How is velocity affected by Locked Breech, vs Delayed Blowback, vs Blowback?

[Dr.Rob]

I'll have to weigh both but my locked breech Colt 380 Govt model kicks a hell of a lot more than my FEG Pa-63 in .380. Ok the Colt weighs in at just over 1lb 4oz, and the FEG at 1lb 4 oz. the Colt is just slightly heavier. (Goofed and measured the first time sans magazine in the FEG for a 2oz difference.)

The PA has a slightly longer barrel (1/2 inch) and is a fixed barrel blowback where the Colt is a locked breech (though the saftey doesn't lock the slide like on a 1911) tilting barrel design.

The Colt seems to kick harder with lead bullets than the PA-63. Maybe it's a tighter bore? Could be the difference in grip angles but everyone seems to think the 1911 grip angle is better than the Luger-style grip angle for managing recoil. Both clocked very similar velocities with handloads (90 gr bullet at 950fps). The Colt is all steel, the FEG is aluminum alloy and steel. the Colt is SA the FEG is DA/SA. Even with jacketed ammo the Colt seems to have more muzzle flip.

I'd say, between the two there are too many variables to pick ONE for the noticable difference in recoil. They ALL add up.

Oh and since I found my 'kitchen scale" dad's 5 shot 3 inch .357 SP101 outwieghs my 6 shot 2 inch .357 Magnum carry by two ounces 1lb 10oz vs 1lb 8oz, that 2oz difference is HUGE when shooting heavy loads.

And my Luger checks in at a hefty 1 lb 14 oz while a BHP clone weighs in at 2lbs. The luger likes hotter ammo, but the muzzle flip is minimal, though it has a lot more moving parts than the BHP.

All that math doesn't always translate to a side by side comparison, hope it helps.

 

[1911Tuner]

re:

Doc Rob sez:

>I'll have to weigh both but my locked breech Colt 380 Govt model kicks a hell of a lot more than my FEG Pa-63 in .380.<
****************

Howdy Doc, and thanks for steerin' this one back on topic.

My theory on it is that the blowback gets the heavier recoil spring involved right away...during the initial impulse...and causes more of a "push" in your hand than the sharper punch of the locked breech system. Think of two shotguns of similar weight. One is gas-operated, and the other is a pump. When firing the same ammo, the gas gun's kick is more of a push, while recoil with the pumpgun's fixed breechblock is sharper. Even the Browning's long recoil scattergun seems to be more gentle than a fixed breechblock gun...at least to me.

Of course, other factors come into play. The amount of drop in the stock is a major influence in how the gun kicks. (Figgered I'd better get that in before it got jumped on.) Assuming that all else is equal, though...the self-shuckers don't generally hurt as much. There are exceptions. The Benelli that I had for awhile was wicked.

 

[jungle]

Dr Rob, Felt recoil in two guns can vary quite a bit despite small weight differences. Width of backstrap, balance, length of grip, etc. As Tuner pointed out our impression can also be altered by action type to some degree, because the recoil impulse may be spread over a longer time, as in the example of the Browning long recoil shotguns.

For a given gun weight and equal mass and velocity of the projectile, recoil will always be the same-how we perceive that recoil quality does have many other factors involved. The momentum coming out the front of the gun is the same, it is also the same to the shooter. That same momentum may be felt over slightly more or less time, with more or less torque, over more or less area of the hand or shoulder. This is one of the reasons low bore axis is seen as an aid to comfortable pistols, it is roughly akin to stock drop in rifles.

 

[Dr.Rob]

Recoil is recoil...

I'd sort of disagree with that... given that in riflles, say Springfield vs. Garand while the recoil impulse might be the same, the Garand soaks up a great deal of that energy operating the action, while the old bolt gun just kicks you in the teeth.

What I am saying is that in handguns there are so many other variables, grip angle, weight, barrel length, weight of the slide in ratio to the frame (trust me the FEG slide is a lot more massive), locked vs. blowback vs. retarded vs. single action vs. DA vs... etc etc. that any ONE of them could factor into 'percieved recoil' but the chronograph is the ONLY thing that will settle the score.

Whay you need is 3 pistols with equal barrel lengths in the same caliber from each group... and I doubt you'll find them.

Because in 9mm:
to have a retarded blowback you'd need an HK P7
for a locked breech (with a similar barrel length) you'd need a Browning Hi-Power or Colt Commander
and for a pure blowback you'd need an Astra 400/600... which nobody is still carrying.

In .380 I can't think of a single retarded blow-back pistol currently being made.

And your chronograph results would likely be negligible, and within 30 or so FPS of the manufacturer's claim from a 4 inch barrel. Which means fire 100 rounds or so of the same lot of ammo through a chrono from each gun and average them all, then compare the three averages right?

That's a lot of work to say... "I really doubt it makes much difference."

However, since the engineers aren't still designing blow-back 9mm's that does tell you something about the limit of the strength of this particular action.

A BHP and a Luger firing the same ammo look pretty much the same on a chrono. I don't own an Astra or a P7 for comparison.

 

[usp9]

DrRob said,
[QUOTEIn .380 I can't think of a single retarded blow-back pistol currently being made.][/QUOTE]


Not that it helps in your quest but, the Seecamp 380 is retarded blowback.

 

[Dr.Rob]

Well color me surprised. I did not know that. I'll bet it kicks more than a Gov't 380 or a PA-63, because it's a lot smaller.

Ok so you need a Seecamp a Walther and a Colt and a chronograph, and 300 rds and a long day at the range.

You might want a spreadsheet to do the math.

 

[1911Tuner]

Compare

Rob...Part of the sharper kick with the Springfield '03 is probably the difference in weight. They're a bit lighter than the Garands. One way to get a direct comparison is to shoot an M1A. You can turn the gas system off and see what the difference is when it's turned back on. I'm assuming that the cylinder still has that feature. Haven't looked at a recent-production rifle in a while.

 

[jungle]

The gas tapped off to operate a Garand, M14, or M16 is quite negligible in comparrison to the total energy of the round and the movement of the parts starts after the bullet has left the barrel and during recoil of the rifle. It may be thought of as another mass propelled in the opposite direction of the bullet over the recoil time of the rifle, thus mitigating some of the recoil imparted to the rifle.

The AK-107/108 is an interesting and complicated solution to recoil reduction that works by allowing the major components to "float" in opposing directions.

 

[Plink]

Folks, I haven't read all the replies, so excuse me if this has been covered already. The mass of the slide, plus the spring rate (effective mass) are combined to make sure that the bullet has left the barrel, thus lowering pressure to a safe range, before the slide has moved rearward enough to expose areas of the case not suited for handling the unsupported pressures. The guns are engineered specifically for that. If they weren't, you could expect case failures. Any velocity differences would be negligible for similar barrel lengths.

There's no "magic bullet" (pardon the pun) for increasing velocities other than using lighter bullets with their inherent insufficiensies, higher pressures, or a larger caliber. All the internal trickeries in the world like micro polished bores, polygonal rifling, etc., won't turn the .380/.32 ACP into something it isn't.