Umarex M&P 40 premature slide lock

[Sublimemoon0000]

Hey guys, I'm back. I posted some stuff about my break barrels eating scopes a while back. You guys were super helpful with all my questions and this is an awesome web sight so thank you .
Ok, so I recently got an S&W MP 40 (umarex) CO2 pistol. Freaking bad... I love this little gun. However, now, the slide is locking back on me even when there are bbs in the mag. It is pretty much doing it every single shot. I reach my finger around and push on the front of the barrel and it slides forward again, like I have to assist it everytime. Basically I'm having to do that everytime after every shot. Obviously this isn't right, anyone experienced this? Is it a lube problem ? Any help is appreciated guys thank you!!! I am loving airguns and everything about them, this is all new to me though, still learning .

 

[Sublimemoon0000]

So I feel simple lol, the CO2 cartridge was too low, after replacing it. It functions fine, every 4th or 5th shot, it will still lock back when it has bbs in the mag.,Just not as often with a new cartridge. I guess I need lube ? I'm going to get some RWS chamber lube and start using it, I bet it helps .

 

[ninersix]

Sublimemoon000, May I ask you what kind of lubricant you are using on your MP-40? I had the same issue after firing my MP-40 and I switched to 100% silicone oil. Silicone oil is better for Co2 guns and here is why.

1) It is very, VARY slippery.
2) It will not affect any metal at all and will coat rubber, synthetic rubber and coat and protect it.
3) This is the big one, it displaces water, frost and ice.
4) it will NOT evaporate or deteriorate over time.
5) It is a oil not a Dry lube, I do not recommend any dry lubricant for air guns.

it is also comes in oil and spray form and is just about everywhere.
check AMAZON or your local hardware store look for WD-40 Specialist Silicone spray or any 100% silicone oil or spray.

 

[Hawkeye51]

Krytox is an extremely good lubricant that can be used with all types of airguns. It's not cheap, but highly recommended. You will have to do a little research to understand why it's so expensive, but a very small amount goes a long way. I use it for all of my airguns.

 

[Sublimemoon0000]

Sublimemoon000, May I ask you what kind of lubricant you are using on your MP-40? I had the same issue after firing my MP-40 and I switched to 100% silicone oil. Silicone oil is better for Co2 guns and here is why.

1) It is very, VARY slippery.
2) It will not affect any metal at all and will coat rubber, synthetic rubber and coat and protect it.
3) This is the bug one, it displaces water, frost and ice.
4) it will NOT evaporate or deteriorate over time.

it is also comes in oil and spray form and is just about everywhere.
check AMAZON or your local hardware store look for WD-40 Specialist Silicone spray or any 100% silicone oil or spray.

I wasn't using any oil, then I started using 100 percent pure silicone oil and I haven't had a single issue since ! It's smooth as butter ! You are correct sir ! Silicone oil is the way to go !!

 

[ninersix]

I am happy you solved your issue.
When I purchased my First Umarex MP-40 with automatic fire It was not long before I noticed that pellgun oil was not silicone oil. I use a number of silicone sprays, oil, molding silicone rubber etc. so it was easy to switch. Yes, you can purchase 100% silicone gun oil (Crossman) in a very small tube but it is VERY Expensive. I remember shooting the MP-40 in the back yard, doing some tests the Co2 was almost gone I had a full clip I was wondering if the gun would fire at all? I pulled the trigger and at first about 6 or so BB's came out followed by a literal "stream" of silver slow moving BB's, kind of like a squirt gun. So Moral of the story is, us 100% silicone oil it works and will keep your BB, Pellet air guns in very good condition.

 

[ninersix]

I wasn't using any oil, then I started using 100 percent pure silicone oil and I haven't had a single issue since ! It's smooth as butter ! You are correct sir ! Silicone oil is the way to go !!

If you wish I just posted a YouTube video, this German fellow takes apart a Umarex MP-40you have to set you computer to auto translate into English but he takes it apart. A lot of screws and parts.

I wasn't using any oil, then I started using 100 percent pure silicone oil and I haven't had a single issue since ! It's smooth as butter ! You are correct sir ! Silicone oil is the way to go !!

If you wish I just posted a YouTube video, this German fellow takes apart a Umarex MP-40; you have to set your computer to auto translate into English but he takes it apart. A lot of screws and parts.

https://www.youtube.com/@DocSnyderGunChannel