SBS vs. 18.5" and Velocity Lost?

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10-25-18, 00:10
WS6

SBS vs. 18.5" and Velocity Lost?

When it comes to shotguns, we have all heard the "Don't get an SBS, it limits your range!" and then we have people chime in saying "No it doesn't, with equal chokes, you get nearly equal patterns, and with slugs, they are just as accurate", to which the rebuttal "But the velocity will be less and the shot/slug won't hit nearly as hard from your SBS as from a "full size" tactical shotgun barrel like an 18.5 or 20""

Then we are left with a bunch of conjecture and confusion and very little real data and both sides kindof walk away without having actually unpackaged anything from the debate.

I have long held the opinion that with at least low-recoil ammunition, the girth matters more than the length, when it comes to shotguns. Bore VOLUME is what matters, and considering the amount of powder in a shotgun shell vs. length vs bore ID, there has, in my mind, always been plenty of bore volume to make up for lopping off several inches of length because of the large ID of a 12 gauge bore.

Regardless, conjecture is what we want to get away from, so I decided to actually test the theory and see if the bore ID of the 12 gauge made up for the bore shortening in the case of the SBS. Today, I tested low recoil ammunition, since it's so popular. Tomorrow, or soon, I will also test full-power ammunition, and see if the trend changes because of the larger amount of powder involved.

http://www.youtube.com/watch?v=1su03xHY69g

Average velocity of 14" firing LEB127LRS (rated velocity, 1300fps)
1180.6fps, calculated kinetic energy (assuming 438gr), 1356ft-lb

Average velocity of 18.5" firing LEB127LRS (rated velocity,1300fps)
1215.2fps, calculated kinetic energy (assuming 438gr), 1436ft-lb

Average velocity of 14" firing LE13200 (rated velocity, 1145fps)
1088fps, (energy per pellet, assuming 50gr pellet weight) 131ft-lb

Average velocity of 18.5" firing LE13200 (rated velocity, 1145fps)
1125.25fps,(energy per pellet, assuming 50gr pellet weight)141ft-lb

With the slugs, the 14" SBS gave up 34.6fps, and 90ft-lb of kinetic energy. With buckshot, it gave up 37.25fps, and 10ft-lb per pellet (90 total) of kinetic energy. This is the equivalent of 6 yards in distance of flight travel, presuming a G1 BC of 0.07.

Across Federal's low-recoil LE ammunition, this is a very uniform result, and I have a high level of confidence in its accuracy due to this.

Thank-you for watching, and I hope this answered any questions you may have had on the topic.
10-25-18, 08:13
GH41

Thanks for the report. All of the difference you are seeing may not be directly related to barrel length. Some barrels are faster/slower than others. I am not saying your test was flawed but if you chronographed an 18" barrel then cut the same barrel to 14" the results may be different. A long time ago we took a 18" barreled pump to the range with a cordless drill. We drilled half inch holes in the barrel closer and closer to the chamber until we saw velocity loss. If I remember correctly it slowed down at around 12-13 inches. Your results do prove that shorter is slower but the loss isn't worth worrying about if you need a shorter gun IMO. Thanks again for doing the test.
10-25-18, 10:18
markm

My only issue with my 14" SBS is that without "flight control" it's a 12" spread with 00 ammo at like 7 yards.
10-25-18, 15:30
GH41

Quote:

Originally Posted by markm

My only issue with my 14" SBS is that without "flight control" it's a 12" spread with 00 ammo at like 7 yards.

That's the residual pressure in the short barrel blowing the pattern apart. 32-34 inch barrels dominate sporting clays. The longer the barrel the less holes in the patterns at longer ranges. Do you remember the Cutts Compensator?
10-25-18, 16:29
markm

Quote:

Originally Posted by GH41

Do you remember the Cutts Compensator?

No, but it sounds familiar.
10-25-18, 16:59
GH41

Quote:

Originally Posted by markm

No, but it sounds familiar.

Here is a link >> https://www.lymanproducts.com/media/...ompensator.pdf I had one on a dedicated turkey shoot gun. I can explain if you don't have turkey shoots in your world. The ventilated chamber prevented the shot column from being disturbed by the gas pressure when exiting the muzzle. It worked pretty good.
10-26-18, 10:29
WS6

I checked my views, I don't think anyone watched the damn video, and truthfully it was boring, so here's just raw data:

Fiocchi 1560fps 1oz slug
Chronographed at 3m from muzzle

14":1358.6 fps /// 1794.8 ft-lb (assuming 438gr slug)
18.5": 1429 fps /// 1985.7ft-lb (assuming 438gr slug)

70.4fps deficit for the 14" barrel. Translates to 190.9 ft-lb (presuming 438gr slug weight, which this slug weighed in at when dissected, although the wad is attached and I did not account for it.)

Federal LE12700 1325fps Buckshot
Chronographed 3m from the muzzle

14": 1244.6 //// FPE per pellet @ 50gr per pellet: 171.9
18.5": 1261.2 //// FPE per pellet @ 50gr per pellet: 176.6

*Chronographing the buckshot proved problematic, only 3 rounds registered properly from the 14", and all 5 registered from the 18.5" barrel, although one round was low, at 1202, but was included in this average. The average would rise to 1276, without it.

Based on this data, I plan to run the low-recoil LE13200 and 1300fps rated low recoil Truball slugs from my shotguns, both. Shooting either at night makes a HUGE difference in flash signature, the noise and concussion is notably different, and recoil doesn't much matter to me and my split times don't seem to care, but I do feel less beat up after shooting a lot with the LR stuff, but mainly, it's wear and tear on the gun that while I'm sure it will take it (The military tested the M4 to over 4 million rounds during development across their samples, and derived a 25,000 round between major part replacement schedule from such), I see no need in it, given the other factors.
11-06-18, 18:44
Stickman

Quote:

Originally Posted by WS6

I checked my views, I don't think anyone watched the damn video, and truthfully it was boring, so here's just raw data:

Fiocchi 1560fps 1oz slug
Chronographed at 3m from muzzle

14":1358.6 fps /// 1794.8 ft-lb (assuming 438gr slug)
18.5": 1429 fps /// 1985.7ft-lb (assuming 438gr slug)

70.4fps deficit for the 14" barrel. Translates to 190.9 ft-lb (presuming 438gr slug weight, which this slug weighed in at when dissected, although the wad is attached and I did not account for it.)

Federal LE12700 1325fps Buckshot
Chronographed 3m from the muzzle

14": 1244.6 //// FPE per pellet @ 50gr per pellet: 171.9
18.5": 1261.2 //// FPE per pellet @ 50gr per pellet: 176.6

*Chronographing the buckshot proved problematic, only 3 rounds registered properly from the 14", and all 5 registered from the 18.5" barrel, although one round was low, at 1202, but was included in this average. The average would rise to 1276, without it.

Based on this data, I plan to run the low-recoil LE13200 and 1300fps rated low recoil Truball slugs from my shotguns, both. Shooting either at night makes a HUGE difference in flash signature, the noise and concussion is notably different, and recoil doesn't much matter to me and my split times don't seem to care, but I do feel less beat up after shooting a lot with the LR stuff, but mainly, it's wear and tear on the gun that while I'm sure it will take it (The military tested the M4 to over 4 million rounds during development across their samples, and derived a 25,000 round between major part replacement schedule from such), I see no need in it, given the other factors.

I didn't watch the video, but only because my internet is horrid. I find the information very usable, and appreciate the write up as I sit here with a SBS (military mossberg configuration) right next to me.