I made a mistake cutting my barrel
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I made a mistake cutting my barrel
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Topic: I made a mistake cutting my barrel (Read 22096 times))
Mark 611
GTA Senior Contributor
Posts: 8044
Yoda!!!!!!!!!!!
Real Name: Mark
Re: I made a mistake cutting my barrel
«
Reply #40 on:
March 31, 2011, 11:20:33 AM »
you done a very nice job on the work with the MB looks good, the only thing I can think of is if you've got everything else right with the crown than the barrel must have some ill rifling in that area of the barrel, or lose you might check that.
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VAFarmer
Sharp Shooter
Posts: 874
Re: I made a mistake cutting my barrel
«
Reply #41 on:
March 31, 2011, 02:50:44 PM »
Is your seal in good shape?
Sounds like you have really gone thru alot of work.
You did manage to choke it, and groups didn't tighten up, correct? I would think choking would help with velocities being more consistant.
You could be having seal issues with the piston seal, which would explain velocity changes. A bad crown or loose barrel, I could see causing accuracy issues, but if your crown is smooth, I just cant see a bad or uneven crown causing that much fluctuation in velocity.
I seem to recall Mike M. mentioning that some guys had velocity issues out of the B-25's which are the same series as yours. Best I remember, he indicated that using a Tesla seal might work over the Apex, or more flexible seal.
With the lube tune, did you replace the seal?
These guns are easy to get apart.....
one more time can't hurt. Really inspect the seal, go around the inside lip with a feeler guage and see if you can gently force open any cracks, splits, etc.......
If the gun is in great shape, other than the bbl, another cheap fix might be go to Compasseco, buy the refurb version of this. I think you can get the Blackhawk (should be IDENTICAL) version, refurbed for 69 bucks. For the combo. This way, you can swap all the stuff in and out that you want. 70 bucks for a complete extra set of parts aint too bad. and a scope and mounts......and synthetic stock.
Pull the stock screws, action, remove both pivots and swap barrel assemblies. If you still get the rough groups, inconsistant velocities, then you know the prob lies in the action/firing cycle. Likewise, the new assembly should either shoot your modded barrel fine, or not so good.
How does your trigger break? Is it a manageable pull? BTW, how long is the barrel now?
God bless and keep plugging. This is frustrating, but when you resolve, you will feel great.
The dross must be burned off of gold for it to shine properly!!!
God bless again,
Farmer
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chronic
Plinker
Posts: 200
Re: I made a mistake cutting my barrel
«
Reply #42 on:
March 31, 2011, 05:16:35 PM »
Thanks for the heads up on the black hawk! Seals not bad, not great either though. However m rws pellets shoot consistent velocities, just not the h&n field pellets. But both tins of the .177 h&n's I got are horrible looking, so I am blaming the velocity on them.
Yeah I choked it using my lathes steady rest, collapsed the barrel until I got light rifling marks on my rws pellets and I had no improvement. So I chopped it off, re crowned it on my lathe and saw no improvement either. Barrels 12.300" long now
Trigger is good, I haven't touched it besides adjusting the break point to the end of the stroke and it's my favorite trigger of all my guns.
Only thing that seems to be helping is the weighted muzzle brake.
Or like I said the fresh moly?
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Ray
VAFarmer
Sharp Shooter
Posts: 874
Re: I made a mistake cutting my barrel
«
Reply #43 on:
April 01, 2011, 09:59:26 AM »
I don't think you are doing anything wrong in your crowning....I haven't seen your process, but like you mentioned earlier, it's all about being careful and thorough, not about rocket science.
Also know, I am no authority. Most stuff I have learned, but Mike Melick is kind enough to be very open with his expertise, and I have learned alot from him. So alot of the stuff I spout, I have taken from his advice....really, take the time to call him over at Best. Really nice guy to talk with.
Along those lines, I will repeat another piece of advice he gave me awhile back. Seems that I recally him saying not to go shorter than 14 inches on the b-25 barrel.
2 other things I could see happening here, other than a funky shot cycle.
With that length, perhaps you are at a less than optimal barrel length for your cylinder's capacity, and this might be causing the rough shot cycle. This could be tamed with a milder spring, I believe, or maybe some type of spring inserts. Could be that the shot cycle is SO rough because the resistance supplied by the pellet is gone before the piston reaches the end of the shot cycle. Still, just seems like it would be wasting air, and not causing bad groups. I have seen barrels go shorter than this. Don't know how they grouped, but have seen it done.
Also, as you shorten a barrel, just like anything else that has flex, it becomes more rigid in a sense. you have gone from what, ~20 inches on this barrel...to under 13. We are getting close to cutting this bad boy in half. Still, what bothers me is that you have re-crowned AND choked. Surely the choking would have helped some. I wonder if the weight up front HAS helped it some. An easy way to test that theory is to add more weight. And I would start at the far end of the brake, and work my way in. Maybe use some electrical tape around the barrel to provide a tight almost "pressed" type seal.
Not leaking at the breech, right? I replace the breech seal on the B-25 every time I lube tune, just seems like those flatten out, and I'm just using rubber "o" rings anyway.
Get ya some of the Air arms pellets. They seem to be JSB's just rebranded. they have that thin, really flexible lead skirt, that makes a great "parachute" for all the air to catch.
If you do decide to get the refurb model blackhawk and replace that barrel, I might be interested in the stock if it will fit the b-25.
Really, this is all just rambling at this point. Time to bring in reinforcements...call Mike.
God bless and good luck,
Farmer
P.S. on your trigger. I know, I had mine adjusted all the way, too. Love that light, almost no effort pull. what I didn't like was the pull,pull,pull,pull.....okay, pull some more...and there! She brakes.
When you do the trigger mod, you can still have that nice, very light pull. Just that you can adjust it to where it breaks right past the point that the safety is disengaged. MUCH BETTER...trust me on this.
And if you don't like it, it can just be adjusted back to where you had it
«
Last Edit: April 01, 2011, 10:05:19 AM by VAFarmer
»
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chronic
Plinker
Posts: 200
Re: I made a mistake cutting my barrel
«
Reply #44 on:
April 01, 2011, 01:39:18 PM »
Thanks man, I pulled the old breech seal and put in a new one. Maybe I was getting a leak and didn't know?
I'll put some shots across my chrony at lunch here and see what it says. It would be nice if there was a difference.
Found someone with jsbs the next province over. So I have some 4.52mm exacts coming, hopefully the tighter fit helps. Maybe I should even try the 4.53's?
Well see, hopefully I am nearing the end. I really like this thing.
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Ray
chronic
Plinker
Posts: 200
Re: I made a mistake cutting my barrel
«
Reply #45 on:
April 01, 2011, 04:00:00 PM »
Apparently the breech seal was fine since there is no change in velocity. I guess those h&n field target long distance pellets are just terrible pellets because my rws all fire within 5-10 fps of each other.
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Ray
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I made a mistake cutting my barrel