Tuesday, August 15, 2006

Spring gun tune: Part 13
Range-testing the R1 we tuned

Spring gun tuning: Part 1
Spring gun tuning: Part 2 - Building a mainspring compressor
Spring gun tuning: Part 3 - Mainspring compressor continued
Spring gun tuning: Part 4 - Let's disassemble a gun!
Spring gun tuning: Part 5 - Powerplant disassembly
Spring gun tuning: Part 6 - Disassembly completed
Spring gun tuning: Part 7 - Disassembly of other spring guns
Spring gun tuning: Part 8 - Disassembly of other spring guns, continued
Spring gun tuning: Part 9 - Cleaning and deburring
Spring gun tuning: Part 10 - Lubrication and reassembly
Spring gun tuning: Part 11 - Lubrication and reassembly continued
Spring gun tuning: Part 12 - Finish reassembly and test the gun

by B.B. Pelletier

Well, it's time to range-test the results of our Beeman R1 tuneup. You may recall that I said I wanted to lower the power to have a light-cocking, smooth-shooting rifle. What I didn't tell you was that my R1 had a gas spring in it before the tuneup. It was working fine, but I was tired of having to cock 50 lbs. every time I wanted to shoot. I had a special low-powered mainspring that I used with the factory piston and spring guide. After the tuneup, I knew the gun was easy to cock and shooting smoothly, but I had to take it to the range to learn the rest.

My R1 has a plain walnut stock, a Vortec muzzlebrake and a Bushnell Trophy 6-18x in Leapers Accushot medium rings. The low-power tune makes it very enjoyable.

I hadn't counted on this benefit, but the R1 is now extremely quiet. I doubt my neighbors would know I was shooting if they didn't see the gun or hear the strike of the pellet. After testing magnum guns for the past 6 months, it was a real pleasure to shoot a rifle this smooth and quiet; sort of the reason I got into airgunning in the first place.

Low power - but not THAT low
The tuned R1 spits out a 15.8-grain JSB Exact at 645 f.p.s., on average. That works out to 14.67 foot-pounds at the muzzle. A factory R1 in .22 caliber will generate about 17-19 foot-pounds, so this tune is definitely lower, but not so much that I can't do the same things with the rifle. And, that was also tested at the range.

Shooting an R1 requires a lot of technique. You simply cannot grab the stock and hope to hit anything. But, let it float and watch out! My results with JSBs at 40 yards were not as good as I had hoped. Usually, the JSB Exact groups tighter than any other pellet, but not in my R1. The best I could do was still slightly over an inch.

Beeman Kodiaks, however, brightened the day. They sailed through group after group and nothing measured larger than one inch. The best for the day was 0.847". It looks like only four holes, but two pellets went through one of them.

Having also had some luck with heavy Logun Penetrators in the past, I tried them, as well. The best group of five measured over 1.3". That left Kodiaks as the pellet of choice.

One of these holes passed two pellets. This was the best group of Beeman Kodiaks.

Barrel joint loosened
The barrel joint loosened during the shooting, so it would not stay in any position other than closed once the gun was cocked. I expected this to happen because of the lubrication. It didn't affect accuracy, but I still tightened it once I returned home. Remember, the test for the pivot bolt being tight enough is that the barrel of a cocked gun will stay where it's put.

This rifle is now a genuine pleasure to shoot. I am inclined to just sight it in at 20 yards and leave it that way. It might even become a "go-to" rifle, because it is just as quiet as my TX200 or Talon SS and lots of fun to shoot.


At August 15, 2006 1:08 PM, Anonymous said...

I think a lot of people would be very reluctant to have a gun tuned to lower power. I believe that this is because of a) marketing (companies sell rifles by fps and b) a lack of knowlesge of
how much energy they need to accomplish their needs in shooting.

Of course if an unruly rifle is neither accurate nor precise, then all the energy in the world won't matter.

The real issue is what are the cutoffs for power in various calibers that you would want to stay above?

For example, you lowered your R-1 to 14.67 foot-pounds. If 14.67 is better than 17-19, then why not 13? or 12? or 11?

What exactly is it about 14.67 that made you comfortable with that number?

I assume at some point in the power curve there is a point of diminishing returns where the gun doesn't really vibrate any less and doesn't shoot any more accurately.

It would be interesting to hear you comment on this.


At August 15, 2006 1:17 PM, B.B. Pelletier said...

My comment is - that's where the gun ended up. I didn't plan on that power lever any more than any spring airgun tuner can guess closer than about 10 percent of what he will get from a tune. I was going for something in the 13 foot-pound range and that's where I wound up.

Could I have fiddled with the tune to get a different number? Of course. Would it have mattered? As you point out - probably not.

The UK shooter have to stay below 12 foot-pounds because of their law. Is 12 a good number? Probably not, but who is to say it isn't one (good number) of many? This is not a precise science.


At August 15, 2006 6:55 PM, Anonymous said...

Hi BB,

As a UK airgunner, I'm used to 12ftlb and find it is enough power for the job I want it to do. I take many rabbits, sqirrels, pigeons and crows up to ranges of 40m without any trouble using my 5.5 mm Slavia 634 (11.6ftlb with 1.04 gram JSB Exacts). I find for these sorts of varmint, even 12ftlb can cause over penetration at 25m.

Accuracy is the most important asset for a hunting gun and a smooth, easy to handle gun helps me keep my shots consistantly inside the magic 1" kill zone.

This is a great blog - Keep up the good work



At August 15, 2006 7:44 PM, Anonymous said...

B.B. i have a question regarding the seal on a gamo hunter 1250 that arrived in the mail a few days ago I noticed that the seal had a chunk equal to about 1/8 the perimeter of the seal. im not sure if its leaking air or not as im not sure how to test it with a springer. should i take it to a repair shop?

thanks for the advice, scopestop guy

At August 16, 2006 7:08 AM, B.B. Pelletier said...

scopestop guy,

You test a springer with a chronograph. It's the only way to do it. If velocity is where you expects it to be, the gun isn't leaking.


At August 16, 2006 8:36 AM, Anonymous said...

B.B. how could i get my hands on a chronograph short of buying one. thanks scopestop

At September 16, 2006 12:18 PM, Disapointed said...

I am A UK QB 78 owner and have been unimpressed with its power. On various sites it has been quoted with a ft-lb ratio of between 6-9. Is there asite i could vist to get detailed drawings to tune it up myself or somwhere to send it. I know this a long shot please advise.


At September 16, 2006 1:40 PM, B.B. Pelletier said...


You need to connect to the UK tuners. The way to do that is to get on the UK chat forums.

The U.S. forums will not be as helpful because we don't have power limits and our QB78s are much more powerful.

There is no question the power in your gun can be increased. All it takes is a valve modification.



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