Pressure Increase from two Bullets of Same Grain Weight

[BowBaboon]

I started reloading for my 6.5cm with Hornady BTHP Match bullets in 140 grains and using H4350 at 39.6 grains with a COAL of 2.82. I shot about 50 of these and didn't have an issue with pressure marks on my brass. When I reloaded the second batch, I ran out of the BTHP Match bullets and threw some 140 grain ELDM in the remaining 10 with the same charge and primer (CCI 200) and COAL. However, I started to notice slight ejector marks on the bullets with the ELDM. On the 8th shot with the ELDM I noticed significant recoil (in comparison), had a heavy bolt lift, and a definite ejector mark on that piece of brass.

My question is this: would seating the ELDM at the same distance as the BTHP result in a compressed load and more pressure? My thinking is that because the ELDM is "longer" with the polymer tip, the bullet is actually seating deeper and compressing the charge.

Hope this all makes sense. Thanks for the help!

 

[JFK]

Using coal as a comparison is not very useful. Especially when talking tipped and non tipped bullets. You want to get an ogive comparator. Bearing surface of a bullet, and how much of the bullet is sitting below the neck and eating into your case capacity. That’s why new bullet equals dropping down a couple grains and working up.

 

[BowBaboon]

Appreciate the insight!