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Barrel Comparison: PDI 6.01 vs. First Factory 6.03


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At times, I've wondered which is truly best for accuracy: PDI's 6.01mm barrel, or FF's 6.03. This review compares one to the other, in the same pistol and with the same barrel length. With a sample size of one, it shouldn't be considered a be all and end all guide to barrel accuracy, but it does allow one to draw some reasonable conclusions.

 

First, let's look closely at the two barrels. They're both stainless steel, and as such won't tarnish like a stock brass barrel. Additionally, they are both cut to fit a Tokyo Marui Hi-Capa 5.1 or M1911A1, 112mm in length with a hop-up cutout for a VSR type bucking.

 

barrels1.jpg

barrels3.jpg

 

The most noticeable distinguishing feature between the two is that while the First Factory barrel lacks any markings, the PDI barrel is conveniently engraved with ".01 PDI Japan". Certainly helpful for keeping your upgrade parts bin in order.

 

barrels4.jpg

 

With a very close look, however, we start to see more differences. Notice that the FF barrel is cut for the same hop-up type as the PDI, but the retaining cut for the bucking has beveled edges, while the PDI uses straight ones. This is nice for removing the hop-up bucking without tearing it, but could mean a less secure seal.

 

barrels6.jpg

 

Moving to the back of the barrel, another difference is readily apparent. The top portion of the barrel is cut away to allow the nub of the hop up to protrude into the barrel and contact the BB. This cut is slightly different on the PDI - in addition to the main portion milled away, there is a surface perpendicular to the bore axis, perhaps to garner a little extra room for the hop up with a smaller main cut. Additionally, the rim of the barrel along the bottom and sides is beveled on both the PDI and FF products, but noticeably more so on the First Factory barrel.

 

barrels5.jpg

 

Additionally, a few machining marks can be seen on the flat area on the top of the PDI barrel, not as completely polished out as on the FF tightbore.

 

barrels7.jpg

 

Flipping both barrels around, a significant difference is clear on the front rims of the barrels. Both are crowned with a beveled area sunk partway into the bore, however the FF uses a more steep crown which extends deeper into the barrel.

 

barrels8.jpg

 

The exterior finish of the tightbores is virtually identical to the eye with the First Factory barrel slightly shinier in bright sunlight.

 

barrels9.jpg

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Enough on the physical differences - time for the tests. My testing platform is a Tokyo Marui Glock 17 with the following upgrades that could potentially affect accuracy:

BoomArms Shuey Custom G34 Slide and Outer Barrel

FireFly Recoil guide w/ bearings

FireFly Aluminum Floating Valve for G26

Firefly soft V-hop bucking

SD Hammer spring

SD 150% recoil spring

PDI Piston head

 

It was very important to avoid variances in assembly of the barrel unit that could throw off the tests. As such each barrel was cleaned with seven cotton patches and hop-up unit parts were dusted with computer duster to keep tiny debris from affecting the consistency of reassembly. Both barrels were to be tested with the hop-up turned all the way down to ensure the setting would be the same. First up is the PDI 6.01mm barrel:

 

barrels2.jpg

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When conducting an accuracy test with a pistol, it's important to be sure of what you're testing. For example, clamping the frame or grip of the pistol in place and firing away at a target tests how accurate the pistol will be for someone who uses the frame or grip to aim (which is useful for certain pistols using red dot sights anchored to the frame). The outer barrel, slide, recoil rod, and inner barrel will be moving in relation to the frame with each shot; as such you are testing the variation between inner barrel and frame in addition to the variation in the barrel itself. Most people use a slide mounted sight - that is, iron sights or an Optima 2000 type red dot, so in this test I will be using the sights on the pistol to align it for each shot (testing with variation between inner barrel and slide in play).

 

For this purpose I spent a few minutes constructing a crude adaptor for an old camera tripod. The adaptor consists of a piece of polycarbonate sheet which mounts to the camera tripod with a nut, then to the bottom half of a scope ring via two Allen screws. This allows the tripod to be used for anything with a Weaver or Picatinny accessory rail in a suitable location, including the Glock pistol to be tested.

 

I loaded the pistol's magazine with 10 KSC Perfect .25g BBs, a common brand and weight. Then I filled the magazine with unlubricated propane until excess gas spurted from around the fill valve. For general use, propane should be lubricated to maintain the O-rings of the magazine valves and piston head, but to ensure consistency of the tests unlubricated propane is best. After allowing the magazine to sit for 10 minutes for its temperature to return to normal, I locked the slide of the pistol back, inserted the magazine, and hit the slide stop lever to chamber the first BB.

 

barrels11.jpg

 

My target was taped to a cardboard box, so that every BB would make a hole in the target, but not ricochet back through and distort the grouping. The tripod was positioned so that the pistol's barrel measured 20 feet away from the target. I aimed carefully at the center of the target, ignoring the three dots of the sights and instead focusing on the dark outlines of front and rear sights for the most precise sight picture. When satisfied, I locked the tripod's mounting bracket in place and fired. For the subsequent shots, I allowed 10 seconds for the magazine to warm, carefully checked the alignment of the sights, adjusted if completely necessary, and fired again.

 

When the test was complete, I removed the upper assembly from the pistol, leaving its frame locked into the tripod, and replaced the barrel with the First Factory unit. I then taped a new target in place and repeated the process exactly.

 

The results? Surprising. The PDI 6.01mm barrel grouped thusly (1" grid):

barrels13.jpg

 

Whereas the First Factory 6.03mm barrel actually performed a little better:

barrels12.jpg

 

On measuring the size of the groups, from center to center of the holes farthest apart, it turns out that the FF barrel produced a grouping of 28mm, while the PDI barrel came in at 39mm. About a centimeter of difference in group size at 20'.

 

I felt that another test was required to cement the groups. This time, I used the same testing procedures, but fired at 35' and with 15 shots. My hope was that the greater distance and number of rounds fired would lessen the possibility of error. Additionally, I considered the possibility of variance in assembly, and uninstalled and reinstalled the 6.03 barrel before performing more tests. For obvious reasons the 6.01 barrel would also be reinstalled.

 

Once again, the First Factory barrel outperformed the PDI barrel in accuracy. This time, the group produced by the PDI 6.01 measured 59mm, while the First Factory grouped a tad tighter at 50mm. So, the difference is not as great in this test, especially considering the increased distance, however the PDI still didn't beat out the FF.

barrels16.jpg

barrels17.jpg

 

Comparing products using a sample size of one is unlikely to produce exact numbers that can be applied over an entire range of products. However, I would cautiously conclude that, at least in a Tokyo Marui Glock with a barrel length of 112mm, a First Factory 6.03mm barrel is slightly preferable from an accuracy standpoint. The 6.01mm barrel can be expected to produce a bit more power in a gas gun, though I do not have a chronograph and so will have to wait until a skirmish to confirm this.

 

Of course, I am left to wonder why a 6.03mm barrel would have better accuracy than a 6.01mm barrel. The immediate answer which comes to mind is the quality of the barrel in matters other than interior diameter, and this test offers one possible explanation. The pictures and a very rudimentary knowledge of German make it clear that a precise measuring machine was taken to a number of barrels, measuring their roundness. Scrolling down, one can see that PDI and Prometheus both were very close to a perfect microscopic circle, but Prometheus (AKA First Factory) was a little better. Notably, the PDI barrel beat out both DB Customs 6.01 barrels.

 

In conclusion, inner barrel quality is more than mere diameter - accuracy tests may bear this out. Both PDI and Prometheus/FF make great choices for inner barrels, but based on what I have observed in my testing and experience, out of the two PDI is the choice for power, Prometheus/First Factory for top accuracy. If you have a different testing procedure to suggest I would be happy to read it and if it is not too time consuming or expensive, try it out.

 

barrels18.jpg

 

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I might try a PDI .05 because so many people seem to either be interested in them or swear by them, but of course it will depend on whether I find room for it in the airsoft fund to throw one in. It's not that they are very expensive - just that in purchasing a barrel vs. purchasing several thousand more BBs and some gas I usually give the edge to the gun food.

Edited by RSP1
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Thanks for all the comments. I am leaving on vacation and so will not be able to reply to any further comments on this review until the 19th. As far as the PDI .05 barrel, my curiousity is piqued but I've got a busy schedule - a few days after I get back I'm leaving again for a month. We'll see.

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As much as I like this, I feel there are a few "possible" flaws to the data.

 

1. The airsoft round (bb) takes far longer to leave a barrel in airsoft than real steel, therefore movement can affect accuracy. So shooting from a rest does not mimic reality and creates a false reading. Most shots in airsoft are moving and offhand, especially with a pistol.

 

2. To shoot without a hop up is to shoot without part of the system in place. If it is true that hop up creates rolling along the top of the barrel then not using it causes false readings again. Hop up should be adjusted so as to create the longest level flight possible without rising the bb up.

 

3. If you can, repeat the test with at least 4 brands of bb's and 2 weights of each bb.

 

Just those three would make it more accurate to reality (IMO only). I know you are trying to remove possible variables, but by doing so you added in two larger ones IMO (This coming from my own testings of replicas I found that how a barrel performs without hop is in no relation to how it performs with hop, especially in longer barrels) Same goes with off hand shooting. If the barrel moves from kickback does the tighterbore allow re-stabalization faster?

 

OK, maybe just add these variables into the testing, to see if possible different results.

Edited by mannerofliving
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The airsoft round (bb) takes far longer to leave a barrel in airsoft than real steel, therefore movement can affect accuracy. So shooting from a rest does not mimic reality and creates a false reading. Most shots in airsoft are moving and offhand, especially with a pistol.

Increased lock time (time from pulling the trigger to the projectile leaving the barrel) does not affect accuracy when the weapon is static. It is a static "laboratory test" if you will, but still shows a difference in the mechanical accuracy.

 

If the results are applied to a practical situation where the shooter is not a perfect stable platform, this is only an argument to use a shorter barrel. Personally I prefer all my Airsoft guns to have a barrel length of 300 mm or less.

 

2. To shoot without a hop up is to shoot without part of the system in place.

 

Same goes with off hand shooting. If the barrel moves from kickback does the tighterbore allow re-stabalization faster?

I agree that hop-up should be applied for test-shooting. The TM GBBs do apply a bit of hop-up even at "zero" setting, but I'd set it to give the optimal backspin. I've seen inconsistent chrono results with the hop-up set off, and the velocities became consistent when hop-up was applied... Consistent velocities are a sure way to improve accuracy.

 

As for shooting off-hand, didn't you say earlier that the test should mimic reality better? Off-hand shooting is reality if anything. I've shot 30mm groupings with five shots from 10 meters (33 ft), so I trust my shooting to measure the actual performance of the pistol.

 

Why is the 6.05 PDI barrel purported to be the best?

It is argued that the gap between the barrel bore and BB becomes too small when the barrel is made too tight. I can say for sure that it is possible to make a too small gap. I don't argue at this point what the optimal gap is, but PDI says their 6.05 barrels are more accurate than 6.01 barrels. In the above test we have seen that a 6.03 barrel beat a 6.01 barrel. Further tests are necessary to form a consensus on this matter.

 

-Sale

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It is argued that the gap between the barrel bore and BB becomes too small when the barrel is made too tight. I can say for sure that it is possible to make a too small gap. I don't argue at this point what the optimal gap is, but PDI says their 6.05 barrels are more accurate than 6.01 barrels. In the above test we have seen that a 6.03 barrel beat a 6.01 barrel. Further tests are necessary to form a consensus on this matter.

 

Ah ok, thanks. I might get a 450mm 6.05 PDI for my M14, and see how it compares to my friends 500mm 6.03 Prometheus in his M14.

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It still seems there are more variables that arent exposed. I wished that german site would have looked at bb's for roundness.

BBs have already been checked for consistent weight, size and roundness by Airsoft Mechanics. http://www.airsoftmechanics.com/reviews.php?aid=12

 

Long story short: Marushin and KSC know how to make BBs.

 

-Sale

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My next line of thinking

If larger barrels (6.03,6.05) are presumably better for gas pistols than 6.01, would the same hold true for AEG's, given the differing nature of the bb's propulsion?

(AEG's push air while propane/duster/co2 is actively expanding)

 

Im wondering if more room in the barrel on these pistols allows the gas itself to stabilize the bb some along with the increased tightness. 6.03 would allow perhaps a good medium of the barrel holding the bb steady and the gas helping cushion, giving the better accuracy.

Edited by Azulsky
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I'm not a fluid dynamics expert, but I would say it doesn't matter. The problem with a too tight barrel stems from the fact that a light BB is spinning at a high rate and moving forward in the barrel. Too much contact area between the BB and barrel bore can easily disturb the spin.

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