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Variations in MV


Miseryguts

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Hi, one of the calibres that I reload is the 45LC for an LBR. I chronographed some rounds the other day and was surprised at the variations in SD and MV

All rounds are loaded in Star Brass at 1.276+/- 0.001

Powder is VvN320 6.0gn measured using a Hornady auto trickler to throw a nominal 5.9gn and the  trickle up to 6.0gn with a Frankford Arsenal trickler on a Redding Beam Scale

bullet is 250gn LNRNFP with lubed groove and Alox coatingloaded  to 1.600 +/- 0.001 and crimped

Each batch of 10 was shot in two 5 round series. Format is Batch; Average MV; ES; SD

Batch A 753  66  18

Batch B  729 46 14

Batch C 761  74  23

Batch D 753  94  28

With the other pistol calibres I reload(357M & 44M) using the same technique, I have ES between 20 and 35fps, and SD 6 to 10.

The only thing I can think of here is that the case is large with a small volume of powder giving variations in burn time.

Or possibly temperature - it was around 0deg C that day

Any thoughts any one??

Suggestions for a fix??

M

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