Difference truing an action makes? *UPDATE TEST RESUTLS*

Ok, here is the results. This is a Stevens rifle in 308, bedded, trigger tuned with a 5-15 power bushnell 3200 on it and a factory bbl.


Prior to action truing I shot 2 different loads for a reference of accuracy. One load was a good shooting load, that out of this rifle would do at worst 1.75" for 5 shots and at best 1" for 5 shot groups. I fired 50 rounds of this so I am very confident of this is the actual accuracy. I set 25 rounds of this ammo aside, to use after truing. The other load this rifle shot poorly, 3" to 2" for 5 shot groups, I also set some ammo aside to test after.


I pulled the bbl off and noted how the nut snugged up. You could clearly see that the nut would contact one side of the recoil lug (I think the bottom) first as it was tightened. Clearly the action face/recoil lug were crooked the the threads/nut face.

I then put the action in a jig in the lathe and indicated it in using a threaded stub that abutted against the locking lugs. I do not feel this is as good as using the bolt race way as the reference point but I did not have a mandrel and bushings to do this. Once the action was indicated true to the threads I cut the action face true. I found it was out a few thou and the face it's self was not square but tapered in towards the threads. I also skimmed the locking lugs true but they were very close.

Put my blolt head in the lathe and took a cut off the back side of the lugs which were true but tapered a bit, then I took a cut off the bolt face to make it square as well.

The recoil lug was definitely the worst offender of all, it was out quite a bit, as it is just a stamped part. I stoned one side of the lug flat on a stone then I built a little jig to hold the lug and I turned the other side to be as parallel as I could get it.

I put my threaded stub in the lathe and butted the nut up against the true shoulder of the stub. I took a cut of one side of the nut, then put it on the other way and took another cut off the other side, then back to the original side and took another cut. I did this a few times because I did not want an un square nut face to tilt the nut in the threads. Not perfect but I feel it worked OK.



Then I assembled the rifle. As I thignend up the nut I held it up to the light to look for a gap on one side of the nut. The nut tightened up very square to the recoil lug/action face. I was happy. My methodology may not be perfect, and if careful measurements were taken indicating off the bolt raceway the action may not be exactly perfectly square, but it is light years ahead of where it was.


Then I put the action in the stock and noted the bbl now just about touched the for end, mabey 1/6" or less gap. Previously there was a fair gap between the bbl and forend. This tells me that the bbl is now angled differently off the action face. The crooked action face, recoil lug and nut caused the bbl to snug up pointing upwards before. Now, cutting the action face true to the threads and making the recoil lug and nut square the bbl is probably snugging up square to the threads. I then sanded the bbl channel down to be sure the bbl would be fully floated as before.



Then I took it to the range to see if all of this made any difference. I fired the same batches of ammo that I had set aside from before. The ammo that it shot poorly before made groups that were 2 to 2.5", possibly slightly better than before. The real eye opener was the ammo that it shot well before. My first five shot group was .75" with 4 of the 5 shots being in 1/2". I fired off the rest of the 25 rounds of ammo and never had a group much over 1". Before truing I never had a group under 1" ever.

What is real interesting is the shape of the groups. Previously the groups would be random fliers here and there. Now the groups showed vertical stringing, and the horizontal was never over 1/2" apart. This allows me to see that I need to tune the load to reduce vertical dispersion or possibly get a different stock that is not so springy on the forend.



I feel this was worth my time and effort, lots was learned and positive results were seen.
 
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Add a bolt lift kit. Its a 38 spec case cut very short and a ball bearing placed in the primer flash hole. Remove approx .080" off the bolt assembly screw due to the added length of the exposed ball bearing and case lip.

For cratering, sand down the firing pin tip to increase the radius. Make it less sharp. Set protrusion .040" - .045".
 
northern skies said:
Interesting! I have noticed that mine has a stiff lift. How is that taken care of?

Also noticed the cratering. Thanks for the explanation about, it makes sense.
Click to expand...

It's called bolt timing and it involves several steps in the bolt. Makes for a much smoother and lighter bolt lift. Let me know if this is something I can help you with.

As for the cratering, it is a by product of the large exit hole in the bolt head on the last gen actions. It is not dangerous and actually very helpful.

You will know that you are in magnum pressure territory when LR primers like CCI BR2 show slight cratering. I actually consider this one of the best pressure indicators I have.

The new gen bolt heads have a small firing pin exit hole and cratering at standard magnum pressures is not really evident.

RofA, interesting results and congrats on gaining some accuracy.

Jerry
 
I just did another Stevens action that I had. This is one of the newer center feed models.

I used the same procedure as last time and found the action face to be within 0.002" of square to the threads, the locking lugs were also very true. The stamped recoil lug was again the worst offender and was way out.

I also had a very good point of reference for the accuracy of this rifle and had ammo to test the results. Before and after truing the action it shot exactly the same.

So there you have it.
 
RofA, I just read your earlier post and see you talked about a jig. I use a jig for other actions but not for a Savage action unless I need to do the threads for some reason. The stub I was talking about is a piece of aliminum stock chucked up in the lathe and threaded for the action. It should be made so it extends fully inside the action and when you thread on the action, the internal action lugs hit the face of the stub. You have an action hanging off a threaded stub in your chuck. Gently touch up the face of the action and now the threads, lugs and face are true to each other. You can use the same stub several times. Every time you use it, chase the threads and re-face it. If it gets too loose, make another.

If you check this against a digitized tang and find it out more than .001", recheck your setup. The only way it can be out at all is from heat treating.
 
PEI ROB said:
RofA, I just read your earlier post and see you talked about a jig. I use a jig for other actions but not for a Savage action unless I need to do the threads for some reason. The stub I was talking about is a piece of aliminum stock chucked up in the lathe and threaded for the action. It should be made so it extends fully inside the action and when you thread on the action, the internal action lugs hit the face of the stub. You have an action hanging off a threaded stub in your chuck. Gently touch up the face of the action and now the threads, lugs and face are true to each other. You can use the same stub several times. Every time you use it, chase the threads and re-face it. If it gets too loose, make another.

If you check this against a digitized tang and find it out more than .001", recheck your setup. The only way it can be out at all is from heat treating.
Click to expand...



Yes that is exactly what I made. But I used an action jig to hold the action in the lathe then used the stub to indicate the action in. I did it this way so I could take a pass off the lugs. With the action being centered by the threads and stub butting against the action lugs the lugs were pretty much dead on when I took a skim of of them. There were true to the threads but somewhat tapered towards the raceway. This allows me to kind of check and confirm my work dialing in the action. If the lugs were not true then something went wrong. The entire exercise is more about learning and confirming than to make this Stevens shoot good.
 
No, I think the threads and locking lugs are always true due to being cut with one cutter in a single operation during manufacture (this is a guess). The action face, and the angle of the threads relative to the bolt raceway may not be true. The stamped Recoil lugs are definitely not true and the bbl nut may not be true either. The floating bolt head will square it's self up with the locking lugs but it is no guarantee the bolt face is square to the chamber.


On the newer center feed Stevens I tried after (the first action was a stagger feed) the action face was quite true to the threads and lugs, could have been luck or they could have changed the cutters to cut threads, locking lugs and action face all with one tool.


I would say the best bet for anyone doing a bbl swap is to get rid of that dam recoil lug and put on a precision ground one. It will get you 75% of the way there and is easy to do when installing a new bbl.
 
Here is a pic of the stub, made out of a pump jack polish rod.

The shoulder of the stub does not contact the action face, the front of the stub butts against the lugs. The threads, front of the stub and outer surface (for indicating) were all turned at the same time so all are true to each other.


100_0842.jpg
 
Jerry, the new Savage and Stevens actions that have a digitized number under the tang are made with brand new CNC machines. The lugs, threads and face are all machined in the same operation and are true as a new CNC machine can make them. Heat treating is done afterwards but since the length form the lugs to the face is short, warpage is very low. You do not need to true these actions.

The older actions were made differently. After the raceways were cut, the action was just a hollow tube with slots inside. A worker placed the action in a V block and by hand he slid it into a large diameter grinding wheel to deburr it. It was as crude as it sounds but the V block method produced an action to about .003 out in the face, not bad when you think about it.

RofA, I understand your thinking now. Good to check your work. I did the same to the first of the new ones I chucked in my lathe. Immediately I did notice the action face was milled and not ground like the older actions but I did not expect it to be true. It took me forever to check it because I couldn't find anthing wrong. I thought I was loosing it and cleaned my test indicators, moved them around etc until I realized my setup was good and the action was perfect. Then Fred Moreo told me he visited the Savage plant again and saw the new machines.
 
PEI Rob, thanks for the info.

I am sure not alot of Rem fans are going to like reading this :)

I just picked up a lightly used Edge (aka Axis or whatever they are called now). It needed a bit of TLC but man, Savage took care of a whole bunch of things.

I have yet to shoot it but expect typical Savage accuracy. The action/bolt, trigger, and operation is arguably SUPERIOR to the basic 111FCNS in form and function.

The bedding certainly is

I'll put up a link when I get the rifle tested and an article posted. It is bizarre to find an IMPROVED product at a lesser price point.

The rifle marketplace is changing very very fast.

Jerry
 
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