hard recoil in gas delayed blowback pistols

aric84

aric84

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Brought my new Norinco M77b to the range Sunday and fed it 100 rounds of winclean bulk pack ammo. I couldn't believe how snappy it was, felt like the pistol was smacking my palm. Ran 100% of the time though. I had a couple of IVI rounds that I picked up off the ground at the range that were clean and still useable. I fed them through the M77 expecting a heavier punch since I would assume them to be loaded to NATO specs(close to +P) and I assume 147 gr. Well suprise suprise it was beautifully soft to shoot.

Maybe the higher pressure slows down the cycle more via the piston? Stumped here.
 
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Well, if the IVI rounds were 147's then yeah, they'd be softer in the recoil department if they were shooting to a normal energy level.

I had to go and look up which model it was. It SEEMS like a small and light gun even if it is all metal. If it's much lighter than about 34 oz empty that would explain some of the snappiness. Also if you were shooting 115gn rounds again that would explain some of the snap.
 
Thanks BCRider. The M77 is certainly not as light or small as the pics online make it seem. Weighs somewhere in between my Hi-Power and SP-01 Shadow. I don't buy much factory ammo anymore, so it explains why I was surprised at the snap from the 115 grain stuff. I guess I will try loading up some 147's for it and see how that pans out.
 
A bullet seated closer to, or touching the rifling would exhibit more pressure than one seated farther into the case provided it's not seated deeper than SAAMI spec.

Lead bullets will cause more pressure as your barrel accumulates more lead as well.
 
IVI's where almost surely 124gn loaded +p, borderline +p+

the gun will shoot softer with nato spec as the higher pressure holds it shut longer, or so I would speculate. I have fired it back to back with a P7, no comparison. It was the only 9mm i ever shot that made my hand sore....
The P7 on the other hand is beautifully soft shooting with everything, i suspect they just did a better job engineering the gas flow/breaking effect. The chinese probably based theirs on nato/military spec ammo rather then the civilian spec/sami rated stuff.
 
Hmmm, Interesting. Thanks C&L.

I'll probably try loading up some different loads and seeing how they shoot, but I'll need to pick up some jacketed 9mm. I wonder if the real difference is in the fit of the piston, maybe allowing more gas to get by and making lower pressure rounds open the breech sooner. I could not believe how hard it was recoiling, but if that can be solved by loading it hotter, then it will be worth a try. I'll update my results when I get there.
 
aric84 said:
Hmmm, Interesting. Thanks C&L.

I'll probably try loading up some different loads and seeing how they shoot, but I'll need to pick up some jacketed 9mm. I wonder if the real difference is in the fit of the piston, maybe allowing more gas to get by and making lower pressure rounds open the breech sooner. I could not believe how hard it was recoiling, but if that can be solved by loading it hotter, then it will be worth a try. I'll update my results when I get there.
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yeah, my brother bought one on a whim, and after i shot it for a bit my hand was sore. From a 9?! i switched to a M27 with full house 357 for a break lol
make sure you only run jacketed not cast. lead vapor deposit will solder it self onto the piston assembly and can be a ##### to scrub off or solder the action shut in a severe case
 
No worries there, already discussed the use of cast and plated bullets in the reloading section. Will not be going there!

I hope I can get this sorted out because I originally got the pistol so that the wife could shoot it, she has tiny hands and it fits the bill. Unfortunately she did not like shooting it because of the recoil though. If I can get a comfortable load then she will definitely shoot it.
 
I have a Styer GB-80 pistol, and I find it painfull to shoot too much, which I atribute to the design of the grips and frame. Doesn't seem to kick any harder compared to my other locked breech 9mms.

I think CockedandLocked is right on the money about hotter loads holding the gun closed longer and so spreading the recioil out over a longer time.
 
I'm going to try some plain 147's as well to see if maybe the lower velocity will result in the gas piston being under pressure for a longer period of time(ie longer time in the barrel should mean slower unlock)
 
Interesting comments on gas retarded pistols and the GB and P7 comments. I own both. Some facts for both: they were set up for NATO ammo, the GB for sure and I believe the P7 as well. NATO ammo is rated at +42,000 psi so it's hotter than +p and perhaps a tad hotter than +p+ but the Europeans measure the pressure a bit closer to the chamber than SAAMI does. Generally, all gas retarded (or delayed) pistols have more of a snap on the web of the shooting hand than Browning tilt-barrel designs or even rotating barrel designs. The reason is that the barrel is fixed and does not move back at all, thus all the impulse of the firing process goes on the slide that slams against the frame. On the other hand, by not tilting the barrel, there's no upward motion, the barrel lies lower to begin with and the result is less muzzle rise. The GB has a broad grip and it's not that punishing after a few hundred rounds but the P7 is a different story. Great concealed gun, however.
 
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