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OK.. Now what..!?!

 
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  #8  
Old 05-31-2003, 08:18 AM
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Join Date: Oct 2002
Posts: 328
Re: OK.. Now what..!?!

.. Hey Chris & DC.. I'm pretty sure there's nothing wrong with the chambering.. It seems to be some sort of buildup causing this.. I've had no trouble prior to this and the first five rounds I had with the 240's did chamber OK even though I didn't think to try and catch them to see if there were any unusual scratches on them.. It just may be a characteristic of this style chamber that I have to incorporate some kindof carbon ring reduction maintenance.. I'll be working on it a little more today.. d:^) JiNC

PS- The new Jewell trigger was a cinch to install and is a pleasure to use.. As usual.. Great product..Great company..
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  #9  
Old 05-31-2003, 09:01 AM
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Join Date: May 2001
Location: Pennsylvania
Posts: 1,757
Re: OK.. Now what..!?!

Jake

Make sure the bullets are not oversize.

I have found there are variances in boxes of 500 bullets.

Your OK up to .3081" or .3082". I have seen some to .3085" though and this could be your problem. Sierra wants to know about any bullets that got by them that are .3085" or with the 338 going to .3385"

If you had five that fired fine and at the same seating depth, then I would say the bullet in the pic is oversize. If you have some sort of a copper ring, put the "sweets" to it.

Later
DC [img]images/icons/smile.gif[/img]
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  #10  
Old 05-31-2003, 10:10 AM
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Join Date: Dec 2002
Location: Northwest MN
Posts: 76
Re: OK.. Now what..!?!

Hum...well, godd*mn--that's a new one. Looking at the bullet's shank as best I can tell, the "scratches" or marks appear to be linear in nature, and consistent with the chambering--the wavy pattern toward the rear of the bullet is from the shear moment when the bolt closes, so...I think we can say the problem IS in the throat. A bur?--fairly unlikely--look at the marks. From looking at the picture, those marks appear to be present around a good portion of the circumference of the bullet. Carbon build-up is almost surely the cause, so now...what the hell is causing such a dramatic build-up of carbon? You seem pretty compentent to me, so I'm going to venture that your cleaning methods aren't something bizzare, or ineffective, normally. [img]images/icons/confused.gif[/img] Hum...slippeth me the friends, let me think... Has anyone asked what *type* or powder you're running? I would venture the guess that you're one of WW's slower ball powders <military grade, mabye?> Perhaps Retumbo, maybe RL25. I have also noticed, with certain powders that burn a little hotter, that they typically fowl "less", but that the fowling that is left may sometimes be more difficult to remove. Beats me, I really don't know. DC may be very close with bullet diameters--I would definitely mic them. I get in the habit of microing them, anyhow, as I've noticed differences in OD of the bullets do seem to play a very big part in velocity variations, and a couple other factors. I'd mic the bullets, clean the bore, paying <obviously> lots of attention to the throat, both look and feel, clean them cases up to spiffy-clean, and chamber another round. If the problem goes away, then I'd keep asking myself what some possible causes for such throat fowling might be--all that fowling in there may act as an abrasive that you just don't need! [img]images/icons/wink.gif[/img] Hey, best of luck, brother--I'm going to go enjoy my day off. [img]images/icons/grin.gif[/img]

Dave
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  #11  
Old 05-31-2003, 10:10 AM
 
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Re: OK.. Now what..!?!

That bullet would have to be .3088" to mark that badly, and in a properly cut chamber the marks would not look like that even if the bullet was oversized.
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  #12  
Old 05-31-2003, 07:45 PM
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Join Date: Oct 2002
Posts: 328
Re: OK.. Now what..!?!

.. Methinks it was the dreaded carbon ring.. I took a little JB and dabbed a patch into it.. I then wrapped this around a nylon brush and kindof wallowed in the throat area.. After about two patches worth of this the bullets started chambering normally.. It seemed almost too easy so I'll work on it a little more tomorrow.. Then maybe we'll get the borescope after it again to see what progress may have been made..
.. So far as I can tell this my just be a quirk not necessarily specific to this type of throat but accentuated by it's "tightness".. How's that.? d:^) JiNC

PS- Anyone care to venture why the bore is black.? I don't think there's been any moly used in this barrel but can't really swear to it..
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  #13  
Old 05-31-2003, 08:25 PM
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Join Date: Jun 2001
Location: Palmer, Alaska
Posts: 2,539
Re: OK.. Now what..!?!

Jake,
If those scuff marks haven't been made "all" the way around the bullet, and are only half way around or so, you're in trouble! That would mean it has an offset neck and/or leade (freebore). The leade is usually around .0005" over bullet diameter, which would be .3085" in your case. If the scuff marks are all the way around the bullet and not just the side we can see in the pic, the bullets are oversize. If you think the end of the chamber where the case mouth starts into the leade has a burr around it and is shaving copper, you can polish it up to make sure it isn't. This transition from the mouth to the leade is usually cut at a 45 degree angle, so it doesn't cause burrs anyway. Sierra bullets are sometimes oversize, my brother couldn't throat his 338/378wby because his 300gr SMK's were all .3388" in diameter. They had the reamer ground with a .3385" diameter leade, so they now had to polish the chambers leade up to .3388" just to handle that 500 lot of 300's he had. They only noticed the problem when attempting to throat the thing.

I can put those same marks on "one half" of a side in my 300 Ultra ammo if I chamber the rounds 180 degrees off from the position where they were originally fireformed in. This is because the neck in my chamber is eccentric, and it really sucks too! [img]images/icons/frown.gif[/img]

If you were able to easily seat a bullet up to the lands to measure the OAL to land contact, I would assume the chamber is eccentric in either the neck or the leade area. First, I'd measure the RO (runout) on the case necks (fireformed ones) to see where you're at there. If they are .003-.006" eccentric, you could easily get scuff marks on one side of the bullet if they are chambered with the RO at 9 O'Clock when that case was originally fired with the RO in the 3 O'Clock position. The quick cure for this problem is to alway FL size the cases to reduce or elliminate RO, or mark and index your cases when firing them all the time. Mine happens to shoot much tighter groups by indexing and neck sizing so that's what I do... it's a pain in the ass though!

If you don't find marks on just one side, and they show up all the way around the bullet, I'd suggest calling Sierra and having a talk with them on getting some smaller bullets... FREE! Second, I'd call Mr. Romain and have him measure that reamer he uses in the leade area and segregate the bullets you have on hand so you end up with some to try that are .0001" under size, .0002" undersize and so on to find how much smaller the need to be to chamber easily. My guess is, they will work at .0000" or maybe even +.0001" larger than his reamer spec. A chamber caste will tell you exactly how big your leade diameter is too.

I can tell by the pic that you are not into the lands at all, they leave distinct grooves in the bullet... not scuffs. By the marks toward the tip of the bullet, you may be pressing the lands, but not into them.

Besides, you'd never get them that far into the throat if you drove the bolt closed with a hammer... it would push the bullet into the case LONG before that point, you'd also leave the bullet in the barrel and powder in the mag when withdrawn too. I'd say yours and Chris's OAL measurements are right on the money!

The bullet is either not being allowed to align with the throats axis ( chamber and/or Leade eccentric), or it's too big to fit into the leade itself.

The helix marks at the rear just indicate the bullet rotated in the leade a little but, much less than the case head did on the boltface or the bullet inside the neck when camming and closing the bolt.

I'd worry little about the carbon on the neck, but it does look like it's up the length of the neck farther on the "top" of the pic than that of the "bottom." This could indicate better sealing on the lower side and thus and an offset neck to that side... that's a big maybe though. [img]images/icons/wink.gif[/img]

I wouldn't let the carbon build up there or headspace can get tight. Clean em off each time and when they get sooted the whole length, I'd anneal them. You obviously sized the neck down to hold this bullet here, so maybe the neck already is hard enough it sooted up badly and was just cleaned up by the bushing passing over the neck.

I doubt Ray cut an eccentric neck or throat, unless he used a seperate neck and throat reamer and had a loose fitting pilot...

I'll bet your bullets are just tooooooo big. [img]images/icons/wink.gif[/img] Mic the bullets and the reamer and you'll clear that one up quick. [img]images/icons/smile.gif[/img]

Good luck, and I hope that's all it is too. Believe me, you don't want nothin to do with an eccentric chamber!! Factory chambers suck hind tit!
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