Extra heavy buffer for 9mm blowback rifle

[jdgabbard]

I’m using the AR platform because it’s relatively cheap and they don’t require a lot of specialty tools to work on in the garage at home.

If I was going to spend real money, I’d find a 223 bolt action donor rifle and get my 24” 9mm blank installed.

Oh, I get it. But I don't think you're going to get there with a buffer. There just isn't enough room for enough mass in the buffer and still be able to cycle manually. I'm not saying it can't be done, I have been surprised. I just don't see how you're going to get there without getting more mass in the either the buffer or the bolt. I guess you could try to find a REALLY strong spring to make up for some of the mass. But then you're going to have a rifle that is difficult to manipulate when charging.

[steve urquell]

Barry, how light of a load are you OK with?

I know I could probably use my .308 spring and heavy buffer and defeat cycling with light loaded 90-115gr bullets.

[Barry54]

Barry, how light of a load are you OK with?

I know I could probably use my .308 spring and heavy buffer and defeat cycling with light loaded 90-115gr bullets.

I want this to compliment my 200 grain subsonic loads. 1.2 grains of Vihtavuori N310. The bolt moving is the loudest part of using that load. Well, the steel ringing when hit is loud too.

[steve urquell]

I want this to compliment my 200 grain subsonic loads. 1.2 grains of Vihtavuori N310. The bolt moving is the loudest part of using that load. Well, the steel ringing when hit is loud too.

That's harder than flyweight bullets. Heavy is great to push that bolt back with light charges. I'm pretty OK with my suppressed sub loads. Do you have a suppressor?

[Barry54]

No. I don’t. But the 200 grain load doesn’t need one on a 16” barrel.

[country gent]

After our conversation tonight I had another thought. If the buffer tubes are somewhat consistent size wise, a couple o-rings installed in the bearing dia of the rifle buffer to create drag might do it. Reducing the dia between the 2 rings would help. also drilling and filling with lead or carbide. Brass would add more weight but Im afraid its softness would allow it to mushroom out and bind over time.
Increasing the dia between the 2 rings may add 1 1/2 -2 ounces there going from the 3/8" reduced area to .100 ( .050 on a side.). If drilled in from the BCG end a larger hole is available then a smaller down to the nylon cushion. This may get the rifle buffer up to around 20 ounces. another is with the rifle buffer tube extending the buffers length an 1" would add weight and spring tension.

Another is to Go to mc master carr springs dept and look for a compression spring outside dia and wire dia and length find one same od a larger wire dia and the same length or longer.

[Barry54]

Attachment 328576

I like the o ring idea as well.

My aluminum spacer is 0.975” and 2.750 long. The buffer is steel, so building it out of brass is straining at a gnat. I think making a brass spacer and putting it where it reciprocates is the simplest way to get the most weight added. Maybe bore it for tungsten weights later down the road.

The spring is another option. But I would think that the od of the buffer and the id of the buffer tube will restrict being able to use a different spring?

Maybe I’m barking up the wrong tree with weight increases and spring pressure is the ticket?

Oh, I found a 6” by 1” diameter piece of brass bar stock on amazon for $20

[Moleman-]

It’s blowback. There is no gas system.

You'd have to make it yourself or have someone make one. They're out there. The gas port ends up being about 1.25" in front of the casemouth.

[Barry54]

Learn something everyday!

I’m just using the AR platform because it’s easy. I’d be a lot more comfortable experimenting with deep seated heavy subsonic boolits in a locked breech platform. And if I’m gonna do all that, I think a bolt action will be the platform I’ll go with.

[Moleman-]

I haven't seen one in person, but the RIA 22tcm bolt action can be rebarreled to 9mm fairly easily.

[Barry54]

Nice! I bet it would likely feed from a magazine too!

[Moleman-]

Guy on another site rebarreled the tactical model in 9mm and threaded it for a suppressor. It looks pretty nice. It does feed from a mag.

[steve urquell]

Shame we can't get the Bergara BA13 over here. It is imported as the CVA V2 here but in limited calibers. Overseas it can be had in 9mm. I'd snap one up in a second if it were available here.

[country gent]

Weigh your spacer with the buffer maybe adding the extra spacer to a custom buffer would add what you want

[country gent]

as discussed turning the spacer longer ( adding the spacer length to it) would increase the length. I could drop the end dia down to make up for the smaller inside dia of the larger spring dia.

[Barry54]

Still mulling it over. Is the machined section on the rifle buffer between the spring seat and the face where it contacts the bolt carrier group purposely put there. Is that reduced section needed to get the buffer in the tube over the hammer?

[Barry54]

https://www.theworldmaterial.com/density-of-metals/

So according to this chart brass beats steel, iron and stainless steel. Then lead, but it’s soft, so best as a filler in a more durable shell. Then tungsten as the best in the exotic category.

I’m not too concerned about using the rifle enough to beat up the brass spacer/weight badly. It takes some good licks on a brass punch with a 2lb hammer to mushroom it. In my simple mind, a 2lb hammer impacting a stationary punch is worse than the brass weight being in contact with the bolt and the buffer. Maybe I’m wrong?

Getting tungsten shot inside the spacer is probably the the cheapest way to get the maximum reciprocating weight. Not sure about the losses from the interstitial space from tungsten shot though.

[steve urquell]

https://www.theworldmaterial.com/density-of-metals/

So according to this chart brass beats steel, iron and stainless steel. Then lead, but it’s soft, so best as a filler in a more durable shell. Then tungsten as the best in the exotic category.

I’m not too concerned about using the rifle enough to beat up the brass spacer/weight badly. It takes some good licks on a brass punch with a 2lb hammer to mushroom it. In my simple mind, a 2lb hammer impacting a stationary punch is worse than the brass weight being in contact with the bolt and the buffer. Maybe I’m wrong?

Getting tungsten shot inside the spacer is probably the the cheapest way to get the maximum reciprocating weight. Not sure about the losses from the interstitial space from tungsten shot though.

My tungsten buffer has sliding weights so little air space. These buffers are good because they eliminate bolt bounce which can cause an out of battery discharge.

[Barry54]

Tungsten shot is about $50 per pound. Last I checked it was about a $25 increase to get the three little tungsten weights in an H3 buffer vs the regular buffer. A little airspace with the shot should give it the same dead blow hammer effect as an off the shelf buffer. No?

[Barry54]

My aluminum spacer calculates to 2.05 cubic inches. That converts to 33.5cc and using 18 g/cc shot as a reference, that gives me 603 grams. So the maximum weight I could replace my aluminum spacer with is 21 ounces if it was sold tungsten.