chamfer the breach?
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chamfer the breach?
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Topic: chamfer the breach? (Read 2452 times))
aidave
Plinker
Posts: 153
yes
chamfer the breach?
«
on:
May 06, 2013, 08:28:49 PM »
all the pellets I've been using, when placed into the breach, stick out a bit from the breach and sometimes would leave lead shavings off after firing. Looking at it I tried to use a punch to gently push the pellet in, but that, too, shaved off some lead.
It dawned on me that if the breach were chamfered a bit, the pellet would sit in more flush and also obtain a cleaner mating to the barrel as pressure built up behind it, so instead of shaving it, it would get reformed.
I thought this idea would be too simple and that others would have done it -- but I didn't see it being done anywhere -- so now I have the question, why not chamfer it? Would that hurt anything? Help anything?
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Tacoma, WA
QVTom
GTA Senior Contributor
Posts: 3695
Real Name: Tom
Re: chamfer the breach?
«
Reply #1 on:
May 06, 2013, 08:52:25 PM »
Yes, it should be chamfered from the factory. 45deg. about 0.015- 0.020" with a nice edge break on both adjoining faces is pretty standard. Assuming you have a break barrel.
Tom
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Acton, CA
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dukemeister
Sharp Shooter
Posts: 754
Practice hasn't made me perfect
Re: chamfer the breach?
«
Reply #2 on:
May 06, 2013, 09:55:08 PM »
Chamfer away; this is a very common solution to the breech issue. I have done it to many rifles with good results... sometimes absolutely necessary like when the pellet skirts are being crushed on closing the breech.
Anyhow, Cardews showed a rounded profile gives the maximum and most consistent velocity, so try to get a rounded profile like this:
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The Gun Whisperer
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Paul68
Why in the heck did you move here? There's nothing out here!" They say. "EXACTLY" I say
GTA Senior Contributor
Posts: 2767
yes
Re: chamfer the breach?
«
Reply #3 on:
May 06, 2013, 10:44:10 PM »
Yup. Put chamfers on a couple rifles with the same problem. Solves it quite well.
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North Carolina
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aidave
Plinker
Posts: 153
yes
Re: chamfer the breach?
«
Reply #4 on:
May 07, 2013, 12:44:27 AM »
I don't have a lathe, but do have a drill press; think I could do it, or should I find a machinist? (any volunteers for the task - let me know cost & address -- I'd rather it be done right) Barrels are cheap; but I appear to have a good one, I'd really like to avoid trashing it)
It was kind of a surprise to me after I started pulling led shavings out after each shot that it wasn't already done at the factory...
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Tacoma, WA
Paul68
Why in the heck did you move here? There's nothing out here!" They say. "EXACTLY" I say
GTA Senior Contributor
Posts: 2767
yes
Re: chamfer the breach?
«
Reply #5 on:
May 07, 2013, 01:04:41 AM »
I cheat and use a Dremel with conical stone. Then I use a piece or 600 grit on the end of a conical polishing pad to smooth it. Not as accurate geometry wise, but its been very effective in improving accuracy consistency. The trick is to go very slow do to little rather than too much.
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North Carolina
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Bullit
GTA Senior Contributor
Posts: 8152
Re: chamfer the breach?
«
Reply #6 on:
May 07, 2013, 12:03:11 PM »
As the other guys posted, it isn't uncommon. You may also look to see if there's just rough chamferring done, and you can clean it up by hand, or slow speed drill. Since you've pulled slivers out already...keep an eye on your breech seal for leakage problems.
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Kentucky
aidave
Plinker
Posts: 153
yes
Re: chamfer the breach?
«
Reply #7 on:
May 08, 2013, 01:30:44 AM »
That dremel tool -- I always seem to forget about it until after I've done something that could have used it.
I have several conical stones, and can set the dremel to very low speed, so perfect idea -- I also have a selection of some really fine sand paper -- so I can give it a nice polish when I'm done ... perfect!
No work tomorrow so I'll be able to take advantage of some sunny weather.. Thanks for the tip.
It's now 'habit' for me -- as I load a pellet, before I close the breach, I swipe a finger across the piston side; by the end of a session, the tip of my finger is gray -- maybe this chamfer job will take care of it. When I first noticed the shavings, I realized they could damage the o-ring, so I make sure to keep it clean...
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Tacoma, WA
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chamfer the breach?