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PostPosted: Fri Jan 11, 2008 8:35 pm 
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I have a QB barrel that just won't group.....hoping to get this rig setup for the up coming FT matches.....Consistency over the Chrony is very good....

Took off the barrel and cleaned it only to discover the slightest burr inside the barrel at the transfer port.... Carefully removed the burr and cleaned the barrel pushing patches through with a bit of polishing compound on them till she began to gleam.....

I then ran the pellet test.... placed a pellet in the loading port and moved it forward with a brass push rod.... you can see the pellet go past the transfer port hole before it contacts the rifling ... Now it take a bit of force to start the pellet into the barrel, then as you push it along the drag lightens up.... Half way down the barrel the pellet begins to really lighten up, almost effortless before it begins a slight drag again.... just as the pellet reached the crown it feels as if it snags at that point.... I've used a light and magnifications and all looks normal.....
Question to those with experience... What would be my next move to try to bring the groups tighter with this barrel if even possible?.....TIA

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PostPosted: Fri Jan 11, 2008 10:54 pm 
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Personaly, I might try honeing it out to a uniform bore.
I've had a few crowns that took a lot of work to get perfectly smooth, all looked perfect with a 10x loupe but required careful polishing of the bore/crown to eliminate the source of the drag. I try to get a barrel to the point that there are no abrupt changes in pressure when manualy pushing a pellet through. I just want a slight increase in effort at the muzzle (choke) and no sudden hang as the skirt exits the barrel.

I would concentrate on eliminating any disruptive factors at the muzzle end..

I have found that a transfer port can be rather tricky to smooth out fully. I'll use up many, many pellets testing and re-testing both ends of a barrel. Try pushing a pellet in past the transfer port while peeping at it through the transfer port with a high powered loupe, watch for any lead being shaved off the pellet. Push the pellet back out the breach end and inspect the skirt for any signs of abrasion or uneven wear.

"YMMV" since this is all "IMO"...

MB

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PostPosted: Fri Jan 11, 2008 11:03 pm 
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When I push the pellet through just past the transfer port there are definite rifling marks, but they look very uniform....this area at the rear of the barrel is the tightest throughout the entire length then at the crown there is a slight grab just before the pellet exits....
I'll try to work the area just ahead of the transfer port and take it from there first.... much tighter there then any other area.....
Thanks for your input MiltonBradly

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PostPosted: Sat Jan 12, 2008 11:25 am 
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Spent several hours working the area behind the transfer port and got it to where the pellet enters without as much resistance .....
Kept pushing pellets through as I went along and noticed that there was a much more even feel as the pellet went from the back to the front....
After reinstalling the barrel and shooting it, a very definite improvement was noticed .... I'll have to repeat this process to see if it can be refined to the point where groups are into one hole...LOL
The best groupings were with the Gamo hunters.... I was able to shoot cloverleaf 5 shot groups at 12 yards from a bench rest and mounted bipod....Much better then the spread I was getting before... :wink:
Wish I had some JSB's or boxed CR PRM's....ran out of those a couple of days ago.....

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PostPosted: Sat Jan 12, 2008 3:55 pm 
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Parker 101 ,
I have recently had a very similar experience . I have documented my progress in the general section under "the barrel blues".I spent hours reworking the leadin to the rifling . Effectively what I had to do was hone in a transition to the rifling after the transfer port . I also noticed a slight constriction in the loading port between the breach and the transfer port I eased and polished these areas untill the pellet could be pushed smoothly past the transfer port into the rifling .

But the groups were still poor . :(

At this point I had a smooth loading breach progressing to the middle of the barrel where there seemed to be no resistance to the pellet being pushed through. About 6" from the muzzle there was slight resistance up until the last 3/8 of an inch where there seemed to be a choke . Another member (Chris?) told me of a similar experience resolved by removing 1/2" from the muzzle . I could see no imperfections in the last inch or so of the muzzle . Nonetheless something was wrong . :?
My solution was to cut 3/4" off the muzzle , reface and recrown . I also tried to gently lap the muzzle to remove any microscopic burrs created by the crowning process .Initial results were not promising, however , the more I shot the rifle the tighter the groups have gotten . I think that firing pellets through it has cleaned/deburred the barrel , and is still doing so .
Initially I was getting the best groups from Gamo hunters but eventually my groups have shrunk from under 2 " at 15m to 1/2" at 15m . I think they will get better yet . For a while I switched around trying out a bunch of different pellets and I think that process also helped smooth out the barrel . The Crosman pointed pellets seem to be a harder lead alloy, better suited to this . I will keep you posted of future changes .

I hope this helps . :D

Warren


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PostPosted: Sat Jan 12, 2008 4:05 pm 
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Thanks warren....
I've spent several more hours working this particular barrel and still the Gamo hunters group best....1/2' 12yards.....
I'm spoiled by my other QB's that can hit a hole in one just about every shot if I do my part...LOL....

I'm now considering retiring this barrel at least until I can get some JSB or CR PRM's boxed to test with or something of that caliber ... no less then a 1000 shots and several CO2 refills later it's time to lay that project aside for another... :lol:

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PostPosted: Sat Feb 16, 2008 8:28 pm 
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That barrel was sent out for some experimental work....

What I did was acquired a new barrel for my QB79 ....

20-5 shot groups with the same QB79 in .22CAL with the newly acquired barrel for a total of 100 shots.... :P :twisted: :lol:
Crosman Premier Die #2 for pellets and shooting 12 yards from bench rest bi-pod, Optics used was the REX 3-9X40AO ....LOL
I'm looking forward to bringing this combo to the range for some longer shots to see if it hold true...
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PostPosted: Sat Feb 16, 2008 8:54 pm 
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Potential is there. Next is the scope to be upgraded, lol. It never stops, hehe.

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PostPosted: Sun Mar 02, 2008 10:53 am 
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Here's an experimental process that was tried on this barrel with success I might add... :shock: :D 8) ...
First try at choking a barrel

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PostPosted: Sun Mar 02, 2008 2:11 pm 
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How many rounds have you put through it since your first tests?

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PostPosted: Sun Mar 02, 2008 3:06 pm 
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DoctorFrankengun wrote:
How many rounds have you put through it since your first tests?


Several hundreds of rounds through it now, but still haven't got my hands on a quality round nose pellet for testing.... :evil:
I did pick up some RWS R10's and at 12yards they shoot like laser beams as did the RWS Meisterkugeins.... 8)

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PostPosted: Sun Mar 02, 2008 3:24 pm 
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Parker_101_ wrote:
..... still haven't got my hands on a quality round nose pellet for testing.... :evil:

I've got all kinds of different round nose pellets that could be tried in your QB. Perchance we could arrange a "play date" to do some shooting, and I'll bring along a good selection for you to try. Also, I don't know if you've tried those Champion Allouette pellets that Sniper has, but they are an excellent pellet.


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PostPosted: Tue Mar 11, 2008 5:41 am 
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Suprmatic wrote:
Parker_101_ wrote:
..... still haven't got my hands on a quality round nose pellet for testing.... :evil:

I've got all kinds of different round nose pellets that could be tried in your QB. Perchance we could arrange a "play date" to do some shooting, and I'll bring along a good selection for you to try. Also, I don't know if you've tried those Champion Allouette pellets that Sniper has, but they are an excellent pellet.


That sounds like fun!... :wink:
I did try the Campion Allouette's and at 12yards they grouped small clover leaf ... The Gamo hunters faired slightly better with groups being a bit tighter....

I am very happy with the results of the first choked barrel that I sent out one of my .22CAL barrels to have the same procedure done to it....
I'll report back when all is said and done.... :twisted:

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PostPosted: Tue Mar 11, 2008 10:27 pm 
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Thanks for your hospitality on the weekend :wink: That is a fun shooter. I'll be very interested to try it again when you get the new scope mounted.

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