Hacking the CP-2

[George Schmermund]

The CP-2 from Mrodair arrived a couple of days ago and I've had a chance to give it a cursory inspection. So far I've just done a mechanical inspection and switched the 2 barrels in and out and pushed around the rest of the moving parts. I haven't loaded and used the magazines yet, but the single shot pellet tray registers well.

The pistol grip is somewhat awkward for my hand, but the shoulder stock arrangement for converting it to a carbine makes a more comfortable grip. The length of pull with the stock installed is quite short for me. The overall ergonomics seem to be designed for the average Chinese customer. None of these traits are really a negative to me because my plan is to customize the gun to what I want anyway. This is a project gun and the basic foundation appears to be sound.

Most of the action parts have a gritty feel to them, but that's all part of tuning things up. The left-side bolt is desirable in my case. The 'thing?' that screws onto the end of the barrel is very effective. I took it apart and there is an assortment of unusual compartments inside. I think they are for storing extra pellets when you're traveling.

Today's project is to clean the barrels and do some testing from the vise. I'm going to remove the open sights and replace then with a red dot or telescopic sight. I'm curious to see how the CP-2 accuracy compares to the Vigilante carbine build.

There are several tests and experiments that I've been planing to do with this new gun. This should be good year for the test bench!

[dv8eod]

In for following.... 

[Rob M]

subscribed 

[renowntwo]

Can't wait to get more information. Keep us updated

[tejon]

Subscribed...

[Wayne52]

This should really be interesting. 

[George Schmermund]

I had a chance to spend some time with the CP-2 this afternoon. I started with cleaning the longer barrel.  After having spritzed the bore with some Rem Oil, a cleaning patch was pushed through using a marshmallow roasting stick . What I witnessed coming out on the first pass was, well.... unspeakable! I was going to call my wife in to confirm what I was seeing, but thought it would be wiser to just go and get another beer, knowing I'd need a bracer to do the second pass. After the 10th patch I started to see some white corners of the patch coming out and continued for several more passes. They never really came out clean, but I decided to let the pellets finish the job.

Anyhow, It was getting late in the afternoon and I wanted to see what the starting point in accuracy testing was going be. Some preliminary shots were done in the shop using the vise and the results were nominal at 15 feet. I decided to take the gun out to the back patio and test it at 30 feet. It was probably not the best choice for doing the test seeing how we're in the dead of winter here in San Diego and the temperature by late afternoon had plummeted to a brutal 64º F. I ventured to give it a try anyway and went back inside for my mittens. I couldn't find them so I moved everything back to the shop. At that point my wife insisted that I have a couple snifters of brandy to return some color to my visage. That sort of wrapped up the testing for today. I'll give it another go tomorrow.

[Rob M]

lol, this week there is an aftermarket trigger being released that will have the trigger at 1lb a few ounces.. made by a nasa scientist not to be mentioned here.

[George Schmermund]

After taking a few shots back in the shop with the short barrel in the vise there was nothing special about the results. The group of five shots was in the 1/2" range, but the target was only 15' away. This is a .22 cal version of the CP-2. I removed the barrel to clean it and got the same grossness as was in the longer barrel. The photo is of the muzzle. Obviously there are some burrs that snagged the patch material. The machining, as can be seen, is certainly not any better than the sample of the Crosman Vigilante barrel 'out of the box'.

I'm disappointed in the image quality. I guess it's time to go back to focus stacking. I just wanted to represent the view of an 'out of the box' CP-2 barrel. This is where I'll start the muzzle treatments.   

[George Schmermund]

The short CP-2 barrel was going to start with just the muzzle fix and then be tested before doing the breech. After taking a look down the breech end with the borescope it became clear that just doing the muzzle was not going to be easy to evaluate alone. The machining at the breech is as horrific as the muzzle. Maybe even worse. As long as the barrel was out loose I decided to push a few pellets through by hand to see how what I saw with the scope would effect the smoothness of pellet loading in general.

I was thinking about setting up a load cell experiment to get some numbers to evaluate the before and after effects of redoing the machining. After viewing the breech and pushing some pellets by hand I decided that it wasn't worth the trouble at this point. The situation was too deplorable not to just address the problems and move on to do the shooting tests.

I recommend that anyone interested in experiencing what I'm talking about (if you own a CP-1 or CP-2 airgun) to remove the barrel and try pushing a pellet of your choice down the barrel from the breech. There are a series of resistance steps that will be met as you push. With the Barrel free from having to be loaded by the bolt probe the pellet should just drop into the barrel. This avoids the shearing effect that is usually felt as the pellet is forced into the breech during normal loading. This shearing can be seen on the sides of pellets when they are carefully and safely captured and examined after the pellet is normally fired. I attribute this shearing of the pellet on loading as the result of an insufficient entry slope.

Anyhow, the first big resistance when hand pushing will be just getting the pellet's skirt into the breech. The second resistance will be felt when the pellet drags past all of the burrs left in the grooves and lands of the rifling by the rough edges of the transfer port. The third big resistance step will be when the pellet finally gets pushed into the actual barrel's bore diameter.

I certainly wouldn't expect there to be no resistance in this process of loading a pellet, but I'm confident that the process can be made a lot smoother with some corrective machining operations.

My goal now is to rework the short barrel using the grinding and polishing techniques with the lathe and Dremel tool setup that was used to greatly improve the performance of the Vigilante barrels. The choke will be a little tricky due to the muzzle threads, but this can be dealt with when we get that far.

The CP-2 is now everything that I was hoping for in a project airgun. I think that just about everything important to it's performance can be improved with a little attention to details.

[Rob M]

sounds interesting.. the barrel will be quite the challenge reaching in there far enough and straight enough to properly deburr.. looking forward to pics   

[Wayne52]

I sure do like the looks of the old school rifling that's used in all the SPA guns.  It's hard to beat something that's been time tested in the powder burners for many decades.  I never was a fan of the micro groove.

[George Schmermund]

I was going to just jump right into the breech machining and report my impression of improvements in loading pellets. I then decided that just doing that was sorta cheating and not doing any of the measurements that I got the gun for in the first place. Actually, I got pretty excited about offering up numbers instead of opinions because it's such an easy measurement to make.

The photos are of the lathe method of doing the pellet pushing that was also used in the Vigilante hack. I'll get the measurements done tomorrow and report back.

[George Schmermund]

I did a couple of quick tests pushing RWS wadcutters. The screen shot shows the 3 resistance points that the pellet encounters when being loaded. The full screen pressure value is 12 lbs. I'll try to get in some more measurements later if I get the time.

[Rob M]

that's a lot of resistance for just the rifling ( 10 lbs or so

[George Schmermund]

I did a little more push testing and there may be some good information here. The last post was what the RWS wadcutters looked like. In that post the photo showed the 3 peaks that were readily detected just by hand pushing. The scope showed more detail about the three major peaks. Each large peak was proceeded by a smaller peak. The smaller peaks are the head meeting the resistance followed by the large skirt peak. The trailing resistance after the last peak is the whole pellet engaged with the rifling. The rifling is obviously rough.

The photos here show what different pellets look like in the same setup. The first photo is a Crosman wadcutter. The 2nd one is a Crosman super dome. The 3rd one is a Crosman hollow point. There are only 2 distinct peaks with these pellets. There are virtually no small peaks in front of the larger peaks. This indicates that the heads are not engaging.

This may explain some things about why many guns are fussy about what they can shoot well. Without a choke at the muzzle some pellet heads just can't engage well with the rifling when they leave the muzzle. This is all speculation at this point, but I think it it's worth considering. I offer it up for your own speculation.

 

[George Schmermund]

Here's another photo of the 8" barrel. Still not so good for detail, but I wanted to get something for the 'before' regrinding and polishing treatment on the lathe. The microscope detail is much better without the camera. Notice that the machining burr is pushed up into the groves. This barrel will undoubtedly be much more accurate with a new crown.

[Wayne52]

George you can sure tell that they've cut the corners they can by that closeup of the barrel.  I like the brass screw method with some lapping compound, it really cleans up those rough cuts like that.

[George Schmermund]

There was a question about how to reach far enough in to grind and polish the deeper areas of the breach. This is the method I use for most barrel treatments. The tool is a Temo 4mm green rubber burr. The final polishing is done using traditional methods.

[George Schmermund]

Please disregard this post.