My new to me house howitzer

[meistermash]

Friends, new guy here.
Bought a used 870 Express. Synthetic stock.
Looks like it hasn't been used much. Couple hundred rounds maybe.
Wanted a house howitzer barrel, 18 1/2" so I found a place selling Mossberg made 870 barrels. Under a $100 out the door cylinder bore. It looks like a 2 piece affair however.
Shot it today with some really old fed steel 3" loads. Think 30 years or so old.
My question is, had a few times where I pulled back on the slide and fired it. Then of course I slammed the slide shut but only there was no shell being chambered. It extracted fine.
Am I just to quick with this thing or is there a problem I should look for?
I believe the slide was all the way back in those instances.
Also, what do you make of the Mossberg made barrels?
The really squishy recoil pad made shooting those 3" magnums bearable enough but can a guy improve the recoil by working on the free bore?
I don't intend to shoot lots of 3" magnums. I just was looking to get rid of those old shells.

[Synchronizor]

Wanted a house howitzer barrel, 18 1/2" so I found a place selling Mossberg made 870 barrels. Under a $100 out the door cylinder bore. It looks like a 2 piece affair however.

What do you mean by two-piece? Factory 870 barrels consist of a single-piece barrel/extension with a brazed-on guide ring. Is this how the Mossberg barrel is built? Or does it have an extension that's separate from the barrel?

Shot it today with some really old fed steel 3" loads. Think 30 years or so old.
My question is, had a few times where I pulled back on the slide and fired it. Then of course I slammed the slide shut but only there was no shell being chambered. It extracted fine.
Am I just to quick with this thing or is there a problem I should look for?
I believe the slide was all the way back in those instances.

A short-stroke is always a possibility if you're focusing on speed over everything else; but if you're yanking back on the fore-end as you're pulling the trigger, and using the gun's recoil to help slam the action open as quickly as possible, you can cause a no-feed malfunction where nothing is released from the magazine. As a result of the shells moving "forward" due to inertia and recoil (technically, the shells try to stay in place as the gun recoils rear-ward, but relative to the gun, they're shifting forward), the shell that is supposed to be feeding into the receiver ends up on the forward shell latch (the latch that's supposed to catch the next shell in the magazine) instead. A full magazine, especially an extended magazine, increases the likelihood of this, since more shells mean more inertia for the magazine spring to overcome. Shells that have more mass and/or more recoil (like 3" magnums, for example) also make no-feeds more likely, as does a worn-out or weak magazine spring. Here are a couple images illustrating how this works:




I would check your magazine spring; but as long as that's giving you good feed force, you shouldn't worry about this. There is a mod that can prevent no-feeds, but it has some drawbacks, and it really isn't necessary for hunting/sporting or combat/defensive 870s. Realistically, cycling that quickly isn't the most effective way to shoot outside of some competition applications, and even then, it can easily make for sloppy technique. Plus, you generally don't want to use anything with magnum-level recoil for defense duty, since it'll slow down follow-up shots without adding enough lethality to make it worth it.

If you're interested in the physics, recoil energy scales off the square of momentum, so you hit diminishing returns pretty hard when moving up to heavier payloads. For example, if velocity is held constant, 12 00B pellets (a common 2.75" short magnum buckshot load) instead of 9 (standard 2.75" express load) means a 33.3% increase in pellets for a 77.8% increase in recoil, while 15 00B pellets (standard 3" 00B load) gets you 66.7% more pellets for a 177.8% jump in recoil.

[meistermash]

Thank you for the info on the no feed issue. Inertia of the shells in the magazine acting against the spring pressure. I may see if I can get an extra power spring anyway. Maybe wolf makes one or a police model version that is stouter due to the extra cap tube. For strictly home defense, I have Winchester reduced recoil buckshot. Standard 2 3/4" I doubt that I will ever buy any more 3" and the steel loads I was blasting with, I mostly just wanted gone.

Like I was saying, this is a Mossberg made 18 1/2" barrel that is for a Remington 870. Not a factory Remington barrel.
I can clearly see the barrel was turned and the extention added around the chambered end and then brazed or silver soldered on.
I doubt if I could capture that with my camera phone though.

[Banshee]

Thank you for the info on the no feed issue. Inertia of the shells in the magazine acting against the spring pressure. I may see if I can get an extra power spring anyway. Maybe wolf makes one or a police model version that is stouter due to the extra cap tube. For strictly home defense, I have Winchester reduced recoil buckshot. Standard 2 3/4" I doubt that I will ever buy any more 3" and the steel loads I was blasting with, I mostly just wanted gone.

Like I was saying, this is a Mossberg made 18 1/2" barrel that is for a Remington 870. Not a factory Remington barrel.
I can clearly see the barrel was turned and the extention added around the chambered end and then brazed or silver soldered on.
I doubt if I could capture that with my camera phone though.

Mossberg made barrels for the 870 are made from two pieces. When I built my shorty 870 I used a mossberg made barrel and you can see the difference in color of the Parkerizing on the two pieces. The rear 2-1/4 inches is black and the rest of the barrel a dark grey.

[meistermash]

Right on. Mine is blued and I can bairly see the joint.

[Synchronizor]

Interesting. I had assumed that the Mossberg barrels were machined as one piece like the factory ones. Thanks for the info.

I may see if I can get an extra power spring anyway. Maybe wolf makes one or a police model version that is stouter due to the extra cap tube.

If you're getting a Police 870, it'll either come with a heavier-duty 4-round spring, or a standard extension spring (if equipped with a factory +2 or +3 extension kit). Either should be more than strong enough for reliable function, especially with low-recoil loads.

There is very much such a thing as a magazine spring that's too stiff. To much force on the shells can deform them, leading to feed malfunctions. This is of special concern for home defense shotguns that are loaded and left to sit for long periods of time. I've also observed that if shells are shoved too hard and fast from the magazine, they can interfere with the fired shell that the gun is in the process of ejecting, causing a jam.

[meistermash]

Just an Express model.
I am leaving the mag tube alone and not adding an extention.
If the whole magazine on the express model isn't enough to repel a home envasion, you got way more problems than that.
Plus if it isn't enough, they have way more problems than an 870.
It is just a light hearted attempt at humour calling my new 870 a house howitzer.
I can mess with this 870 and leave my prized Berretta cased safe and clean for hunting and showing off.
I do have an old m30 Monkey Wards that I rescued from a gun show where the barrel was amaturly sawed off at 20". I put the barrel in the lathe and squared up the muzzle. I used to leave that one loaded and ready but it is showing it's age. I also have that m30s predissesor the Savage double hump 520 but that one I need to find a way to keep the slide from pulling out of the bolt carrier assembly while working the slide.