Form 1 Question

[littlematt]

Hi! First post.

I have an 805 pistol that I bought with the intention of SBRing on a form 1. I have other SBRs and am familiar with the process. However, I can't find an overall length to use on the form. Is there any variation in stock lengths that should be considered? I thought about subtracting 5 inches from the rifle length but wasn't sure what everyone else put on their approved forms. Ideally, I'd like to use a czusa made kit that most resembles the factory set up and not an after market set up. thoughts? Hopefully someone will post up or send me a pm.

I also have legal suppressors and would like to be able to use one on it. Anyone on here using a suppressor on the 11 inch barrel? I'm curious if the gun seems over gassed or if there are any issues I should be aware of? 

Thanks! I hope to be able to contribute one day soon.

-matt

[mrar15]

Overall length (with factory stock) can be found here
https://en.wikipedia.org/wiki/CZ-805_BREN
The overall length is based on extended stock, which is about 33.7" (855mm) for 11" pistol barrel. It will take a little over 3 months to get form1 approved.  Depending on the type of your suppressor, most should be able to handle 11" barrel in 556 (.223). You will need an adapter to convert 14x1 LHT to 1/5x28 threads that will work for most 556 suppressor or to 5/8x24 if you want to use it on 7.62 suppressor.

[RSR]

The CQB upper receiver, HK416 and other special forces uppers intended for use primarily w/ suppressors are in the 10-11" range.  If you look to quality suppressor manufacturers you should be kosher, but pressure and wear and tear will be much higher.  Small Arms Defense Journal did a study on 5.56 barrel lengths. http://www.sadefensejournal.com/wp/?p=1093

Five-round average pressure in the bore at the moment of bullet uncorking is plotted against barrel length. It is apparent that the pressure rises exponentially with decreasing barrel length. This rapidly increasing pressure produces significantly higher sound levels as well as flash and strain on suppressor design. The values for 10.5 and 14.5 inches were calculated by averaging the adjacent measurements.

I also have legal suppressors and would like to be able to use one on it. Anyone on here using a suppressor on the 11 inch barrel? I'm curious if the gun seems over gassed or if there are any issues I should be aware of? 

Curious on this as well.  Just posted regarding similar in another thread where a member cut down his barrel slightly...
Generally, short stroke piston designs are less finicky w/ pressures than DI as blow off ports help to relieve excess gas before full pressure increase is transmitted to bolt carrier.

[littlematt]

I also have legal suppressors and would like to be able to use one on it. Anyone on here using a suppressor on the 11 inch barrel? I'm curious if the gun seems over gassed or if there are any issues I should be aware of? 

Curious on this as well.  Just posted regarding similar in another thread where a member cut down his barrel slightly...
Generally, short stroke piston designs are less finicky w/ pressures than DI as blow off ports help to relieve excess gas before full pressure increase is transmitted to bolt carrier.
[/quote]

that is what I'm hoping. My sbr'd ar15's were a bit over gassed with the cans on them which I know how to fix. hopefully I'll have an answer in a little over 2 months.

[Gunman9]

I shoot my Bren 95% of the time suppressed. And the barrel is 2" shorter than factory since I had it cut, crowned, and threaded. I used my Form 1 Titanium suppressor that I built. No over gassing, no pressure issues. From my understanding the Bren was built and designed for 308 so the entire gun is over built for the 5.56. Here is a video of mine suppressed.

http://youtu.be/FvDKrlW-0r0

[RSR]

I think it's safe to say that the upper receiver was built to handle .308/7.62 Nato.  As to what weapon components (spring, bolt, etc) may need to be upgraded to make it safe to operate, that is currently unknown.

How is the ejection pattern suppressed vs unsuppressed?  Throwing cases further and how much further?  In brief, equal and opposite reaction for every action -- a faster bolt release to the rear should eject spent cases further than unsuppressed...

[hANNAbONE]

A friend of mine that makes SS Compensators mentioned he wouldn't purchase anything with 10" or shorter barrel.

I assume he must know the numbers above for pressures and different lengths of barrels.

Interesting to say the least.

[z00mie]

One of the deciding factors for me to get into the BREN 805 was that it was purpose designed to operate in a 10" kurtz" type configuration. I'll bet that suppression was also considered  in design but that assumption would be a leap of faith on my part.

To the question: The overall length can be gleaned from CZ's LE portion of their website...