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Author
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Topic: Measuring freebore from a dummy round?
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Aaron Rhoades
Knows what it's all about
Member # 4234
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posted April 17, 2016 08:39 AM
I'm wondering if there is a way to measure freebore from a dummy round so I can specify it for my reamer. What the deal is, I have a bunch of 130 6.5 Jlk's and I want to rebarrel a 6.5x47 Lapua because it is setup for 127 Barnes Lrx bullets with a looooong freebore, such that the 130 Jlk bullet is barely seated in the case at the lands.
Posts: 155 | From: Washington | Registered: Oct 2012
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Leonard
HMFIC
Member # 2
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posted April 17, 2016 11:36 AM
I've heard of some attempts using a short parting off of a neck of a cartridge case. I think the idea is to slide it over a long bullet and chambering it. The sliding "sleeve" should stop at the end of the freebore and when it is extracted, you can measure exactly how long it is. Of course, the "sleeve" cannot be so long that there isn't room to chamber the testing round so you need to shorten the case neck to compensate. Might take a few trials but I think it would give you a number to work with?
Good hunting. El Bee
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EL BEE Knows It All and Done It All.
Don't piss me off!
Posts: 31461 | From: Upland, CA | Registered: Jan 2003
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knockemdown
Our staff photo editing Guru, par excellence
Member # 3588
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posted April 18, 2016 03:59 AM
Those JLKs have a radical tangent ogive profile & don't need as much freebore one would think. What c.o.a.l. are you seating them to hit the lands?
And, before you settle on a freebore length, I'd ask if you are married to that 130JLK, or will you be shooting any other bullets?
123Amax, 130VLD, 130Hybrid, etc...
Also, will your rifle have any c.o.a.l. limitations to feeding & function? BDL setup, DBM, blind mag... how much room are you working with?
Just sayin', there's point where rifle magazine constraints, bullet choice(s), jump/jam, room to chasing lands, case efficiency (yadda yadda) that freebore length should address, harmoniously...
Posts: 2202 | From: behind fascist lines | Registered: Mar 2010
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Leonard
HMFIC
Member # 2
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posted April 18, 2016 06:00 AM
I somehow forgot issue #1, in a magazine rifle: check to see if your assembled cartridges will function in the magazine. Unless you intend to single load them the overall length of cartridges for a bolt action rifle is determined by the length of the magazine. Actually didn't forget, but there are a couple of things you can do to the magazine, incrementally; if you really HAVE to shoot a certain bullet at a certain length. In 93.5 percent of cases, it's not worth it.
Good hunting. El Bee
edit: but, that's good advice, above.
[ April 18, 2016, 06:01 AM: Message edited by: Leonard ]
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EL BEE Knows It All and Done It All.
Don't piss me off!
Posts: 31461 | From: Upland, CA | Registered: Jan 2003
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Aaron Rhoades
Knows what it's all about
Member # 4234
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posted April 18, 2016 09:54 AM
I plan on using Jlks pretty much exclusively but for sure not over 130gr if I do use another bullet.
Posts: 155 | From: Washington | Registered: Oct 2012
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knockemdown
Our staff photo editing Guru, par excellence
Member # 3588
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posted April 19, 2016 03:46 AM
How far along is that long troated barrel?
If it's still got life, you could prolly run 'jump tolerant' 123Amaxs or 130Hybrids in that one & save your stash of 130JLKs for the next barrel...
I'd prolly do a .125-.150 FB, next time around. That'll keep ya 'round the 2.800" vicinity for overall length with several bullets. Plenty of room to chase lands and well within magazine limitations of most every short action...
Good luck!
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