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First time shoulder bumper

 
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  #1  
Old 01-20-2011, 06:46 PM
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First time shoulder bumper

Howdy everyone,

Long time lurker, first time (I think) poster.

Well, I went out and got one of those fancy rifles that have chambers so tight they require all sorts of voodoo magic to make 'em work right. It's built on a 260 Remington. I got myself some Sinclair bump gauges and according to what I've read, I need to fire a few rounds, then measure off the shoulders of the fired rounds with the bump gauge and then set up my die so that it bumps the shoulders back .002. I'm using Forster reloading dies by the way.

So, I fired some rounds, and measured them with the bump gauge and got a reading of 1.555 +/- .001. I then ran them through the re-sizer and was only able to bump them to 1.554.

The problem is, I've screwed the die body down so far that the shell holder, sitting on top of the ram, is contacting the bottom of the die. I'm still getting a fairly full length re-size (I always full length re-size), but the handle of the RCBS rockchucker is not going down as far as it used to. My question is, what do I do to insure the ram goes as far up as it should? I've been told that the bottom of the die needs to be ground off a bit. But how much? I have no tools to do this sort of thing which, I'm thinking, would require a machinist.

Your wise and experienced answers are most appreciated.
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Old 01-20-2011, 06:53 PM
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Join Date: Mar 2008
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Re: First time shoulder bumper

i am sure someone will chime in to answer your question, but i just wanted to add that i knock the primer out manually before i measure the fired headspace. this will ensure an accurate reading.

you may have already done this, but i have found it to make a difference and thought it was worth mentioning.

good luck
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Old 01-20-2011, 06:57 PM
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Re: First time shoulder bumper

That's a good point. I use an RCBS priming tool and it doesn't always seat the primers as deeply as I'd like. Not so much a problem with the 260, but seating primers for the 264 Win Mag can be...trying.

Thanks.
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Old 01-20-2011, 07:27 PM
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Location: So. California
Posts: 409
Re: First time shoulder bumper

Take care with shoulder bumping sir, Sometimes less is more If I were you, I would run with what you can bump and see how it works. SD / ES will tell you a story about enough / not-enough bump. Also, of course, Neck Annealing. You probably already know that it is important to consistent ES/SD but I thought perhaps it might be worth tossing out there as well.

Good Shooting sir,
Gary
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Old 01-20-2011, 07:42 PM
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Posts: 42
Re: First time shoulder bumper

Believe me, I'm a reluctant shoulder bumper. Despite having read up on it, I certainly do not consider myself an expert so no, I didn't know about the importance of annealing. I'd rather not have rifle that required bumping the shoulder but I learned about the tight chamber after I'd bought the rifle. I suppose though, it was inevitable since the cases get lengthened by repeated firings/re-sizings. I had some 264 rounds that were trimmed to length and then bullet seated off the ogives and they were still hard to chamber. A clear case for shoulder bumping I've been told.

I'm beginning to think I should have started this thread by writing "I'm a shooter and I have a shoulder bumping problem."

Last edited by Nobody; 01-20-2011 at 07:45 PM.
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Old 01-20-2011, 07:47 PM
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Location: So. California
Posts: 409
Re: First time shoulder bumper

Does the current max bump you can do give you enough to chamber a round easily? If not, I would consider sending that stick in to a gunsmith who can open it up just a little bit. MOST reloading dies, when you FL resize, will put you at a happy spot where you could just go out and buy ammo if you ever needed to and shoot. If your dies will not resize enough to allow for this....I would say you are not in a happy place.

Some times too tight really is!
Gary
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Old 01-20-2011, 07:52 PM
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Location: Salmon, Idaho
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Re: First time shoulder bumper

Back your die out until you get full stroke with your press then begin screwing the die in in small incriments while sizing a lubed case. If you hold your hand up behind the die/shellholder contact area and look to see if there is any visible light ie space between the shell holder and the sizer when you are at the bottom of the stroke. You will feel the opperating mechanism "cam over", this is all the tolerance in the moving parts being taken up. If there still a sliver of light you can turn the die in a little more continueing with this process until you get zero gap between the two at full stroke on a case on it's first pass through the die. I reccomend you measure every time you make an adjustment. If at this point you are still only getting .001 bump then the die may need to have .001 turned off the bottom. Be careful, too much bump will generate an excessive headspace condition which will cause more problems. A .001 bump is probably OK but you may run into a chambering problem if your chamber is dirty or you don't get your primer seated properly.
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