147gr 5" vs 4"

[v1911]

I decided to run a comparison of loads to see what velocity difference was being had between the 5" barrel of my STI and the 4" barrel. Obviously your results may vary but I wanted people to get a ballpark idea of what could be expected. I took my time and ran 10 shots over the chrony set at 10'. In an attempt to be as consistent between shots, I would raise the barrel in a vain attempt to keep the powder in the rounds in the back of the casing then slowly lower my sights. In hind sight this probably didn't accomplish anything seeing as the 147gr bullet is probably already kissing powder when seated. Following the chrony test I put 10 shot groups for comparison. The groupings were fired from the 5" at a range of just 7 yards.

The 3 bullets we have today are the coated Acme 147gr (no lube ring), Bayou Bullet 147gr (lube ring) and Zero 147gr JHP. All rounds were loaded to an OAL of 1.150 with 3.2gr of Clay Dot. The 2 guns peforming the tests are the 5" Gans Guns 9mm STI w/ schuemann barrel and STI Costa VIP 4.0 w/ STI barrel. Again, YMMV.

Zero 147gr 5"

Avg: 897fps

SD: 8.5

ES: 27

PF: 131

Acme 147gr 5"

Avg: 919fps

SD: 9.3

ES: 31

PF: 135

Bayou Bullets 5"

Avg: 925fps

SD: 9.6

ES: 32

PF: 135

Zero 147gr 4"

Avg: 887fps

SD: 15.9

ES: 53

PF: 130

Acme 147gr 4"

Avg: 883fps

SD: 15.4

ES: 48

PF: 129

Bayou Bullets 147gr 4"

Avg: 902fps

SD: 15.6

ES: 40

PF: 132

5" Test gun

4" Test Gun

Edited April 15, 2016 by v1911

[LilBunniFuFu]

Interesting to see how the sd and the es are consistent and so much better in the 5 inch gun than the 4. Do you think you would have the same result with a different 4 inch gun/barrel combo?

[v1911]

I suppose if I were to take out the STI guardian as well, I'd have another 4" reference.

I can't say for certain, but Internet lore seems to be saying that each gun and barrel is unique and that each will have its own, if not trivial, differences.

[Hi-Power Jack]

Be fascinating to see group sizes at 20 - 25 yards.

Thanks for sharing.

[SNSCaster2]

Were you using a ransom rest? It would also be great to know your OAL and seating depth for each. ES is not a true indicator of accuracy in this case if the groups didn't come from a solid ransom rest IMO

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[3djedi]

You sure that's not a 6" and a 5"? Lol

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Edited April 17, 2016 by 3djedi