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Old June 12, 2009, 07:03 PM   #56
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Join Date: September 15, 2007
Posts: 1,707
smartwhois...The force that acts on the case in roller-delayed blowback occurs in the chamber, and on the case itself, not in the rifle action. It also only occurs after pressure has dropped to a safe level and the bullet has already fired from the barrel.

GSUeagle1089, the roller delayed blowback design has less moving parts than the M-16. You've got that backwards. The blowback design is also more accurate because the action is more direct and consistent, so you've got that backwards too.
The force that acts on a case acts in the chamber in all firearms, I'm pretty sure. If it is acting on the case outside of the chamber, the case will easily rupture, being capable of withstanding maybe 5,000 psi of the 50,000 psi generated. That there is little if any force in the Vorgrimmler action dedicated to extraction is an arguable benefit, as the case is forced out the back by the action of firing, not by the action of the bolt group.

If we count the parts in the bolt/bolt carrier group, this is what I come up with:

M16: Bolt. Extractor, extractor spring, extractor pivot pin, Ejector. Ejector spring/plunger, ejector roll pin, cam pin, firing pin, firing pin cotter key, bolt carrier (and gas key maybe). 11 parts, maybe 12 parts?

G3: Bolt, extractor, extractor spring, rollers (2) roller retaining plate, roller retaining plate retaining pin, locking piece, locking lever, locking lever pivot pin, locking lever spring, firing pin, firing pin spring, bolt carrier. 14 parts?

To look at the action of these two devices, they work in line with the bore/chamber of the rifle, and act by parting the bolt from the bolt carrier in each instance, with the added twist of the AR perhaps inducing a little torque to the whole thing. Moving parts include the bolt assembly and bolt carrier assembly on the G3, and the bolt assembly and bolt carrier assembly on the AR. Perhaps including the pivot pin as an additional moving part is justified. So, grossly, 2 moving parts in the G3, and 3 moving parts in the AR.


As far as accuracy in these designs, the difference in parts between the really accurate PSG rifle and an issue G3 is both the length of the barrel trunnion, which offers more support to the barrel in the PSG, and the reinforcing plates on the receiver to reduce flexing. Both already have floated barrels.

The accuracy in the DI AR15 is enhanced by adding a float tube. Little else. The receiver parts are stiff as can be, not needing additional reinforcement to arrive at great accuracy. While folks are concerned about movement between the upper and lower receivers, a properly made AR rifle will still shoot exceptionally well even with the movement.

I've owned and shot both. I prefer the Vorgrimmler action as to me it is easier to clean, and lubrication isn't as critical as it is in the Stoner action. But if I were to pick one as more accurate, it would be the AR series.


Contrary to what people keep saying, I have never noticed the so called increased recoil in the G3. Simple physics suggests that Newton's law applies. Given a rifle of the same weight, shooting the same projectile, at the same velocity, one will get the same recoil. The moment of recoil in the G3, if properly gapped, is spread over a longer recoil impulse, IME than say the M14. Some find this objectionable, but the recoil is not, nor can it be, any greater... in fact I'm pretty sure the G3 weighs more than the M14 in stock trim, so physics suggests that the recoil transmitted to the shoulder of the shooter in the M14 is greater...


When comparing more of apples to apples, the HK93 vs. the M16, the Hk93 has a much more pleasant recoil impulse than the M16, and it doesn't bounce as much on auto fire, IME. HK got it right with the angles and particulars of the HK93 action. Again, properly constructed, the HK93 with good ammo will shoot as well or better than the standard M16A2. When you put the float tube on the AR series, the equation changes. I don't think this is due to the action per se, but due to receiver flexing and the length of the barrel trunnion of the HK. Fortify these two parts like in the PSG, and I feel confident that the rifle will shoot right alongside an accurized AR.

Either design can be made to shoot exceptionally well. Both designs have an action that acts in line with the bore, and that is where they excel. The mechanism for unlocking the breech in the AR or the HK differs in detail, but accomplishes the same linear unlocking action, which is what makes them such stellar rifles, from the standpoint of inherent accuracy potential.

Last edited by stubbicatt; June 12, 2009 at 07:15 PM.
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