Disassembling & Reassembling Precihole Air Rifle

[GNV]

This is a photo illustrated guide to dissemble a Precihole SX-100 Air Gun to its components form and reassembling it.

Tools Needed:

1. Large Flat Headed Screw Driver.
2. Different Sized Allen Keys. I don't know the exact sizes as I already have them in my tool kits in my home workshop.
3. Spring Compressor.

First remove the action from the stock by removing the two screws in the fore end and one behind the trigger guard.

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CAUTION: Don't try to cock the rifle when the action is out of the stock. Trying to do that would damage the cocking slot in the receiver tube.

Remove the cocking lever out of the cocking slot by lifting it out.

Now break the barrel and unscrew the grub screw in the breech block jaw as shown in the photo using the correct sized allen key.

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Now unscrew the barrel hinge screw using a large flat headed screw driver and remove the barrle along with the two thin breech block washers.

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It is not necessary to disassemble the trigger to decompress the spring. But I am continuing with Trigger Disassembly as disassembling and assembling the trigger is very easy.

Study the trigger drawing so kindly provided by Mr.Prateek.

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Loosen the trigger adjusting spring plunger's locking nut and unscrew the spring plunger.

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Unscrew the trigger blade screw using an allen key and remove the trigger blade. However this is completely unnecessary.

.........continued

[GNV]

To disassemble the trigger simply push out all the pins in the trigger housing and shake out all the trigger parts.

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Trigger Parts:

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I think the area shown by the arrow in the below photo and the travel of the ball in the trigger spring plunger determine the trigger second stage travel. But I may be wrong.

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Trigger Safety Lock

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My cheap simple spring compressor

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............... continued.

[GNV]

Now to decompress the spring and take out the piston etc.

Place the receiver tube in the spring compressor and apply slight pressure on the rear end cap and push out the cross pin.

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Now if you unwind the compressor screw the spring would push the end cap out. But in my ORION the end cap was stuck and wouldn't come out.

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I had to slightly open the compressor screw a few mm out at a time and insert a screw driver through the trigger housing and tap out the end plug until it starts to come out freely under springs tension.

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Use your left hand to hold the action in the compressor while unwinding the compressor screw with your right hand.

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Completely decompress the spring and take out the Spring guide, Spring, thrust washers, front spring guide and piston out of the receiver tube.

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...........continued.

[GNV]

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Piston Washer

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Clean all parts using kerosene and degrease them using surgical spirit.

My receiver tube cleaning wooden dowel

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Wrap a tissue towel around a wooden dowel and clean the receiver tube thoroughly. The inside surface of the receiver tube is not completely polished. The entire inner surface is full of small pits like shown in the below photo. May be they were for retaining some moly lubricant in them.

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Now put some moly grease on a tissue napkin wrapped around the wooden dowel and give a thin coat of moly to the entire inner surface of the receiver tube. Don't over do it or the rifle would diesel for a long time.

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Now also apply moly grease to the inner surface of the piston using a wooden dowel and tissue napkin. Also apply moly grease to the outer surface of the piston where it comes into contact with the receiver tubes inner surface and push the piston only into the receiver tube all the way in. It should move smooth and nice inside the receiver tube and you can hear air being compressed when you move the piston to and fro in the compression chamber.

Now is time to assemble the trigger.

I'll post the rest tomorrow morning. Good Night.

[GNV]

Now to assemble the trigger.

If you removed the trigger blade from the bottom sear attach it. Put a little moly in the hole where the spring sits and stick the spring in it.

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Now feed the sear into the trigger housing by holding it by the trigger blade.

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When the rear of the bottom sear is flush with the trigger housing lift it up till the pin holes in them aligns and put the pin in place. Check the trigger spring for proper placement on the small projection inside the trigger housing.

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Place the trigger safety lock in place and push the pin in place

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The upper sear torsion spring has one long arm and one short arm. Holding it by the long arm which pushes the upper sear up like shown in the photo place in the housing and push the pin in.

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[GNV]

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Now feed the upper sear into position as shown

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Holding it in position with left hand, insert your right hand fore finger into the receiver rear end and push the upper sear against the torsion spring upwards and guide the sear into position so that pin holes align and insert the pin.

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[GNV]

Now apply moly grease to front spring guide, Spring, Thrust washers,and spring guide and assemble them together.

You will find the upper sear inside the receiver like shown in the photo.

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Holding the upper sear out of way with left fore finger feed the spring unit into the receiver tube.

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Now place the receiver in the compressor, put end cap in position and compress them in.

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While compressing make sure that holes in the receiver tube end and end plug align properly.

when fully compressed push the cross pin into place.

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[GNV]

You can also remove the piston without disassemble the trigger.

Place the receiver in compressor and remove the cross pin.

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Push the safety to OFF position. Using a screw driver push the upper sear towards the rear.

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Pull the trigger back and lift the upper sear up using a small screw driver.

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Holding the sear in up position decompress and remove the spring, piston etc.

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Use the same procedure while assembling and compressing.

[GNV]

Now to fix the barrel. Aplly a little moly to breech block, Shims and breech block jaws and place the breech block in the jaws making sure that shims are in position. Insert the Barrel hinge bolt and tighten it. Don't over tighten it. If the barrel stays in any place it is left without support in the entire arc of the cocking stroke then it is correctly tightened.

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Insert the grub screw and tighten it

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Now screw the spring plunger in the trigger housing without the locking nut.

Fix the action in the stock using the three screws.

Cock the rifle and shoot a few pellets. The gun may diesel for three or four shots but then it disappears. Adjust the trigger to your preference. I drilled a hole in the trigger guard to insert a screw driver for trigger adjustments. Once the trigger is adjusted as you wanted it, remove the action from the stock, put the locking nut on the spring plunger and tighten it taking care that the spring plungers position doesn't change. Fix the action in the stock.
That is it.

Note: To adjust the trigger always loosen the locking nut first or the spring plunger would break like this

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[ganeshn]

Fantastic job GNV.

[GNV]

Thank You ganeshn

[pratik_mahale]

GNV I really appreciate the effort you took to post it

Excellent job

[GNV]

Thank You Pratik

[aadhaulya]

Very nice and clear instructions. It is like a professional 'Service Manual'

Regards

Atul

[AnandNair]

A really good effort with clear instructions. would greatly help first time DIYers. Great Job GNV.