Barrel Length and Velocity


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JustsayMo
May 6, 2006, 05:12 PM
I have three Marlin 39's all with different barrel lengths. Golden 39A with 24" barrel, Golden 39A Mountie with 20" barrel and a Marlin 39TDS with a 16" barrel. I thought it might be interesting to compare velocities with a few varieties of ammo. I also tested some pistols with 5.5", 4-5/8" & 2" barrels to compare.

Sunny, Breeze 7-18 mph, some higher gusts, quartering from rear. 65* F. Chrony Alpha master set up 12' in front of muzzle. Up to 15 shot strings. Listed fastest to slowest.

FEDRAL 550 Pack 37g copper HP
-Marlin 39A (39A) 24" barrel 1263 fps (averaged). Very good+ accuracy
-Marlin Golden 39A Mountie (Mountie) 20" barrel 1254 fps Very good+ accuracy
-Marlin 39TDS (TDS) 16" barrel: 1254 fps Very good Accuracy
-Ruger Single Six (RSS4") 4-5/8" barrel: 1110 fps, Very good accuracy
-Ruger Single Six (RSS5") 5.5" barrel: 1072 fps, Very good accuracy
-Iver Johnson TP22 (TP22) 2" barrel: 961 fps, OK accuracy

CCI Mini Mag 40g solid, copper
-39A: 1255 fps, OK accuracy
-Mountie: 1225, Good accuracy
-TDS: 1221 fps, Fair accuracy
-RSS5": 1067 fps, OK accuracy
-RSS4": 1063 fps, OK- accuracy
-TP22: 923 fps, OK accuracy
Notes: This was the only ammo that the 5.5" Ruger Single six shot faster than the 4-5/8" barrel

Aguila SE Subsonic 38g lead hollow point
-TDS: 1007 fps, Good+ accuracy
-Mountie: 994 fps, Very Good+ Accuracy
-39A: 984 fps, Very good accuracy
-RSS4": 923 fps, Very good Accuracy
-RSS5": 901 fps, Very good Accuracy
-TP22: will not cycle this ammo
Notes: It was interesting to see that the 16" barrel produced the greatest velocity.

CCI CB Long 29g Lead Solid
39A: 677 fps, Fair- accuracy, VERY quiet
Mountie: 675 fps, OK accuracy
TDS: 668 fps, Good accuracy
RSS4": 573 fps, OK- accuracy
RSS5": 561 fps, OK- accuracy
TP22: Did not test

CCI Blazer 40g Lead Solid (20-30 years old)
39A: 1230 fps, OK accuracy
Mountie: 1203 fps, Very good- accuracy
TDS: Did not test
RSS5": 1012 fps, Good accuracy
RSS4": Did not test
TP22: Did not test

Accuracy definitions; 25 yards for rifle, 25 feet for pistols.
Excellent= 5 shot group covered by a tack
Very Good= 5 shot group covered by dime
Good = 5 shot group covered by a nickle
OK = 5 shot group covered by Quarter
Fair= 5 shot group covered by a Fitty cent piece
Poor= anything bigger

Other Notes:
-The Chrony Alpha Master was easy to use. I had it set up within minutes the very first time.
-The Marlin Mountie is my least Ammo finnicky of my rimfires. It seems to shoot everything at least OK.
-The Marlin TDS is the most finnicky. Amazingly though it shoots the CB longs better than anything else I own. It must be a female.
-The TDS also produced the highest velosity of the subsonic ammo.
-I was suprised to see that the 4-5/8" Ruger Single Six usually produced better velocity than the 5.5" version. Cyclinder gap? tighter bore?

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45crittergitter
May 9, 2006, 10:13 PM
It's commonly accepted that the .22 LR begins to lose velocity after about 16" of barrel. Of course, each lot of ammo and each barrel will vary....

MachIVshooter
May 9, 2006, 10:21 PM
I wouldn't say they loose velocity after 16", but the gain is so minimal that there is no reason to go longer other than sight radius. With various types of ammunition, very negligable average gains going from 16" to 22". Certainly not worth mention, since the standard deviation of rimfire ammo can easily be that much.

CB's and the powderless aguila's, however, do loose velocity in longer barrels. The Aguila's are actually much faster out of a short handgun barrel.

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