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28 July, 2010

Now we can really understand temperature effects on our QB78 family air rifles!

I've always been interested in the effect of temperature on CO2-powered air rifles such as the Crosman 160, QB78 and Crosman 2260.

As all CO2 air rifles exhibit a change in muzzle velocity with changes in temperature - due to the physical properties of CO2 - I've tried to measure this effect in the past. In tests, I found that QB78 family air rifles - such as the QB79 and AR2078 - all show an increase in muzzle velocity with temperature of 2 fps per degree F. So, a gun shooting at 600fps at 65 degrees F will shoot at 640pfs at 85 degrees F, due to the effect of temperature alone. And I measured the point of "valve lock" on a QB78 air rifle to be at 96 degrees F.

But, like everyone else, I've concentrated on the air temperature to measure these things. Now, there's a completely new way to measure the temperature of your QB78 family air rifle. It's the Archer Airguns QB78 Temperature Monitoring Kit.

Thanks to the suggestion of Rochester-area airgunner Doug Wall, Archer Airguns has introduced a simple kit that allows you to monitor the temperature of the CO2 in the gas tube of your air rifle. This kit uses self-adhesive thermometers that attach to the main tube of the gun and, therefore, measure the temperature of the gas tube rather than the surrounding air.

These thermometers allow measurement of main tube (and therefore CO2) temperature to 1 degree F. If the temperature is highlighted in green, it's exactly the value indicated. Brown highlight shows that the temperature is just above the temperature, while bluehighlight shows a figure just below. In this way, you can see differences in muzzle velocity of 2 fps!

Here, the thermometer shows a main tube temperature of 73 degrees F.
You can use this kit to maximize the muzzle velocity of your QB78 air rifle. In testing, I found that simply piercing a fresh pair of 12 gram Powerlets in a QB78 reduced the main tube temperature by 10 degrees F. That's a loss of 20fps!

And, using the Temperature Monitoring Kit, I saw that it took 5 minutes for the temperature of the main tube (and, therefore, the CO2) to return to 65 degrees, re-gaining 10 fps in muzzle velocity in the process.

As the Archer Airguns QB78 Temperature Monitoring Kit is new, there's lots of information on the performance of our favorite air rifles that can now be explored in a way that was previously unattainable. Watch out for more data, or use the kit yourself and contribute to our increased understanding of how these air rifles really behave!


17 July, 2010

Why the Generation-II GTX 2-Stage Replacement Trigger is Better Than All Its Predecessors. The story of a screw

Post by Steve_in_NC.

For more than a decade, one of the most popular trigger designs – adopted by such easily-recognized airgun marques as Benjamin, BSA, Crosman, Gamo, Remington, Stoeger, Tech Force, Theoben, and Xisico – has been the so-called “Gamo-style Adjustable Two-Stage” trigger.

The enthusiasm for this trigger among manufacturers is easy to understand. The design is mature, proven, reliable, robust, safe, and incorporates resettable safety and automatic anti-beartrap features. Unfortunately, the lack of enthusiasm for it among shooters is also easy to understand. In use, this trigger is heavy, rough, and creepy with an unpredictable break, and the “two-stage” feature is only simulated. In short, it’s a trigger that works reliably and well, but can pose a real obstacle to fun and accurate shooting.

This unique combination of popularity with less than ideal performance is the reason that, in 2004, I undertook the design and manufacture of the GTX replacement trigger. In the intervening years, thousands of GTXs and GTX copies (not all of them authorized) have been sold, installed, and helped to make good airguns better – some say much better. But there was still room for improvement. So in 2009 I took a hard look at the original GTX concept and design from the vantage of a half-decade of experience with trigger re-engineering. The GTX generation II is the result.

From day one (over a half-decade ago), the GTX's (including the unauthorized knock-offs) biggest shortcoming as a first-class sporter trigger, has been a 2nd stage that's too easy to pull through. 

All 2-stage triggers, by their very nature, must always have a 2nd stage with a heavier pull than the 1st stage. This difference in stage weights isn't super fussy, but it does have to be large enough for the shooter's finger to reliably detect it. Otherwise the shooter may inadvertently pull through the second stage - release the shot before he's ready - and miss. 

An ideal ratio of 2nd to 1st stage weights is at least 1.5:1.

Unfortunately, the GTX (and all knock-offs) have never achieved ratios anywhere near that large. An anemic 1.2:1 was always typical. And since designing and beginning production in 2004, I've never quite known why - until I got involved with the development of the GTX Generation-II trigger. As part of reviewing my design files leading up to its production for the reintroduction, I did some long overdue experimentation and found out that the problem all along had been the inadequacies of a rough and asymmetrical screw tip. 

Unlike all other Gamo replacement triggers, the new GTX uses an adjustment screw with a precision polished bearing tip (picture on the right), instead of an ordinary fastener-type machine screw (left).

After six years, the problem is finally fixed. The result is typical measured weight of: 

1st Stage = 14 oz. 

2nd Stage = 1 lb, 5 oz.

2nd:1st Ratio = 1.5:1. 

Nobody who shoots with the new GTX will be likely to miss the difference in feel - nor as likely to miss his target. 

The Generation II GTX Trigger is available from Archer Airguns.


10 July, 2010

Day Two of the Crosman FT Shoot - and a "Tactical" Prototype Marauder

Day two of the Crosman-sponsored FT shoot saw an excellent shoot in perfect weather. Somewhat cooler than yesterday, there was no rain - just some wind to disturb the shooters on the more open sections of the course.

The WFTF rules contest saw Ray Apelles and Harold Rushton shoot identical scores. The winner was decided by a 55-yard "sudden death" shoot off with Harold the winner.

Below, Harold and Ray congratulate each other after the shoot off.

Above. Art Duel prepares to shoot.

Crosman supplied a wonderful range of "door prizes" that were distributed at the conclusion of the shoot. The many lucky winners - whose name was pulled out of the hat (well, actually a paper cup!) - won pellets, knife sets, Center Point scopes (not cheap ones either) and air rifles. There was also a large selection of plaques, one each for first, second and third prize winners in each category. Photo below.

And, out for pubic viewing, was the most interesting prototype "tactical" Marauder shown below. I want one!!!

Everyone who attended agreed that it was a fine shoot and that Crosman hosted it fabulously. Don't miss this event next year!


09 July, 2010

Crosman Northeast Regional Field Target Championship - First Day

Today was the first day of the Northeast Regional Field Target Championship held at the Crosman headquarters in Bloomfield NY.

The match was directed by Hans and Ray Apelles, while Crosman supplied the venue and logistics - including much needed cold drinks as the temperature hovered in the mid 90s with high humidity until well after Noon. Those of us fielding QB78 air rifles suffered from valve lock in the intense heat!

Hans Apelles and Dave Carpenter enjoy the practice session.

The morning offered open practice on the range, which was set-up on the former Crosman paintball field. Around 64 competitors registered to shoot - by my count, at least - and many were there for the practice session.

A highlight of the day for many of us was a guided tour of the Crosman factory. Around 50 people took the tour, divided into three groups. I joined the group led by Crosman Director of Manufacturing Ed Schultz.

We were saw all aspects of the facility, from the stock making shop to pellet production, the airgun assembly lines, barrel rifling, Powerlet manufacturing - VERY noisy but so interesting, the experimental shop and the Crosman Museum.

Crosman Manufacturing Director Ed Schultz (center) guides us through the Crosman Museum.

An afternoon cloudburst cut the heat, but did nothing to dispel interest in the "Quigley Bucket Challenge" contest. That's 5 shots per competitor at a 1.75-inch bucket at 55 yards range with a 6.5 ft/lb limit muzzle energy limit and iron sights only. Amazingly, this contest went to a tie-breaking shoot out with Paul Bishop being the winner. Great shooting! I noted with interest that the only shooters to hit the target did so after it started raining - go figure!

Day two - tomorrow - is the main field target match, with 80 shots per competitor in the multiple FT disciplines, PCP, Piston, Hunter, WFTF and Offhand. They say the weather will be cooler but rainless. Crosman has donated some excellent prizes. It's going to be a great day and I'll get back there as soon as I can...


About This Blog

This blog shares information, ideas and knowledge about air rifles. It compliments the information Stephen publishes on the Archer Airguns website, on YouTube and the Chinese Airgun Forum.

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