Estimated power factor loss/popples

[Jules1985]

Good Morning 
 

I would like to know if there are empirical values of how much power factor you lose through popple holes.

My gunsmith says that the five inch barrel of my gun would probably have very big problems reaching the required power factor of 160 when I start porting the barrel. It would be approximately 3,75 inches to the first popple.

As a powder I use vectan SP2 with a Power factor of 172.

Caliber 9mm Major 

[dansedgli]

In both 38 super and 9mm I lost 3pf with 3 holes. 

 

 

Edited July 12, 2021 by dansedgli

[Jules1985]

3 per hole or 3 in total?

Thank you !

[dansedgli]

in total. 

[36873687]

3 pf is what I seen also

[zzt]

3 PF in one gun after adding two 3/16" poppels; 4 in another.  You gunsmith is nuts.  You will have zero problem making major using SP2.  You will get a little harder hit to the hand.  9mm cases do not have enough capacity to shoot flat and soft at the same time.  You have to settle for some of both.

 

The last three Open guns had two 3/16" poppels.  For the backup I just built I decided to go with three 5/32"..  Although the total area is the same, the three 5/32" shoot a bit flatter.

[Jules1985]

many, many thanks to everyone for your help so far. usually my gunsmith is one of the good guys, but so far he has little experience with ports in open pistols.

His experience with popples comes from the area of the former modified division but i am not sure whether the two divisions can be compared.

I think I'll start with a 5/32 port and add one after another so I can compare.

[NoSteel]

I saw ~ 3Pf drop adding 2 popples to my 5” barrel.  Some of the affect is going to be dependent on how high your current PF is ( I was about 176 as that is what my comp liked ) and how efficient your current comp is, assuming your running one…. Either way,  you should only need to make a slight powder adjustment to make up the loss if your already close to min PF IMO.

[zzt]

2 hours ago, Jules1985 said:

I think I'll start with a 5/32 port and add one after another so I can compare.

 

Go ahead if you want to, but you are not going to feel much difference with a single 5/32 poppel.  They way I started with the last three I built was comp only.  If they had shot as flat as I wanted I'd have left them alone.  Both my hands are damaged to the point where I can squeeze 75 lbs. on a good day.  One of my shooting buddies can crush an apple with his bare hand.  We have identical comps.  He can shoot his flat with no poppels, but I need them.

[191138sc]

On 7/12/2021 at 3:29 PM, NoSteel said:

I saw ~ 3Pf drop adding 2 popples to my 5” barrel.

Same with my gun. 3 PFS with 2 holes. My comp works best with a PF of 172-178 so 3 FPS was no big deal.

[Squirrel45]

I as well lost around 3PF when I put 2, 3\16" ers in my Czechmate. Going to put one more in and call it good Im thinking. I actually thought that I would loose more, but that was the chrono on three different days just to make sure.