.303 Chrono Results |
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britrifles
Senior Member Joined: February 03 2018 Location: Atlanta, GA Status: Online Points: 6539 |
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Posted: October 12 2019 at 6:33am |
I finally had the opportunity to chronograph some Mk VIIz Service Ball ammunition and my .303 hand loads. I also made some direct comparisons between the Mk VII service bullet and the 174 gr Sierra MatchKing by pulling bullets from the Mk VIIZ cartridges and substituted the bullet with the 174 SMK. These results may be of interest.
Rifle: 1944 BSA No. 4 Mk I(T), No. 32 Mk III scope, Long Branch 6 groove barrel Temp: 50 deg F Chrono: Shooting Chrony Alpha Master 15 feet from muzzle Acronyms: Mean Velocity (MV) Extreme Spread (ES) Standard Deviation (SD) Sierra MatchKing (SMK) Cartridge Overall Length (COL) All groups 10 shots from bench at 100 yards 1. Dominion Arsenal DAC 1951 Mk VIIZ Service Ball Ammunition (174 gr, .312 dia flat base bullet). MV 2412 fps ES 78 fps SD 25 fps Group Size 2.2 in. 2. R-P Case, WLR primer, 40.0 gr. Varget, 174 gr, .311 dia HPBT SMK, 3.05 COL MV 2368 fps ES 64 fps SD 21 fps Group Size 2.0 in. 3. DAC ‘51 MK VIIZ Service Ball Ammunition, bullet pulled and substituted with 174 gr SMK MV 2507 fps ES 44 fps SD 14 fps Group Size 2.0 in. 4. R-P case, WLR primer, 40.0 gr. Varget, 174 gr DAC MK VII Service Bullet, 3.05 COL MV 2366 fps ES 47 fps SD 15 fps Group Size 1.5 in. DAC 1951 MK VIIz was loaded for the 1952 DCRA matches and clearly performs well and still retains the specified velocity. The bullet quality appears to be on par with the SMK for group size, although the SMK gives slightly higher velocity in the same load, particularly with the DAC military case. My No. 4 .303 match load of 40 gr Varget with 174 gr SMK runs about 70 fps under MKVII specified muzzle velocity (2440 fps). I expect pressures are somewhat lower than MK VII given the slower powder and faster bullet. Here’s what the sight picture looks like thru the No. 32 Scope, the chrono can be seen in the field of view. Results with pulled DAC 1951 MK VII service bullet loaded into R-P Case, 40.0 gr Varget. |
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Shamu
Admin Group Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 17603 |
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Was that South African VIIz? Its very similar to the results I had with the ball round. Incidentally you can use the VIIz with no problems, its just MkVII loaded with nitrocellulose instead of cordite. Its the VIIIz that eats barrels.
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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britrifles
Senior Member Joined: February 03 2018 Location: Atlanta, GA Status: Online Points: 6539 |
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Shamu, this is 1951 Dominion Arsenal (Quebec, Canada) Mk VIIz ball ammunition. Yes, it is nitro cellulose (powder). My dad got 800 rounds thru the DCRA. Fortunately, it had been stored in cool conditions all these years. I’ve shot about 400 rounds of it and it is quite accurate.
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Shamu
Admin Group Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 17603 |
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I think they'll be fine. It was the rebated boat tail Mk8 bullet that was the problem. These should be a standard Mk 7.
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Goosic
Senior Member Joined: September 12 2017 Location: Phoenix Arizona Status: Offline Points: 8792 |
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Results with pulled DAC 1951 MK VII service bullet loaded into R-P Case, 40.0 gr Varget with an overall average of 2413 fps. I enlarged the photo to coincide with my digital caliper. Very good results...
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britrifles
Senior Member Joined: February 03 2018 Location: Atlanta, GA Status: Online Points: 6539 |
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Goosic, I think I should be able to do a bit better with this rifle. The average group size of the eight 10 shot groups I fired (20 rounds of each load) was 2 inches measured center to center extreme spread. A few groups were under that. 1.5 inches would be quite respectable if it was consistent. I’m going to also shoot the rifle with the Mk I service aperture sight just to rule out any problem with the scope.
After shooting the rifle, I removed the hand guards. There is a wood barrel bearing just behind the sling swivel band, and there is lots of pressure there, takes about 12 lbs at the muzzle to lift the barrel off the bearing. When I was lifting the muzzle, I heard a “pop” (not a cracking noise!) and the rear of the receiver seated a bit further into the forend (the draws are very tight on this forend). After that happened, I could put another full turn on the main screw. Here is one of the groups with my match load: R-P Case, WLR primer, 40 gr Varget, 174 gr SMK. Measured 1.5 x 1.5 in. I hadn’t centered the groups on the target yet, I was shooting to get chrono results and group size. The elevation spread on the second group was 1.0 inches, but other groups were strung vertically. |
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