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View Full Version : Urethane as a stock bedding material?


saands
November 10, 2001, 07:52 PM
Just a little history ... I have started to look at making myself a muzzle brake and I ran across a Browning with their BOSS system which in addition to being a muzzle brake has a moveable weight at the muzzle that allows you to fine tune the barrel's vibrations for a given load. As a mechanical engineer I have to admit that the idea appealed to me, so I looked up their patent at the US Patent Office (incredibly informative ... as patent applications are required to be) and it mentioned their action bedding process and referred to Devcon's Flexane 94 polyurethane (I believe that the 94 refers to the durometer) which is a pretty hard rubber. I have alway seen Acraglass mentioned as the standby, and have always assumed that it is like an epoxy (very rigid). Am I mistaken about the Acraglass being rigid? Has anyone tried bedding with a firm moldable rubber?

This was just a passing curiosity until I started getting more and more impresssed with the engineering at Browning (at least that which was reflected in their BOSS patent) ... I am inclined to give them the benefit of the doubt on the polyurethane idea ;)

Thanks,
Saands

UK2TX
November 12, 2001, 01:58 PM
Hello Saands,

What was the patent number? I'd like to review it as well.

As for Acraglass v. flexable bedding, since the Acraglass would make a flexible receiver "stiffer" that might explain it being the de facto choice. I guess, and it is a SWAG, the flexable bedding would allow the damping to be uniform, a very desirable feature, especially with the BOSS system. The damping would provide gross damping of the barrel with the BOSS part actually providing the fine tuning.

FWIW New Ultra Light Arms use full contact bedding to allow the POI to remain the same no matter what the weight of bullet. I'm sure that it was mentioned in an web interview with the founder of NULA ( if any one has the link I'd like to have it ).

Regards,

UK2TX

saands
November 12, 2001, 02:56 PM
UK2TX:

There are actually 3 patents of interest:
1&2: Re. 35,381 is the re-issue of Patent 5,279,200 "Ballistic Optimizing System for Rifles" (Clyde E. Rose)

3: 5,698,810 is a modification/enhancement "Convertible Ballistic Optimizing System" (Clyde E. Rose)

Both are a pretty good read. Mr. Rose certainly did his homework and gets cudos from this mechanical engineer! I would have liked to have seen some dynamic models that predict the effects, but after running the system through an FEA package myself, I concluded that there are vibrational systems at play that are well beyond first and second order approximations! The re-issue actually is quite interesting as it has the original and the modifications in italics so you can follow the progress of their understanding of the state of the art. The USPTO is an AMAZING resource!

Have fun and share more if you learn more!

Saands

UK2TX
November 12, 2001, 04:04 PM
Hello saands,

Thanks for the information, I'll read it tonight.

Regards,

UK2TX

UK2TX
November 14, 2001, 01:41 AM
Hello Saands,

I "found" the link for the Melvin Forbes interview:

http://www.theaccuraterifle.com/jul01.html

It makes for an interesting read.

Regards,

UK2TX

saands
November 15, 2001, 05:45 PM
Eighty "reads" and Zero responses from anyone who has tried anything compliant for a bedding material ... amazing!

UK2TX
November 15, 2001, 05:47 PM
Hello Saands,

I'm planning to, once deer season closes!

Regards,

UK2TX

saands
November 15, 2001, 06:05 PM
Me too ... but I thought I'd check first. What are you planning on using ... I was thinking about following the lead of the aforementioned professionals. I have found a couple of places that advertize that they carry the Flexane 94 ... and one that can special order it for me. It will be a few dollars more than some brand X polyurethane ($20 to $30 for a pound), but this doesn't seem like the time to get cheap ;) ... and if it works, I should have enough to do at least a couple of rifles ... maybe even a recoil pad if I get ambitious.

Saands

UK2TX
November 15, 2001, 06:18 PM
Hello Saands

McMaster-Carr, http://www.mcmaster-carr.com carry a generic "Flexane equivalent" in two hardness's:

80 Shore A Durometer - 1lb resin/hardener - p/n 8644K11 $20.88 94 Shore A Durometer - 1lb resin/hardener - p/n 8644K18 $20.88

Which company did you plan to get the Devcon from?

Regards,

UK2TX

saands
November 15, 2001, 06:50 PM
I saw their generic 94 Durometer Urethane. Actually McMaster-Carr will special order the Flexane 94 from Devcon for you for $29.96 a pound with an 8 day lead time. The part number that they gave me was 8644k999 but that might refer back to my particular quote. I saw the Flexane for as little as 17.10 a pound on another site, but that was a case price and if you wanted just one pound it ran $69 ... EXCUSE ME! I think I'll be going with the brand name manufacturer and the known vendor!

Saands