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OK.. Now what..!?!

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Unread 05-30-2003, 12:51 PM
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Join Date: Oct 2002
Posts: 328
OK.. Now what..!?!

.. I got everything loaded and went to load development camp.. When I tried to chamber the Tommy with the 240's they wouldn't go without a LOT of pressure on the bolt handle.. The brass is OK.. It does fine w/o the bullet and the sizer is set up right on.. Here's a pic of what one looks like after being fully chambered.. I decided against shooting these.. I cleaned the heck outta the barrel and chamber area thinking I may have a "carbon ring"..Whatever that's s'posed to be.. Any ideas.? [img]images/icons/confused.gif[/img] [img]images/icons/mad.gif[/img] [img]images/icons/confused.gif[/img] JiNC
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Unread 05-30-2003, 01:13 PM
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Join Date: Jun 2007
Location: Wilmington NC
Posts: 4,758
Re: OK.. Now what..!?!


1. Your case shows a lot of carbon at neck/ shoulder juntion. Clean that up and retry.

2. The bullet in the picture looks like it has about .250-.400 land engagement. How did you determine initial seating depth for the 240? What are the marks on the bullet?

3. Assume that it is not tight neck chamber?

4. Assume that gun is used, if this is first time firing it.

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Unread 05-30-2003, 04:56 PM
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Re: OK.. Now what..!?!

Your throat is way too short for that OAL. Seat the bullet much deeper into the case and this should go away.

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Unread 05-30-2003, 05:50 PM
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Re: OK.. Now what..!?!

I have yet to meet the magician who can engrave a bullet .250" without shoving the bullet back in the neck of the case. If you view the marks carefully, you might find they represent a tight free bore area with burrs. Notice that the helix of the marks change, this probably represents the internal burrs marking the bullet when the bolt is indexed to full lock-up. I doubt JB will fix this one, but I would try it anyway, the alternative is much more expensive. On the outside chance your bullets are oversized, you might want to mic them and make sure they are .3083" or smaller.

Those are not likely to be land marks, does not look right, unless the rifle is used and the lands have dissappeared....
The other possibility may be the throat is burnt out, I would say take a peek with a bore scope, but I am afraid what you find might induce nightmares.

Either way, the dude who cut that chamber...... well, I promised Len I would try to be nice.

[ 05-30-2003: Message edited by: S1 ]
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Unread 05-30-2003, 07:29 PM
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Join Date: Oct 2002
Posts: 328
Re: OK.. Now what..!?!

Hey guys.. Thanks for the input.. They aren't land marks.. I spent a good deal of time getting the seating deapth correct for these bullets.. (4.380 comparator OAL, if I remember) I talked to Mr Romaine and he says these chambers are throated very tight.. We borescoped the chamber tonight and all looks new except for a little ring of copper right where the tight freebore starts.. I can't say that I've ever had to deal with this issue before.. Could be I've just never noticed it with looser tolerances.. Who knows.. What's the scoop for getting rid of this thing.? Is this what's referred to as a "carbon ring".?
.. The bore is completely black.. I usually shoot with moly but didn't with this project.. I don't think DC used it either and I don't remember if I asked CJ about it or not.. I wonder what that could be.. I'm somewhat certain I'm cleaning OK.. Or maybe I've been "moly-spoilt".. d:^) JiNC
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Unread 05-30-2003, 07:41 PM
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Join Date: May 2001
Location: Pennsylvania
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Re: OK.. Now what..!?!


Clean up the necks on the cases first.

What thickness are you turning the necks to?

It looks like your really jambing those bullets way up in the lands to far and the cases are extremely dirty. Seat them deeper into the case after measuring the Over all length needed.

You must have very tight neck tension on those bullets for them to hold like that when you cam the bolt handle down.

I'm not sure if it's a burr, but try the JB like S1 suggested.

Check your die and make sure it is clean especially in the neck and shoulder area.

Get hold of Chris Jamison. He had some excellent groups with that rifle and 240 grain bullets. Get the overall length he was using.

I did get hold of a batch of Sierra 338 300 gr bullets that did mic .3385 and almost reuned a hunting trip until I figured out what had happened.

Good thing I take quite a few rounds with me and had some loaded with another lot of bullets that were .3381" to .3382"

Those .3385" would NOT go in the rifle without extreme force. You can imagine what would have happened to the pressure.

The bullets I sent you to try were just picked out of the box of 500. I did not mic them so maybe you want to do that. They may be oversize?

Email Chris Jamison.

DC [img]images/icons/wink.gif[/img]

[ 05-31-2003: Message edited by: Darryl Cassel ]
Darryl Cassel
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Unread 05-30-2003, 09:04 PM
Posts: n/a
Re: OK.. Now what..!?!

Jake --I have been following your dilemma and am really dumbfounded...Ray cut the chamber lees than a month before you got the rifle and I only put twenty something rounds through it. Yor are correct in the fact that they are not land marks. My comparator touch point was 4.390", which is right on with yours, as my comparator body is 1.010" with the bushing installed. I had no problem chambering rounds set to the touch point, with no pressure required on the bolt. I'm guessing your bullets are probably a little oversize or you have a burr in the parallel throat... Let me know what you find... CJ

[ 05-30-2003: Message edited by: Chris Jamison ]
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