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 Post subject: Pulse Rifle Barrel
PostPosted: Mon Dec 22, 2014 1:35 am 
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Hello guys, long time no speak, I'm back from the shadows with questions...

The Hero PR did not have a round barrel if I remember correctly?

It definitely wasn't round like a normal barrel and I know that the Prop Store London sold one around 2 years ago. It had a screw thread on one end and 2 recesses machined into the barrels rim, presumably for tightening the barrel tip into a tapped Thompson barrel

At one stage I had all the info and had drawn blueprints on the dimensions and shape, but it seems a harddrive crash a few years back cost me that data and I gave up on it. I had planned to build one and share the info with the board - Thinking we could get someone to do a run. I remember the barrel was wider, which would require a custom triangular barrel support.

I remember there were discussions about the barrel potentially being some sort of industrial valve and someone else had taken direct measurements from the 1:1 scale black and white Bapty photos, but I cannot find them now?!?

Anyone else have info on this??

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Last edited by treeboar on Wed Dec 24, 2014 1:51 am, edited 1 time in total.

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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Tue Dec 23, 2014 7:32 pm 
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No response from you guys so far... but after much digging, I turned this up:

Image

Jogging anyones memories?


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PostPosted: Tue Dec 23, 2014 8:03 pm 
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Location: United Kingdom
Service Number: A08/TQ1.0.02136E1
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There was one for sale on the Propstore website in January 2008, here are the details:

"Aliens - Pulse Rifle Grips and Barrel Extension: A grip and barrel extension section of a Pulse rifle used on James Camerons sci-fi classic Aliens. The grip is made from resin with a small metal plate on the left side. The barrel extension was used as a restrictor for the Thompson section of the rifle and to also extended its barrel to bring it inline with the front of the rifle. The grip measures 13cm (5") and the barrel extension measures 8cm (3"). £495.00 / $839.00"
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Harry

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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Tue Dec 23, 2014 9:59 pm 
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Hi Harry, How's tricks?

The Prop Store definitely had some front-on shots of the barrel.

Do you have those - Lost all mine in the harddrive crash!!! :(


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PostPosted: Tue Dec 23, 2014 10:02 pm 
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Service Number: A08/TQ1.0.02136E1
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Those are the only shots that I saved so I'm pretty sure that was all that were posted, but I didn't search that thoroughly. I'll check again when I can.

Harry

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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Tue Dec 23, 2014 11:00 pm 
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Location: Virginia
Service Number: A03/TQ2.0.02146E1
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I gotta say this is all new to me, but its handy info considering I was just mulling how to tackle the barrel on my latest pulse build. I was considering extending the air-soft Thompson instead of replacing it. I was worried about a "seem" and now i am far less concerned with that, as it appears screen accurate. Definitely something to think about.

But it doesnt really jive with the bapty photo of the pulse construction that has been circulating. That seemed to be clearly made from a thompson with the factory extended barrel? No? A clever weld and blend job?

Or is this a case of multiple Thompson's each being built a little different from each other? Perhaps there were not enough factory extended barrels to go around so some got the screw on extension?

Regardless, thanks guys! Fascinating.


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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Tue Dec 23, 2014 11:10 pm 
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Service Number: A07/TQ2.0.12129E1
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The pulse rifles made by baptys would all have been done so they can be returned to standard use after filming so I doubt if they welded the barrels, film use automatic weapons have whats known as a Hollywood blank fire adaptor which is a restrictor screwed into the barrel to increase the back pressure so a real weapon can fire blank rounds with less power, the extention in Harry's pic would have served both purposes, as the Thompson barrel would already have had a thread in the end of the barrel, the non firing pulseys were probably a one piece barrel but not the firers,

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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Wed Dec 24, 2014 12:41 am 
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So the real Bapty Hero's would've had one of these screwed into it's barrel

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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Wed Dec 24, 2014 1:11 am 
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Ahhhh... YES! :dropship:

This was driving me nuts but I found what I was after... so allow me to share.

Firstly PHOTO CREDITS out to Jon and Stefan!!

This is a pic from an SF&FM photoshoot that Jon (member: b26354) posted - and as he noted you can see that the diameter of the front support on the barrel vent is pretty much the same diameter as the Remington barrel:
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This can be seen on the original Bapty black and white 1:1 images
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Stefan (Bugstomper) then came up with this:
"The outline you see is a CAD-Model of an actual, unmodified M1A1 barrel (with the barrel adapter attached) with dimensions taken from the real deal and cross checked with blueprints of the Thompson. As you can see - it matches perfectly to the picture of the photo. So unless they (Bapty) modified the whole length of the Thompson barrel (which I find unlikely) the front diameter is 0.75"/19.05mm.
I guess the problem arises from the perspective that's in the picture. The side wall of the SPAS cage is slightly near to the camera than the barrel. So when the side wall in the picture matches perfectly to the real deal, the barrel will show up slightly smaller in the picture.
You can see the effect at the slots of the SPAS cage too - if it would be a true isometric picture the slots of the rear wall would align perfectly with the front slots. "

Image

And it was Jon that made this mod to his PR:
Image
Image


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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Wed Dec 24, 2014 2:39 am 
THAT guy
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Location: Virginia
Service Number: A03/TQ2.0.02146E1
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Well damn. Learn something knew every day. Cool.


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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Wed Dec 24, 2014 1:49 pm 
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Hey Harry,

Hope you do not mind me hotlinking your pictures here, but you have some decent images on your site of this barrell too.

Image
Image


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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Sat Dec 27, 2014 11:28 pm 
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FOUND THE MOTHER LODE.

I knew I had not imagined it.

It was Stefan (Bugstomper) who nailed this I believe (maybe he can chime in and confirm that all details are correct). Here is the link: http://forum.alienslegacy.com/viewtopic.php?f=3&t=9737&start=25

I have also added images and info that Stefan had posted below, in the hope that will all info gathered in one place we can archive this post as the definitive PR Hero Barrel guide:

Stefan based his work on the picture of the Barrel Extension sold by the Propstore (the same as provided by Harry further up this thread), and made this overlay:

Image

Based on the fact that the thread had to fit into the Thompson barrel Stefan theorised that the only metric thread fitting that would be possible was an M14x2. He then theorised that the outer diameter of the barrel extension would appear to be approx. 18mm

He noted that the Propstore pictures makes it look like the extension is made of two parts:
- A tube with an outer diameter of 18mm and and inner diameter of 14mm
- A hollow 'screw' that holds the extension tube in place and at the same time acts as a restrictor to create enough gas pressure to cycle the bolt

He drew the whole thing up as a CAD using the comparison of a standard Thompson barrel at the top of the page with the modified and extended barrel at the bottom of the page:

Image

AND then he built it...

Image

Stefan's Barrel cage is built from 3mm thick steel, which started life as 40mm x 40mm steel box section tubing (which unlike aluminium squared tubing is slight rounded, not truly square). This is then machined, before having two sides bent in towards each other to form the triangle.

As he notes the bend inwards does not start in the corners of the square tubing, it actually starts further up, where the Barrel cage has been machined, at the bottom of the milled slots (the weakest point). If you look at the original vents you can see the same effect.

This is the 10 hole vent/triangle. The sides the 8 hole triangle are shaped differently (straight) as the slot between the triangle and the vent is milled down to the bottom as you will see from this CAD that Stefan created:

Image

His assessment was that bending the part is actually quite easy for the front part. Just a vice needed to clamp down the bottom to keep it straight. This is especially important for the rear part as the material is not weakened by the cutouts. Luckily, you don't need to bend it much there due to the taper of the barrel. Nevertheless, he had to heat that area with a blowtorch to get it done.

So... Bugstomper... Firstly a million thanks and secondly... can you confirm all of the above? Where any modifications/changes missed? How far did you get with the 8-holer?


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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Wed Dec 31, 2014 2:15 am 
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Location: Germany
Hi Tom,

I just got back from my X-mas holidays - so I'm a little late to answer your questions.
However, it looks like you did a great job with the search engine.
The dimensions for the barrel extension are indeed the latest version.

Btw.: Where did you find that picture of the cut open barrel with the blank firing adapter? Did it come with any additional info?

Cheers,
Stefan


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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Wed Dec 31, 2014 3:16 pm 
THAT guy
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Location: Virginia
Service Number: A03/TQ2.0.02146E1
Country: United States
I have been obsessed with trying to find the extensions now in every photo I see. Another pic for the 'file' that maybe useful is this closeup of from the shot of the hero pulse next to the ruler. Now to replicate it myself...

Attachment:
Barrel Extension.jpg
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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Thu Jan 01, 2015 1:36 pm 
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Hi Stefan,

The cut away image is of a Thompson barrel with blank adapter added - exactly what we are discussing!

See more here: http://www.machinegunboards.com/forums/index.php?showtopic=12570

Tom


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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Thu Jan 01, 2015 2:51 pm 
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Location: Germany
Thanks for the link!

It's interesting that the oriface diameter (4.75mm) of the blank firing adapter is quite a bit smaller than on the PR (7mm).
So in Aliens they were probably using even "hotter" loads than then standard .45 blanks.

Cheers,
Stefan


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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Thu Jan 01, 2015 3:25 pm 
THAT guy
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Location: Virginia
Service Number: A03/TQ2.0.02146E1
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Bug Stomper wrote:
Thanks for the link!

It's interesting that the oriface diameter (4.75mm) of the blank firing adapter is quite a bit smaller than on the PR (7mm).
So in Aliens they were probably using even "hotter" loads than then standard .45 blanks.

Cheers,
Stefan


Would a hotter load produce a brighter muzzle flash? If so then it's pretty safe to bet they went as hot as they could get.


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 Post subject: Re: Pulse Rifle Barrel
PostPosted: Thu Jan 01, 2015 8:20 pm 
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Yeah bigbisont, bigger flashes! AND bigger bangs!


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