1 popple hole

[Rick88]

In general terms excluding variables of powder, bullet, comp etc, how much of a PF drop could you expect to see by adding 1, 1/8 hole in your barrel using you current set up? I'm guessing 5 to 8 does that sound about right.

[Whoops!]

5 to 8 PF from one popple hole???? No way. It depends on where it is in your barrel, even then, due to the other variables in loads, I doubt you'll see any, as in no appreciable average change, from just one popple hole. This should hold true almost regardless of the length of the barrel and the powder used.

Edited November 21, 2013 by Whoops!

[Rick88]

So your saying that if you have a PF of 175 and drill a 1/8 hole in your barrel your PF will still be 175?

[Flatland Shooter]

I have 2 open guns in 9 Major. In addition to comps, one has 4 popple holes in the barrel.

The same ammo runs 169.0 PF in the gun with holes and 172.4 PF in gun without holes.

So in my case, 4 holes equal a 3.4 PF drop.

But lots of other factors may be involved. The gun with holes has over 20K rounds through it. The one without holes has less than 2000 rds through it.

Bill

[kneelingatlas]

I have one barrel 5.1" (no holes) and another 5.25" with 12 holes (and polygonal rifling which in theory makes it faster); with the same load the speed is 13PF so I think 1-2PF per hole is a good estimate.

[Chris iliff]

Yep, not much, my load went about 2-3 PF lower after I had 2 holes added.

[Rick88]

Ok, my guess was high I'm glad to hear that. Thanks for the info.

[Whoops!]

So your saying that if you have a PF of 175 and drill a 1/8 hole in your barrel your PF will still be 175?

I'm saying that your barrel and loads probably aren't consistent enough to show any average difference from the one 1/8th inch hole. Most of my loads change PF by 2 to 5 every single shot. One of my fast loads even changes by 10 PF every shot. The law of averages comes into play and if you're firing say, 5 to 10 shots through each platform and averaging them together, you'll likely see zero difference. Hence the reason so many people who responded to you thought that popple holes change PF by so many different amounts. I don't think anyone knows how much it really changes PF excluding the variables of powder, barrel length and construction method along with material, elevation, temperature, etc. All of them play so much more of a factor than 1 popple hole ever will.

Now then, if you have equivalent platforms, and by equivalent I mean machined the exact same way with identical pieces of equipment on identical barrels (a physical impossibility) on the exact same day with one having a properly EDM'd popple hole toward the end of the barrel and the other not and you shoot a thousand rounds through each of them on the same day, at the same time, you may be able to tell almost exactly how much of a difference one popple hole makes. I'm betting 1 PF or less is barking up the right tree with a moderately slow pistol powder in a 38s/9mm platform.

In other words, I wouldn't worry about it.

There is one thing that's important here though, make sure the popple hole is done right and leaves no added imperfection in the barrel. I believe Kneelingatlas is referencing a Tanfoglio Gold Custom with his 12 hole barrel. I had one of those and was not convinced that those barrel holes were done right by the factory. They were not only likely larger than necessary, the metal surrounding them was of iffy quality.

Edited November 21, 2013 by Whoops!