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Old September 5, 2005, 06:39 PM   #1
DimitriS
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Join Date: August 14, 2005
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Compition Rifles

Sorry I dont know where to post this so staff feel free to move it. But its about compition shooting (I think)

Anyways whats this "Blueprinting" I see around then net when I am on competition shooting sites and why is it needed ??

Arnt most actions from factory built to blue prints that are pretty close to the aready known numbers ?? Or is there something more to it then just finding the specs of a action ??

Thanks in advance!

Dimitri
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Old September 5, 2005, 10:53 PM   #2
milanuk
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Usually the term used is 'trueing', as opposed to 'blueprinting' (normally I've heard that term in association w/ car engines ;p )

At any rate, the basic idea and reasons I presume are the same... that action came off a mass production line. Each tool that was involved in making it has a certain amount of plus/minus tolerance, and in the interests of making sure that production goes along smoothly w/o stoppages, generally tends to be a bit on the 'plus' side of what most accuracy minded people would like to see. Take for an example, a regular run-of-the-mill Remington 700 Varmint Special like you might find on the rack at Wal-Mart... the action can serve as a good basis for a reasonable competitive gun in any number of shooting venues, as well as live varmint shooting, etc. Often times you get lucky and all the plus/minuses work to negate each other, and everything works well, and the gun shoots about as well as can be expected, usually better than the shooter can hold the gun steady. But, for the sake of argument, let's look at what can be improved upon...

For starters, the receiver of this particular gun is a round tube, i.e. cylindrical in shape, made from heat-treated steel. Generally speaking, it is round 'enough' for what most people want. But if you ever really check it... they ain't perfectly round by any stretch of the imagination. Not a big deal, but it's a start. Similarly, the rails that the bolt runs on are only finished so smooth, often times coated w/ some sort of anti-reflective coating. This may look cool or maybe prevent spooking something (maybe), but the bolt tends to not move fore and aft all that smoothly. Unless you've handled and operated a rifle that's had this area polished and honed... you won't truly understand the difference. My father's saying 'slicker n snot on a porcelain door knob' comes to mind as being pretty close! After that, the bolt lug recesses aren't always completely true i.e. coplanar w/ one another, nor are the bearing surfaces of the bolt lugs. Often when these are checked, one lug may be making contact on only a very small amount of its surface, and the other may not be making contact at all! This can cause the action or bolt body to literally 'flex' on firing, which can play havoc w/ groups. The 'face' of the action, or where the barrel shoulder sandwiches the recoil lug against the end of the receiver is frequently not square, and often the threads of the action for the barrel are not cut cleanly or properly (mass production here). Milling the face of the receiver perfectly perpendicular w/ the centerline axis of the receiver, then a perfectly flat recoil lug (surface ground on special machinery rather than stamped out of sheet stock) mated up w/ a barrel made to where the threads exactly match the thread in the receiver also go a good ways to making things more correct. Another aspect of the recoil lug is that this is where your recoil is transferred from the action to the stock, and is a critical bedding point... if it isn't flat and square, it may not bear evenly against the bedding and have some room to shift around... again, adversely affecting group size.

Mostly this all falls under the category of a lot of little things that individually may or may not make a big difference, but can make a significant difference when done as a package deal of 'trueing' an action... but it's a good idea to discuss w/ the gunsmith just what all they actually *do* when they true an action... some don't do things that others do routinely, and some may check dimensions of some of the things mentioned above and if the readings are w/i a certain spec (here's that plus/minus again), usually tighter than the factory toleranes, they don't waste the time actually fixing something that ain't broke. Some 'smiths will charge you a flat fee to true the action, regardless of how much they have to do, and others may knock off a bit if they got to skip a step or two (conversely, if they have to do the full-meal-deal on it, you'll see that on the bill too!).

All in all... sometimes you get a gun that shoots awfully doggone good out of the box, and it may not be worth screwing with. If your gun/load are capable of shooting sub half MOA, you might not want to spend the money until it's time to put a new barrel on (most gunsmiths I've dealt with won't put a new barrel on an action unless it's trued... by them). Even sub MOA you might want to seriously think about whether you are really going to see a meaningful increase in group size, especially if you aren't planning on replacing the factory barrel just yet (a lot of gunsmiths I've talked too won't waste a good action trueing on a factory barrel... their words, not mine). And in the final analysis... if you just can't hold all that well, it's not a magic cure for that!

HTH,

Monte
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Old September 5, 2005, 11:25 PM   #3
DimitriS
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Thanks for the input Monte

That clears things up

Well I am not really thinking about doing this now. I am not in need of a rifle that can shoot a perfect score or anything in a shooting comptition.

I might replace the barrel with one from ER Shaw since I hear so many good things from them. But other then the increase in accuracy that gives me I dont see a reason to over do changes to my gun since I wouldnt be able to shoot as good as the rifle can

Dimitri
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Old October 24, 2005, 07:19 PM   #4
ColdZero
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The Full Monte!

What a great explanation. Thanks!
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