Barrel Porting (drilling holes) to reduce muzzle-flip

chuckjordan · Post by **chuckjordan** » Sat Aug 21, 2010 8:54 am

I have an older Hammerli and was wondering about having someone drill holes to further reduce the muzzle-flip. I know there's not much flip on ths light AP, I want to futher reduce it.

The older AP's didn't have this technique, but the new ones (Steye LP10, Walther LP300XT, etc.) do.

I figure it's working for them, why can't this technique work for me?

Has anyone performed this before and also (just as important); does this violate any AP rules?

I don't want to go the route of barrel weights, I want to keep this as light as possible.

ronpistolero · Post by **ronpistolero** » Sat Aug 21, 2010 9:12 am

Porting the barrel would require some extra skill so as not to damage the rifling within the barrel. It might be much easier, as what I have done, to add a compensator instead.

Just my thoughts.

Ron

Tycho · Post by **Tycho** » Sat Aug 21, 2010 9:23 am

No problems with the rulebook, comps and similar stuff on AP are allowed (shows how much they are deemed to be worth). I've never heard of anybody successfully doing a aftermarket job like this, but why not. On the other hand, a good comp may well be cheaper, just as effective, and would be no problem with a potential future buyer. Which type of Hammerli AP is it?

Rover · Post by **Rover** » Sat Aug 21, 2010 10:13 am

MagnaPort used to do this (maybe still does) by electrical discharge maching (EDM). They would cut longitudinal slots on top of the barrel near the muzzle in about any kind of barrel.

My own feeling about this is; don't bother. But, if you have a drill press have a go at it. A problem might be getting the burrs off the bottom of the hole. You can always shorten or replace the barrel, perhaps with a superior custom job.

Any machine shop could drill the holes for you, it wouldn't have to be a gunsmith. You probably have a friend with a drill press or you could buy a cheapie from Home Depot or Harbor Freight.

Ask your friend Bubba to help you out.

chuckjordan · Post by **chuckjordan** » Sat Aug 21, 2010 10:30 am

It's an olde 480K.

If the factory drills holes or uses an EDM to port (roughly accomplishes the same thing), why not? Yes, they have CNC, but the ports must be drilled/EDM'd one way or another. Either way impacts the rifling (unless they properly machine using a dowel/rod inside the bore when drilling).

I thought of a new compensator, maybe even getting a similar manufacturers compensator and placing it on the barrel. I know the OD of all the barrels are not the same, but, I'd be willing to bet that some are.

As good as the compensator would be, the manufacturers now have the Comp AND the holes ported.

The new Hammerli AP Balance has 3 port holes, maybe better(and cheaper) to buy the barrel and Comp ?

Just thinking outloud, trying to wring the last bit of blood from this old turnip

Tycho · Post by **Tycho** » Sat Aug 21, 2010 1:02 pm

Not sure if the AP40 barrel fits the 480K. And (not to sour anyone, just 5 cent of info) if it's the first version of the 480K, with the fat tank, I'm not sure if I would invest anything in it - something fails, nobody's going to repair that thing. Hammerli started to replace 480 tanks with AP40 years ago, but that is one expensive replacement.

My SAM K11 has no ports, and muzzle jump is only discernible at more than 155 m/sec of V0. The SAM comp obviously works very well. FWB used to port even the C25, back in the old days, and IMHO it was good for nothing, couldn't see a difference to the standard barrel. Remember that newest generation AP all have absorbers which bring a lot more than comp and ports. Many AP use a 12mm barrel, so a lot of the comps and front sight holders are interchangeable.

Misny · Post by **Misny** » Sat Aug 21, 2010 1:56 pm

No offense intended, but what are the advantages to having less muzzle flip? I can see it in a pistol where the shooter makes quick follow-up shots, like international rapid fire pistol, but cannot see any benefit to air pistol shooting.

ben · Post by **ben** » Sat Aug 21, 2010 2:56 pm

Yes. This can be done and I did it many years ago on a .22 Rapid-Fire pistol which was used to collect a bronze or silver in one of the Commonwealth Games.

I cannot recommend doing it. It is extremely difficult, though not impossible, to remove the inevitable burr in the bore (no matter how careful the drilling technique) It would possibly be easier with EDM.

Like other posters I do not see the point with an AP. I possess an LP5 which I found too heavy. I removed the sleeve containing the muzzle brake (compensator) and fitted an LP2 sight, which of necessity did not include the brake. The handling was dramatically improved, and the grouping before and after was indistinguishable.

Hope this helps, Ben

JamesH · Post by **JamesH** » Sun Aug 22, 2010 5:55 am

Rover wrote:MagnaPort used to do this (maybe still does) by electrical discharge maching (EDM). They would cut longitudinal slots on top of the barrel near the muzzle in about any kind of barrel.

My own feeling about this is; don't bother. But, if you have a drill press have a go at it. A problem might be getting the burrs off the bottom of the hole. You can always shorten or replace the barrel, perhaps with a superior custom job.

Any machine shop could drill the holes for you, it wouldn't have to be a gunsmith. You probably have a friend with a drill press or you could buy a cheapie from Home Depot or Harbor Freight.

Ask your friend Bubba to help you out.

I wouldn't even consider drilling it, either EDM the holes or fit a separate compensator.

Shooting Kiwi · Post by **Shooting Kiwi** » Mon Aug 23, 2010 3:12 am

As far as I can see, drilled barrels and compensators do not achieve the same thing. A compensator directs muzzle blast upwards, to force the barrel downwards, but only after the bullet has exited. Thus, it gets the pistol back on aim quicker, but it does nothing to reduce the upwards flip of the barrel whilst the projectile is travelling down the barrel. Thus, it doesn't improve accuracy (if such inaccuracy results from the recoil-induced barrel movement).

Whether drilled barrels keep the barrel alignment on target whilst the projectile is in the barrel I don't really know, particularly when a recoiling-mass recoil-compensator is included. Presumably, the empirical evidence is out there. I would have thought the velocity of the gas jets would have to be enormous in order to be effective, since the mass of gas ejected would be so small. I'd assume that, for best effect, the nozzle design would be critical. As far as I know, 'holy' barrels don't have clever nozzles, just parallel-sided holes.

Also, since a drilled barrel dumps propelling gas pressure, presumably the projectile doesn't accelerate much downstream from the drillings. Why not therefore just amputate the barrel, just after the last hole, to give a shorter barrel-time, which can only be a good thing?

Can anyone enlighten?

Spencer · Post by **Spencer** » Mon Aug 23, 2010 5:14 am

The question must be asked - why?
If you think muzzle flip is a problem with AP it is probably a matter for a coach to address rather than machining the pistol.

but if you have to for some percieved advantage, refer the answers above.

chuckjordan · Post by **chuckjordan** » Mon Aug 23, 2010 7:32 pm

I was asking the question. Why? Why do the major AP manufacturers do it?

I bet if the major AP manufacturers offered retro-fit barrels (ported) for our older AP, many would buy them.

Thanks for the responses.

serafino · Post by **serafino** » Mon Aug 30, 2010 11:40 am

chuckjordan wrote: I was asking the question. Why? Why do the major AP manufacturers do it?

As far as I know (wasn't Walther CPM1, in CO2, the first to use that?) those holes reduce the chaotic movement of the air behind, around, and in front of the pellet. So the pellet movement is unperturbed by those chaotic movements. (Of course they also stabilize the barrel during the release of the shot, but this is a sort of secondary effect.)

BEA · Post by **BEA** » Mon Aug 30, 2010 7:41 pm

The first person that I knew to go down this road was Don Nygord with his "Turbo Comp". I think he sold quite a few of them but do not know if the idea was his or someone elses. At any rate, the AP manufacturers picked up on the idea sometime after that. I had a Steyr CO2 and they came out with a ported sleeve to replace the unported one. I then started shooting a Walther CPM 1 that had their version of the Turbo Comp. Both seemed to work very well.

The question that started this thread was from someone who was thinking about doing their own porting. If you did this yourself, my guess is you could kiss goodbye any accuracy that you had.

Rover · Post by **Rover** » Mon Aug 30, 2010 9:17 pm

Boy, that post brought back some memories.

Back in the early 90's there was a guy named Phil Saccio on Long Island who sold match air pistols by mail. He was the biggest Pardini dealer in the country. He even went to Italy to chat with old man Pardini about his guns.

This guy went so far as to acquire "Challenger" grade O-rings from the aero-space industry there and substitute them for the somewhat inferior ones on the guns he sold, also taking a batch to Italy with him.

Anyway, he showed me a muzzle brake he made that could be mounted on many guns using a set screw and gave me one to test. He told me he had talked with Nygord about the concept and showed him one.

Unfortunately, there was little love between the two because Phil was selling so many guns out from under Don's nose.

It was shortly afterward that Don started marketing his own unit.

chuckjordan · Post by **chuckjordan** » Tue Aug 31, 2010 6:47 am

To the poster that stated if I perform the work, accuracy would suffer.

Are you saying that I'm a bad machinist? Or that a burr inside the barrel would make the pellet not fly true?

The leade, the choke, and the crown. That's really what matters. How many AP/AR barrels are out there with a spec (or more) of rust in them and they still stack them? I have maybe 2. See, I collect the older 10M AP/AP and I have some that will keep up with my pristine FWB P70.

With all the members on this forum, probability-wise someone here has a flaw in one of our barrels. Yet it still shoots accurate.

The leade starts the pellet, the choke sizes the pellet (and builds back-pressure for a spring AP/AR) and the crown makes sure it leaves the barrel true.

BEA · Post by **BEA** » Tue Aug 31, 2010 8:56 am

Chuck, my comment on porting was nothing personal concerning your machining abilities...that did not enter my mind. I don't take jabs at people here, just share my thoughts. My concern is the edge left in the barrel and the location of the ports. Due to the pellets being so soft, my guess is they are very sensitive to disturbances. I am an experienced AP shooter (not suggesting you aren't) and fired lots of rounds out of a vice looking for small groups. Not bragging, just telling you where I am coming from, but I have broken 580 dozens of times over the years and have always sought 1 hole groups trying to eek out another point or two. My opinion over the years, for the most part, is to let the gun companies do the engineering. They do this stuff all the time, put alot of thought into it and are always looking for an edge over their competitors. They have to know infinitely more than I do. If I fool with something on my guns, it has always been something that could be undone if need be. Porting is permanent, and if it doesn't work, too bad. My suggestion is that if you feel that you can benefit from the small benefit that porting can offer, purchase a pistol that is already ported. When new models come out, some the old stuff that is just as capable goes on sale. It is just a matter of being in the right place at the right time. Thank you for your note and good shooting.

RB6 · Post by **RB6** » Tue Aug 31, 2010 2:42 pm

[quoteChuck, my comment on porting was nothing personal concerning your machining abilities...that did not enter my mind. I don't take jabs at people here, just share my thoughts. My concern is the edge left in the barrel and the location of the ports. Due to the pellets being so soft, my guess is they are very sensitive to disturbances. I am an experienced AP shooter (not suggesting you aren't) and fired lots of rounds out of a vice looking for small groups. Not bragging, just telling you where I am coming from, but I have broken 580 dozens of times over the years and have always sought 1 hole groups trying to eek out another point or two. My opinion over the years, for the most part, is to let the gun companies do the engineering. They do this stuff all the time, put alot of thought into it and are always looking for an edge over their competitors. They have to know infinitely more than I do. If I fool with something on my guns, it has always been something that could be undone if need be. Porting is permanent, and if it doesn't work, too bad. My suggestion is that if you feel that you can benefit from the small benefit that porting can offer, purchase a pistol that is already ported. When new models come out, some the old stuff that is just as capable goes on sale. It is just a matter of being in the right place at the right time. Thank you for your note and good shooting.[/quote]

chuckjordan · Post by **chuckjordan** » Tue Aug 31, 2010 7:51 pm

Thanks BEA, thanks to all.

Since there were no other posts about this and nobody asked, I wanted to ask. Since it was a new feature on the new APs, I was wondering what it could accomplish on an old workhorse.

Again, I was thinking out load. I appreciate everyone's feedback.

I didn't expect this thread to keep on moving, I thought there would be 2-3 replies and that was it.

I'm going to leave it just the way it is.

BEA · Post by **BEA** » Tue Aug 31, 2010 8:12 pm

Charles, is your old Ham CO2 or compressed air?

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