The thread on the M4 uppers and all the SL8 stuff has left me asking this question. To me the beauty of the HK rifles is the simplicity of it. Everybody cries about the gas system on ARs, talks about having to adjust it on the FAL, and how it screws up accuracy on the M1 platform. I'm not a weapons engineer, but am very mechanically inclined and good with other type designs, and I still can't see whats so wonderful about a gas system. Even Benelli has one now. I love my ARs and M1s, but it just seems to me a straight blowback sould be more reliable.

Isn't HK's roller lock system more complex and expensive also?

The way I understand it, the roller lock system keeps the bolt locked until pressure drops. As far as expensive , it's expensive if it's HK,cones run close to AR prices. Not that many moving parts, and fewer that can cause problems than in a gas system.

Quoted: Isn't HK's roller lock system more complex and expensive also?

No it's really not...there is 2 rollers and a plate that is held in place by a roll pin. replacement of the rollers takes about 2-3 minutes at most.

When the bolt enters battery, the bolt head seats and pushes the rollers out. When the round is fired, the rollers keep the bolt in place until the pressure drops to a safe level and the releases the rollers...

It's got more recoil,  but I have never had a problem with this system....

Quoted: Quoted: Isn't HK's roller lock system more complex and expensive also? No it's really not...there is 2 rollers and a plate that is held in place by a roll pin. replacement of the rollers takes about 2-3 minutes at most. When the bolt enters battery, the bolt head seats and pushes the rollers out. When the round is fired, the rollers keep the bolt in place until the pressure drops to a safe level and the releases the rollers... It's got more recoil,  but I have never had a problem with this system....

Wouldn't that cost more to engineer ?

Quoted: Quoted: Quoted: Isn't HK's roller lock system more complex and expensive also? No it's really not...there is 2 rollers and a plate that is held in place by a roll pin. replacement of the rollers takes about 2-3 minutes at most. When the bolt enters battery, the bolt head seats and pushes the rollers out. When the round is fired, the rollers keep the bolt in place until the pressure drops to a safe level and the releases the rollers... It's got more recoil,  but I have never had a problem with this system.... Wouldn't that cost more to engineer ?

I should have said that, IMO, that it's not that complex...as for the engineering...well I did sleep at a Holiday Inn Express once...

The roller system transfers the energy to the carrier and the time it takes to move back it unlocks the bolt and cycles.  Great system and very easy to build (Germans could kick them out in 9 hours!), BUT the delay of the carrier causes the need for the flutes to float the shell or it will tear the back off the shell.  It is a very neat system.  

Straight "blow back" will allow the bolt to begin to move before the bullet has left the barrel.  This will throw the aim off, like an open bolt weapon moving forward before the round even fires.

The gas-operated weapons are smoother.  The load smooth, shoot smooth and cycle smooth.  Don't get me wrong I love my delayed roller rifles, but the slamming of the bolt into battery, the pretty violent recoil and HOT hand guards is characteristic of these very accurate weapons.  I was surprised to see HK dropping the system.

My $.02

So basically it's a manual vs. automatic trans. kind of thing? Gas is smoother and easier on the operator, roller  lock is maybe simpler and more rugged (AK being excepted) but a bit harsher to deal with.
Hmmm, harsher to deal with, think I like it!

Quoted: So basically it's a manual vs. automatic trans. kind of thing? Gas is smoother and easier on the operator, roller  lock is maybe simpler and more rugged (AK being excepted) but a bit harsher to deal with. Hmmm, harsher to deal with, think I like it!

Not quite. I honestly think the feel of the HK 9X series rifles is exetremely good (when shooting with a solid fixed stock). for me, the 91 had less felt recoil then a M1A, and a 53 had less felt recoil then a AR15.