal SSG path and see what I can come up with there using the stock hammer. I need to measure the hammer stroke, but this is what I'm thinking:





I tried the BSTALEY (through the hammer) SSG version with the lightweight hammer, but it actually took even more hammer spring force than the short stiff version I was able to get 100+ shots out of. Since I can't just call up and order a spare hammer, I've been holding out on cutting into the stock hammer (though I suppose I could machine an all steel replacement if needed).

I plan to measure everything up tonight and hopefully have a working prototype tomorrow afternoon.

On a side note, has anyone found any tricks to making the magazines load a little easier? I chamfered and polished the breech where the pellet enters from the magazine, but I haven't been in the magazines yet. I have 2 that feed awesome, one that is almost useless so I need to pull it apart and see if I can give it any love. Thought maybe someone else stumbled on something for tuning these mags that would point me in the right direction.

[ScarletFire186304]

my .22 cp1-m just arrived today.  It definitely need some tuning as each shot is accompanied by a huge puff of CO2 and I'm only getting about 24 shots before a noticeable drop in POI.  At the current state, the noise level is not garage friendly.  The crown is not quite as mangled as Jason's but I think I will give the brass screw trick a try.

yeah, mine is doing the same thing.

any suggestions.

haven't taken anything apart yet. still waiting for o-rings from the O-ring store (back ordered).

as always , thanks

Bob

[imadunatic]

haven't taken anything apart yet. still waiting for o-rings from the O-ring store (back ordered).

The 2x6 O-rings? Apparently I cleaned them out... website said ~19000 in stock, but then they sent me an email about the backorder so I told them I'd just take what they had as order in full. Haven't counted them, but I probably got the last.... 

On a brighter note, I didn't actually destroy any of mine during disassembly. Was worried about the barrel o-rings, but they seemed to survive just fine. I do plan on changing them out during the next teardown though.

[ScarletFire186304]

yeah, i can look inside the breach and see bits and pieces of bbl.  o-ring in there.
seems like having a few around was probably a good thing and shipping is the same for all of them vs. a few.
thanks,   bob   

[Bob Pratl]

I just did the recommended mods on me new CP-1M such as re-crown, polish hammer, polish tube, trigger sear sides and contact points, trigger set screw,  adjusted trigger and slight Moly lube all contact points. Deffently smoother cocking and crisper trigger pull. Presently waiting for a 2x20 BSA scope so that I can finish testing as we have been getting warmer weather on the East coast. Next mods, modify grip for better hold and fabricate a full shroud with baffles for more quiet backyard time. Does anyone have a list of all of the O-Ring sizes, as I failed to measure them before I re-assembled it?  Bob

[imadunatic]

Does anyone have a list of all of the O-Ring sizes, as I failed to measure them before I re-assembled it?  Bob

Bob,

Jason listed them here: http://www.gatewaytoairguns.org/GTA/index.php?topic=124266.msg1214042#msg1214042

Theoringstore.com is backordered on one of these for another day or 2.