Sunday, June 13, 2010

Converting A B.S. Super Streak With A Nitro Piston

These pictures were taken over the course of 2 weeks and during different phases of fabrication and assemblage, using two different Super Streak air rifles, both of which were in .22 caliber. Once I had the guns apart, I deburred the receiver tube and thoroughly cleaned it out. Then it was to the shop to get the internal parts modified and a new one made. I ordered J. Maccari seals before I did anything and once they arrived, the fun began. At the shop,

the spring guide rod needed to come out from inside of the Piston Assembly, all the way flush to the backside of the top hat, so that the inner spring guide sleeve could be reused.

Here is the piston assembly minus the internal spring guide rod and before a new seal went on.

Then the back spring guide was cut where the flat part ends and the round part begins. There are two variations of this back spring guide - one has two flat surfaces on opposite sides with one flat surface closer to the stock link pin threaded hole than the other. This flat surface closest to the threaded hole is where you want to cut. When you cut this part, it will expose a hole where the ram rod will go through and where you will seat the new rear ram rod guide. Since there was no longer a spring, this part merely served to attach the stock link pin. A new rear ram rod guide was needed, so I made one:

Using a 1/2" diameter x 2-1/2" long hex bolt, I put it into a heavy duty drill press and turned down the hex head with a file until it fit into the receiver tube end cap,

and then a recess was drilled out the center about 1/16" deep to receive the gas ram's ram rod end.

Here, the modified back spring guide, which I will now call the "stock link pin block" has the rear ram rod guide inserted into it. Notice that I cut the hex bolt to the exact length where it wouldn't interfere with the stock link pin when it is screwed in to hold down the trigger assembly.

Here is the assembled nitro piston with masking tape shimming around the body to fit snugly inside the inner guide sleeve (that used to keep the spring straight when it was compressed). A 3/4" dia. brass washer was also turned down to 47/64" and was installed between the nitro piston body's end and the inner guide sleeve for uniform pressure to the top hat.

Here is the rear ram rod guide sitting perfectly inside the receiver tube's screw-on end cap,

The assembled powerplant with a new Tesla seal, a nitro piston inside the inner sleeve inside the piston assembly, with the ram rod through the stock link pin block and the rear ram rod guide sitting inside the receiver tube rear end cap. Assembly was straightforward: carefully insert the piston assembly without damaging the piston seal; push entire assembly into the receiver tube completely; insert stock link pin block (with the cut side towards the inside) and install the trigger & stock link pin using some blue loctite; then install the rear ram rod guide and receiver tube end cap carefully and tighten it down. Make sure the bear trap lever is properly reinstalled and then reinstall the stock, using blue loctite on the 3 stock screws.

Oh, and if you hadn't already done so, get yourself a GTX trigger from Airguns of Arizona (http://www.airgunsofarizona.com/GTX.htm) and replace the crappy stock trigger before you reinstall the stock.

After all was said and done, the gun was shot through the chronograph. With 14.3 grain pellets, it was averaging 905 fps, and accuracy to 35 yards was much improved with pellets dancing all around a nickel-sized bullseye. All the movements associated with a spring were gone and all you felt and heard was the solid thump of the nitro piston. And as the guns were being shot, points of impact were going up, as I suspect the pellets were shooting faster due to the parts meshing together better.

Needless to say, both of my friends were ecstatic with their much-improved Super Streak rifles, which they used to call The Beast, because of the way it used to shoot. The beasts have now been tamed. Let's see now if they can pick off starlings at 40 yards with their Nitro Piston Super Streaks, like I was doing with my Theoben-upgraded .22 cal. Gamo CFX.

So, there you have it. A complete conversion of a Benjamin Sheridan Super Streak to a Nitro Piston air rifle. I have to give a lot of credit to David Slade of Airgunwerks.com, Tom Gore of VortekProducts.com, James Maccari of AirRifleHeadquarters.com and Steve Woodward, inventor of the GTX trigger, without whom, none of this conversion would have been possible. Thanks, guys.

**Edit**
Disclaimer: I take no responsibility for any injury or death, to anyone who attempts to do what I have done in this conversion or any future conversion that I may post. Anyone following my instructions do so at his/her own risk. Modifying your air gun most likely will void the warranty and the user assumes the risks inherent in any modifications to his/her air gun.

9 comments:

  1. Hi there... I'm one of the lucky two to have had Orangeneck convert my Super Streak to a gas piston. The rifle pictured is mine and has a Leapers 3-9x40 AO scope mounted on it. The spring tore up the Centerpoint 4-16x40.
    With no spring torque, the shot groupings are much improved. No more 'double recoil' or twisting feeling. It's a real pleasure to shoot.
    If you can, do the conversion. And if you feel you can't, by all means, contact Orangeneck and see if he can do it for you. It'd be the best investment you could make for this rifle!

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  3. I also own the Super Streak 0.22, and so in love with your courage to modify the gun with the new nitro piston. I'm still researching it fully before modifying, beside lubing it with the Lubriplate Heavy Gear tar to quiet the spring vibration down. It only reduce the total vibration by 40%, but, reduced the noise by 60%, but still retaining the power to deliver the 18 grain at 600 to 650 fps. I want that noise reduce to at least 70%, and the vibration gone, and increase on the total delivery power to send that 18 grain to 900+ fps.

    Just a few idiotic question, but did you drill/dremel the spring guide out of the piston assembly? or is there a way to remove the spring guide out of the piston assembly?

    Why debur the spring chamber, since the nitro piston fits inside the piston assembly so nicely?

    Why drill that lock pin block, since it acts as the primary safety measure to prevent the power plant from blowing backwards towards the user? The end cap is the 2nd security measure to reinforce the power plant from breaking through.

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    1. You can easily convert your Super Streak now using Benjamin Trail NPXL parts. I did not have these parts available to me when I fabricated and modified parts for the gun.

      I did have to drill out the spring guide inside the piston assembly, as it was cast/machined as part of the top hat.

      Deburring the piston chamber prevents gouges in the new Maccari piston seal when the piston assembly is reinserted into the piston chamber. This creates a nice, tight seal with no possibility for air leakage.

      I had to cut the lock pin block so the piston's ramrod could go through. Otherwise the piston would be too long and you'd never be able to cock it all the way back, and I would have had to use a shorter nitro piston, which would have decreased the power and pellet speed. The end cap insert I machined spreads the force of impact over a larger surface, rather than just having the ramrod focus all its pressure on a small point on the end cap.

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  4. 4888blues here)I converted a Crosman optimist to a nitro piston,It was easy hears what i did.
    I went to Crosman website and ordered parts for there Benjamin nitro trail parts from #1 thru #6 they have a pdf diagrams and part list

    all came to 53.00 / all i had to mod was 2 things the new end piece that the "gas spring" end sits in, the same piece has the locking pin hole and the trigger bolt hole where the end cap slips over at the end. that had to be cut so that it would be flush with the inside end of the receiver/ its about 3/16 to long, no big deal saw all and a fine metal blade cut just fine.
    then the trigger assembly's"large mounting hole" where threaded bolt goes thru to secure the rear of rifle to the stock, that hole had to be enlarged a tad, I used a tapered step bit That's it. works fantastic
    the new parts 1 thru 6 fit perfectly other then i sanded down the "new piston seal" a tad, it was a tad big, honed and cleaned the "new" "piston" inside and out.
    the new rear part that the fat part of the gas spring sits in was also honed inside so that the gas spring would move and turn freely it was tight fit originally
    53 dollars, it was worth buying the same parts 1 thru 6 of the Benjamin trail/ shipping from Crosman was dirt cheep they sent priority mail it took a while about 8 days.
    now the optimist is a cool rifle now its time to sand and refinish the stock in golden pecan my favorite color cause it makes the black metal parts pop when its all done
    "you did a "great job on your rifle".

    the new Crosman piston from the Benjamin parts list, had the divot built into it making my job easy to install the gas spring.

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  5. if you want to employ certain rubber seals or rubber products for your rifle modifications, contact our website at darcoid for recomendations

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  6. Hi was the gas spring one that was designed to be used within a air rifle or was it a normal one from a gas spring/strut supplier.
    Regards jon

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  7. Hello Frndz....
    Great Information! Nice post,it is really very helpful for me.One of the few articles I’ve read today.I’m saying thanks

    Gas springs

    ReplyDelete

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