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.303 Chrono Results

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britrifles View Drop Down
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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

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, 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 just under MKVII specified velocity.  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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: October 12 2019 at 10:21am
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.
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: October 12 2019 at 1:45pm
Shamu, this is 1951 Dominion Arsenal’s (Quebec, Canadian) Mk VIIz ball ammunition. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: October 12 2019 at 3:44pm
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.
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Posted: October 12 2019 at 11:02pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: 22 hours 46 minutes ago at 5:34am
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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