JRH6856
Member
Good point, k dawg. Now how do you compensate for the barrel/cylinder gap which the S/A doesn't have? 
How much power is lost with a 2" barrel?
- Thread starter vito
- Start date
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I have shot a boat load of 38 Special ammunition in my snubbies and in a 4" K frame Smith. I did a lot of chronographing.
You can see just how much velocity you lose with a standard pressure load:
You can see just how much velocity you lose with a standard pressure load:
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[SIZE="3"]
Colt Detective Special mfgr 1963 24-Jul-99 T = 100 F !
158 gr LRN 3.5 grs Bullseye thrown, CCI primers mixed cases
Average 751 fps
Standard Deviation 32 fps
Extreme Spread 90 fps
High 805
Low 715
Recorded shots 22
158 LRN 3.5 grs Bullseye WSP Mixed cases 8-Jan-06 T = 52 F
Ave Vel = 675.9
Std Dev = 18.6
ES 96.18
High 723.9
Low 627.7
N = 50
158 LSWC 3.5 grs Bullseye WSP Mixed cases 8-Jan-06 T = 58 F
Ave Vel = 706.8
Std Dev = 15.55
ES 65.87
High 742.9
Low 677
N = 50
[ATTACH=full]660732[/ATTACH]
Colt Detective Special mfgr 1974
158gr LSWC 3.3 grs Bullseye CCI 500 primers, Dillon Loads 17-Oct-93 T = 65-70F
Ave Vel = 682 fps
Std Dev = 33
ES 96
High 733
Low 637
N = 6
Colt Cobra 2" barrel 30-Jan-05 T = 42 F
158 gr LRN 3.5 grs Bullseye thrown, Fed 100 primers mixed cases
Average 696.6
Std Dev 20.49
Extreme Spread 72.93
High 745.5
Low 672.6
13 recorded shots
shoots point of aim when properly held, otherwise goes left
Taurus M85 B2UL 2" Barrel
158 LSWC 3.5 grs Bullseye thrown, Mixed Brass WSP 11-Dec-04 T = 54 F
Ave Vel = 686.3
Std Dev = 13.63
ES 58.48
High 718.8
Low 660.3
N = 30
shot little high and centered
158 LRN Master Factory Ammo 30-Dec-04 T = 56 F
Ave Vel = 698.2
Std Dev = 20.56
ES 105.8
High 753.5
Low 647.6
N = 50
shot 6" high centered,until barrel leaded
158 LSWC 3.5 grs Bullseye Mixed brass Fed 100 30-Dec-04 T = 56 F
Ave Vel = 706.2
Std Dev = 23.45
ES 81.94
High 748
Low 666.1
N = 48
[ATTACH=full]660733[/ATTACH]
S&W M638-3 Airweight Bodyguard
148 LWC Lead 2.7 grs Bullseye thrown Mixed Brass WSP
18-Mar-07 T = 52 °F
Ave Vel = 611.6
Std Dev = 22.04
ES 75.92
High 648.1
Low 572.2
N = 25
little high
158 LSWC 3.5 grs Bullseye Mixed brass WSP
18-Mar-07 T = 52 °F
Ave Vel = 611.1
Std Dev = 9.64
ES 28.05
High 626.3
Low 598.3
N = 32
4-6" High accurate
[ATTACH=full]660734[/ATTACH]
S&W M637-2 2" barrel
158 LRN 3.5 grs Bullseye WSP Mixed cases
6-Apr-07 T = 48 °F
Ave Vel =679
Std Dev =16.48
ES 56.11
High 698.2
Low 642
N = 18
125 Lead BBRNFP 4.0 grs Bullseye Lot BE 532 Mixed cases CCI 500
6-Apr-07 T = 48 °F
Ave Vel = 763.9
Std Dev = 22
ES 78
High 806.5
Low 728.5
N = 15
Point aim OK
125 Lead BBRNFP 4.0 grs Bullseye Mixed cases WSP
9-Apr-06 T = 59 °F
Ave Vel = 760.4
Std Dev = 27.33
ES = 82.1
High = 798.9
Low = 716.8
N = 19
125 Lead BBRNFP 4.5 grs Bullseye Mixed cases WSP
9-Apr-06 T = 64 °F
Ave Vel = 827.9
Std Dev = 23.21
ES = 92.27
High = 879.4
Low = 787.1
N = 20
125 Lead BBRNFP 4.5 grs Green Dot Lot 178 Mixed cases CCI 500
6-Apr-07 T = 48 °F
Ave Vel = 813.2
Std Dev = 44.55
ES 176.5
High 903.3
Low 726.8
N = 24
v. accurate at 7 yards, POI at 25 yards, little leading
125 Lead BBRNFP 5.0 grs Green Dot Lot 178 Mixed cases CCI 500
6-Apr-07 T = 48 °F
Ave Vel = 867.3
Std Dev = 57.54
ES 178.1
High 966
Low 787.8
N = 21
v.accurate at 7 yds, 1-2" above POI at 25 yards, more leading
125 JHP (W/W) 4.5 grs Green Dot Lot 178 Mixed cases CCI 500
6-Apr-07 T = 48 °F
Ave Vel = 760.4
Std Dev = 68
ES 56
High 205.1
Low 885.4
N = 13
125 JHP (W/W) 5.0 grs Green Dot Lot 178 Mixed cases CCI 500
6-Apr-07 T = 48 °F
Ave Vel = 808.9
Std Dev = 56.82
ES 95.46
High 914.2
Low 712.8
N = 20
25 yds accuracy OK, accurate POI @ 7 yds[ATTACH=full]660735[/ATTACH]
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[SIZE="3"]4" S&W M10-5
148 LWC Valiant 2.7grs Bullseye W/W cases WSP
19-Apr-09 T ≈ 60-65 ° F
Ave Vel = 696.2
Std Dev = 12.04
ES = 48
High = 721.3
Low = 673.3
N = 32
v accurate, about 2" low, no leading, mild recoil
158 LRN Valiant 3.5grs Bullseye Mixed cases WSP
19-Apr-09 T ≈ 60-65 ° F
Ave Vel = 758
Std Dev = 22.86
ES = 100.9
High = 810.5
Low = 709.5
N = 32
158 LRN 3.5grs Bullseye Mixed cases WSP Gamma Chrony
5-Aug-06 T = 100 °F
Ave Vel = 796
Std Dev = 13.89
ES = 55.24
High = 813
Low = 757.9
N = 23
158 LRN 3.5grs Bullseye Mixed cases WSP
22-Dec-07 T = 52 °F
Ave Vel = 768.6
Std Dev = 15.58
ES = 48.52
High = 787.6
Low = 739.1
N = 18
125 Valiant BBRNFP 4.0 grs Bullseye Mixed cases WSP
9-Apr-06 T = 59 °F
Ave Vel = 863.4
Std Dev = 30
ES = 70.78
High = 907.5
Low = 836.7
N = 6
Windage centered accurate
Elevation at least 4" low
125 Valiant BBRNFP 4.5 grs Bullseye Mixed cases WSP
9-Apr-06 T = 64 °F
Ave Vel = 945.6
Std Dev = 27.28
ES = 75.21
High = 995.2
Low = 920
N = 6
Windage centered accurate
Elevation at least 4" low[/SIZE]Attachments
JRH6856
Member
FWIW, I used QuickLoad to generate a comparison of seven different powders with loads standardized for 18000psi (high+P) and standard pressure at 14875.
Powders in both tables are sorted from fastest to slowest. As you can see, QL calculates an average loss with +P of 249fps with a 2" barrel. and with standard loads a loss of 238fps. Also note the burn rates and muzzle pressures. Red Dot gives the most complete burn in a 2" barrel with less pressure loss between 2" and 4". It is also the lowest velocity loss, but still over 200fps.
It is also worthwhile to note that higher pressures give a more complete burn in a 2" barrel with all powders, with an average burn of 91% for +P over 87% with standard pressure.
It may be no surprise that Bullseye gives the highest velocity from a 2" barrel at both pressure levels, while from a 4" barrel it is Herco. Unique is in second place at for both lengths at both levels and perhaps would be the best choice for a single load for both barrel lengths.
As always, with QL, YMMV in real life.
Powders in both tables are sorted from fastest to slowest. As you can see, QL calculates an average loss with +P of 249fps with a 2" barrel. and with standard loads a loss of 238fps. Also note the burn rates and muzzle pressures. Red Dot gives the most complete burn in a 2" barrel with less pressure loss between 2" and 4". It is also the lowest velocity loss, but still over 200fps.
It is also worthwhile to note that higher pressures give a more complete burn in a 2" barrel with all powders, with an average burn of 91% for +P over 87% with standard pressure.
It may be no surprise that Bullseye gives the highest velocity from a 2" barrel at both pressure levels, while from a 4" barrel it is Herco. Unique is in second place at for both lengths at both levels and perhaps would be the best choice for a single load for both barrel lengths.
As always, with QL, YMMV in real life.
Attachments
rcmodel
Member in memoriam
Thanks for the QL info.
I still do not see any of those 300-350 FPS figures though?
As a point of interest?
The old timey cop gun loads were in fact loaded with 158 LRN bullets over Bullseye powder.
And they didn't go only 300-350 FPS out of a snubby either!
rc
I still do not see any of those 300-350 FPS figures though?
As a point of interest?
The old timey cop gun loads were in fact loaded with 158 LRN bullets over Bullseye powder.
And they didn't go only 300-350 FPS out of a snubby either!
rc
tipoc
Member
- Joined
- Mar 9, 2006
- Messages
- 3,563
Over to Ballistics by the inch as well as the other sites previously linked to they do know how to measure the length of an actual barrel and tehy do use real guns as well as test barrels.
This is not the case from the real world guns section of Ballistics by the Inch which you can see here...
http://www.ballisticsbytheinch.com/38special.html
As is usual they measure the length of the barrel from the cylinder to the end of the barrel.
I encourage folks to go there and see the amount of velocity actually lost from the drop from a 4" to 2" barrel.
tipoc
This is not the case from the real world guns section of Ballistics by the Inch which you can see here...
http://www.ballisticsbytheinch.com/38special.html
As is usual they measure the length of the barrel from the cylinder to the end of the barrel.
I encourage folks to go there and see the amount of velocity actually lost from the drop from a 4" to 2" barrel.
tipoc
JRH6856
Member
rcmodel, According to QL, any loads producing only 300-350fps are extremely light loads producing low pressure. For example, 2.8gr of Unique will produce 5836psi to drive that 158gr LSWC at 350 fps. For Bullseye, it is 2.4gr for 350fps at 5645psi. You might be able to get that using only a small rifle primer. 
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JRH6856
Member
tipoc, As noted on the BBTI page, cylinder gap makes a difference. Basically, what it appears BBTI are saying is that a longer barrel loses pressure through the gap that with a shorter barrel, would be lost through the muzzle, since the longer the bullet is in the barrel, the more pressure is lost via the gap. (QuickLoad does not account for this.)
I once saw some pressure tests with a transducer fitted to a revolver accompanied by HS photos showing that at the moment of peak pressure, the bullet is in the process of jumping the gap and thus creating a sealed environment for the pressure to act on the bullet. As pressure begins to drop, the bullet clears the gap and pressure begins to bleed off so it drops even faster than if the gap remained sealed. But just how much faster, nobody really seems to know.
I once saw some pressure tests with a transducer fitted to a revolver accompanied by HS photos showing that at the moment of peak pressure, the bullet is in the process of jumping the gap and thus creating a sealed environment for the pressure to act on the bullet. As pressure begins to drop, the bullet clears the gap and pressure begins to bleed off so it drops even faster than if the gap remained sealed. But just how much faster, nobody really seems to know.
arizona98tj
Member
My carry .38 Spl carry ammo, 125gr +P Speer Gold Dots, average 913 FPS out of my 2" Ruger LCR. I've not shot in my 4" Security Six.
However, 130 gr WWB out of my 2" S&W 637 runs 792 FPS while the same load out of my 4" Security Six hit 848 FPS. 130 gr Military ball runs 795 FPS out of my Security Six.
However, 130 gr WWB out of my 2" S&W 637 runs 792 FPS while the same load out of my 4" Security Six hit 848 FPS. 130 gr Military ball runs 795 FPS out of my Security Six.
rcmodel
Member in memoriam
Yes, I am aware of that.
But factory loads the old cops carried were loaded with nearly half again that amount of Bullseye.
Try 3.5 - 3.7 grains for instance.
I still contend there were no 300-350 FPS .38 Spl factory loads shot out of snub-nose guns.
Unless the windshield tester intended them to be.
rc
JRH6856
Member
And I still completely agree. That is my point. 300-350fps can only result from a seriously (perhaps intentionally) reduced load.
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