Shot velocity with semi-auto compared to pump/single

53Izzy744

53Izzy744

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May be a dumb question but i was thinking about this the other day while with my dad breaking in his new semi auto shotty.

His uses a gas system and not inertia so i was wondering if his shot are going slightly slower because some of the gas is being stolen to work the autoloading function?

I would imagine it would affect the velocity compared to a single shot or pump that doesnt need any of the gases that forces the shot down range.

Not having a chrony i cant test to confirm but was just wondering if anyone knows off hand? Couldnt come up with anything in google searching either.

Cheers
 
madtrapper143 said:
Shotgun experts say the difference may be about 20 fps so it does not affect performance in the least. I am referring to Elmer Keith and Jack O'Connor as my sources.

Darryl
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Okay great thanks! I remember seeing a study done that barrel length affects it quite a bit (they were chronying a mosin and cutting the barrel back an inch at a time) but makes sense a little fps would be lost when stealing some gasses in a semi.
 
A lot of shotgun shells have a very hi ES 50 FPS isn’t uncommon.

Bore size and choke constriction is the answer.
 
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No straight forward answer. Yes, their is some loss in velocity, but their is so many other variables also at work here that a straight answer is not easy. Bore size,forcing cone length, shotshell acceptable variance, temperature, piston design, choke sizes and barrel will all effect muzzle velocity.
 
I set my chrono up the other day. My skeet loads are between 1350 and 1400fps generally. 3/4 oz loads. I shot a beretta a303 3" 28" mod choke
a beretta a400 explore 28" ic optima hp choke
A rem 1100 23" cyl barrel
Mossberg 535 ats 28" .650 custom turkey choke
Ithaca 37 26" cyl barrel
Baikal ij58 sxs f/m 28.5" barrel iirc
Arizaga sxs 26.5" barrel f/cyl
Giuseppe sxs 30" f/m barrels

All of these guns produced between 1330 and 1392 fps. A400 being 2nd fastest. My 30" sxs was the slowest. In a glorious waste of ammo id conclude there is no real difference. In the heat of the summer vs the cold snap we had the other day i gain 10 to 20fps on my loads. Id say any variations are from throwing powder and not exact weights as for shot as well. I was going to also bring a canuck 13" pump but the truck was getting full. Kids car seat takes up so much room in the back seat
 
brybenn said:
I set my chrono up the other day. My skeet loads are between 1350 and 1400fps generally. 3/4 oz loads. I shot a beretta a303 3" 28" mod choke
a beretta a400 explore 28" ic optima hp choke
A rem 1100 23" cyl barrel
Mossberg 535 ats 28" .650 custom turkey choke
Ithaca 37 26" cyl barrel
Baikal ij58 sxs f/m 28.5" barrel iirc
Arizaga sxs 26.5" barrel f/cyl
Giuseppe sxs 30" f/m barrels

All of these guns produced between 1330 and 1392 fps. A400 being 2nd fastest. My 30" sxs was the slowest. In a glorious waste of ammo id conclude there is no real difference. In the heat of the summer vs the cold snap we had the other day i gain 10 to 20fps on my loads. Id say any variations are from throwing powder and not exact weights as for shot as well. I was going to also bring a canuck 13" pump but the truck was getting full. Kids car seat takes up so much room in the back seat
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Never a waste of ammo! :)
 
brybenn said:
I set my chrono up the other day. My skeet loads are between 1350 and 1400fps generally. 3/4 oz loads. I shot a beretta a303 3" 28" mod choke
a beretta a400 explore 28" ic optima hp choke
A rem 1100 23" cyl barrel
Mossberg 535 ats 28" .650 custom turkey choke
Ithaca 37 26" cyl barrel
Baikal ij58 sxs f/m 28.5" barrel iirc
Arizaga sxs 26.5" barrel f/cyl
Giuseppe sxs 30" f/m barrels

All of these guns produced between 1330 and 1392 fps. A400 being 2nd fastest. My 30" sxs was the slowest. In a glorious waste of ammo id conclude there is no real difference. In the heat of the summer vs the cold snap we had the other day i gain 10 to 20fps on my loads. Id say any variations are from throwing powder and not exact weights as for shot as well. I was going to also bring a canuck 13" pump but the truck was getting full. Kids car seat takes up so much room in the back seat
Click to expand...

That’s a lot of effort thanks for doing that. It would have been very interesting to have measured the 13 inch gun.
 
As I understand it, most shotgun loads have reached almost full velocity within the first foot or so of barrel length so bleeding off a small amount of gas would be insignificant in comparison with all the other variables - as the above experiments have showed. A duck would never notice the difference.
 
My canuck pump 3" 13" barrel with a i believe a primos brand turkey choke its a .655 mobile choke anyway averaged 1287fps. Although the temp was up maybe 12 or 15 degrees f. Its not enough to change my leads in skeet for what its worth. I broke 17/25 with it last time out. I had a bad station 2 lol. Big change from the beretta a400 ive been shooting lately but considering the turkey choke i think it proved capable enough. Its the precieved lead that changes and causes many to swear off short barreled guns
 
So 9 guns various barrel lengths and chokes with thrown handloads theres quite a variation in fps at the muzzle but doing the math by the time the pellets are spit 20 yards theyre all basically the same speed at that point.

The chrono is a fun toy. Years ago i built a shield for it and shot 1700fps rem hyper sonics vrs rem sportman 1300fps both in BB steel at 30 yards velocities were basicslly equal. The faster higher speed start slows down much faster as round pellets suck ballistically. Proved my point of not needing expensive hyped up shot that resulted in way more muzzle rise and muzzle blast and slower follow up shots.
My skeet handloads i use for small game hunting and bird hunting including turkey. I just change the shot size which plays with shot weight a bit. My loads bounce between 3/4 oz and slightly over 7/8oz depending on whether i load 6 shot or 9 shot.
Anyway i hope all my ramblings helped someone. Either way i enjoy playing.
As a side note ive measured variations in factory shot shells of over 100fps from shell to shell. Ive learned to not worry about velocity and focus on the target and keep the gun swinging and that works for me
 
SGW forum has some graphs . The one I looked at showed the highest pressure is generated in the first 5 inches of barrel . By 12 inches pressure has drop be low 2000 psi from its high of 11500 psi . So the ports effect is minimal on over all velocity .
 
If you wish to enlighten yourself in the world of shotgunning Tom Roster , ken zutz . Stan baker . Read all you can find by these guys they have PHD”s in shotgunning and shotgunning ballistics
 
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