Canadian Airgun Forum

So I attempted a Longer P17.

I bought one on boxing day for 49.99 with free shipping. It chrony at 396 FPS with Daisy 7.9grn wad cutters. After seeing Huskydude thread and having a 1377 barrel on the bench I was like HMM..

Im no machinist. Just someone willing to try.

So I hacksaw the barrel forward of the transfer port. Using my drill press I put the barrel in it. Stuck a file on the base and lowered the barrel down on it to square it up. Just using my eye to and hand to watch the barrel to see if it wobbles. Then changed to a plate of steel and sand paper to smooth it more and more.

Making a nice square cut.





Then I made a make shift lathe by putting my drill in a vise and making a barrel support from a piece of 1x2 screwed to the bench. Gave me enough support to push down with the files.





Got the barrel turned down.



So having that done, I deburred and polished the barrel face and chamber a bit.

Here where it went down hill.

So I started to drill out the upper for the larger barrel. Everything went great. I thought the barrel had enough room but caught one of the ports on the fake muzzle brake and broke it off.



I must got low blood sugar because I started to shake a bit and dropping it. Because I went to put in pin and cracked the frame.



I figure I try it.. Bandaid it back together. Loaded up same 7.9s I used for a base number. And 421 FPS. 25fps increase over stock. Loaded some 8.2s 395 FPS. I might try the blocking the air intake breech intake mod. See if I get any gains.



Now I'm gathering some parts to fix the frame and ordering another one. To make it cleaner. I think I'm just going to cut the ports off the brake from the get go. Made putting the barrel in on angle to clip in much better. And still having a tight fitting barrel.

I'm not afraid to mess up and admit it.

Sorry to hear about the broken parts. But I don't think it should effect the shooting or accuracy at all.
Glad to see such a gain in FPS by adding a bit to the barrel length.
Now that you have a standard chrony result just for the longer barrel.
It will be interesting to see if there is any gain by filling in the air hole and pulling in air from the breech.
I'm was hoping for an increase in air volume enough to gain a higher FPS...
The other mod I'm now thinking of is playing around with the end of the piston design. Too increase the psi that way.
If I get some time today I'll see if I can get my chrony working. Really is invaluable.
Maybe taking it outside will do the trick.

Having a blued barrel instead of the silver looks good too.

We can rebuild, we got the technology. Pattyfritz sending me a new lower.

But like saying in the PM. Having the louvers removed ( broken off ) made the barrel going in much easier. Its still quite tight. I bet if it was cut straight, it wouldn't be too bad.

Well Ill see about filling the air hole. I never took the internals apart so have no idea where it is.

440 or so FPS wouldn't be bad. If it improves on a 177, should help on a 22.

Might make a new rat gun.

I suddenly think about that, why we use longer barrel, first is to increase accuracy : if not for the barrel itself ( like the LW vs the normal Crosman barrels), the other reason is to have longer distance from the rear sight and the front sight.

The second to have faster FPS.

But for the P17, looks increasing 3 inches barrel length can't help very much in FPS. (20 more FPS is good, but I think not enough...). Should we try to add more? Maybe a 12 inches barrel?! I think for the same power plant, 14 inches or more is too much for the P17.

And accuracy, P17 is outstanding already. Don't know if we can find a way to move the front sight to the muzzle? Add a muzzle brake?!

Just my 2 cents ~

Sent from my LG mobile

_________________
~Plinkers~
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~Target~
HW 30s/35e/97k/40+Extender/P3+Scope/70#CZ200s Laminated@10fpe#AA ProSport-177@12fpe

Well now I can shoot a 8.2 heavier pellet just as fast as a the stock FPS with a 7.9. I don't think I cut off much barrel. 1/4" maybe. So sitting around 9.8", vs the 4.5", which got me 25fps. Problem is longer barrel might drag and lose FPS. Then you run into a issue that might not be able to cock it. Barrel would hit the trigger guard.

If I wasn't going to add a red dot. I would put a crosman muzzle brake with front post on it. I might actually put one on.

Only problem is would need to find a longer 177 barrel, to cut down to 12, unless you want 22 cal.

I think an 20 or so increase in FPS for a 3" barrel increase is not bad!
Now a person would have to have a whole bunch of barrels lengths or start off with a long one (14") and cut off maybe a 1/4" at a time, do a chrony test, cut another 1/4" off, another test etc.. to find out the highest FPS vs barrel length to prove optimal length.
Somewhere there's got to be a correlation between the volume of compressed air in the guns reservoir vs the volume of air behind the pellet before leaving the entire length of the barrel. Sooner or later too much length would start to slow the pellet down.
Variables would be the guns air reservoir volume, reservoir psi and barrel length. Wonder if there is a formula for this or how you could measure the volume...just thinking out loud here....
Edit: And barrel dia. (.177 vs .22) in my case...

I think you could add a lot more length without a problem.

stock FPS will depend on what year and model P-17 you have

_________________
"A candle loses nothing by lighting another candle"

I chrony mine ( fiber sight one ) Said 410 FPS on the clam shell. Out of the box and it avg around 396 FPS with a 7.9 grn.

This is an interesting read. Earlier today I went to the postal outlet and picked up a package with a new P17 and a 10"Crosman 2300 barrel. I was hoping for a 40-50 fps gain with the 3" of additional barrel length. I guess SSP pistols gain a lot less than CO2 pistols.

I was going to thin out the 2300 barrel to the original P17 thickness but leave full thickness from beyond the end of frame. I'm still trying to figure out how to secured the barrel at the end of the frame. Maybe some o-rings? I have also heard of set screws in the plastic frame. Getting the breach end of the barrel into the strap section without damaging the frame ports might be tricky.

Did you just hand drill the small hole in the frame for the fat barrel to slide? 7/16?

There is adding a shim and the blocking the intake. So might get more FPS.

There is 2 areas that look like they were meant for a set screw. I gotta do that on the new P17. Broke it before I did.

Husky said he elongated the opening to get the barrel to go in an angle.

And I just drilled for 7/16. Than you gotta dremel the area in the frame for the barrel. When you open the barrel doesn't hit the frame.

Ill be gathering parts for a attempt #2. That ill be D&T for a setscrew. Ill bore out the opening for the barrel. Then Ill use a very fine knife and cut the ports off, so I can install the barrel and glue it back on. Save me elongating the upper and removing more than I need to.

Next week, I might be picking up another one for parts.

You can mod them to be MSP rather than single stroke. Pistons can also be cut down to give a lot more volume.

_________________
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants." - Thomas Jefferson.

I'm still trying to figure out the best way to secure the front end of the barrel. As was said, an elongated hole and set screws is an option. Other ideas.....

Elongated hole and then use silicone to secure. A good tug should break the silicone hold if you wanted to change things around later.

A smaller diameter barrel from a Crosman 2100 rifle would work too and allow more room at the front end. Possibly an o-ring or two could be used to secure the muzzle end. The o-ring would flex to allow the breach end to pivot into position.

A skinny 2100 barrel could be used with a bushing at the muzzle end. The metal or plastic tube bushing could be slid into position after the barrel is installed. Another bushing might be needed on the breach end to get the barrel thick enough for the breach seal.

A skinny 2100 barrel could be used. First install a thin metal sleeve inside the port area with epoxy. Slide o-rings onto end of barrel to make upon gap between bushing and barrel.

There are a few different options to help secure the barrel to the top body.
In the end I thought it was important to have a adjustable setting. Thus a removable set screw.
It is also important to have the top body hole and barrel tolerance as close as possible. The tighter the fit the better.
If you glue or have an Oring, that would kinda be a one shot deal in regards to the proper pressure of barrel against breech Oring.
If you didn't get it right the first time...you would have to rip it apart and start over.

Agreed. My barrel can shift back and forth a 1/8". But you should be able to close it. Tap at the muzzle, to seat it against the breech seal and open. Then able to tighten the barrel in place.

Having breaking it trying to put the barrel in. Its something you don't want to be doing all the time.

I'm thinking round 2, I'm going to bore it out to 7/16, then use a hobby knife to cut the ports off, install the barrel, then glue it back on.