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View Full Version : Subsonic 7.62 Experiment 4


Artful
April 28, 2007, 09:05
Date-April-26-2007
Rifle-Mossburg 800A bolt action Barrel Length-22 inches
Twist-1:12
Temperature-94 (warming up)
Case-Remington mostly
Case Prep-Epoxy Filled to bottom of neck. Flash hole drilled to 1/8”, ˝” up from bottom of case. 17/64” drilled from Case mouth to meet flash hole, Leaving reduced capacity casing. Which was filled with
-8.2 grns of Blue Dot Gun Powder.
Bullet-150gr SP Remington Moly coated loader to the canalure Lee factory crimp applied.
Primer-CCI 250 LR Mag

10 Rounds created and Fired for test.
1st 5 with gun on bench rest cartridge inserted into chamber
1334,_ 1321, _1241, _1270, _1214
2nd 5 with cartrdige chambered rifle tipped up and tapped
1079, 1156, 1191, 1723, 1092

Comments,
Didn’t use same maker in all cases. (we thought we had)
Epoxy fill may not have been consistent as it was loaded to
same area but wasn't weighted or measured but the epoxy stated in same state after first firing. Can only be neck sized at this point.
Powder load was exact in all loads so unsure of why the 1723 fps round?
All rounds fired showed no keyhole effect pretty good grouping.
try varying the powder charge on next go round.

Hot Diggity
April 28, 2007, 15:26
Interesting results, and very slick case prep. I'd still look into Secondary Explosive Effect (S.E.E.) and be sure that wasn't partially to blame for the
1700+ pfs round. There are a couple European authors on-line who have written about "cat sneeze" rounds. I think it was on Gun Writers Online. (#1
Son erased ALL my favorites, so that's a best guess.) They're getting round ball loads down to .22 Super Colibri noise levels.

We had a guy shooting extreme low velocity .308 in a Spanish FR8 at the local range, and blew it up. I never got to see it, but I've heard it was quite spectacular. Remembering him talking about stuffing yellow foam hearing protection in the cases to hold the powder against the primer makes me wonder if he wasn't a victim of the dreaded S.E.E.

HD

Artful
May 01, 2007, 00:17
Originally posted by Hot Diggity
Interesting results, and very slick case prep. I'd still look into Secondary Explosive Effect (S.E.E.) and be sure that wasn't partially to blame for the
1700+ pfs round. There are a couple European authors on-line who have written about "cat sneeze" rounds. I think it was on Gun Writers Online. (#1
Son erased ALL my favorites, so that's a best guess.) They're getting round ball loads down to .22 Super Colibri noise levels.

We had a guy shooting extreme low velocity .308 in a Spanish FR8 at the local range, and blew it up. I never got to see it, but I've heard it was quite spectacular. Remembering him talking about stuffing yellow foam hearing protection in the cases to hold the powder against the primer makes me wonder if he wasn't a victim of the dreaded S.E.E.

HD

S.E.E. isn't an issue as the reduced volume after the epoxy was input - Trail boss was bulky just to fill up the standard case so no expoxy was required. Created cases now hold about 1.74 CC compared to 1.52 for 357 mag case or 1.92 for 44 Spl case.

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