Author Topic: Crosman 66 Modding. (Read 18669 times))

Dave180 · « **Reply #60 on:** August 22, 2016, 09:07:28 PM »

Cut back my bolt probe. Pellets are not being pushed into the barrel anymore. It's the correct length now.

Dave180 · « **Reply #61 on:** August 24, 2016, 12:44:17 AM »

Latest reading- 733 fps on 10 pumps 7.4g

Rob M · « **Reply #62 on:** August 24, 2016, 12:48:13 AM »

dave , have u exhausted all options ? flat top and pinning the valve etc?

Dave180 · « **Reply #63 on:** August 24, 2016, 01:02:54 AM »

I haven't exhausted everything. There's always more options out there. I replaced the o-ring again. The plastic piston has slots which make indents into the o-ring. After awhile, the o-ring somehow causes a leak. I think a flat top piston would be great or maybe make a longer piston to get rid of the o-ring and washer under the pump cup.

Rob M · « **Reply #64 on:** August 24, 2016, 01:16:44 AM »

yep, flat topping would bypass those issues .. probably gain u 100 fps too , especially of accompanied by pinning..I also stand by my claim that tightening up the pivot point yeilds gains, ive proven it so people sayin it wont have never tried..

Rob M · « **Reply #65 on:** August 24, 2016, 01:19:33 AM »

Another thing on the older guns that gets really good gains is stuffing the piston with nails and Jb weld ( in the 4 slots because apparently theres a lot of flex in the plastic)

Rob M · « **Reply #66 on:** August 24, 2016, 01:20:48 AM »

http://www.network54.com/Forum/275684/message/1166912292/Here%27s+something+else+you+can+do+with+drill+rod-+Stuffing+the+stock+1377+piston+rod

Dave180 · « **Reply #67 on:** August 24, 2016, 01:31:14 AM »

I did the nail stuffing awhile back. There's a picture of it in here somewhere. Whats impressive is how much the little washer and o-ring under the pump cup does. I took them out today and took a loss of 60 fps. So length is key.

Rob M · « **Reply #68 on:** August 24, 2016, 01:35:09 AM »

okay.. try tightening the pump pivot , it cant hurt thats for sure.. the piston would need to be adjustable to be dialed in for the proper stroke.. seeing as how the valve would also be flat topped leaving a 1/4inch gap from stock lenght./. really simple id suspect , but since no one is mass producing em for the 2100 model series its not like specs are floating around.. i know the valve and piston are slightly different than lets say a 760

Rob M · « **Reply #69 on:** August 24, 2016, 01:36:15 AM »

i gotta go back in ur post and see what the piston looks like

Dave180 · « **Reply #70 on:** August 24, 2016, 07:01:06 AM »

I found a picture with the oring on it. I don't think too many people are doing this trick anymore. They just buy an adjustable one. Since the bolt blows back at 750fps, why bother.

Rivers3Plinker · « **Reply #71 on:** August 24, 2016, 11:59:49 AM »

Quote from: Dave180 on August 24, 2016, 07:01:06 AM

I found a picture with the oring on it. I don't think too many people are doing this trick anymore. They just buy an adjustable one. Since the bolt blows back at 750fps, why bother.

Yep!
Reached the limit of the design parameters for the gun I'd say.
All considered though, it does shoot harder and is more accurate than stock right?
Similar mods to one of my MK-177 and it shoots a lot harder than the stock one. It's louder too, which makes sense.
My boys and I were shooting them a few weeks ago having a blast and you could really tell.
I had the probe tip too long at first too, and could not load pellets initially.

Dave180 · « **Reply #72 on:** August 24, 2016, 12:25:03 PM »

In stock form, the 66 shoots around 625 fps so going to 733 fps is a nice improvement.

Rob M · « **Reply #73 on:** August 24, 2016, 12:49:20 PM »

theres gotta be a mod to stop the bolt blow back , this happens on my co2 crosman m4-177 also, the thing is shooting hot ( like 700 +) I would think a small 6-32 grub screw on the exposed part of the bolt.. the friction along the bolt housing would stop this instantly..

Rob M · « **Reply #74 on:** August 24, 2016, 12:53:29 PM »

So basically behind the finger tab ( cocking knob) a grub screw goes into the traveling bolt that rides along the frame. it either directly runs the side cover ( barely ) or has a small oring on it which does the same.. This will allow the user to percieve almost no additional force , yet arrest the bolt in the forward postion

plinker99 · « **Reply #75 on:** August 27, 2016, 01:31:43 AM »

hi all,
i've been following this thread & finally got something......
for...dave----(Cut back my bolt probe. Pellets are not being pushed into the barrel anymore. It's the correct length now. )....
..i have a 760 that has the same receiver as the 66 and had that same problem a while back. to fix....
1)with a soldering iron, i made the slot for the bolt a 3\16" longer at the back end of the slot. 2)with a soldering iron, i melted off the back end of the bolt so it could go back & use the longer slot. 3) again with a soldering iron, i increases the slot on the bottom of the bolt that pulls on the striker cocking pin.
these 3 mods allows the probe to be longer & still pulls back enough to properly load the pellets.
after doing this most of my pellets loads into the barrel past the transfer port. the one i use the most the crosman pointed hunting 7.4g still did not. so i made a flow thru bolt. here's a link to a post i made..
...http://www.gatewaytoairguns.org/GTA/index.php?topic=48761.msg460291#msg460291

as for the bolt blowing back.... i did some mods for it too. see my reply in the thread http://www.gatewaytoairguns.org/GTA/index.php?topic=113637.msg1090795#new

plinker

Dave180 · « **Reply #76 on:** August 27, 2016, 01:28:47 PM »

Thanks plinker99. Nice mods. I was thinking of filling the slot on the bottom of the bolt to get rid of the gap. But, somehow I don't trust this design for high power. Too much plastic and not beefy enough. Needs more metal parts. I do like the gun though.

Rob M · « **Reply #77 on:** August 27, 2016, 03:17:00 PM »

thats what i like about the 880, the steel chassis.. Is the clamshell flexing on your gun at pump 10 and up?

Dave180 · « **Reply #78 on:** August 27, 2016, 03:51:44 PM »

I pump it with the stock on my thigh so that there's no excessive force on the receiver. There's only 1 bolt holding the stock. Another weak spot. I don't know why they made the transfer port barrel thing plastic. I can see that splitting if overpowered. I also don't care for the bolt which is too small in diameter. I've read of people actually sleeving it with metal tubing to increase strength. Don't know if that would work with a clip. Funny thing is they use the same diameter bolt on the 2100. The 880 has a beefy bolt compared to the crosman's.

Rob M · « **Reply #79 on:** August 27, 2016, 03:58:10 PM »

yep,,, i noticed a bunch of little issues like that on my crosman m4-177 co2 conversion, just soo many weak points , and the bolt blows back hard now that its shooting faster than stock

Thank you to our advertisers!

Crosman 66 Modding.

Author Topic: Crosman 66 Modding. (Read 18669 times))