9mm carbine blowback owners...

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08-26-12, 20:30
SCatalyst

9mm carbine blowback owners...

I've read on a thread that the slug in the rear of a 9mm blowback bolt can be removed and removal helps with reduced recoil making follow up shots more accurate.

1)Has anyone else heard of this modification?

2)It has to be there for a reason. Or is it there just because it's part of the fabrication process and removal would just be more costly for the manufactuer?

3)If you removed it, how did you do it and how do you like the perfomance now?

I'd love some feedback on this. I'll even take some math cyclic inertia theories to convince me to do it or not. :laugh:
08-26-12, 21:11
KalashniKEV

Quote:

Originally Posted by SCatalyst

I've read on a thread that the slug in the rear of a 9mm blowback bolt can be removed and removal helps with reduced recoil making follow up shots more accurate.

1)Has anyone else heard of this modification?

2)It has to be there for a reason. Or is it there just because it's part of the fabrication process and removal would just be more costly for the manufactuer?

3)If you removed it, how did you do it and how do you like the perfomance now?

I'd love some feedback on this. I'll even take some math cyclic inertia theories to convince me to do it or not. :laugh:

1) No. That's completely stupid. Your bolt velocity would be insane. It would probably insta-snap even an extended, SS hammer pin.

2) It's pinned in there to get your bolt weight up. You need about a 5.5oz buffer to get the weight of the system where it needs to be as well. No one is trying to reduce the total weight on a straight blowback gun.

3) Are you experiencing a performance issue? Tell us about your configuration and we might be able to diagnose it...
08-26-12, 23:10
SCatalyst

Quote:

Originally Posted by KalashniKEV

1) No. That's completely stupid. Your bolt velocity would be insane. It would probably insta-snap even an extended, SS hammer pin.

That's quite a confident statement. You must have first hand knowledge. Have the stainless steel hammer pins you've seen snap new or old and what caliber did it happen on?

The reason why I asked the original posted question, is because of the 3rd post on this page.

http://www.ar15.com/mobile/topic.htm...=549070&page=5

Granted I know it was for a application in FA with a 7.5" barrel. But in theory, the perceived recoil reduction would be the same for a shooter with a 16" barrel in SA.

I didn't want to thread jack that topic, so I tried contacting the person who posted it. No dice.

I'm aware of the extra counter pressure needed by a blowback AR. But if the weighted recoil pressure was taken out of the bolt and applied to a Wolff High Power pistol caliber buffer spring, and maybe, combined with a much heavier buffer or one of those hydraulic buffers, could create a different shooting experiance on a blowback 9mm.

I just wanted to see if anyone else has changed the buffering aspect of thier 9mm ARs (namely bolt slug removal) and 'felt' a significant change in recoil. I could trial and error and buy things to test it out, but if you figured out a great buffering combo, I'll replicate your combo and let you know if I got the same result.

My carbine runs perfectly fine, I just want to find the formula for reduced recoil for effortless, accurate follow up shots. (other than larger deltoids and traps)

It's a 16" Spikes 9mm blowback upper on a dedicated CMMG 9mm lower, ST-T2 buffer, ST-9BS spacer, and Spikes MIL-SPEC buffer spring.

Let me know what worked for you guys. Especially if you had the slug removed.
08-27-12, 18:46
Todd.K

Try a Vltor A5-H4 buffer and rifle spring.

I don't think removing the weight will work. It will increase bolt speed, so the bolt will probably bottom out harder on the receiver extension. The bolt bottoming out is where a lot of the perceived recoil comes from.
08-27-12, 19:58
KalashniKEV

Quote:

Originally Posted by SCatalyst

That's quite a confident statement. You must have first hand knowledge.

Yes, I've shot thousands and thousands of rounds through 9mm ARs.

Here are two I own currently:

http://i145.photobucket.com/albums/r...s/IMG_1205.jpg

Quote:

Originally Posted by SCatalyst

Have the stainless steel hammer pins you've seen snap new or old and what caliber did it happen on?

I have snapped standard hammer pins, but not extended SS pins. I have seen bolt catch roll pins snap, but since I can only shoot one gun at at at time, my preference is to use the VM-Hytech block with unmodified Uzi mags.

Quote:

Originally Posted by SCatalyst

The reason why I asked the original posted question, is because of the 3rd post on this page.

http://www.ar15.com/mobile/topic.htm...=549070&page=5

OK now it makes sense, or... not sense...

That thread is about a 9mm DGI (Direct Gas Impingement) system. You would need a light combined weight to the whole system to operate with 9mm gas after it goes back through the tube and acts on the key.

But why in the world would someone be trying to create a gas operated 9mm AR???

The poster in post three seems to be an even bigger genius than the rest on that thread. Not only does he already own a DGI pistol caliber AR, but he's experimenting with his 9mm blowback and lighter bolt weight.

Good thing he runs 115 gr for OOB "detection." :rolleyes:

As Todd K. said, you would be send your bolt flying backward at a much greater speed than desired, have a bunch of extra gas in your face, probably snap your hammer pin, and smack the back of your RE for what would likely amount to the most recoil you could ever feel from that AR type.

Quote:

Originally Posted by SCatalyst

Granted I know it was for a application in FA with a 7.5" barrel. But in theory, the perceived recoil reduction would be the same for a shooter with a 16" barrel in SA.

Check your theory. His pressure dissipates after 7.5". Yours takes more than twice as long. I'm not going to address SA/FA.

Quote:

Originally Posted by SCatalyst

I didn't want to thread jack that topic, so I tried contacting the person who posted it. No dice.

No one's heard from him since he made some sweet mods to an M48A Mauser to chamber .841 Schwarzenegger.

Quote:

Originally Posted by SCatalyst

I'm aware of the extra counter pressure needed by a blowback AR. But if the weighted recoil pressure was taken out of the bolt and applied to a Wolff High Power pistol caliber buffer spring, and maybe, combined with a much heavier buffer or one of those hydraulic buffers, could create a different shooting experiance on a blowback 9mm.

That's awesome. You should play the stock market.

Is the goal here really to achieve a different shooting "experiance???"

Quote:

Originally Posted by SCatalyst

I could trial and error and buy things to test it out, but if you figured out a great buffering combo, I'll replicate your combo and let you know if I got the same result.

Here's a "great buffering" combo:

A complete Colt or RRA 9mm carrier

+

1) a 5.5 oz inertial buffer (H3)
2) a 5.5 oz solid buffer (9mm Buffer)

I'd still recommend extended SS pins and no BHO if you can stand it.

All the Slash-Q stuff and taping pennies (or dimes?) to a standard carrier is... ummm... well, it's up to you, but 9mm ARs are easy to troubleshoot because there's always something wacky or insane or stupid about a person's setup.

Quote:

Originally Posted by SCatalyst

My carbine runs perfectly fine, I just want to find the formula for reduced recoil for effortless, accurate follow up shots. (other than larger deltoids and traps)

PRACTICE. Run that gun.

A Slash Q is $75. An XH is $125. Neither will make you as fast or accurate as the equivalent amount of ammunition.
08-28-12, 00:28
SCatalyst

Quote:

Originally Posted by Todd.K

Try a Vltor A5-H4 buffer and rifle spring.

I don't think removing the weight will work. It will increase bolt speed, so the bolt will probably bottom out harder on the receiver extension. The bolt bottoming out is where a lot of the perceived recoil comes from.

Yeah, I was reading about those.

It's 3.995" long and weighs 6.8oz. I read someone had it combined with a Wolff XP ‘RIFLE’ (I don’t know why) buffer spring in his carbine tube. He had about ¼ inch of space from the bolt face to the bolt catch when compressed.

He reported with factory 115gr that shells were ejecting shortly to the side. He was satisfied with the results, but I thought slowing of the bolt that sluggish was undesired. So if he shot a heavier round, with ejection that poor, could cause the system to short cycle. I’d prolly go this route just with the ‘CARBINE’ spring instead.

Quote:

Originally Posted by KalashniKEV

I have snapped standard hammer pins, but not extended SS pins. I have seen bolt catch roll pins snap, but since I can only shoot one gun at at at time.

Cool that’s good to hear, I was about think my SS pins were a waste of cash. Yeah, I can see my bolt catch pin in my CMMG 9mm lower breaking in the future, diameter for the pin hole is too large and has too much play in it.

Quote:

Originally Posted by KalashniKEV

But why in the world would someone be trying to create a gas operated 9mm AR???

The people who own one say it’s great to shoot with the benefits of DI (less recoil, efficiency, yata yata). You never tried anything new? Someone asked Ron Williams once, “Why in the world would you be trying to create a gas operated .45auto AR?”

Quote:

Originally Posted by KalashniKEV

The poster in post three seems to be an even bigger genius than the rest on that thread. Not only does he already own a DGI pistol caliber AR, but he's experimenting with his 9mm blowback and lighter bolt weight.

I was curious myself, that’s why I wondered who else has heard of such a thing. I looked online, put my head on it for a bit and everyone is right, logically it’s not a good idea.

Look brother, if someone says they got it to work and it’s great, I’m all ears. Wouldn’t you be incline to at least inquire about something new that you’re interested in? I don’t know if you’d been paying attention to your own collection, but firearms change as time goes on, and the only way to know what’s possible is to try something different to what’s already available. Who saw designs like the KRISS coming or that Slide Fire coming? Some things are not good for all, but they're good for some. And it started by trying something different.

If you’re worried about our safety, that’s awfully nice of you. If you think it’s a recipe for a slam fire, out of battery explosions, and were creating a situation for lost fingers, and potentially destroying a perfectly good weapon and it’s a silly idea; well this is America brother, and we always do silly things with our money all the time.

Now help me do more silly things with my money and tell me what type of buffer system you got and why!:D

Quote:

Originally Posted by KalashniKEV

Is the goal here really to achieve a different shooting "experiance???"

Yes. This is a philosophy difference here. As much as a weapon is a tool, it’s also an extension of you when mastered. Feel it, most fighters do and if something’s just not right, they change it if they can.

Quote:

Originally Posted by KalashniKEV

Here's a "great buffering" combo:
A complete Colt or RRA 9mm carrier
+
1) a 5.5 oz inertial buffer (H3)
2) a 5.5 oz solid buffer (9mm Buffer)

I’ll have to look into that, but why with the 5.5oz? Why not the heavier buffers? What do you think of this:

I found the AR57 uses a 230g (8.2oz) carbine buffer for which is also 3.5" where combined with the ST-9BS spacer (that I have) will make it roughly equivalent to the length as the Vltor A5H4 with 8+oz weight...and it's $37.

http://www.57center.com/6m8/parts-accessories.html

http://i1157.photobucket.com/albums/...1/e0265f76.jpg

This chart says it's roughly the same weight as the 9mm Q (I won’t be coin stuffing). What's the length of the 9mm Q anyway? I can't seem to find the length anywhere.

Quote:

Originally Posted by KalashniKEV

PRACTICE. Run that gun.
Neither will make you as fast or accurate as the equivalent amount of ammunition

I totally agree with you. I definitely need more range time with it. I just want to change something really quick before I really get to know her.

So what do you think? AR57 buffer, Spikes spacer, and Wolff XP 'CARBINE' length spring. Sound like a good recipe?

And thanks for the reply, you took some time.
08-30-12, 10:38
Todd.K

Does the AR57 buffer use sliding weights?
08-30-12, 13:23
SCatalyst

Sliding weights. I should have tried the buffer on the 9mm before I sold the 57.

There's someone else trying out the combo on another forum.
They'll have the buffer length of a Vltor but weight of a 9mm Q. I think they're using a MIL-SPEC buffer spring.

I'd like to hear their interpretation of the results because they also have a standard carbine buffer to compare.

Regardless of the outcome, I'm pretty sure I'll end up getting the XP Carbine spring as well because I saw this video.

I know it's not blowback or even the same caliber, but the buffer weight had little to do with dampening. It actually looked worse as the buffer weight increased.