QB79 Ninja - The $200 PCP

[wll2506]

I'll probably try bending it a little more after all. I can't get the valve poppet to seal with my hand pump, so I'm gonna pull it all the way down again. So I guess I'll work on the barrel while it's out.

BTW, did I mention that the stock nut was stripped, out of the box? These things really are parts kits, in my experience. Don't get me wrong; I fully intend to make this a viable airgun, and am enjoying the process of doing so. But if I were like some of my fellow MPP consumers, I would have already written this thing off as a piece of junk and sent it back; and would now be telling everyone who would listen to save their money. 

And I'm not referring to the poppet seal problem; that one was my doing by choosing the wrong spring.

I had read a while back on the Flying Dragon website that the newer QBs are not as well make as the older guns. As you have mentioned these are project guns which can be fixed to perform better.

I had a couple of very old QB 78's many, many years ago, and through them out when I did not know any better.

As I remember they were not made as well as the guns that are coming through now, The guns now seem pretty nice, at least I think so ?

wll

[vigilandy]

I picked up an older one recently.  Haven't shot it,  but the wood quality is definitely nicer on the new ones.  No more of that yellowish varnish!

[southern gun]

I have ordered a QB78 and was wanting to know the best tank block to put on it
Thanks

[WECSOG]

    Sorry, as I haven't read through this whole thread yet. The tank the original poster suggests, are they fillable with a hand pump, such as used on Crosman Discovery airguns?

    Thanks, Jon

Yes. I use a Hill pump to fill mine.

[Buldawg76]

I have ordered a QB78 and was wanting to know the best tank block to put on it
Thanks

+2 on that as I have acquired a QB 78 as well and would like to know which tank block is best to use the older two o ring style or the new four o ring style or is there any real difference other than the extra o rings. Does one flow better than the other or anything else we should know so as to get the best one for the job at hand.

Mike

[nervoustrigger]

No real advantage to the 2 vs 4 O-ring version.  The idea is more = better but reality is if there is a burr in the air tube, it will cut 4 o-rings instead of 2.  Deburring and using silicone grease for assembly are the keys to success.

[SpiralGroove]

Hey Guys,
Most people will find it difficult to find a tank block for a QB78 HPA conversion -> Period
I bought two from Arrrcher Airguns last month, but he isn't listing them anymore?
The cheapest they can be found is $35+ shipping, JDS have them for $75+ (which I refuse to pay since the whole gun only cost $95).

Good Luck

[Buldawg76]

Hey Guys,
Most people will find it difficult to find a tank block for a QB78 HPA conversion -> Period
I bought two from Arrrcher Airguns last month, but he isn't listing them anymore?
The cheapest they can be found is $35+ shipping, JDS have them for $75+ (which I refuse to pay since the whole gun only cost $95).

Good Luck

So the ones listed on the site for 35 bucks now are not suitable for HPA even when regulated to 1500 psi or less as they state not to exceed 1100 psi and not for HPA but regulated its really no more pressure than CO2 at 90 plus degree temps.

Any thoughts

Mike

[rsterne]

I would think the warning is a just a CYA for the lawyers, because CO2 at 120*F reaches 1900 psi.... The biggest problem with the stock QB tank block is that the screws are soft, and too close to the end of the tube.... The JDS block moves them further from the end, and if you use high-tensile screws is a much safer arrangement.... One thing that concerns me slightly is when I see guys using the stock QB tank block in a QB78 (or Crosman) tube without inletting the stock for the block and using the two side stock screws as used in the QB79.... Since I am aware of one QB79 tank block that pulled out of the end of a tube (when not in a stock) by shearing the screws and nearly ripping the holes out, at only 2600 psi.... That tells you what the safety margin is at 1800 psi.... less than 1.5:1.... It must be a bit better with the stock screws in place, no?.... I would not recommend even removing a QB79 action from the stock while pressurized....

Bob

[Buldawg76]

I would think the warning is a just a CYA for the lawyers, because CO2 at 120*F reaches 1900 psi.... The biggest problem with the stock QB tank block is that the screws are soft, and too close to the end of the tube.... The JDS block moves them further from the end, and if you use high-tensile screws is a much safer arrangement.... One thing that concerns me slightly is when I see guys using the stock QB tank block in a QB78 (or Crosman) tube without inletting the stock for the block and using the two side stock screws as used in the QB79.... Since I am aware of one QB79 tank block that pulled out of the end of a tube (when not in a stock) by shearing the screws and nearly ripping the holes out, at only 2600 psi.... That tells you what the safety margin is at 1800 psi.... less than 1.5:1.... It must be a bit better with the stock screws in place, no?.... I would not recommend even removing a QB79 action from the stock while pressurized....

Bob

Bob
Is it possible with the 2 o ring block to not only upgrade the screws to grade 8 screws but add two more screws between the 2 o rings in the block to have a total of 4 screws holding it in the guns tube and thereby increasing the safety factor close to the preferred 3:1 ratio. I don't have my QB 78 as of yet it will be here tomorrow so not exactly sure how the stock helps secure the block since I don't have a visual in front of me, but I was planning on modifying an extra FWB 300 target stock I have to accept the QB action and can inlet or modify the stock to add support for the screws as well if needed. I don't have a block either to visualize so just guessing at this point.

If just adding two more screws in between the 2 o rings on the block would be acceptable then that would be an easy modification and put me at ease with it being safe or if you think the JDS block is the way I should go then that is what I will go with so just asking your opinion on the correct safe way to proceed.

Mike
 

[SpiralGroove]

Hey Mike,
They are still listed - just not with a picture   They are now $36.99+ shipping.  He raised the price since I bought them.  These blocks are fine.  Just make sure the Block is well secured to the stock as well as the air cylinder or pinned if not attached to stock.



Before, I only saw the Co2, thread on adapter for $31.99, which is Not for HPA.

 

[nervoustrigger]

You can certainly do that.  Other approaches are to add one screw underneath or by adding a shear pin.  Any of these significantly improve the integrity.

The biggest risk in my opinion is not that the pressure is likely to blow the tank block off the end, rather it's what happens if the gun gets dropped or something slams into the bottle and puts a lot of torque and stress on it. 

[pllagunos]

My qb79 is running a 850psi output regged bottle, I haven't changed the tank block screws to higher quality ones, is it really needed for such a low pressure?

[nervoustrigger]

If your bottle is fitted with a 1.5k low side burst disk, not really but it's an easy thing to do for some peace of mind.

[SpiralGroove]

Pablo,
If you've got kids around, every day accidents seem to be part of life.
The screws in question are about .35 to .50 cents each at the local hardware store, so well worth the time & $$ to replace.

I don't want to make an "accident video" to submit to the GTA   The guy who took the Disco valve in the thigh, easily could have died if a take #2 was produced.   

[Buldawg76]

Hey Mike,
They are still listed - just not with a picture   They are now $36.99+ shipping.  He raised the price since I bought them.  These blocks are fine.  Just make sure the Block is well secured to the stock as well as the air cylinder or pinned if not attached to stock.



Before, I only saw the Co2, thread on adapter for $31.99, which is Not for HPA.

 

Kirk and all
Thanks as that's what I wanted to know and was going to grab one up before he runs out again and the one extra screw underneath sounds like the best route to go for ease of modifying.

I see he has the 2 and 4 o ring blocks priced the same so might as well get the extra sealing protection of 4 o rings.

Mike

[pllagunos]

Pablo,
If you've got kids around, every day accidents seem to be part of life.
The screws in question are about .35 to .50 cents each at the local hardware store, so well worth the time & $$ to replace.

I don't want to make an "accident video" to submit to the GTA   The guy who took the Disco valve in the thigh, easily could have died if a take #2 was produced.

I will buy some, better safe than sorry, which size are they? Also are they the ones that secure the bock to the stock or the block to the tube?

[SpiralGroove]

I believe they're both 4mm.
 - The air cylinder screws use an Allen Wrench.
- The Stock screws have a round head and take a Phillips driver.

I usually buy them longer than necessary, say 7mm/10mm in length, and grind down to fit.

Home Depot is your best bet

[southern gun]

Just so I'm clear we are talking about grade 8 bolts correct? My QB 78 came yesterday so I'm ready to get this started.

[rsterne]

I used a 3/16" shear pin when installing a QB block into a tube where the block is not also bolted into the stock....



I even added one more 8-32 screw in the top as well, with the head set into a pocket in the block.... It is cut the right length to touch the through-pin (which has a flat) to hold it in place.... Overkill, but the stock screws were so close to the end they scared me.... With this installation they could be left out, in fact the tube would be stronger without drilling holes for them....

Bob