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PostPosted: Wed Jan 25, 2017 12:10 am 
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Joined: Sat Dec 22, 2012 10:17 pm
Posts: 43
Location: King Ralph's Land
The gun: Crosman 0.177 10" barrel on a 2240 with a gmac breach and hollow extended probe (severely detuned/weaker hammer spring to keep legal fps).

The issue: When loading a flat nosed pellet I get resistance in the foreword movement of the bolt in 2 spots: 1) the full length of the pellet before it is appropriately seated and 2) at about 1/3 the length of the pellet before it seats. I think that the flat nose and then the bottom of the skirt is getting hung up on the barrel port.

Two factors seem to support this: 1) pointed pellets only seem to get hung up at the last 1/3 of the pellet length before it fully seats, leading me to think that the "point" passes by the port easily and the is skirt catching on the port; 2) pellets with larger diameters get hung up worse (RWS Hobbies at 0.188" are worse than Crosman Pointed at 0.182").

So, does the port need to be chamfered somehow from the inside of the barrel because it is too sharp? Or maybe the 0.177 hollow probe is starting to seat the pellets crooked (there is a lot of "wiggle" room inside the breach because they are sized for both 0.177 and 0.22 and therefore too big for the 0.177)?

Maybe they're getting hung up on the start of the rifling, does this start at the port or does it extend all the way back to the end of the barrel.

This doesn't happen on my 1377 with crosman steel breach and standard bolt probe...maybe is it the hollow probe? I did see recently on gmac's site that their brass bolt handles aren't to be used on hollow probe bolts as the handle is too weak..are hollow probe bolts inherently that much harder use?

BTW by resistance I mean I have to wrap my finger around the bolt handle and really apply force, a child wouldn't be able to do it.

Thanks for your opinions/solutions.


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PostPosted: Thu Jan 26, 2017 4:10 am 
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Joined: Wed Oct 17, 2007 3:27 am
Posts: 2588
Location: Winnipeg, Canada
I'm not familiar with the gmac custom parts- especially their breeches.

Is this the same bbl off of your 13-77?
Running a phosphor bronze brush through the bore may help- dried metal preservatives can be incredibly hard.

Had similar trouble once with a crosman bbl that was mis-cut...

-D.S.

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