Crosman 1389 fps

[Dave180]

I've had my 1389 for a long time.  Bought it new from Kmart.   I've done a few mods.  Nothing major.    Won't have to mod the bolt because it doesn't have one.  It has a light spring in the valve and the angle port.  Anyway here are some fps numbers with 7.4g pellets. 

Stock short barrel     10 pumps  550 fps

Long barrel 23.5"      10 pumps  610 fps
                                  15 pumps  661 fps

Nail stuffed piston     10 pumps 645 fps
Long barrel                12 pumps 672 fps
                                  15 pumps 712 fps
                                 

[johnnyfoos]

OK, I'll bite-
"Won't have to mod the bolt because it doesn't have one"
Maybe you could explain that one to us?

[Dave180]

It has a side loader.   Don't know if that helps or hurts the speed but sometimes it smashes the pellets if I'm not paying attention when loading it. 

[Dave180]

I've found the long barrel whips around being on a pistol frame.  So you pick up some speed and then loose some accuracy. 

[johnnyfoos]

"It has a side loader."
Never heard of, Looks like a clip maybe?
"the long barrel whips around being on a pistol frame."
This I know about,
 my 1377 has a 24"
 plus a couple more with the MiniMag FlashLight
Lead Dust catcher on it.
 Seems like it gets banged around a lot
more than my 14.5" 1322 version does.

[moorepower]

Thats close to what my long barrel did. 13" more length and mine was less than 50 fps gain. For "me" not worth it. I want to try a 14.5 which with a TKO, would be plenty long for me.

[Dave180]

I shortened my barrel to 20".  Lost some velocity but the accuracy is much better. 

Only getting 618 fps on 10 pumps.

[Dave180]

I took the gun apart and figured I better figure out what's wrong with this thing since my pumpmaster 760 was kicking it's butt in fps. I sanded the valve nose to match pump cup.  Big mistake.  Fps dropped to 595 fps on 10 pumps.  Put in a washer behind the pump cup.  Got it back to 615 fps.  Tried an o-ring but it wouldn't pressurize.  Decided to get the torch out and see if I could wreck it.    Moved the pivot to compensate for the shaved valve nose.    Removed washer behind pump cup.  Just a stuffed piston with no shims. 

Results:  675 fps on 10 pumps! 


I have new pump cups on order.  Mine is worn out and hissing slightly.  Might even get better.

[Spark Master]

I picked up one of these almost perfect. The stock is &^^&, but I guess if I drill it then put in a nut/bolt it would be fine. I only shot it a few times and it it feels fine.

I would like to get another loading device if anyone can direct me, as crosman made them now can't be bothered. If this gun had the box and instruction manual it would be cherry.  So what simple mods are doable? it is pretty wimpy, but, I bought a pig in poke. I might even consider changing the breach, but I do not think that is doable on these.

ciao

[Dave180]

The part number on the loader is 151A024.  I see it on ebay.  They want 20 bucks for just the seal.   
The original barrel was a kind of a joke.  They drilled into the rifling to mount the front site.  I cut that off but still couldn't get it to group.  Getting a new barrel is easy because you can use any barrel.  Just a small taper past the loader and crown the end if needed.  There is no transfer port hole on the barrel. Just cut that part off of the new barrel.

[Dave180]

I picked up one of these almost perfect. The stock is &^^&, but I guess if I drill it then put in a nut/bolt it would be fine. I only shot it a few times and it it feels fine.

ciao

Mine was loose even after I added the screws.  What you want to do is add a strip of rubber like from a bicycle tube and lay it in the bottom of the stock.  Problem fixed!

[Blutroop]

I was worried originally that it would leak out to much pressure around the loading port, but I just put pressure on the seal by pushing on the barrel while I tighten the barrel set screw and the barrel band. I welded onto a 2100 pump tube to get a long pump and was retaining air after 3 pumps. If your done playing with it I'd be interested in it.

[Dave180]

That sounds interesting.  So you ran the shorter 2100 valve?  I'm not a fan of short valves or big check valves.  It's pretty hard on the linkage.

[Blutroop]

I used a 1389 valve back half opened up and a front half off a second variant 760. (Flat from factory and has the threaded hole for front of pistol grip) I used a oringed plastic piston head for the other side epoxied to a threaded shaft with a nut on it to lock in my adjustment. I could pump it up to 30 and get 4 powerful shots followed by a weak one without pumping

[Dave180]

Wow.  Sounds pretty crazy.

[Dave180]

I put a new rubber pump cup in and the gun is shooting slower now.  Only 639fps on 10 pumps.  So the older one was faster then the new one.  Looks like I just wasted some money.  Maybe they take awhile to break in I hope.   I also picked up a couple of the new crosman plastic pistons.  Interesting that the new pistons are a bit longer then the older ones.

[Dave180]

Tested again today on 7.4 crosman pointed, 20" barrel:
10 pumps 641 fps
12 pumps 675 fps
15 pumps 724 fps

[Dave180]

One thing I noticed is that the barrel sits slightly higher then all the other 13xx models. The barrel band is taller also.  The side loader steel breech is the reason.  Too bad they didn't get it right the first time.  The barrel band has a crack in it.  Maybe crosman still sells the part.

[Dave180]

Decided to glue it with Cyanoacrylate.

[johnnyfoos]

Hey Dave and Blutroop-
"The side loader steel breech"
Could you put up a picture of this maybe?

"The part number on the loader is 151A024"
is that the number for just the clip or the whole side loader @@@?