Hold Sensitivity( Long)

(3 posts from the Yellow, reformatted)

Recent posts about the AirForce Talon and it’s hold sensitivity issues got me to thinking.

Haven’t shot mine in quite some time, so dug it out for a little play time.

Have to admit, I stopped using it as a PCP some years back, selling off the air tank and dedicating this one to co2. Still think it might be the best co2 gun made, but it has the same hold problems that were outlined in the above posts. This one is 5mm

Got it out of storage, checked screws, scope mounts, ran a patch down the bore, and generally checked it out like I would any gun coming out of the safe after a few months rest. Screwed on the fist co2 tank to come to hand (happened to be a 9 oz).

Started with a kind of base line. Added two pounds of weight to the tube, rested front and rear. Rear is a big block of modeling clay, wrapped in thick plastic, and then wrapped in cloth (and old set of scrubs). Can beat on the clay, forming whatever shape you want.

Nothing fancy, just taped the lead ingots to the tube to add weight:

Talon SS 5mm
co2: 90F
14.3gr. Benjamin Cylindrical
5 hots/20yards

Ended up firing two sets of test targets. Fired 15 shots for each on the first run. Had a little breakfast, couple of cups of coffee, watched the news, and fired 10 rounds for each test about 90 minutes later. Didn’t know if it would make a difference or not, but it made for an ugly spliced together target picture.

Test #1: FREE HOLD: Gun was set up as shown in the pictures above. Have to beat on the clay bag a bit to get it lined up and stable (can make some vertical adjustments by squeezing the bag). Was fired almost untouched. Fired with ONLY my finger touching the trigger and my thumb behind the grip, shot out of almost all human contact and only gravity holding it in place.

Test #2: SOFT HOLD. Shoulder in light contact with the butt, hand softly wrapped around the grip.

Test #: FIRM HOLD. Shoulder firmly in contact with the butt, hand firmly wrapped around grip as if shooting a pistol.

Only 20 yards, so maybe looking tat the average groups size in terms of MOA would help.

#1. .93MOA
#2. 1.23MOA
#3. 1.50 MOA

Have cut off the 2 pounds of lead and will run the tests again as time allows. May be surprised, but expect the results to follow the same pattern, just with larger sized groups for each test.

THOUGHTS:

Has shot a lot worse than this, and possibly would shoot better with JSB 13.5gr. I’m a bit over stocked in 14.3 Benjamins and know it shoots them well enough for a decent comparison.

Could clamp it in a vice to get a base line, which would probably be a bit smaller, but somehow that felt like cheating.

Test #2 is my normal shooting style. Even off hand or in the field, can usually manage to duplicate it one way or another.

Continuing the Talon SS hold sensitivity tests.

Ran the exact tests as last time, but had slipped a .177 barrel in place of the 5mm barrel. This barrel came from a Gamo 126 SSP match rifle (long story…but ended up with a junker to strip for parts to keep another one running). Might be key that I made some chunky black Delrin barrel bushings, and made them to be a push fit to the frame (need about 8-10 pounds of force to slide them in while the factory busings just fall out of the frame once the screws are undone).

Shot the same way as this previous post on the 5mm:
8.3gr. RWS SuperDomes
90F
5 shots/ 20 yards

Last post, converted the group averages into MOA to get a better feel for the differences. Will do that again:
.177:
Free: .88MOA
Soft: 1.12MOA
Firm: 1.47MOA

.5mm:
Free: .97MOA
Soft: 1.12MOA
Firm: 1.50MOA

RESULTS:
This .177 barrel shoots slightly smaller groups than the 5mm LW barrel when shot in “free hold” mode. For all intents,with these pellet selections, they are dead even.

The .177 groups are more stable to point of impact than the 5mm groups. This is probably due to both the tighter bushing fit and the vibration deadening of Delrin vs Al bushings.

Still seems to follow the following: the tighter the hold on the gun, the larger the groups average.

BELIEF:
The size of the group is a function of the barrel quality and the pellet/barrel match. Other pellets will shoot better or worse.

The LOCATION of the groups is a function of the fit of the barrel to the frame (and possibly the vibration deadening of the material of the bushings).

(In other words, how you hold the gun makes a difference in groups size if the barrel fits the frame right, and makes BOTH a difference in groups size AND location if the barrel does not fit the frame right. The 5mm’s porblem is not accuracy, it is stability.)

SUGGESTIONS:
A. The size of the group can be from many things. Pellet fit, velocity variation, human error, or being out of a PCP’s sweet spot. If just accuracy is the issue, would:

Clean the barrel
Try different pellets
Concentrate on technique.

B. If the groups keep shifting location, would look to the fit of the barrel bushings to the frame. Old springer guys will remember buttons. Would try pulling the barrel, using Teflon tape to take up the slack in the bushings to frame fit, get it to be a push fit.

Could be the bushing construction. Black Delrin has a vibration deadening ability. If buttoning the 5mm’s Al bushings doesn’t help, will make new Delrin bushings.

Could be the extra weight of the .177 barrel. Screwed here as I will not take apart the .177 barrel assembly and lathe it to a skinny profile…just not going to risk screwing up a good shooting barrel to find out.

3rd test:

Third installment of the Talon (SS) hold sensitivity tests.

This is the standard Talon SS barrel (5mm).

Front bushing vented (and you can see, an LDC really does collect lead dust):

The bushings measure very close to 1.01”. The inside of the frame is slightly larger, measuring about 1.0125”, Tighten up the 4 set screws, and thee doesn’t seem to be any measurable slack.

Previous test showed that point of impact varied with the strength of the shooter’s hold on the rifle. Showed that a different barrel with different bushings did not show that POI shift.

So looked for a fast and easy way to increase the size of the standard bushings. Painting them with finger nail polish was suggested, as was JB weld lathed down, and there was always the option of making new bushings.

What I did was to lathe rings around the bushings, looking for the little raised edges of the lathed grooves to increase the diameter very slightly.

Have to deburr the screw holes, but these bushings gained .03” in diameter. Made the barrel a push fit to the frame, but no any stronger than hand pressure.

5mm TEST TARGETS (same rules as before…and I’ve not touched the adjustments throughout the test).
14.3gr. Benjamin Cylindrical pellets
90F
5 shots @ 20 yards

For the other tests, converted to MOA to give an easier to see reference:
Free: .87MOA
Soft: 1.27MOA
Firm: 1.60MOA

BUT…and this was the whole point…the POI stayed a lot more stable.

BELIEFS:
Accuracy really didn’t change. POI did get more stable the firmer the barrel bushings were to the frame.

The 5mm barrel is every bit as accurate as the match .177 barrel.

In every test so far, the harder the gun is gripped, the larger the average groups.

QUESTIONS:
Why does a tighter barrel bushing fit (and through that, a tighter barrel fit) to the frame DECREASE wandering POI as grip pressure changes?

Wouldn’t it be more logical that the tighter the barrel to the frame, the MORE reactive to changes in pressure? Or is that then if they aren’t supported fully around the bushing, they tend to tweak independently of the frame? Or is it that if the bushings are loose, setting the grub screws gives some kind of odd-ball unever stress to the barrel that makes it sensitive to pressure?

Suspect I will never know…and don’t need to know. The gun is more stable when the barrel is tight to the frame. It doesn’t really shoot any better, but the groups it does produce are all closer to the POI under different grip pressures when the bushings are a push fit to the frame than when the bushings are a drop in fit to the frame.