Bumping Shoulder with Spark Plug Feeler Gage?

[Taxman1002587]

If I run the ram with the shell holder to the top, put a spark plug feeler gage (mine is just various strips of metal that fan out like a deck of cards) say the .006 gage on top of the shell holder and then turn a Redding body die down on to the feeler gage and lock the die - then resize a case - try it in the gun to see if it chambers - if not reset the die using ever smaller feeler gages (say .001 at a time) until the resized brass chambers smoothly - will this work by work I'm mean result in the least amount of shoulder bump necessary?

Thanks in advance for any insight?

 

[CanusLatransSnpr]

The best way to determine shoulder bump is to get your self a comparator body, that will attach to a "good calibrated" set of calipers, and a bump gauge comparator for whatever cartridge your shooting. Take several once fired pieces of brass, preferably with a near max load of whatever powder your using, and measure them with bump gauge comparator. The reason for the near max load is so the brass will be properly fireformed to your chamber. Take this measurement and then size a piece brass with Redding die and measure it with the comparator. From this you will know which way to go with your adjustment on your die. You only want to bump your shoulders .002" max. Also, check your brass for trim length! I have to trim brass after full length sizing! Good luck!

Mike

 

[watercam]

First of all you are looking for .001-.003" set back at most. It would be easier and more precise to screw the die down to touch the shell holder, back the die off a quarter turn or so. Blacken the shoulder of a fired case with a match, candle, kerosene flame, lip stick or the like. Size the case, check for contact, screw down a bit, size again until you have a solid contact with the shoulder. Then chamber with ejector removed and trigger pulled and see if you feel any resistance.
Truly, the best way is to spend $7 and buy the appropriate bump gauge from Sinclair International and actually measure the set back of a sized case when the die is fully hard against the shell holder. Then unscrew the die as needed. 7/8-14 threads on the die body equals .071" per revolution. 1/16 turn would then be .004" or so.

 

[BoydAllen]

Your fundamental error is that when you use feel to come up with your die setting, you make the assumption that the die is small enough to size the body of the case to the desired feel , as the bolt is closed, without setting the shoulder back excessively. If, for some reason, it is not, you can end up with excessive shoulder bump by the time that you get the feel that you are looking for. For that reason, it is better to have some sort of bump gage, to use with your dial or digital caliper, so that you can accurately compare the measurement of a case before and after sizing. If you do not get the feel that you are looking for at what ever you choose as your maximum bump, you will need a different die for that chamber. These tools are not expensive, and there can be no real argument against actually knowing how far you are bumping a case's shoulder. If someone protests that they have been doing it by feel and it has worked, and therefore no other method is needed, then what they are really saying is that their chambers and FL dies are properly matched or that they do not reload their cases enough times to see the effects of excessive shoulder bump. In any case, even though they have gotten away with the method, because their dies and chambers have a workable dimensional relation, does not guarantee that yours do. Knowing is better than guessing.

 

[Winchester69]

The method you are asking about is widely accepted and will result in the desired results. It's the same as using Redding's Competition Shellholder Set. Size until it chambers, and then lock 'er down. Much better than the "1/8 turn at a time" method that is so frequently recommended. Always use the same shell holder.

 

[CanusLatransSnpr]

+1 on Boyd Allen's comment! You stated the situation superbly!

Mike

 

[blawton]

Shoulder bump gauge is really what you need. I make them with the chamber reamers out of the waste material thats cut off a barrel blank. For a quick fix you can use a pistol case in the same way. Just place on the end and measure. You just need to make sure its good and square so you get a consistent measurement. I do this and start the die high and work my way down until i get around a .002 bump. I have played with bumping them different distances and .002 is usually the best but some of my rifles like more or less. I have noticed that on the larger magnums and improved magnums like more bump around .005. You dont want to bump them much more then that. The best thing to do is get the right tools so there is no question except what to try next. Using feeler gauges is not a accurate way of doing this. Good luck.

 

[jo191145]

Can't argue with Boyds assesment. Knowing is always better than quessing. The proper tools take the quesswork out of it.
I will say this though Taxman. Your described method is much better than the one size fits all directions most dies come with.
I've never had a sizing die that created snug bodys with correct headspace. Does'nt mean my next die purchase won't tho. Measuring is the only way to know.

It is possible to have webs stretched by heavy loads that cannot be sized down enough to chamber freely. Once again, As Boyd stated, theres only one way to know for sure.

 

[necchi]

Yes,
You have the right idea for measuring, at least you have a known measurement to work with. What the guy's are all explaining is "How" to find the right measurement.
You can do it the old fashion way and experiment,,I did the "smoke" method watercam explained and found I was too tight. I ended up working down to the .0015 feeler to set my die as you describe and it's fine.( I may try the .0025 for a few rounds) But the blade is not sqeezed tight,,it's set so I can just pull the feeler with "some" resistance,,my measurement may not work for you,,ya gotta find what's good for your gun
Mines just a factory hunting gun, tolerances are important, but there is only so much I can do,, super precise measurements aren't going to do me alot of good,,but I'll beat factory ammo everyday!

 

[1shot]

I use a combination of the techniques stated previously in this thread. When I set up a new sizing die, I put several die shims between the die lock ring and the top of the press, intentionally setting the die up .008 -.010 short. I take a measurement of a fired case using the stub cut from the muzzle end of a new bbl. of appropriate caliber after having run my reamer in deep enough to cut to the full shoulder dimension. If I use the same reamer that was used to cut the chamber, I have a gage that is identical to the chamber. I then size the case, and try to chamber it using the bolt body only. (Firing pin assembly removed). I then start removing the shims a couple thousands at a time until the case will just close in the chamber with finger pressure on the bolt handle. If the bolt handle just falls to the closed position, you’re over sizing the brass. I then take another measurement of the now properly sized case with the gage and record it. This method has served me well for years, but a fired pistol case with the primer removed will work well in a pinch as stated above.
I hope this helps,
Lloyd

 

[tenring]

I tried the Harrell's "thingy", had another made by a gunsmith, and found them difficult to repeat accurately. Bought the Hornady tool, same result. Last year, I ordered two Redding Instant indicators with dials for my competition calibers. These are extremely easy to operate and read bump. You can check bump to .001", as your sizer is slowly lowered. Very quickly and accurately.

 

[blawton]

If you get one made from the chamber reamer used in your barrel they will repeat well below .001".