NR cz bren

[beltfed]

I'd add Sig PE-90s and the KAC SR15s that are light profile to that list.

I get that people want to keep to 5 round groups due to ammo costs, but mostly it just tells them they either suck as shooters or their guns are simply not capable of better than 2-3moa when firing 10 rounds, and nobody wants to admit their shooting or their gun sucks when the internet tells them the rifle they bought is 1moa.

 

[Bartok5]

OK, let's say for the sake of argument that there is no correlation between the additional moving parts of a short-stroke piston system and the relative degree of accuracy achieved with any given barrel. How then do we account for the behaviour of the R18? What was causing the unacceptable barrel-whip and 4 MOA 5-round groups, if not the additional movement associated with the short-stroke piston system? Barrel-whip that could only be tamed with a heavy barrel profile, bringing the group size down to an "acceptable" MOA to 1.5 MOA?

How do we explain the poor accuracy of the R18's pencil-weight barrel versus the Heavy-weight profie? If the piston system is not responsible for poor accuracy with the pencil barrel, then what is? Heat and inadequate stress-relief of the pencil barrel could certainly be one culprit, I suppose. But it seems intuitive to me that the movement of the Piston system must also play a role in the pencil barrel's inaccuracy. I reckon that I will continue to swin against the CGN current on this issue, as I continue to believe that short-stroke pistons adversely impact the accuracy potential of a rifle, particluarly one equipped with a pencil-profile barrel. This is based on my recent first-hand experience with both the R18 and Bren 2 in pencil barrel form, versus my experience with the HK MR223 and G36, both of which have a medium-heavy profile between the Chamber and the Gas Journal.

 

[Northern Shooter]

It sounds like many hear want the Bren 2 and other affordable semi-auto .223 rifles to be DMR style precision rigs, which they're not.

These are blasters that are meant for 3 gun and blasting steel at 100m.

 

[Ustauk]

How do we explain the poor accuracy of the R18's pencil-weight barrel versus the Heavy-weight profie? If the piston system is not responsible for poor accuracy with the pencil barrel, then what is? Heat and inadequate stress-relief of the pencil barrel could certainly be one culprit, I suppose. But it seems intuitive to me that the movement of the Piston system must also play a role in the pencil barrel's inaccuracy. I reckon that I will continue to swin against the CGN current on this issue, as I continue to believe that short-stroke pistons adversely impact the accuracy potential of a rifle, particluarly one equipped with a pencil-profile barrel. This is based on my recent first-hand experience with both the R18 and Bren 2 in pencil barrel form, versus my experience with the HK MR223 and G36, both of which have a medium-heavy profile between the Chamber and the Gas Journal.

It would be an interesting experiment to take an R18 pencil barrel, seal the rifle length gas port with a piece of crimped tube, drill out a carbine length port, cut down a spare R18 piston group to carbine length or use an MCR's if it works, and see if the pencil barrel still has as bad a POI shift as on the rifle length. You could then take the barrel and throw it on an SBI Lynx whenever they get around to making a DI'ish BCG to see how the barrel does with no piston. I wonder if the SBI DI BCG will work in the R18 when it comes out?

 

[Bartok5]

I'd add Sig PE-90s and the KAC SR15s that are light profile to that list.

I get that people want to keep to 5 round groups due to ammo costs, but mostly it just tells them they either suck as shooters or their guns are simply not capable of better than 2-3moa when firing 10 rounds, and nobody wants to admit their shooting or their gun sucks when the internet tells them the rifle they bought is 1moa.

I fully expect that the heavy-barrelled R18 will turn in 1-1.5 MOA 10-round groups just as easily as it produced 5-round groups with those same results. I simply don't have the ammo on-hand to be firing 10-round groups like some folks evidently do....

At least we're not talking 3-round groups with a free flier....

 

[BlackVoid]

....

 

[Bartok5]

I don't know what profile military issue Bren2 uses. But I watched an interview with former US marine fighting in UA, he liked it. FNC, which they got initially, not so much.

It uses the pencil profile the exact same as my 14" rifle (less the lightweight G36 Buttstock).

 

[greentips]

I'd add Sig PE-90s and the KAC SR15s that are light profile to that list.

I get that people want to keep to 5 round groups due to ammo costs, but mostly it just tells them they either suck as shooters or their guns are simply not capable of better than 2-3moa when firing 10 rounds, and nobody wants to admit their shooting or their gun sucks when the internet tells them the rifle they bought is 1moa.

But Swiss arms is a 9lb affair with a super stiff steel trapezoidal receiver and a block of steel as a locking lug. That thing is massive. ( also their barrel quality)

My personal experience with KAC SR15 - they are just so so nothing special. Noveske N4 using FN CHF is more consistent and better IMHO.

At the end of the day, some systems may need a heavier barrel to work, some can get away with less. But if you look at the overall weight, they may come out within the same ball park if you want a certain MOA.

The problem is that people always want less weight and more accuracy, it is not easy and sometimes unrealistic. And the definition of accuracy also varies. Joe said his gun is 1MOA and he got 1 MOA using 5 rounds with match ammo and takes a long time to fire each shot. But the factory ( like the one on HK website ) said 1 MOA it is based on 10 rounds and a certain rate of fire, and that number is probably based on firing at least 20 groups and it is the size within 1 stand deviation, etc etc, so they have backup to the spec in tendering documents.

 

[BlackVoid]

.....

 

[the radium king]

a agree with Bartok that a piston is going to exert more force on a barrel than you would see with a gas system so if going for accuracy then consider an hbar profile on a piston gun. for that reason my grendel build is hbar (much to my dismay; makes for a heavy gun).

however, no reason to speculate, just look at existing data. look at piston guns (not gas) and look at free-float barrels (not cold war era piston guns with forends supporting the gas block). the ruger sr-556 is a popular piston gun in the american market and is said to shoot about 1 to 1.5 moa. and from what i can see it has a medium profile barrel. damn; i should've got a ligher barrel for my grendel build ...

but the ruger is not a pencil profile, so perhaps medium profile can manage the whip and hbar not required.

 

[Rich LPS]

The older KAC's from a few years back all had Colt Canada hammer forged barrels. This was due to Mr. Knight's success with his lawsuit against Colt Defence / USA. Part of the settlement was Colt Canada (owned by Colt Defense / USA) was required to supply KAC ###x number of their hammer forged barrels.

Side note there was an NDA on the massive amount of cash Mr. Knight got......and.....he got the entire Colt Museum....that's right KAC has it down in Florida!!!!! Been there twice, it's spectacular.

Back to KAC, mine with a 11.5" Colt Canada supplied CHF barrel was spectacular for accuracy.

I had HK MR223 heavy barrel turned down to lighten in (Gunsmith said he would never do another one as the HK barrel was soooo dammm hard) and it shot just as tight of groups as before when it was heavier.

Rich

 

[greentips]

I had HK MR223 heavy barrel turned down to lighten in (Gunsmith said he would never do another one as the HK barrel was soooo dammm hard) and it shot just as tight of groups as before when it was heavier.

Rich

This must be like at 7 or 8 year year ago.

Exact same experience. I had a MR556 turned down by Tactical Ordnance and this is the same comment he gave, from 1" dia to 0.7" behind gas block, and 0.65" in front.

I also had it nitro carburized by a commercial processor - back then I studied those metallurgy charts pretty hard to figure out which process to use. Had to go back to dig out my text book from university.

That thing put 10 rounds AE XM855 ammo into a perfect 4" square at 200m out at Connaught in zeroing. I just propped the magazine on the ground to shoot it - no sandbanging all that stuff.

HK 416 / MR 223/MR556 accuracy is amazing. It was amazing to be 8 years younger too haha, and be able to pull things off so easily ( both shooting and patience to do all these mods).

 

[Ustauk]

RDSC sells the Faxon Gunner profile barrel , https://www.rdsc.ca/faxon-firearms-20-0-gunner-series-barrel-4150-qpq-nitride-rifle-length-gas-5-56mm.html

The Gunner profile is a blend of two of the best performing profiles of all time, Gov't and Pencil.

Proving that every once and awhile, the Government can do something right, the Gunner's profile from the extension to the gas block mimics that well-known taper. From there, innovation takes over and the Gunner moves to a .625" gas block journal and our famed pencil profile out front.

Removing the weight from the front of the barrel ensures maximum versatility and keeps material to the rear to maximize heat resistance and mitigate whip.

I wonder how am R18 or Bren 2 would do on weight versus accuracy with a barrel with a similar profile. If you were doing a custom barrel for the Bren 2, you could make it pencil width just past where the gas system ends.

 

[Rich LPS]

Weight may play a factor, but I still profess that the quality of the barrel, materials & manufacturing are the most important equation when it comes to accuracy.

Rich

PS: Still suffering from HK Disease

 

[mebiuspower]

Weight may play a factor, but I still profess that the quality of the barrel, materials & manufacturing are the most important equation when it comes to accuracy.

Rich

PS: Still suffering from HK Disease

The special sauce is in the barrel for HK. They source the special steel from France, use Austrian GFM machines for cold hammer forge, then do barrel straightening manually with human eye. I was in Oberndorf, I've seen it.

People were mad to buy those G36 parts gun. It's like buying a Ferrari with a different motor.

 

[the radium king]

Weight may play a factor, but I still profess that the quality of the barrel, materials & manufacturing are the most important equation when it comes to accuracy.

Rich

PS: Still suffering from HK Disease

probably either/or, if you can't do strong then do big.

 

[Bartok5]

The special sauce is in the barrel for HK. They source the special steel from France, use Austrian GFM machines for cold hammer forge, then do barrel straightening manually with human eye. I was in Oberndorf, I've seen it.

People were mad to buy those G36 parts gun. It's like buying a Ferrari with a different motor.

Not everyone bought their G36 with a Lothar Walther barrel. Most of the early guns were sold with all-HK parts, including the barrels....

 

[Bartok5]

RDSC sells the Faxon Gunner profile barrel , https://www.rdsc.ca/faxon-firearms-20-0-gunner-series-barrel-4150-qpq-nitride-rifle-length-gas-5-56mm.html

The Faxon barrel won't work with the R18 Gas System components. The R18 Gas Block is based on a .75 Gas Journal, whereas the Faxon Barrel features a .625 Journal.

 

[Ustauk]

The Faxon barrel won't work with the R18 Gas System components. The R18 Gas Block is based on a .75 Gas Journal, whereas the Faxon Barrel features a .625 Journal.

Thanks for the info! Do you think that style of barrel would be a useful option for TSE/Sterling to consider for the future?

 

[Bartok5]

Thanks for the info! Do you think that style of barrel would be a useful option for TSE/Sterling to consider for the future?

Yes, I do. A medium to heavy-weight Barrel between the Chamber Root and the Gas Journal would offset the interference from the moving parts of the Gas System, while the 'pencil" profile forward of the Gas Journal would assist in reducing weight and any perception of imbalance with an otherwise heavy front end. This would be the ideal compromise Barrel for AR180b-based designs.