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Discussion Starter · #1 ·
I am building a first for me, AR-9mm upper. I plan to drop the upper on top of my existing AR-15 pistol lower and use a Glock style mag well adapter. This is my entry into PCC (Pistol Caliber Carbine). This is a straight budget build. I have not net selected a AR-9 buffer/spring kit.

How do I make that selection? There are so many choices and opinions on weight, spring type, spacers, etc. Any direction is much appreciated.
 

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Colt produced 9mm carbines used a 5.5oz buffer weight.
I like to run heavier buffers. I use a 8.5oz buffer from HeavyBuffers
They aren’t cheap, but they are hand made, right here in the US.

One thing to remember with a 9mm buffer. Use a 9mm length buffer or inserts spacer in the buffer tube. Some people use six quarters as a spacer, but this also increases spring tension. There are a few companies making a polymer spacer that inserts into the rear of the spring.

The above detail ensures long bolt catch life. To check for the need, retract your bolt with charging handle. Apply pressure to the bolt catch. You want about 1/4” between the bolt and the catch.
 

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I use a polymer spacer. A heavier buffer is a good idea, but you can get by with a JP flatwire spring and a stock buffer if you are trying to keep the price down. Shoot 115s with faster powders. Staying away from the heavies and slow powders will decrease wear and tear and keep it a little cleaner.

I still think the best bet is the Blitzkrieg, but not on a budget build.
 
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Discussion Starter · #4 ·
At this point, I want to get the upper functioning well. I have not yet received the components; they are being shipped. I looked at the Blitzkrieg and products from Heavy Buffer. I cannot justify buying a buffer that expensive, not on a budget build, at least not now.

Question about the rubber spacers:
I've seen them on Optics Planet. If I install a spacer, does that mean I would use my stock buffer spring along with a heavy 9mm buffer?

Question about Buffers:
Is it that the heavier the buffer, the more they cost?
Should I go nuts and buy the heaviest buffer I can bet my hands on?
How much does the brand of the bolt determine what weight of the buffer I use?
 

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I went thru similar contemplation when I assembled my first 9 mm upper to use on a standards AR lower.

because I planned to switch out uppers between 9 mm and 5.56, I went with standard carbine spring and a pistol buffer, no insert.

my thinking was that I would just have to switch uppers and buffers between the two calibers, everything else would be the same so minimum hassle when switching.

I also used Mean Arms mag adapters instead of a mag well adapter.

everything worked well and I put over 1000 rds thru it before I sold it, but what I learned with that set up went right into a dedicated 9 mm AR pistol I assemblies with a Fox Trot Mike lower.
 
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Everything AR doubles in price when you deviate from the mass produced general parts. Heavier buffers have started to come down in cost a little.

YES, what bolt you use affects what buffer you use. With blowbacks, it is the mass of the bolt AND buffer, and some the spring, that keep the case in the chamber. If the mass is too low, you will run dirty and risk case ruptures. You probably can't get too heavy with cost effective components.

Before 9mm PCCs were a thing, we poured lead into cylinders and hammered them into the back of bolt carriers.
 

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I like the 7.5 oz buffers. Run well with 4 different uppers.
 

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At this point, I want to get the upper functioning well. I have not yet received the components; they are being shipped. I looked at the Blitzkrieg and products from Heavy Buffer. I cannot justify buying a buffer that expensive, not on a budget build, at least not now.

Question about the rubber spacers:
I've seen them on Optics Planet. If I install a spacer, does that mean I would use my stock buffer spring along with a heavy 9mm buffer?

Question about Buffers:
Is it that the heavier the buffer, the more they cost?
Should I go nuts and buy the heaviest buffer I can bet my hands on?
How much does the brand of the bolt determine what weight of the buffer I use?
buy once, cry once.
 

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Mine run very well using a Foxtrot Mike's 9mm buffer and a .308 Carbine spring.

Neither are expensive, Primary Arms sells FM Products
 

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Discussion Starter · #11 ·
buy once, cry once.
Yeah, I understand that point of view. I read where others have tried several buffers and springs as they attempt to get the right combination components. If price alone were any kind of assurance, I would buy a $75-$100 buffer. But, from what I am reading, there other elements that make the a reliable upper. However, I don't know what those differences are. So, I am here to learn.
 

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Yeah, I understand that point of view. I read where others have tried several buffers and springs as they attempt to get the right combination components. If price alone were any kind of assurance, I would buy a $75-$100 buffer. But, from what I am reading, there other elements that make the a reliable upper. However, I don't know what those differences are. So, I am here to learn.
I understand. Personally, I’ve ran the 9mm AR for about 12 years. The Blitzkrieg hydraulic buffer or a heavy buffer has worked for me. Over the years, I’ve learned, for me, researching the components and buying quality parts, has worked out much better than budget parts. I’ve had the best luck running a bolt/buffer combination that weighs 21-24oz. It has worked well for my ammo

For me, it’s been cheaper to buy good parts the 1st time, vs replacing mediocre parts and selling them at a loss after very little use.

Please don’t take this as a slight toward building a budget AR. Just my experience as to what has worked, and not worked, for me.

MarkCo has a ton of completion experience. He is extremely knowledgeable
 

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Big fan of Foxtrot Mike products. I have several of their bolts and I really think they are a great value. Even on budget builds, their bolt and heavy buffer is a solid choice.
 

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looks like your moving in the right direction, but just remember two things (what I figured out tinkering with buffer weight).

1 - it not just buffer and spring, its bolt, buffer and spring.

2 -most heavy buffers have 3 titanium weights or a compilation of titanium and steel, if your not getting proper function with lighter loads i.e. no LRBHO/FTF, if your buffer has the plastic section pinned in place(looks to be so), you can adjust your buffer weight with standard steel weights.

I'm using a Law Tactical folder adapter and had to cut the weight pinned into the bolt down in order to use the adapter correctly, but I did pick up a few oz. as the adapter stick out the end so bolt weight was heavier than the standard 9 mm bolt with the stock weight in place.

I did have an occasional LRBHO failure/FTF with the bunny fart loads I make up with cast bullets so I tinkered with buffer weight and got it running, but than realized I didn't put my 9 mm AR together to shoot light loads, went back to the original buffer weight and upped the power of my reloads.

ya I kinda went full circle but learned something along the way so it was worth it to me.

good luck with your process and remember what you learn along the way is priceless
 
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