Relationship between popple holes and flatness

[AverageJoeShooting]

I was just wondering what the relationship between number of popple holes and gun flatness is? Is two enough? Is 12 better? Conventional wisdom says that the more popple holes the flatter it shoots, but there must be a point where you are gaining nothing and loosing velocity because theres not enough barrel?

 

Just curious on everyone's insights.

[aandabooks]

Poppel holes can certainly help to flatten out an open gun but it is not the only way.  Grip and load development can help also.  You can always start with a couple poppel holes and add more later but if you start with 12 it would be difficult to go back to 2.  I have 2 in my gun and it helped flatten out the gun.  Of course, they also come with the price of more powder to make the same PF, noise and a little more smoke on the lens.

[AverageJoeShooting]

1 hour ago, aandabooks said:

Poppel holes can certainly help to flatten out an open gun but it is not the only way.  Grip and load development can help also.  You can always start with a couple poppel holes and add more later but if you start with 12 it would be difficult to go back to 2.  I have 2 in my gun and it helped flatten out the gun.  Of course, they also come with the price of more powder to make the same PF, noise and a little more smoke on the lens.

yea but i mean whats the perfect amount?

 

i noticed most of venom customs guns have two or three holes while atlas has 12 with the v12 barrel.  

 

which runs flatter?

[Bwillis]

Atlas has 2

[AverageJoeShooting]

19 minutes ago, Bwillis said:

Atlas has 2

Sorry I meant akai 

 

[Stickman301]

Depends on length of barrel, hole size, caliber, comp, load. At some point the holes will take away gas from allowing the comp to work most effective.

I have 4 on 5” 38 barrel with Akai gill comp

3 on 5” 9mm barrel with Akai gill comp

3 on 4.65” 38 barrel with Akai shoto comp

 

Also depends on what you want.  There’s more to it than just flatness. Like dot movement, how hard it hits your hand, dot tracking, return to zero.

 

5” 38 barrel with 4 holes and gill comp tracks the best.

 

4.65” 38 barrel with 3 holes and shoto comp is the flattest, and fastest return to zero but hits the hardest. 
 

Both are running AA#7 with 125gr BB

[aandabooks]

1 hour ago, AverageJoeShooting said:

yea but i mean whats the perfect amount?

 

i noticed most of venom customs guns have two or three holes while atlas has 12 with the v12 barrel.  

 

which runs flatter?

Those guns that you are buying with the holes already in them require you to develop a load that works with the holes.  If you have an open gun now that does not have holes in it you can start with just a couple and decide if you want to go further.  Working on the powder load as you go.  

 

With my Czechmate I started with no holes and tried several different powders to get the flattest with least dot movement I could get to.  It was at that point that I made the decision to drill 2 holes in the barrel and then load development started all over again.  Got to the point that I'm at now and I don't feel that adding another hole is going to show a noticeable improvement.  I could put in another hole and start the load development again.  Might gain a little more or maybe not.  Possibility of going backwards too.

[donno]

3 hours ago, aandabooks said:

Poppel holes can certainly help to flatten out an open gun but it is not the only way.  Grip and load development can help also.  You can always start with a couple poppel holes and add more later but if you start with 12 it would be difficult to go back to 2.  I have 2 in my gun and it helped flatten out the gun.  Of course, they also come with the price of more powder to make the same PF, noise and a little more smoke on the lens.

 

I have a Brazos 38 super with 3 holes. I have a 9mm shorty with no holes but a very large comp. As aandabooks said, powder and load development is key.

[zzt]

I am a firm believer in poppels.  I've shot with and without them and the guns with poppels always ran flatter.  I've shot 40 Open with and without, and 9mm major with and without.  There is a huge difference between them.  In 9mm, case capacity is the deciding factor.  Put too many holes in the barrel and you cannot make major with any powder that will fit in the case.  More smaller holes do not work as well as fewer larger holes.

 

For 9mm major I currently use a custom 3-chamber comp with two 3/16" poppels in the comp in a V2 configuration.  That, with my load, is the best compromise I could come up with balancing softness with flatness.  I started without the poppels and the gun shot softer, but not as flat as I wanted.  So I had the two poppels added.  That flattened the gun out, but robbed the comp of gas, so it hit the hand harder.  If you want soft and flat at the same time, you need a case with larger capacity.

 

The 40sw has a lot of capacity.  My main gun had a 4-chamber, 5-port comp and two 3/16" poppels in the barrel pointing straight up.  I shot that with WAC and Silhouette, but was not satisfied with the flatness and the recoil characteristics.  I switched to slower powder and discovered the more I added the flatter and softer the gun shot.  I finally ended up with 10.1gr MP under a 155 at 1.150" OAL.  It was a delight to shoot, and much flatter and softer than my current 9mm gun.

 

38SC would do the same.  You can fit gobs of bulky powders like 3N38 in and still make major with lots of poppels.  I would have gone the 38SC route except for the cost of brass.  I lose about 7000 cases a year at what are for me lost brass matches.  So the cost of brass was a prohibiting factor.

[AverageJoeShooting]

I have a venom custom with two popple holes and a binary engineering 3 port comp. Was thinking about adding more 

 

At the same time I'm getting another one built and just wanted to know the ideal setup for the barrel. 

 

Thanks everyone for sharing, I have a lot to mull over!

[zzt]

1 hour ago, AverageJoeShooting said:

I have a venom custom with two popple holes and a binary engineering 3 port comp. Was thinking about adding more 

 

At the same time I'm getting another one built and just wanted to know the ideal setup for the barrel. 

 

Thanks everyone for sharing, I have a lot to mull over!

 

Why?  Is it not flat enough for you?  Take a look at the data from Binary Engineering.  If you are going to use his comp again, ask him what a third 3/16" poppel will add.  I think he will tell you that if you add more holes, go to the 2-port comp.

[echotango]

I have 3x 3/16" holes and a BE 3 port comp. I switched from a BE 2 port and could def feel the difference. It felt much softer that the 2 port. 

 

 

[Corrado_kid]

10 minutes ago, echotango said:

I have 3x 3/16" holes and a BE 3 port comp. I switched from a BE 2 port and could def feel the difference. It felt much softer that the 2 port. 

 

 

What caliper though 38sc?

[CHA-LEE]

The quantity and size of comp ports or popple holes ONLY affects the initial muzzle rise right as the shot fires and before the slide starts to move rearwards. The vast majority of Open guns out there start to muzzle flip when the slide hits the full rearward position. By the time the slide hits the frame in the fully back position the bulk of the gas from the spent round is already gone. Excessive rearward slide velocity is the number one contributor to muzzle flip or in other words "Flatness". You can go comp and popple crazy to try to tame the muzzle flip. But it isn't going to make much of a difference if the slide velocity is crazy. Controlling the rearward slide velocity is just as important as tuning comps, powders and popples.

 

If you don't believe me watch just about any slow motion video of an open gun firing one frame at a time. The bulk of the muzzle flip will happen when the slide slams into the frame in the rearward position.

[zzt]

8 minutes ago, CHA-LEE said:

If you don't believe me watch just about any slow motion video of an open gun firing one frame at a time. The bulk of the muzzle flip will happen when the slide slams into the frame in the rearward position.

 

And that's why you don't let that happen.  There is a HUGE difference in muzzle rise and feel in my gun between 7, 8 and 9 lb. recoil springs.  7 slams, 8 doesn't and 9 is a teeny tiny short stroke (I think) at 169PF with a 115.  Still runs 100%.  9 doesn't work as well for 140PF minor.

[CHA-LEE]

8 minutes ago, zzt said:

 

And that's why you don't let that happen.  There is a HUGE difference in muzzle rise and feel in my gun between 7, 8 and 9 lb. recoil springs.  7 slams, 8 doesn't and 9 is a teeny tiny short stroke (I think) at 169PF with a 115.  Still runs 100%.  9 doesn't work as well for 140PF minor.

 

The recoil spring has an affect on the slide velocity but not as much as the hammer spring or firing pin stop angle. The recoil spring weight should be tuned to optimize the snapping forward motion of the slide so that the muzzle returns directly to level. If you put a heavy recoil spring in there to help reduce the slide velocity it will likely help in that part of the slide movement but it could also ruin the forward motion of the slide by making the muzzle dip low as the slide snaps back forward excessively hard.

 

Once again, observing the movement of the gun during the cycling process via slow motion video one frame at a time will tell you exactly what is causing "Movement" in the gun.

Edited January 21, 2020 by CHA-LEE

[Aircooled6racer]

Hello: When you add more holes in the barrel you are basically making the barrel shorter so you will need more powder to make power factor. Adding more powder will give you more gas but also more push into your hand and arm. I have played around with many comps over the years and also adding holes in the barrels. That is why I built my own comp to give softer shooting and flatter as well. No holes in the barrel are needed. I would play around with recoil springs and mainsprings to see what that does to your setup. Changing the firing pin stop angle does alot as well. Doing the spring changes and firing pin stop( buy a spare flat EGW one) can be done and does not screw up your current setup. Thanks, Eric

[echotango]

3 hours ago, Corrado_kid said:

What caliper though 38sc?

9

[echotango]

I agree with Chalee.  Mainly has to do with the slide hitting the rear and grip also plays a part. I have played with tons of FPS, main and recoil spring combo.  It is endless.....

[AverageJoeShooting]

1 hour ago, Aircooled6racer said:

Hello: When you add more holes in the barrel you are basically making the barrel shorter so you will need more powder to make power factor. Adding more powder will give you more gas but also more push into your hand and arm. I have played around with many comps over the years and also adding holes in the barrels. That is why I built my own comp to give softer shooting and flatter as well. No holes in the barrel are needed. I would play around with recoil springs and mainsprings to see what that does to your setup. Changing the firing pin stop angle does alot as well. Doing the spring changes and firing pin stop( buy a spare flat EGW one) can be done and does not screw up your current setup. Thanks, Eric

So the firing pin stop allows the recoil from the slide slamming backwards to be less? Is the EGW flat the only choice?

[Fo0]

17 minutes ago, AverageJoeShooting said:

So the firing pin stop allows the recoil from the slide slamming backwards to be less? Is the EGW flat the only choice?

 

more angle on the firing pin stop will increase slide speed backwards

[vgdvc]

3 hours ago, echotango said:

I agree with Chalee.  Mainly has to do with the slide hitting the rear and grip also plays a part. I have played with tons of FPS, main and recoil spring combo.  It is endless.....

Not to jump off topic but seeing how it could relate to the need or lack of for popple holes has Echo Tango or anyone else experimented with using an original design FPS with just a small radius at the bottom like the EGW standard unit( seen farthest back in above picture)? I have read on here before that many prefer the Cheely FPS profile but if the intent is to retard/delay rearward slide movement to allow a lighter recoilspring, which would reduce forward momentum of the slide going back into battery, wouldnt a square profile with slightly rounded bottom FPS make most sense?

[Fo0]

12 minutes ago, vgdvc said:

Not to jump off topic but seeing how it could relate to the need or lack of for popple holes has Echo Tango or anyone else experimented with using an original design FPS with just a small radius at the bottom like the EGW standard unit( seen farthest back in above picture)? I have read on here before that many prefer the Cheely FPS profile but if the intent is to retard/delay rearward slide movement to allow a lighter recoilspring, which would reduce forward momentum of the slide going back into battery, wouldnt a square profile with slightly rounded bottom FPS make most sense?

 

theory is supposedly its less recoil but not as 'flat'

[vgdvc]

8 hours ago, Fo0 said:

 

theory is supposedly its less recoil but not as 'flat'

Yes I recognize that theory, and I do have it set up that way on my limited gun. However if Cha lee's theory is correct a majority of the upward dot movement comes from the mass of the slide hitting harder at the rear position when firing. I'm going to play to see if the square-edged FPS has a better recoil sensation for (1)keeping it delayed and locked in battery longer so even more gas is burned prior to slide movement  and (2) slowing the slide momentum to create less reward impact. I know the common

thing seems to be using a higher contact point fps contact point with open guns but when this was mentioned a little while back to some very experienced shooters they actually said they have settled on a square FPS style in there open guns so I will need to try this myself.

[Aircooled6racer]

Hello: Buy a EGW square firing pin stop and try it. Then start filing a radius on the corner to see what it does. I made a fixture so I can mill an angle on the firing pin stop that works very well for me. It makes racking the slide easier so it cycles quicker. Thanks, Eric