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Old 01-12-2011, 12:35 PM   #1
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Default designing a rifle need rough tolerences for .50 cal

hi im designing a bolt action rifle and i would like to know the estimated
tolerances for a .512 or 13.0048mm respective round in a 782 mm long barrel
without twist (ill get to that later on in the designing phase as is a great enhancement to accuracy and flight time)
it would also be great if you could get ballistic data sheets for different twist ratios
this thing is being designed from scratch and im not to sure of the terminology for most parts but know what they do so go easy on the jargon please ill check this regularly so ill respond hopefully quickly



a little about me
im Australian born and bread 18 going to uni this year for mechanical engineering yay



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Old 01-12-2011, 01:07 PM   #2
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Uncle- please do not take this the wrong way, but will be blunt- you may be out of your depth on this one.

If you have not previously designed a rifle in a lesser power range, what you are doing is equal to deciding to run your first race ever as a full marathon.

There are different .50 cal cartridges- I am assuming you mean .50 BMG- and there are some notes attached for you HERE: .50BMG - Specifications, History, Facts and Myth

You should spend some study time learning what the terminology is, and how it is applied, and the forces involved. Otherwise you are likely to violate ethical standards of engineering, wound innocent bystanders, and require members of the Society of the Steel Ring to come to Australia and smack you in the noggin. If you do not know what the Society is, talk to one of your Engineering Profs.

G'day, mate-



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Old 01-12-2011, 01:27 PM   #3
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lol its only a little project nothing serious but if the design works out i might try it and the only reason im doing it with 50 cal is its easier to design cause the measurements arn't that minute, so the tolerances are slightly bigger only slightly
but i would be kewl if someone could find those tolerances. as for the society of the steel ring i know enough about guns and mechanisms to make sure the bullet actually goes out of the barrel in the direction intended ive got the extracting concept in mine that should work and when its build it should only have 4 moving parts excluding the bullet but for first time fire i was going to set up a mechanical firing so im not behind it and other people are protected that way the 50 cal doesn't live up to it's reputation and do something to the user rather than the enemy or target whichever you consider them or what your firing at.

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Old 01-17-2011, 06:45 AM   #4
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i still kinda want those tolerances ie. what size the round is compared to the barrel without twist is it size for size or is there a .001 or .01 mm clearance between the two and info on twists would be great

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Old 01-17-2011, 11:26 PM   #5
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personally i would start by checking the regs on firearms construction in australia.

if your good to go there i would start by making a 22lr. pressures are low and your not as liekly to kill yourself or others through catostrophic failure as starting with 50bmg would be.

my bet is there are pretty stringent penalties for rolling your own down under.

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Old 01-18-2011, 04:15 AM   #6
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yeah i think doing a 50cal was a bit enthusiastic though luckily Ive only got the trigger system and about half the bolt done so i only need to adjust the pin for the 22 and i should be good in that case whats an accurate barrel length and
and whats the average dimension for a bolt for a 22 Ive gone a bit extreme and made a huge bolt Evan for the 50 thinking that it wouldn't be able to handle the pressure and ill need readjust the hammer and stuff so it's a good size.

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Old 01-18-2011, 04:33 AM   #7
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this is what the trigger system looks like
that pole connected to the hammer is spring tensioned into that cylinder at the bottom kinda like the 1911 hand gun and the hammer release is spring with a piece of flat spring steel tensioned against the little curve that finishes vertically (Ive illustrated) i plan on adding stoppers on the receiver to stop the trigger from flipping forward to far and either just leave the trigger and hammer release the way it is or add a joint that connects the two so its a bit more smooth and not grinding together there will be a slot in the bolt for it and re-cocking is simple the bolt will simply push the hammer back into place.



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