I have a 9mm bolt that is lighter weight.  Don't ask, long pointless story.  

Can I make up for the lack of mass by using an 8 oz buffer and a stronger spring?   Or is that just trouble?

I'm asking because I have the bolt and buffer.  I have ACCESS to stronger recoil springs and it would be the cheapest option for me.  

It's a 3 inch barrel with a suppressor.  The suppressor is removable, but it's an older suppressor so it always stays on this upper.

based on posts here, it is my understanding that weight is more important and that a stronger spring won't help, just make it slam forward harder.

so if anything I would see about one of those buffers you can ad weight to, till you get to the price point of a new bolt. 100 bucks or so. hopefully it doesn't get to that point, but I have seen some crazy high dollar stuff out there.

If I were me, I'd probably go with the heaviest A5 buffer.  The extra length also takes up the extra slop that normally allows 9mm's AR's to beat their bolt catch to death.

As an off topic educational point, when would you recommend a heavier spring as opposed to a heavier buffer?   Assuming a non adjustable gas block.  

Back to my system.  I have a JP 9mm bolt that never had the center mass.  It's been further milled (that's the long story).  I'll have to weigh it to give an exact number.  

I also have the Spikes 9mm buffer.  I'll have to weigh it for an exact number, spec say 8 oz (need to verify).  

The JP bolt, the Spikes 9mm buffer and a standard spring?   I'm partial to Sprinco.  So a Sprinco white?

I had a 9mm M16 with a 5" barrel a while ago.  I had an extra heavy tungsten weight in the bolt to help slow things down a bit.  Long story short, the retaining pin sheared and the weight was removed.  I decided to shoot it anyway and it was the best thing that could have happened.  Super smooth shooting gun.

Ramped 9mm RRA bolt with the weight removed
Standard spring
Enidine hydraulic buffer

Has the gun ever been fired ??
Also weigh the bolt. Now you have a base line to figure out what the gun likes for the combined weight of bolt/buffer

I would start with a 6oz to 7oz buffer.....I'm assuming you are using a carbine length tube, so use a carbine spring, and I prefer to use a new frontier buffer-bumper to control stroke length.
Now shoot the gun.
If it works...great ! Verify that everything is working good.....check bolt stop, and the around the threaded portion where the buffer' threads in.
If it's  hard on the felt recoil, you begin to add buffer weight to mitigate it.


,

I will try this set up.  I have very similar things.

The gun has been shot, but I had to rob some (a lot) of the components to another 9mm.  This gun that I am asking about is in semi only, Glock lower.

I have a 9mm hydraulic buffer (KynShot) that wasn't very helpful in 9mm full auto.  To be clear, that is a completely different lower and different upper.

I can use the KynShot in the this Glock, semi only lower.  If I use that buffer, then I don't need to buy anything at all.  Not even a spring.

Just a thought....

But with a super short barrel and lightweight bolt, maybe the easiest thing to do is load your own. Thinking use a light weight 9mm or 380 bullet on a light charge and makes a paper puncher.

Just a thought.

I'm not set up to reload yet.  I've bought the property and construction has started.  There is a time table, and it's coming.

What bolt?

You may be able to have a weight milled to put back into the bolt if the bolt hasn't been machined too much.

If it were mine, I'd just get a 10 oz kak buffer and use it with a standard spring.  As you run different ammo through it, just watch the brass and make sure you don't have any issues.

As for your bolt, I'm sure some/most here would be interested in the back story if you care to share some of it.  People seem to do some goofy chit with their guns.

I have a 9mm bolt that is the in the same category. I had some milled off to work with a gen ii bfs trigger. I would get a bit of a heavier buffer to make up for the lost weight. Make sure it has a dead blow effect on the bolt. Then I'd try a Wolf extra power spring. The sprinco red is good too. How much does your bolt weigh?

Im looking at a KAK adjustable buffer (has moving weights) and the KynShot hydraulic buffer for a dead blow effect.  What buffer would you recommend?

I currently have access to Sprinco white, red white, red and blue.

The 9mm bolt in question is 12.8 oz.

I recently built a 9mm using the NFA LRBHO and their Glock lower.  I used their 16.7oz BCG and a Kaw Valley Precision PCC kit with their 7.5oz buffer (total 24.2oz).  Originally started out with the extra power spring that came in the kit but quickly replaced it with a standard carbine spring.  It was too stiff pulling the side charger back AND it closed the bolt with way too much authority.  I have a few hundred rounds through the gun with the carbine spring and it works very well.  I also would not recommend much less buffer weight than what I have now, it's really smooth and works well.  My LRBHO works 95% of the time.

If you're running suppressed, then a stronger spring might be a good choice due to the higher pressure.

The KAK 9mm configurable buffer would give a max weight of 10oz (total of 22.8oz with your existing bolt) and is the heaviest one I have seen that's readily available.

Regular Bolt with weight is ~16oz, regular buffer is 5.5oz, for 9mm.