How important is blueprinting an action

[J E Custom]

There are apposing views on this process and the results are sometimes hard to prove so it boils down to what a person thinks and wants to believe. I blueprint every action to assure myself that the accuracy potential is available and not impaired with sloppy machining.

I have seen poor dimension on many different parts that when combined canceled out each other and shot well. So just the fact that they shoot well doesn't mean all the parts were dimension-ally close.

I just finished a rifle for a friend and according to my notes, The donor action had dimension problems, but it shot fairly good.

The action face needed .004 thousandths to square up.
The lug abutments were the worst with One lug not even touching and the other was only 20% in contact. There was a .0085 difference in the contact surfaces and I had to remove .010 thousandths to get them even and perpendicular to the bore center line.

The bolt lugs were close and only needed .002 the true them on the contact side and the front was within .0005
so I did not remove anything from the front of the bolt lugs (Non functional)

The factory recoil lug only had a .001 thousandth difference from best to worst so it was ground to flat .000 difference.

The bolt face needed .0035 to square up and the barrel shoulder did not have any differences.

Total material removal to true all parts of assembly was 0.020,5 with the greatest difference in the lug abutments
and in general the rest of the differences were not unusually off and may have been the reason that the rifle shot OK for a hunting rifle.

This is by far not the worst action that I have seen, And without exception I have found "ALL" actions including customs will need something corrected because they are machined the same way as the factory actions and only their quality control catches more that the factory does. But all actions should definitely benefit in my opinion from this truing process.

And this usually makes the firearm more forgiving to different loads and not be so picky about the ammo.

J E CUSTOM

 

[HARPERC]

I like your list of specifics. Trueing, or blueprinting is sometimes hard to pin down what a smith put time into.

 

[Edd]

I'm wondering why the $150,000 machines used to make custom actions aren't as precise as the $15,000 machines used to true them.

 

[shortgrass]

I'm wondering why the $150,000 machines used to make custom actions aren't as precise as the $15,000 machines used to true them.

You mean the $250,000 machines, don't you, Edd?

 

[Jud96]

I'm wondering why the $150,000 machines used to make custom actions aren't as precise as the $15,000 machines used to true them.

They are if they're operated correctly. If the operator doesn't check the work he's producing and adjust the wear offsets on the tools, the inserts and tools can and will wear and cause minor differences. A CNC can produce extremely consistent and tight tolerances, but the machine is only as good as the machinist running it and the tools loaded in it. If every piece of the rifle isn't machined perfect, than tolerances will just stack up like JE said. Surprisingly, the recent 700 actions have excellent tolerances on the receivers. The primary extraction still sucks on some of them, but the tolerances are really good. This is info coming from my smith who has inspected dozens of new 700 actions and he's as impressed with them as I am.

 

[J E Custom]

I'm wondering why the $150,000 machines used to make custom actions aren't as precise as the $15,000 machines used to true them.

The machines are more precise but many times the productivity is more about money and the operator has a big part in the set up and this is normally where the difference is. Time is money, and doing things one at a time allows time to do proper set up.

When things are set up correctly on these $150,000 + machines all dimensions are very consistent, but if not set up correctly, an error will also be repeated many times until it is caught. The only advantage in my mind, is the ability to change the process as you go to improve the finish product.

I don't think that anyone thinks that they can beat the precision of some of these high dollar machines. But a real craftsman can give them a run for their money In the quality department,
but not in the production aspect.

Also the CNC machines have to be set up correctly and then proofed for dimensions and tolerances. many times they have to reject the first few and make adjustments. the smith doesn't have that luxury, when working on someones action.

Also most actions are machined In many steps and parts that are massed produced and any one of these may not be matched to another part and that is where the difference normally is. Many years ago, firearms were individually fitted by a master Gunsmith and often the parts would not work in another firearm of the same maker. CNC machining has all but eliminated this process but a quality truing is worth the effort if only to find one or two discrepancies.

Just my opinion

J E CUSTOM

 

[Edd]

You mean the $250,000 machines, don't you, Edd?

I'll take your word for it. I was guessing and trying not to exaggerate. I probably also overpriced most of the truing machines being used that are said to hold tolerances of .0001".

 

[J E Custom]

I'll take your word for it. I was guessing and trying not to exaggerate. I probably also overpriced most of the truing machines being used that are said to hold tolerances of .0001".

The machine can only do so much and mine has it's limit and can do work within 0.0005 if I do my part. Some of the really expensive CNC machines can/do work within 0.000,01 or better.

So if I can measure in half thousandths and some times depending on the finish 0.000.01 If I can improve it I will, If not so be it.

If the setup doesn't measure within these tolerances you are wasting time trying to improve the action.

The goal is to make the action truer/better than it was.

J E CUSTOM

 

[IdahoCTD]

A lot of times the order of the machining will change things greatly. I wouldnt finish machine the bore, front face and threads until after the rest of the action is machined. Removing pockets of metal here and there will make things move.

 

[aushunter1]

Thanks for this thread JE, I find this sort of topic very interesting.

The last sentence in your OP say's a lot for why the process is important, all part of the accurizing process like bedding etc.

If I had my time again gunsmithing would be something Id be greatly interested in doing as a career.

But back in the 80's/90's in Australia it wasn't such a big thing in demand.

Fitting & turning was a career of course but I guess most people who went onto that sort of thing had it as part of their family history or schooling.

Even now its hard to find a decent smith here & even getting basic stuff done can take forever, getting a rifle built can be a 12 month + wait

 

[J E Custom]

A lot of times the order of the machining will change things greatly. I wouldnt finish machine the bore, front face and threads until after the rest of the action is machined. Removing pockets of metal here and there will make things move.

Absolutely !!!

I do everything in a specific order and the first thing is to establish a bench mark surface that everything is based off of,

Everyone has the order that they like to use and I have mine. It is probably like most. What is the saying? "Measure twice (In my case being anal, it may be 3 or 4 times to be sure) and cut once"

J E CUSTOM

 

[Alex Wheeler]

A lot of times the order of the machining will change things greatly. I wouldnt finish machine the bore, front face and threads until after the rest of the action is machined. Removing pockets of metal here and there will make things move.

And this is why it has nothing to do with how expensive or accurate the machines are that make the parts, someone gets it....

 

[Edd]

And this is why it has nothing to do with how expensive or accurate the machines are that make the parts, someone gets it....

Too bad the people in the custom action manufacturing business don't know this. I suspect many of them have been spending a lot of money buying machines they believe are accurate.

 

[Alex Wheeler]

I said the problem has nothing to do with the accuracy of the machines...