Blueprinting and accuracy improvement - any proof?

[rsilvers]

There is recutting the threads to be concentric with the centerline. I suspect this has zero benefit because even if the threads are 0.004 off-center, the back of the brass will still see the bolt face as a plane.

There is squaring the front of the receiver - but they are probably good to begin with in that area.

There is lapping the recoil lugs. I think this would help. Also it is easy to do yourself.

There is squaring the bolt face. I think this would help - assuming it was out of perpendicularity to begin with - and I would like to see measurements showing how far off they are.

Has anyone ever published results of a properly-conducted test of each of these steps with before/after results for each phase?

I would love to know what matters and what does not.

 

[rsilvers]

Well, I could pose a challenge. Someone could take a great .308 barrel and stock and put them on a 700 action fresh from Walmart. Shoot 5 groups of 5 rounds each. Then do this two more times with two more Walmart actions. Then send each action to a smith who has an excellent reputation. Then put the barrel and stock on each receiver that has been worked on, and re-shoot the groups. This could be an article for Precision Shooting.

If the new results are not better than the old ones, then game over. If they are clearly better, the next phase would be to see what each step did - but that is more work.

 

[watercam]

Obviously it depends upon your needs and expectations of what "accurate" is. If you are happy with 1 moa accuracy there are plenty of factory rifles out there of all price ranges that will satisfy you. If you need less than .2 moa that takes a better built firearm. For myself, I need 1/2 moa out to 600 yards minimum to be competitive in High Power.

 

[rsilvers]

What your proposing, would take a lot of time, work, and expense......
While at the same time, action truing (blueprinting) has been proven repeatedly over and over, for many years gone by.

Best of Luck
Donovan Moran

I am only looking for one example of it improving the groups. Do you have a before and after target and a list of what work was done on the action?

 

[rsilvers]

Obviously it depends upon your needs and expectations of what "accurate" is. If you are happy with 1 moa accuracy there are plenty of factory rifles out there of all price ranges that will satisfy you. If you need less than .2 moa that takes a better built firearm. For myself, I need 1/2 moa out to 600 yards minimum to be competitive in High Power.

Any improvement would make it worth it. I am looking for one example of any improvement from re-cutting receiver threads. Even a 0.100 improvement in group size.

 

[deadlyswift]

Wouldn't it just be easier and less expensive to just invest into a bat action or another good custom action?

 

[rsilvers]

That depends on each person.

If it turns out that re-cutting receiver threads does not have any accuracy gain, then the amount of work one might consider doing on a factory action decreases. I am not sure what the answer is but we must start with a hypothesis. Mine is that re-cutting receiver threads will not improve accuracy. This can be tested either with a stock barrel, stock, and receiver - or with a high-end stock, barrel, and the rest of the receiver worked on first. As long as for the before/after the only thing that changes is the receiver threads being re-cut or not.

 

[Ackman]

Well, I could pose a challenge. Someone could take a great .308 barrel and stock and put them on a 700 action fresh from Walmart. Shoot 5 groups of 5 rounds each. Then do this two more times with two more Walmart actions. Then send each action to a smith who has an excellent reputation. Then put the barrel and stock on each receiver that has been worked on, and re-shoot the groups. This could be an article for Precision Shooting.

If the new results are not better than the old ones, then game over. If they are clearly better, the next phase would be to see what each step did - but that is more work.

Yeah....you "could pose a challenge." But instead of posing a challenge to everyone else, do it yourself. Or is it better when others go to the trouble?

 

[Greg110]

Mr. Silvers,
Think about this please. How far out were the threads cut? I'm certain that there is a threshold here. The point is, maybe we're getting a little to esoteric here. As has been said here before, just buy a quality action and don't worry about anything but shooting. Trigger time is more important. Obvoiusly just my $.02.

 

[Ackman]

What your proposing, would take a lot of time, work, and expense......
While at the same time, action truing (blueprinting) has been proven repeatedly over and over, for many years gone by.

Best of Luck
Donovan Moran

I am only looking for one example of it improving the groups. Do you have a before and after target and a list of what work was done on the action?

There's no way to do a before and after. Recut threads are larger diameter. That same barrel is too loose in an action with larger threads.

 

[rsilvers]

True - the process of blueprinting results in taking in-spec receiver threads and makes them out of spec, so that they will no longer accept standard barrels.

 

[Tozguy]

I love this thread. The same question has been in the back of my mind for a while. It applies to reloading as well ie when do you get to the point of diminishing returns for the work and expense of making everything last dimension perfect. I can feel the improvement in my confidence when I know the gun and ammo is well done and can do its part. That reason alone is enough to get me to try better stuff as my ability improves. Chances are you will have to try new and better stuff for yourself as you progress as a shooter and reach your own conclusions. Some money will be better spent than other money. There are just too many subjective variables for someone else to be able to answer the question for you.

 

[BoydAllen]

A friend, who does his own barreling, chambered a barrel for a short action 700 that showed that its lugs were in contact and the front of the receiver was squared using a mandrel. It drove him nuts with its lack of performance. He tried two different match grade barrels, to no avail. Later he determined that the threads were quite a bit out of square. After they were recut, true to the action's centerline, it was a whole new rifle. He cut the shank off of one of the barrels that refitted it to the larger action threads. He is very happy with the results. There is a lot of bad advice out there. For what it costs to do a rifle today, cutting corners can be expensive. You spend all that money for nothing if the core isn't right.

 

[rsilvers]

I have to ask - threads out of perpendicularity to the end of the receiver? Or do you mean shifted from the centerline?

 

[CPorter]

Why don't you read Rifle Accuracy Facts by Harold R. Vaughn. It's about as scientific as you are going to get.

 

[BoydAllen]

Both

 

[rsilvers]

I have it.

With all this talk it made me go lap the lugs on one of my Rem .308s. I only had 800 grit but even so, it went pretty fast. Maybe 10 minutes for the entire process. Before I had no contact on one lug. Now I have 80% contact on both lugs.

 

[squirrelduster]

I have the experiment in process right now.
I had a Savage action and put a new barrel on it and could not get it to shoot. 7wsm with Berger 168 gr grouping in the 2" range at 200 yards.
I was not happy so I sent the action to be trued up and the receiver face was out of square. When it comes back we shall see what the groups have done.
i will keep you posted with the results.

 

[Ackman]

Re-cutting threads is just one part of it.

About truing an action.......
I got a 700BDL sporter at the gunshow, 22-250, unknown number of rounds through it but the barrel looked very good. Had it rechambered to 22-250AI and shot it for awhile, floated but un-bedded. Load workup, and every time I papered it to check zero, 3 shot groups were consistently about 3/8"-7/16".....no 5 shot groups, this was a sporter truck gun.

Later that action was trued and rebarrelled to something else. The riflebuilder said the action face was way off and everything was way out of true.......that it was the worst 700 he'd ever seen. But it shot well. That 22-250AI sporter barrel was screwed onto a 722 action and it shot with exactly the same accuracy until the throat was gone. Don't know how true the 722 action was, now it's been trued and rebarrelled also. Couldn't really say if truing has a measurable effect on accuracy, but I usually have it done with a new rebarrel.

 

[rsilvers]

I want to see the gunsmith who says "It was nearly dead-nuts on but I still made the skim cuts. Here is the bill."

One should ask for a CMM printout before and after the work. That would make a great article - CMM 5 of them and send them out to 5 gunsmiths, and then CMM them when they return. See if they got better or worse.