new qb78,Do i need to replace factory breach seal?

[Ron3]

Have a new QB78 deluxe on the way and i read that most of the factory breach seals are crushed during assembly. Should i take a chance or just replace it. Don,t hunt and I only shoot in my basement 10 meter and not really wanting to boost the power. rather have more shots. Also where is the best place to get breech seals for this gun.

[Underwhelmed]

I would shoot it first and see how it performs.

I have replaced several in the QB 78/79's using a Crosman 17xx/22xx #130-036 transfer port seal. You can buy them directly from Crosman, or pick them up from eBay.

Some people make their own using ice maker poly tubing.

I prefer the Crosman part as it fits perfectly and is reusable if you end up removing the breech, whereas the poly tubing gets crushed into place and you have to make a new one each time you open up the gun.

[Death_By_Air]

Yeah I'd test it and see how it shoots first. If your happy then just leave it. I replaced mine as I was doing some power mods (extended bolt and transfer seal) and I did get some nice results! It's a pretty easy process to get to the transfer port if you do want to replace it. If your factory one is a little warped/crushed, you may not be getting consistent air flow behind the pellet with each shot.

A's the guy said above, a Crossman 13xx or 22xx transfer seal is cheap and easy to find and fits like a glove. That's what I replaced mine with.

[Ribbonstone]

If it doesn't leak air at the shot and you aren't interested in increasing power, leave it alone.  Considering your use, more power isn't going to help anything, so just test/shoot it as it comes.

However, if you ever want it to go SLOWER (and use a little less gas per shot) could always figure a way of restricting it farther.

[Atomic Powered Gruds]

There are people who replace it and see no increase in performance. from what I read its because the seal may be crummy and a lot if not most obstruct airflow but other act as intended and no gain would be made by replacing it. So yeah see how you like it first. I should be getting mine next week but no clue as to when I will be able to shoot it as its a fixer upper.

If you do need a new seal what others recommended will be what I personally will be reaching for.

[Ron3]

mine is being shipped by airgun depot and has been in transit for 8 days tomorrow. thanks Fex-ex . They tell me it will be here tuesday. Fed-Ex smartpost economy shipping.

[Atomic Powered Gruds]

Mine for me is coming from maybe 3-4 hour drive away distance wise and it is coming FedEx as well. It is taking 5 days to arrive and will be here Tuesday as well lol. From my experience all deliver companies are as bad as each other.

[Ron3]

I think Fedex is the worst. 10 days on the road is to long and to many stops.

[Rocker1]

Had a customer send a  brand new one to me to tune with a after market sidelever,  tore the gun down and the breech seal was deformed over the tp port, haven't done a lot of qbs but the last 2  the seal was deformed. David

[Ron3]

Had a customer send a  brand new one to me to tune with a after market sidelever,  tore the gun down and the breech seal was deformed over the tp port, haven't done a lot of qbs but the last 2  the seal was deformed. David

.  yea that seal seems to be a problem also the filter in the bolt, needs to be removed. really don,t know the purpose of the filter.

[Atomic Powered Gruds]

I think but I could be wrong, its for stuff like dust that gets in the rifle when removing the endcap/replacing CO2 so it does not get pushed through the rifle. Which if your careful should not be a problem anyways.

Looks like mine might come today. I hope mine comes with the Co2 piercing pin part. If not I wonder what I will end up doing to get it working cost effectively. Maybe use a bottle and house as I do own a 24oz Co2 tank.... will be fun seeing how ours both turn out. Cheers to hoping we both get the rifle/ammo pairing with the results we want.

[Ribbonstone]

Would toss out the filter in the valve the first chance you get, but wouldn't make a trip inside the rifle just for that.  Usually takes some time before they start of shed, but eventually they'll just come apart and have fibers wrap around the important stuff in the valve.

As for replacing the port....all depends on (1) if the issue port leaks and (2) if you want the rifle to shoot faster or not.  If you're just shooting targets in the basement or plinking at 2025yards, really don't have to have more power....and often the restricted transfer port gives more shots (lower speed) than one that's wide open(higher speed).  Just so much gas, can use it in a lot of little "blips" or use it in fewer "burrrps".

[Atomic Powered Gruds]

I just got mine a few hours ago, had a basic look over it. I cant figure how to get the bulk adapter off of it. I also think the bolts either an old style I cant find any pics of or its a aftermarket(my bet) because its hollow and straight like a straw. Hope its a standard O-ring size and that if its custom that it seals like it should. Definitely needs some love but nothing wrong with it from what I can tell.

It sure is a beautiful rifle for being generally considered low end.

Would toss out the filter in the valve the first chance you get, but wouldn't make a trip inside the rifle just for that.  Usually takes some time before they start of shed, but eventually they'll just come apart and have fibers wrap around the important stuff in the valve.

Yuck that would be horrible!

[Ron3]

got my qb78 from airgun depot wellpacked double boxed, really nice gun for the price. will try it out and see how it does.

[imadunatic]

The first 2 powerlets I put in my QB lasted about 45 seconds.... one small chunk of brass between the valve stem and seat from when they machined the exhaust body was all it took. Was awesome to have a brand new gun COMPLETELY tore apart in the first 30 minutes I owned it. 

Can someone tell me roughly what the ID of the crosman seal is? I did the icemaker tubing on my first QB, but honestly I'm thinking I'm just gonna order a few of the crosman seals on my next order and use those. Seems so much simpler and I don't hear of anyone having problems with them.

Also, I haven't had to replace the icemaker tubing on mine every time I have it apart, the material has enough elasticity to rebound from the .010" squish (I'm guessing after a few months it may start to develop some memory, but too soon to tell). The last time I had it apart it still measured .155" long on the nose.

[Josan]

The end cap seal and valve seal are made from compressed camel dung. You'll have to replace these or your gun will start leaking soon.
The transferport seal is a flow restrictor. Replacing this one will yield some extra power.

Also have some barrel seals ready, because when you pull out the barrel to replace the valve seal, you will nick the barrel seals on all the rough metal work.

[nervoustrigger]

The ID of the Crosman seal is slightly less than ice maker poly tube (0.170").  Seems like it was 0.160" from memory.

[imadunatic]

The ID of the Crosman seal is slightly less than ice maker poly tube (0.170").  Seems like it was 0.160" from memory.

Thanks Jason. I see no need to bother machining the spot faces for that small amount....