Cometa Fusion 4.5 mm

[AmBraCol]

Earlier this year I picked up a  Cometa Fusion in 4.5 mm for a killer (for Coffee Country) price.  Lovely rifle. Finally got the scope mounted properly so it doesn't creep.  It's been shot off and on since I got it and finally I took the time to haul it to the club and spend some time running it over the chronograph.

Here are the results.

Description:  AA 10.3
Bullet Weight (gr): 10.3
Average: 826.13
StdDev: 8.64
Min: 804
Max: 837
Spread: 33
True MV: 829.16
Up to 3.99%  deviation from average

Crosman Premier Heavy
Bullet Weight (gr): 10.5
Average: 801.40
StdDev: 3.87
Min: 794
Max: 807
Spread: 13
True MV: 804.90
Up to 1.62%  deviation from average

Gamo TS-10
Bullet Weight (gr): 10.5
Average: 789.80
StdDev: 8.74
Min: 768
Max: 802
Spread: 34
True MV: 793.25
Up to 4.30 %  deviation from average

JSB Exact NOS
Bullet Weight (gr): 8.44
Average: 936.13
StdDev: 5.08
Min: 927
Max: 945
Spread: 18
True MV: 941.20
Up to 1.92%  deviation from average


H&N Excite Hammer
Bullet Weight (gr): 7.87
Average: 987.53
StdDev: 4.85
Min: 980
Max: 998
Spread: 18
True MV: 993.15
Up to 1.82%  deviation from average

H&N Excite Hammer 2nd Series
Bullet Weight (gr): 7.87
Average: 990.60
StdDev: 4.65
Min: 984
Max: 997
Spread: 13
True MV: 996.23
Up to 1.31%  deviation from average

H&N FTT
Bullet Weight (gr): 8.64
Average: 922.93
StdDev: 4.11
Min: 915
Max: 932
Spread: 17
True MV: 928.18
Up to 1.84%  deviation from average

H&N FTT 2nd Series
Bullet Weight (gr): 8.64
Average: 918.56
StdDev: 5.03
Min: 911
Max: 925
Spread: 14
True MV: 923.78
Up to 1.52%  deviation from average

H&N FT
Bullet Weight (gr): 8.49
Average: 932.40
StdDev: 1.95
Min: 930
Max: 935
Spread: 5
True MV: 937.70
Up to 0.53%  deviation from average
H&N Sniper Magnum
Bullet Weight (gr): 15.0
Average: 651.67
StdDev: 4.69
Min: 643
Max: 658
Spread: 15
True MV: 654.14
Up to 2.30%  deviation from average

H&N FT 2nd Series
Bullet Weight (gr): 8.49
Average: 927.53
StdDev: 5.48
Min: 917
Max: 939
Spread: 22
True MV: 932.81
Up to 2.37%  deviation from average

Benjamin HP
Bullet Weight (gr): 7.9
Average: 954.20
StdDev: 6.04
Min: 940
Max: 964
Spread: 24
True MV: 958.92
Up to 2.51%  deviation from average

[AmBraCol]

The problem is - nothing would group worth a hoot at 15 meters except the New Old Stock JSB Exact 8.44's that Varmint Air gifted me a while back.  Here's some thoughts, the next post will be pics of the targets shot.

I don't recall the exact order, but the first group fired (AA 10.3) was top, center bull. Holding dead on the center dot.  The top left and top right were likewise heavier pellets, and they hit way high, even off the paper.  The problem, of course, is the lack of consistent grouping.  I don't recall the AA 10.3 series of hits, but even though there's a halfway decent group in the mess, it wasn't pellet after pellet, the surrounding hits were in between tossing them into the group.  The lone hole at 7 o'clock from the AA 10.3 group was actually part of the top left group.

The only halfway decent grouping was the JSB Exact 8.44 titled "NOS" as they come from the old JSB tins that were gifted to me by VarmintAir some time back.  The five widest fliers around that group were actually sighted at the bull immediately above (second from top, left column).  These were the H&N FT 8.49 gr pellets.  When I finally realized where they were hitting, I stopped the series.

Potential problems:
Hold - I tried to be consistent with the "artillery hold" - but admit I'm not the greatest shooter of spring powered rifles, especially the heavier recoiling ones.
Wind - it was mostly a windless morning and I tried to hold off shooting when there was discernible breeze (watching the grass between the muzzle and the target)
Pellets - even the "premium" pellets didn't do much good for the most part, and the "junkers" didn't do that much worse.

[AmBraCol]

The first of the three groups on the second target paper were the Sniper Magnums.  Not my first choice, by a long shot, for a springer, but had some on hand so "why not?" Aimed at the center bull on the paper, they didn't hit as low as I expected them to.  The Benjamin 7.9 hollow points are the ones almost centered on the middle bull of the second row.  Was aiming at the top, center bull.  The center bull of the right hand column are the second series of the H&N FT 8.49 gr, don't recall which holding point I was using, believe it was the second bull from the top - but so much for "I'm sure to remember it"... yeah, right.

[AmBraCol]

Any thoughts on what might be the issue here?

[OleTomCat]

Paul,

Let's run through some of the basics...

Did you clean the barrel before you started shooting?  If so how many pellets did you shoot before you mounted the scope and started trying to get groups?  If not start by cleaning the barrel then shooting about 200 pellets before you start looking for a good pellet that groups.

Have you checked all of the mounting screws, stock to action(should be 3), scope to rail, and barrel pivot?

Are you holding the rifle the same way each and every time?  Google 'the artillery hold'

[joek]

you can also check the barrel crown

[AmBraCol]

Thanks, guys.  It's been a busy week, haven't had a chance to get back to this 'til today.

Yes, I started with a clean barrel when I bought the rifle.  We ran a bunch of pellets through it just "messing around".  Then I got down to shooting for groups - but made a couple of mistakes.  First, was trying to shoot groups PLUS chronograph.  Managed to get the chronograph results as outlined above, which as you can see shows a very stable power plant.  The problem was, it was too distracting (trying to ensure that the pellets made it over both skyscreens each shot) and I neglected other areas.

My analysis is that when I shot the groups above I was running the scope on 24X, but was too distracted to do a good job of ensuring a good cheek weld and the same sight picture each shot.  My best guess is that what I'm seeing in the groups above is parallax error. 

Saturday I was down at the club with another member.  We were checking a Cometa Fusion he just bought for proper function, etc.  So again I was running the chronograph but this time on his rifle.  It, too, is running a nice, tight spread for the most part.  Not quite as tight as mine, but very acceptable.  Then I took my rifle and shot it for groups with a couple of the better pellets.  This time I cranked the power down to 10X after using 24X just to establish the focus/parallax issue.  Groups weren't stellar (I prefer shooting for groups when on my own - too distracting to have a conversation going while shooting) but they were much better than the week previous.  I need to get back down there and do some more work but with less distraction.  Over all I'm quite pleased with this rifle.  And once I find a good pellet for it, and discipline myself to shoot it properly, I'm sure I'll be more than "tickled pink". 

[Mark 611]

The Cometa 400 Star compact I have in .22cal went thru the same issue with accuracy! I purchased several of these rifles back when this thread was posted, the .177cal rifles I had would not group at all, I never did find the issue with them I did not check the crown! I also had 2 of these rifles in .22cal, 1 of them was a tac driver out of the box, the other 1 I sold to my brother, he had the rifle all this time until about a yr ago and I bought it back from him, I started shooting this rifle to discover it would not group consistently with any pellet I shot thur it! so I tore it down and completely rebuilt the internals of the rifle + lapped the bore! no luck! I finally removed the moderator which is not an easy task without risk of damaging it, its splined fitted to the barrel and pressed on! very tight fit! once I got it removed I found the problem!!!! the crown on the barrel is 1 of the worst I ever seen! I sent the barrel off to WHITEFANG and had him nip off the tip of the barrel and recrown it! that fixed the problem, now the rifle shoots sub dime size groups @23yds with Crosman HP's or Pointed Hunting pellets, now the other side to these rifles is the power to weight, these rifle require more or a different hold then say an HW rifle of the same size, due to their power, once u learn this they shoot very well!
[img width= height= alt=SAM_1894.jpg" border="0]https://www.snapagogo.com/images/2019/04/07/SAM_1894.jpg[/img]
[img width= height= alt=SAM_1895.jpg" border="0]https://www.snapagogo.com/images/2019/04/07/SAM_1895.jpg[/img]

[AmBraCol]

Mark, very interesting.  How did you get the shroud off?  It looks like there's a pin. Do you punch that out and then pull the shroud off? I've been wanting to get a look at the crown, but don't have a bore scope to go in through the shroud.  May have to break down and get one for jobs like this.

[Mark 611]

Well here's what I did it my not be necessary? the moderator is aluminum, I took out the baffles, and removed the 2 grub screws then heated up the base of the moderator, then I took a block of wood and placed it at the back of the moderator and took a hammer and tapped at it until it came off! and it wasn't easy to remove at least mine wasn't! to reinstall it I used a wood dowel rod that fit the inside base diameter of the tube and tapped it back on! 

[AmBraCol]

Thanks, Mark!

I forgot you were working on a 400, not the Fusion. Same basic power plant, but different shroud set up. I'm still studying on how to go about removing the Fusion's shroud.  It looks like a bull barrel with a perforated "muzzle break" on the end.  Seems to be pinned on at the base of the shroud. That's why I'd like to run a bore scope in to look at the crown before going through the hassle of removing the shroud. If the crown's bad enough then I'd be motivated to get in there.  If it's not looking bad then I'd kick myself for unnecessary work if I'd pulled the shroud to find that out.   

[Mark 611]

If u have a good breech seal and piston seal? I would bet the crown is not good! also keep in mind these rifle were intended to shoot the JSB pellets! my 220 compact shot the 8.44gr JSB's 1 hole accurate @30yds