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Powder amount - switching from RN to FMJ TC (147gr)


MilkMyDuds

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Currently loading 147gr RN coated Xtreme bullets, 3.1gr Titegroup. Wanna try Precision Delta 147gr FMJ TC because I heard it has less crimping issue and easy to seat the bullet straight. I was having some sporadic accuracy issues with Xtreme in my MP9 Pro 5'' with KKM barrel.

Does anyone know if I should keep my current 3.1gr Titegroup, or make it 3.0gr? Supposedly TC would be seated further into the brass if I keep the same OAL, thus less burning space for the powder so I should lower the powder amount, correct?

Thanks.

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My experience is the PD 147 will use minutely more powder to achieve the same velocity vs the Xtreme. I was very pleased with the accuracy of the PD FMJ TC. OAL will be determined by your guns chamber. I was loading 1.12 in my Glocks.

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If you were comparing two bullets with the same shape and weight, one lead, one plated and one with a jacket, the jacket bullet will require a little more powder to make velocity then the plated, and plated a hair more then the lead bullet. Bullet shape effects pressure and resulting velocity with the same given weight and jacket composition. In most standard throated pistols you are going to have to seat a truncated bullet well into the case so that it will chamber. In a long-throat pistol, the truncated bullet allows you to seat the bullet to a normal length. The shape of the truncated bullet seated long in the case effectively creates more powder space as more of the weight of the bullet is out forward of the case. Truncated bullets also have more bearing surface which is going to create a little more pressure.

Without a loading book in front of me, I cant say what the starting loads would be that you are talking about. I would say that if you are going to drop your loads, then you need to drop by more then .1, your powder measurer is not throwing to .1g. If it was ME, and 3.1 was a starting load, I would make sure that the TC bullets fit and cycled and load and shoot a few to see what happens and go from there. I would also make sure 3.1g is a starting-ish load.

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Just to follow up.

I loaded some Precision Delta 147 FMJ-TC bullets using the same amount of Titegroup I was using for Xtreme 147RN. The only change I did was to back out the seating die a full turn so that I can keep the OAL at 1.140'' with these TC bullets.

Tested on a chrono: the average speed for 10 rnds is 880fps, with a max of 900fps and min of 867fps. This is exactly what I was getting from the Xtreme 147RN in the same pistol (MP9 Pro 5'' with KKM barrel).

Thanks for all the inputs.

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