Tuesday, August 26, 2008

Aguila Super Colibri VS. CCI CB Long, a velocity comparison

This coming weekend I hope to spend some range time sorting through a big box of .22 long rifle, seeking my Marlins favorite. I'd like to do the shooting past my chronograph, charting velocity variations. By doing so I should learn something about the consistency of the various rim fire products.

To that end, after work today I sorted out the parts of my Pact Model 1 chronograph and assembled it near the garden. To be sure it was working properly I needed to do some shooting through it. There were kids swimming not far away, and I preferred to make as little noise as possible. Since I'm not Frank James and don't own a 'sound reduction device', I decided to use truly quiet .22 ammunition.

A box each of Aguila Super Colibri and CCI CB Long ammunition were pulled from the safe, and a'shootin we did go.

Only a few rounds were required to test the Chrono, but I figured "Why waste the opportunity?" I shot ten rounds of each through the screens and made note of the results, as an investigation of the ammunition, while I tested my equipment.

The Aguila Super Colibri with it's 20 grain conical bullet showed considerable drop from my rifle at the range, and poor accuracy. It's possible these chronograph results reveal why. The velocity variations are sharp.

With an average muzzle speed of 565 fps, the extreme spread in velocity of 118 fps was huge. Thats almost a 20% variation in velocity. At least as significant was the standard deviation of 32 fps. It's no wonder my Marlin spit this stuff all over the landscape. On the other hand, the very low velocity helps to explain the extraordinary quietness of this ammunition. It barely goes 'Pfft' out of a long barrel.

Moving on to the CCI CB long with it's 29 grain round nose bullet (a favorite of mine for pest control) I fired another ten rounds. This ammunition was a bit louder, which was backed up by the higher velocity. It averaged 623 fps, and on the whole was much more stable in velocity variations.
There was one clinker round amongst the CCI string, and it heavily skewed the numbers. While shooting the CB longs, I had 'Pop', 'Pop', 'pfft', 'Pop'....

'Scuse me? what is this 'pfft' and where did it come from?

There was round in the bunch which came out of the barrel much slower than the others. Almost 150 fps slower... and this made a huge difference in a ten round string.

Dropping that round from the math brought the extreme spread from 184 fps down to 88 fps. This is still a very wide number accuracy wise. Velocity variations like this have to adversely effect accuracy.

I verified the chronograph works, and also verified something I suspected regarding the super quiet CB and Colibri rounds. They are not very accurate for a good reason..... the manufacturing variations in this type of ammunition seem to be rather extreme. The chrono clearly shows this.

Hmmm................... Perhaps I should take some apart and figure out why......


Anonymous said...

Nice comparison, I hope you do one on the remington CBee. I shot some of them in Australia and they are pretty quiet never heard of them here also they had the zimmer round from winchester, I know.... never heard of them.

Federalist said...

I opened up a CCI CB Long and found just under half a grain of powder in it. (And I thought "CB" rounds were supposed to be powered only by primer compound.)

If my experience loading centerfire is any indication it's a miracle these things produce anything but random velocities between squib and 700fps: With such a tiny powder load the case is mostly empty, so the powder rattles around and when fired it might be close to the primer or it might be pressed up against the bullet. In the latter case it may not even fully burn before the bullet's out of the barrel!

Anonymous said...

I hope you will consider doing a followup on this, but including the new CCI quiets. I find them to be much quieter than the CB shorts, and almost as quiet as the super colibris. IMO they are better than both, because they grouped pretty well, there is little chance of getting a squib (like the super colibris), and they have about twice the energy of the super colibri. They were pretty expensive, but I liked shooting them.

Anonymous said...

My expereience with the Colibri and Super Colibri ammo over three years, fired in my hand built scoped Stevens Favorite with a 16.5" barrel which I built, has been dramatically different. Both types shoot virtually single ragged hole groups at the 25' to 40' distance at which I shoot large, fluffy tailed tree climbing pests. I have dispatched 103 of them in the past 18 months, and every shot was a head shot. That ammo is, in my opinion, as good as it gets. There may be a technical problem with your test rifle.

Phil in Ohio