Interesting problem - pistol length gas block on midlength rail?

[KBScobravert]

Piston parts are in. Time for another range test to see what all the fuss is about with the 300 and piston design.

[KBScobravert]

Shit I'm still in my office. I'll let you know, nothing yet. I can give you a pistol piston to use if you need one, just give me yours when you get it.

I just found where the kits will be delivered to you on the 17th (friday)

My pistol piston has not shown up yet from Adams Arms.

[CJ]

You need to come over this weekend and we can colaborate on it. As a DI gun (10 minutes of work) I can shoot it suppressed this weekend. Besides I have powder and bullets for you.

Did the package from Amazon show up at your house yet with the risers/diffusers?

Shit I'm still in my office. I'll let you know, nothing yet. I can give you a pistol piston to use if you need one, just give me yours when you get it.

[KBScobravert]

sounds like you're losing your nerve! I'll take that rail off your hands if that's the case.

You need to come over this weekend and we can colaborate on it. As a DI gun (10 minutes of work) I can shoot it suppressed this weekend. Besides I have powder and bullets for you.

Did the package from Amazon show up at your house yet with the risers/diffusers?

[CJ]

sounds like you're losing your nerve! I'll take that rail off your hands if that's the case.

[KBScobravert]

I went with the Samson Evolution rails as they had the CLOSEST on the market parts to fit these needs. The initial rail comes with a 4" bolt on rail and 2 2" bolt on rails. Because I have a 9" barrel I opted for their 4" Evolution extension infront of the gas block. All total I have 11" of handguard on a 9" barrelled gun. I wished I could get the sum of the two down to 9.5"-10" with a much shorter spacer or less material past the gas block on the first section.

The quality is great and the fit is very precise to the gun; however I had a few issues with the sum of MY parts which have turned me off.

You can see in this picture the plug needs to milled ever so slightly to push through the front rail extension.


You can see here that hitting the bolts on the gas block required a Allen with a swivel head. Because of this and the ID of the rail being 1.650" you can not add their rail directly beneath the gas block area. When trying to do so the bolt holes start to not line up as you need them. Only way to correct this is to use a pinned style gas block for the piston kit.
I measured and marked the blocks required position to ride center on the barrl's gas port. It can not move forward any and not cover the gas holes.


All said it is a great rail but I think I am putting the gun back to DI. But using a Samson 9" Evolution rail.

[KBScobravert]

Okay, I need to buy AA1680 for subsonic, and H110 for supersonic. Broke at the moment with various jeep projects.

PM me a shoping list.

[CJ]

I need to buy some powder. Need to do some research tonight.

Okay, I need to buy AA1680 for subsonic, and H110 for supersonic. Broke at the moment with various jeep projects.

[CJ]

Speaking of hard work, get back on the presses. I should be up and running this weekend.

Sent from my SAMSUNG-SGH-I727 using Tapatalk

I need to buy some powder. Need to do some research tonight.

[KBScobravert]

Must be nice, I do all the hard work and you just swoop in and steal it, just like that.

Speaking of hard work, get back on the presses. I should be up and running this weekend.

Sent from my SAMSUNG-SGH-I727 using Tapatalk

[CJ]

I just ordered this setup. Should be here in a few days for a fit test. I will be testing it on a .300blk 9" that CJ point me to an adapter to mount my Gemtech 9mm suppressor.

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Must be nice, I do all the hard work and you just swoop in and steal it, just like that.

[KBScobravert]

Well, good news I suppose! I called Samson MFG because I honestly didn't understand wtf their evo rail did exactly. Their website is fairly confusing.

I spoke to Andrew up there and he was great. Apparently, all of their evo series rails have a gap for a piston setup. Then, you can extend the rail another 4" on front of that. Pretty damn cool!










Which means I could buy their pistol gas block rail, which is 4" of top rail, and 3" of side rail. Then add the 4" extension, and I have a complete rail with access to my piston block which measures 11" total. Meaning 2" of my suppressor will be inside the rail (and it's 1.65" ID so it will fit!), and 7" will be exposed. So that's awesome. The best part is their rails are pretty cheap ($165 for the rail I'm looking at). And their huge ID is awesome.

I just ordered this setup. Should be here in a few days for a fit test. I will be testing it on a .300blk 9" that CJ point me to an adapter to mount my Gemtech 9mm suppressor.

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[CJ]

Higher volume, but how is it affected by the larger bore? I guess I could just go read about it.

Yeah it has a substantially higher volume in the barrel, which causes a lower pressure. To counter it they switched to a standard pistol length gas system. The problem is because you have such a small barrel distance to the gas block, it's substantially more effected by small pressure changes in the cartridge. I think it's best described as .223 has a high pressure "click" when it cycles the piston, and a .300 is more of a thump (with it's lower pressure) which can cause issues, so buffer springs etc. play a bigger part.

The truth is, I've only found 1 or maybe 2 guys that have done a piston setup on a .300 BLK, so right now you just need to figure it out yourself.

[ThreeFingerPete]

It's a higher volume of gas, but less pressure. The pressure curve is different, so you have to mess with it more apparently.

Higher volume, but how is it affected by the larger bore? I guess I could just go read about it.

[CJ]

Looks promising! I might have to pick one of those up for my build.

And CJ, thats a badass rail setup. Looks damn near custom built to solve your problem. How does the handguard attach together? In the 4th pic it looks like its being held together by a rail segment, but in the 3rd it looks seamless. Different setups or do they actually attach in a different way?

the side rails do it, I think the second picture is just an extended rail it's less visible.