Author Topic: Crosman 66 Modding. (Read 18703 times))

Dave180 · « **Reply #40 on:** July 27, 2016, 10:33:08 PM »

I have a question about the plastic barrel breech on the 66. Can that be removed or replaced with a new one if it breaks? Seems like it's on there pretty good. How did they attach it? Also, can the aluminum barrel breech on the 2100 be modded/hacked to fit the 66 receiver?

Rivers3Plinker · « **Reply #41 on:** July 28, 2016, 10:50:09 AM »

Quote from: Dave180 on July 27, 2016, 10:33:08 PM

I have a question about the plastic barrel breech on the 66. Can that be removed or replaced with a new one if it breaks? Seems like it's on there pretty good. How did they attach it? Also, can the aluminum barrel breech on the 2100 be modded/hacked to fit the 66 receiver?

I would take a look at the Crosman EVP PDF on the 66 for the parts. Chances are good Crosman sells the parts and they are probably very affordable. Haven't looked into it myself to say for certain but that's where I would start.
Here's the link off the Crosman site for the 2008 to present model 66.
https://support.crosman.com/hc/en-us/article_attachments/201591940/664SB_664GTW_EVP___PL.pdf

rangerfredbob · « **Reply #42 on:** July 28, 2016, 04:52:47 PM »

That little plastic transfer port thing is $1.15 and is just a press fit onto the end of the barrel. it's not hard to remove as I replaced my barrel with a rifled one and reused the stock plastic piece. I took it off by holding the barrel against a wood shelf vertically that has a sharp corner at the top, I slid it against the corner a few times softly, turning it 180* every time to push it off evenly. The end of the barrel is knurled which is why it is hard to get off.

Dave180 · « **Reply #43 on:** July 28, 2016, 07:20:17 PM »

Ok. I get it. I didn't know it was sold separately from the barrel. Thanks.

I did the extended bolt probe! Now to reassemble and try it. Used a 7/64" drill bit. It fits perfectly. I tapered it down once it cleared.

Dave180 · « **Reply #44 on:** July 28, 2016, 08:51:26 PM »

Wow! That was really worth doing!

10 pumps 704 fps
12 pumps 735 fps

I have the brass tubing to put in the valve inlet. That's next.

Dave180 · « **Reply #45 on:** July 28, 2016, 10:28:49 PM »

I had to mod the clip. I didn't account for spring back when cocking the hammer. Works great!

Rob M · « **Reply #46 on:** July 28, 2016, 11:05:58 PM »

653 to 735 fps all on mods sub 5 bux , incredible

Dave180 · « **Reply #47 on:** July 29, 2016, 05:36:02 PM »

Quote from: Rob M on July 28, 2016, 11:05:58 PM

653 to 735 fps all on mods sub 5 bux , incredible

This stuff gets addicting!

I had the larger check valve lying around. I put it in and it was slower. -10 fps. Took it back out, then
put the 1/16" valve inlet brass tubing in. Not enough change to tell if it did anything. I noticed the barrel has a small leak at the plastic part. I glued that up. Just waiting for it to dry.

Rob M · « **Reply #48 on:** July 29, 2016, 05:42:57 PM »

good call.. have u pinned the valve yet?(or waiting to possibly do more valvework) another idea ive seen is stuffing the valve , this works in some cases and others it doesnt. Your basically lowering valve volume to achieve higher pressure

Dave180 · « **Reply #49 on:** July 29, 2016, 05:47:51 PM »

No, I didn't pin the valve. It has a lot of preload from that shim under the pump cup. It might be ok. It would of broke by now if it wasn't. I thought the bigger check valve was stuffing the valve? It didn't like it.

Rob M · « **Reply #50 on:** July 29, 2016, 05:53:11 PM »

hmm. a bigger delrin check seal stem internally? internal added mass is stuffing, adding volume is the opposite.. i probably missed that part.the pinning is a great mod on the 2100, after looking it wont do much in the 66

Rivers3Plinker · « **Reply #51 on:** July 29, 2016, 06:44:48 PM »

Well it's easy to pin the valve and one advantage is it keeps the valve from deflecting under pressure. I wouldn' worry so much about the screw failing but at higher pumps it might start to tilt somewhat. A 90 duro o-ring on it would help too but pinning it would be a safer move.
This 66 mod thread fun to follow but I'm working similar mods on my newly acquired 1377 next. All I've done so far is trigger mods for smoother, lighter pull Not going to hijack - starting my own thread.

rangerfredbob · « **Reply #52 on:** July 29, 2016, 11:12:24 PM »

Dave, just replied to your PM.

With that longer check valve you put in, did you put in the spring that would have went with it? if not, that's why you lost speed because there is more preload on the exhaust valve meaning it probably retained more air than you were before...

Dave180 · « **Reply #53 on:** July 29, 2016, 11:25:59 PM »

I got the message. I'll try some of those things to keep my bolt from blowing back. Thanks.

When I used the longer check valve, instead of using the spring that goes with it, I cut a new one the same length that was lighter.

Dave180 · « **Reply #54 on:** July 30, 2016, 01:50:44 AM »

I guess I'm done modding the 66. I put in a new o-ring with the pump cup which sealed fine this time. Shimmed up the hammerspring a bit, used a piece of rubber to shim the bolt from blowing back. It still blew back though on 12 pumps. The plastic bolt is small diameter and just isn't designed for high power. So I stop pumping at 10 pumps as there are no problems. By the way, I was wearing my safety glasses.

It delivered 726 fps on 10 pumps!!!

Dave180 · « **Reply #55 on:** July 30, 2016, 09:45:05 AM »

One thing I noticed is that the bolt isn't held down by the hammerspring when firing. It just relies on the tiny plastic indent.

2K1TJ · « **Reply #56 on:** July 30, 2016, 11:41:42 AM »

Does the bolt on a 66 have an o-ring? May try adding one if it doesnt.

Dave180 · « **Reply #57 on:** July 30, 2016, 02:04:39 PM »

Quote from: 2K1TJ on July 30, 2016, 11:41:42 AM

Does the bolt on a 66 have an o-ring? May try adding one if it doesnt.

Yes, I put an o-ring on there from the 1377. I just barely grooved the drill bit to get the diameter right.
I think it works pretty good the way it was blowing back. The trigger blew back too stronger then you can hold.

The rubber spacer is worth doing. It's just a piece of fuel line. It makes the action better. Takes the play out too. I'm not sure if the pellet depth is right though. I think it gets pushed into the barrel. Is that ok? By the way, last reading at 12 pumps was 748 fps. It had some air not dumped though.

Rivers3Plinker · « **Reply #58 on:** August 01, 2016, 01:52:56 PM »

Quote from: Dave180 on July 30, 2016, 02:04:39 PM

Quote from: 2K1TJ on July 30, 2016, 11:41:42 AM
Does the bolt on a 66 have an o-ring? May try adding one if it doesnt.
Yes, I put an o-ring on there from the 1377. I just barely grooved the drill bit to get the diameter right.
I think it works pretty good the way it was blowing back. The trigger blew back too stronger then you can hold.
The rubber spacer is worth doing. It's just a piece of fuel line. It makes the action better. Takes the play out too. I'm not sure if the pellet depth is right though. I think it gets pushed into the barrel. Is that ok? By the way, last reading at 12 pumps was 748 fps. It had some air not dumped though.

Exact same problem I had on the MK177. After shooting it a lot for a few months, the catch on the clamshell housing that holds the bolt in the breach while firing was worn out and the bolt would get blown back. That spring action from the bolt was done too. I put rubber under it just like you. That helps but it still gets blown back when firing. The parts are fairly cheap but still...

Dave180 · « **Reply #59 on:** August 01, 2016, 08:04:12 PM »

I saw a guy use a 760 bolt in a 2100 crosman. It must be the same mechanics. Does the hammerspring engage the bolt at the end on the 2100? Or does it leave a gap like the 66? I see people getting 800-900fps on those. What's the difference? Maybe they left a gap because of the clip.

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Crosman 66 Modding.

Author Topic: Crosman 66 Modding. (Read 18703 times))