I think I'm doing it...but I need my gasser and pressure experts!

[Iamero]

Hey guys, I was talking to my smith today and we randomly got on the topics of FALs and that led to my desire to do a PSG-1 clone. He said he's all for taking on the project but I wanted to see what you guys thought about doing one in 6.5 creedmoor. Rim Country can spin me up the barrel in 6.5 if need be, but my smith might take on the task himself as well, we will see.

But what that leads to is pressure...can a rolling block system handle the higher pressure of the 6.5 Creed? I would be building it with a 26" barrel and shooting mostly the cheaper Sellior & Bellot out of it as well as handloads with the 140 ELDm.

I know I can build a more accurate AR-10 for a lot less; hell I already have two barrels here for one, but I'm also into building these odd ball one-of-a-kind rifles and having them in my safe as well.

So, what are your thoughts? Practical? No. But totally badass.

 

[jLorenzo]

Would be cool, but expensive toy. Also would be ruining your brass so it does make sense to shoot cheap factory, American Eagle makes 120gr 6.5 load I saw for 18.99. Id do the PSG over the FAL all day.

 

[jLorenzo]

Makes way more sense in .308 imo

 

[Iamero]

Yea I was kind of thinking that as well. Once fired hornady is cheap for brass, but not lake city 308 cheap.

What about it ruins the brass? Just the hard extraction?

 

[Mike_in_FL]

I don't know your 'smith but it sounds like he has no experience with this. The only person I've ever heard of that can build an accurate FAL is Ed Vanden Berg. I think I'd buy one directly from him before I threw a lot of $ hoping it comes out alright.

 

[RyanScott]

He wants a PSG-1 not an FAL.

I wouldn’t do it. Rumor was even HK couldn’t get some guns to shoot and the high price of the system covered the scrap rate of guns that were rejected.

 

[EXTREMEPREJUDICE]

I wouldn't take a real 91 and experiment with the 6.5 but if your taking a PTR and doing it, rock on with a fun project! If you roll with it, pics please!

 

[Iamero]

Yea you can buy a clone online for $2,999 for a pretty similar setup (converted G3 basically). Right now we are just looking into whether building our own would save us any money while granting us the experience. But you’re right, it’s a gamble for sure!

 

[Mooncake]

Give Jeff at Parabellum Combat Systems a call. He's a really great guy and I don't think there are many people on the planet that know more about roller delayed blowback weapons than he does. If it will work, you'll need the right locking piece for the job and the correct bolt gap, and he can help you with those things. If he says 'no go' I wouldn't try it.

I'm with the guy who said not to F with a real 91 for the project, too. That'd be a shame.

 

[Iamero]

Yea, not touching a real deal for this project. It would be gathering all the pieces for assembly.

I’ll give him a call. He built my SBR MP5 back in the day and I almost forgot all about him.

 

[flyer]

The question for me is who flutes 6.5 Creedmoor chambers?

I think that's the #1 thing to line up.

I don't think I would try it but if you can't get a barrel made right, why start?

 

[Rootshot]

My understanding is that roller delayed blowback systems have a number of benefits and drawbacks. Outside of the cool factor, it sounds like you would be signing up for a pile of hurt trying to adapt and tune a defunct operating system to a modern cartridge.

Copied from: https://www.thehighroad.org/index.p...ges-of-roller-delayed-blowback-system.499212/

Roller-delayed blowback BENEFITS:
-generally reliable when used with ammo that it "likes"
-no moving parts up front, so barrel can be free-floated
-no hole to drill in the barrel for a gas port
-relatively cheap to manufacture (though you wouldn't know that from HK prices)

DRAWBACKS:
-generally ammo sensitive, both to bullet weight and to case type. Switching ammo can cause reliability problems.
-extremely dirty in operation, at least as bad as an AR-15 if not worse
-requires a relatively heavy and complex bolt carrier; overall system is not any simpler than a simple piston system like an AK-47
-hard on brass, due both to chamber flutes and violent ejection
-very high cocking effort when bolt is fully "locked" forward (rollers fully outward)
-lack of a gas port doesn't necessarily benefit velocity due to speed of unlocking (unlocking starts while under high pressure)
-locking strength varies as parts wear (arguably also true to some extent in piston/locked bolt systems, though for different reasons)
-no benefit in perceived recoil compared to a well designed piston system
-recoil felt can vary depending on how clean/dirty chamber is and precise details of the cartridge case
-using significantly different bullet specs (weight or velocity) requires tuning and changing out the locking piece and/or rollers
-not user-tuneable like a piston system with an adjustable gas regulator is

 

[Iamero]

Ouch, those drawbacks hurt. Yea I gave Jeff at PCS a call to see what he’s done on things like this before. Might just do a 308, but then why not just buy an AR10 or M1A? Haha

 

[Mooncake]

I think "defunct operating system" is a bit over the top, but all of the components that would be available to you would be designed to handle a certain pressure and you would be trying to adapt them to work with different pressures. It may prove to be untenable.

 

[Rootshot]

Fair enough on the "defunct" comment. Perhaps "obsolete" is a better term. My view is that the superiority of a design is determined by market share. Outside of firearms for civilian enthusiasts, I'm not seeing any net-new high-pressure roller delayed firearms for the MIL/LE market being introduced. Piston driven and direct impingement dominate because they have been highly refined and are mass produced to keep costs low.

 

[RyanScott]

Delayed blowback is a cool trick in pistol calibers but I don’t see a benefit for rifles.

 

[Rootshot]

Delayed blowback is a cool trick in pistol calibers but I don’t see a benefit for rifles.

Agree - therefore my qualification of "high-pressure" in my prior comment. For pistol caliber carbines it appears to have some benefits. Seeing that nearly all new non-handgun pistol caliber firearms are straight blowback, I'm assuming the benefit is not overcome by the added machining cost.

There is some interesting innovation in the PCC space with the "dual mass slide" in the Grand Power Stribog and CMMG's "Radial Delayed Blowback". These may achieve some of the same benefits as a roller delayed system but at lower costs.

 

[Iamero]

Yea for the cost it makes me reconsider doing a PSG altogether, but I still want to do one regardless haha. Also want to do a stupid heavy barrel m1a but haven’t found anyone willing to custom mod parts yet haha

 

[Mooncake]

I've read a few places that 'roller lock' rifles perform better in extreme cold temperatures. Since I've had piston driven rifles freeze up a couple times, I've decided I'm going to test this theory when it gets cold here. Lows in January in my AO bottom out between -30 and -40. I acquired a pair of HK91s and I'm going to test them against other designs in extreme cold with a variety of lubricants.

If they do perform more reliably and if you live in an environment that gets very cold that's a good reason to have one around...in .308.

 

[RyanScott]

Agree - therefore my qualification of "high-pressure" in my prior comment. For pistol caliber carbines it appears to have some benefits. Seeing that nearly all new non-handgun pistol caliber firearms are straight blowback, I'm assuming the benefit is not overcome by the added machining cost.

There is some interesting innovation in the PCC space with the "dual mass slide" in the Grand Power Stribog and CMMG's "Radial Delayed Blowback". These may achieve some of the same benefits as a roller delayed system but at lower costs.

Sig MPX is short stroke. Not sure about others.

I've read a few places that 'roller lock' rifles perform better in extreme cold temperatures. Since I've had piston driven rifles freeze up a couple times, I've decided I'm going to test this theory when it gets cold here. Lows in January in my AO bottom out between -30 and -40. I acquired a pair of HK91s and I'm going to test them against other designs in extreme cold with a variety of lubricants.

If they do perform more reliably and if you live in an environment that gets very cold that's a good reason to have one around...in .308.

If you look at countries bordering the Arctic circle we see lots of Diemaco internal piston guns, some G3s mostly in reserve service, some AR18 based short stroke guns and some long stroke FN and Kalashnikov guns.

Anyone who tells you that direct impingement won’t run in the cold is inexperienced.

 

[Mooncake]

Unfortunately, of all the auto loading rifles I own none are DI. I’ll try to borrow one for my testing, but I want to keep the subjects all uniform in caliber (7.62x51) and off the top of my head I don’t know anyone who owns an AR-10 and I have no interest in buying one. I would also like to include an AK, despite the different chambering.