Mac1 Flat top oringed Piston Head for 130, 760, 1400 & S&W 77A

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Author Topic: Mac1 Flat top oringed Piston Head for 130, 760, 1400 & S&W 77A  (Read 2113 times)

Offline TimmyMac1

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My Oringed piston head fits the Early 130, 140, 137, 760, 147, 1400, 1300 & S&W 77A and any other gun that uses or has switched to the pressed together brass on aluminum flat top Crosman type piston.
On 140, 147, 1400 etc the tube is stamped with an inlet tract. The soft cups now available simply fill up that tough and disallow the guns to intake air at a reasonable rate. Consequently you would need to open a thru hole in the leading edge of the inlet tract. I made these pistons so they could replace the factory piston and alleviate the problem the guns had intaking air when the pump is opened.
With the Soft Cups now available(from aftermarket seal makers) it requires the pump be left open for a few seconds every stroke or the piston will not intake a full gulp of atmosphere each stroke. It makes the guns horribly inconsistent and/or the pumping effort is ridiculously slow.
Further to make the gun unfriendly to hobbiest rework is the need for a very ridgid puller to avoid trashing the piston assembly when piston rebuild is attempted with a questionable puller. Now you can cut the old brass piece off if it isn't already cracked (as so many are) and throw it away along with the aluminum washer and replace those two pieces with the Mac1 Piston head. The piston head has a simple oring groove with a 90 durometer urethane oring and replacement of that oring is a piece of cake. This is the design that Crosman originally used on the 120 and very early 105's but it made too much sense so the bean counters had to make the pisaton a bespoke item to make servicability more (PIA)exclusive.
With my piston head and a little knowledge about how to change a quad seal (without stabbing yourself with a Dental pick) the service of the early model guns just got as easy as the modern ones.
I plan to do a bunch of short and sweet You Tube (How Too) videos on basic service tricks I've learned, gleaned and developed myself over the years. James Brinkley is going to help me do a US FT Owners Manual CD and the Tips and Tricks stuff will come after we finish that.
The Piston Head with 2 orings is $8. Postage is $3. The Piston will be approximately two turns too long once the head has been changed so an adjustment needs to be made accordingly to the length of the piston and/or valve. It will fit a wide variety of early pump guns and can be made to fit many others to make them a simple oring change when a fresh piston is needed. I like doing stuff this way as it was the way back in the Days before planned obsolecence reared its ugly head.
"No Guns Would be a Riot"

Offline rsterne

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Re: Mac1 Flat top oringed Piston Head for 130, 760, 1400 & S&W 77A
« Reply #1 on: August 17, 2012, 01:07:47 PM »
Nice to see this piston design now readily available and at low cost.... The added advantage is reduced headspace and more efficient pumping, with slightly higher (and more consistent) velocities, particularly at the higher pump numbers.... Having to pump slowly on some 140/1400s was, indeed, a PITA....

Bob
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine (Grouse Gun), 2260 PCP Rifle (37 FPE), 2560 PCP Rifle (52 FPE), .22 BAM B-26, .22 BAM B-51, Hatsan AT-4410 Long (70 FPE),
"Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, .308 & .357 unregulated; working on the Mk.III, a .410 shotgun, and .458 cal)

Offline 1377x

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Re: Mac1 Flat top oringed Piston Head for 130, 760, 1400 & S&W 77A
« Reply #2 on: August 17, 2012, 07:52:47 PM »
great news!
this is what i have been waiting for!!
just so i know im reading this right
i can now chuck the head in the trash and replace it with one of your replacement heads
« Last Edit: August 17, 2012, 08:06:39 PM by 1377x »
short list
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Offline TimmyMac1

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Mac1 Flat top picture
« Reply #3 on: August 18, 2012, 11:04:01 AM »
You simply remove cup, brass and aluminum washer and the Mac1 piston head presses in place of those pieces. It could be put back to stock arrangement easily. Changing piston seals is childsplay now. The prss on cup has always been a huge hassle for Hobbiests and this is the best solution for pros and DIY's.
The slow intaking 1400/140's was the puish I needed to get it done. The only problem with my simple solutions is it just gets copied no matter how cheap I do it. So be ready for (I can do that) knockoffs. Mine uses 90 durometer urethane and comes with two orings. The best solution was also the easiest so go figure who will be the first ME TOO Flat top head maker.
You saw it at Mac1 first. This head will be used on a flat top for the current gun soon. I have to make two more parts to do that. The old piston and the old guide. That will be a while yet as I have too much on my plate right now.
"No Guns Would be a Riot"

Offline 1377x

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Re: Mac1 Flat top oringed Piston Head for 130, 760, 1400 & S&W 77A
« Reply #4 on: August 18, 2012, 05:37:04 PM »
i get it now!
its $11 to my door
how do i order?
i want to order "factory" direct :)
then i know its not a knockoff ;)
short list
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Offline TimmyMac1

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Contact Info
« Reply #5 on: August 19, 2012, 10:28:25 AM »
310-327-3582 Landline Mac1 Shop
I Phone /Voicemail 310-327-3581
orders email is mac1airgun@gmail.com
website is mac1airgun.com but it is info only(old)

Thanks

Tim
"No Guns Would be a Riot"

Offline 1377x

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Re: Mac1 Flat top oringed Piston Head for 130, 760, 1400 & S&W 77A
« Reply #6 on: August 19, 2012, 11:18:57 AM »
thanks!
short list
1) get up!
2) survive!!
3)go to bed!!!

Offline facetjockey

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Re: Mac1 Flat top oringed Piston Head for 130, 760, 1400 & S&W 77A
« Reply #7 on: September 07, 2012, 06:49:12 PM »
Thanks for the comprehensive report. You'll be hearing from me should my efforts fail.
I just finished resealing the quad shuttle.
Here is what I did.  Does it appear to be a sound procedure?


I took a jewelers pointed thin scribe and traced around the juncture between the brass and the steel washer removing minute bits of brass.  I was careful not to remove too much material removing only a very thin line of brass leaving all I could to reseal the washer.  The washer appeared tapered from center to edge. I do not think I removed any steel.  Am I correct?

I filled the cavity with a thick wheel bearing grease paste.
I then used a 3/16" drill with the base flattened.  It is .003-.004" smaller than the hole.
I then placed the flat end into the washer hole and struck it with a small hammer. The washer showed movement on the first strike so I refilled the cavity 3 or 4 times until the washer came completely out.
I replaced the seal, relocated the washer then peened the remaining brass over the washer with that same small hammer. It looks like a factory job to me.

It took me longer to write this than I spend actually working on it.
What do you think?
Dave
  • Averill Park, NY
Crosman 1377c  .177
Crosman 130  .22
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Offline TimmyMac1

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Quad seal
« Reply #8 on: September 10, 2012, 10:40:24 AM »
No machining required. Pick the old one out and slip the new one in. It is a procedure that developed based on my sisters techniques, gleened several decades ago. Donna McMurray did all the valves for all the 760, 140, 1400, and 130 in the late 70's and nobody did more, did it faster or with better reliability. Donna Became a Nurse and stopped getting her hands dirty when she became an RN around the same time I became the owner back in the early 80's.
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