Canadian Airgun Forum

I found some seals for my old .177cal Crosman 38T so it's back running again. I have some extra parts so was able to compare some velocity numbers between barrel lengths. To get top velocity I find it best to reduce the cylinder gap as much as possible without binding the rotation.

I already had a 10" Crosman 2300T barrel from an abandoned project and the barrel was just sitting collecting dust. Forum member Ricksplace cut off the TP, put a fresh taper on the forcing cone, cut a nice crown, and reduced the OD to fit the 38T shrouds. Handy guy to have as a shooting buddy!!!

I spent some time polishing the pellet lead and cleaning up the bore with JB Paste and jeweler's rouge. The lands look nice but the grooves are a bit dark but still shaped okay. I definitely wouldn't spend the money on a Lothar Wather barrel for this revolver.

Being compulsive like I am, I installed the 9.3" 2300T barrel and tested for accuracy and velocity. I switched barrels many times, adjusted cylinder gaps and recorded the numbers for 8 grain H&N Sport pellets. After I was content with the velocity numbers I clamped the pistol in my Black & Decker Workmate and shots some 10M groups (6 shot each). If summer was still here I would be checking 20 and 30 yard groups as well.

VELOCITY TESTS - with 8gr pellet
3.8" barrel = 365-370 fps
6" barrel = 425-430 fps
9.3" barrel = 450-455 fps

Notes: The velocity increases by 30fps per inch when going from the 3.8" to 6" barrel. However, it only gains 8fps per inch when going from the 6" to 9.3" barrel. The 38T has a small valve volume so doesn't seem to benefit much when going beyond the 6" barrel. Crosman seems to have balanced the valve with the 6" barrel length. I won't be hogging out the soft alloy valve interior or bumping up the hammer spring in this old classic pistol.

9.3" barrel on .177cal Crosman 38T

ACCURACY - at 10 metres
First set of groups
H&N Sport = 10 shots into 0.76" ctc
H&N FTT = 6 shots into 0.78" ctc
H&N Finale Match = 6 shots into 0.86" ctc

Second set of groups - 6 shots each
H&N Sport = 0.84, 0.67, 0.56"
H&N FTT = 0.52, 0.66, 1.05"
RWS Hobby = 1.05, 0.97, 0.59"

Notes: The pistol shot 1" or better for all groups. The overall average for the 12 groups was 0.78" ctc. I'll likely test some Crosman pellets and a few others soon.

More pics ...

For sure test the crosman wad cutter or better the pointed one. This 2 give me the smaller group from my homebrew 2300t . I try the crosman 2300t barrel and the lothar walther and both love the crosman, the lw just give smaller group.

Velocity is adjust around 450-460 fps

_________________
Uramex peacemaker
2240 custom
2300 custom
Slavia 630
Daisy 853c
Crosman 422
Beeman p-17
TAU 7
2200 magnum

Those are really tight groups. Not too shabby for a 40+ year old pistol! 450fps with a heavy (for a pistol) pellet is great. My P17 won't do that. Takes a little longer for 6 shots too. How many shots per bulb did you tell me you got? My 38T in .22 gets about 45-50 (which I thought was pretty good). Did you run the light 7gr hobbies through your chrony?

_________________
Theory is when you know how something works, but it doesn't.
Practice is when something works, but you don't know why.
In my shop, Theory and Practice are combined!
Nothing works and I don't know why.

Two lathes and too many projects

The .177cal 38T is currently getting over 60 shots per bulb. I counted the shots on the bulb that I tested accuracy and ended up with 67 shots before POI dropped and the muzzle report changed. The 7gr Hobby gave 470fps at 20 to 21C temp.

Nice work on the project. Good numbers too.
If you're looking for more valve volume, you can take that spacer that the spring sits Inside, and Swiss cheese it.
Sounds like you're pretty good for velocity regardless.

I saw Leonardj did an extended barrel shroud for one of these, looks pretty sweet.

The long barrel .177cal 38T got a bit of a facelift for Christmas. Ricksplace trimmed down the barrel OD and made me a fake brake for style. I transferred the barrel assembly to my red dot frame. The new Crosman 38T Magnum looks pretty slick.

Very slick nice to see projects on these old pistols ....

_________________
VE7SHM//VE7ZJ

Moderator