CORRECTING HEADSPACE WITH BELLM SHIMS
Stop misfires, case stretching, and poor accuracy due to excess headspace.
Use our shim system to correct or fine tune headspace with any factory ammo or new brass and to headspace correctly on the rim of rimmed cases
ust keep in mind that "Head" "Space" is exactly what the name says it is, the actual, true "space" between the case "head" and the breech face. You take two simple measurements to determine what it is.
Ideally, the headspace for best results should be close to zero without the case head touching the breechface.
Thus we recommend you aim for a headspace of .001," but anything in the .001" to .003" range is good.
Anything over .006" by industry/legal standards is "Excess Headspace" and should be corrected.
Unfortunately, you will find with various ammo, barrel, and frame combinations headspace over .015" with no remedy provided by either the gun or ammo manufacturer, leaving you to either correct the problem yourself (the easiest, most practical, smartest, and best way) or "dump" the gun or barrel and take a loss on it needlessly when it can easily be corrected by shimming the firing pin bushing forward. Headspace, How To Get It Right.... Must Read first!
Understanding what headspace is in the first place and what actually determines it is your first step in this very simple but much-confused subject area
Measuring Headspace, steps 1 & 2:
Measure the present barrel-to-frame gap using a common Feeler Gauge Set
Using the ammo or case you will be shooting, measure the actual location of the case head relative to the end of the barrel using our Bellm Headspace Dial indicator Base and your choice of dial indicator
If the case head is:
a) exactly flush with the end of the barrel, the headspace is equal to the barrel-to-frame gap measurement,
b) or if the case head sticks out of the barrel, the barrel-to-frame gap measurement MINUS how much the case sticks out of the barrel equals the headspace,
c) or, more likely, the case head will fall BELOW the end of the barrel, in which case the headspace is the the amount the case head falls below the end of the barrel PLUS the barrel-to-frame gap.
Determine how much the firing pin bushing needs to be moved forward
Let's say you are shooting a belted mag case and have .012" actual headspace. To get down to .001" headspace you need to move the firing pin bushing forward .011".
However, most barrel and frame combinations have a barrel-to-frame gap usually .005" or less.
Thus you must make room for the firing pin bushing to be moved forward.
Remove material from the end of the barrel.
To create clearance you can:
a) face off the end of the barrel in a lathe,
b) mill it off on a milling machine,
c) face it off on a belt sander,
d) or even just file it off with a hand file.
How much gap you leave is NOT important at all and has NO bearing on how good or bad the barrel is, just so long as you KNOW what the gap measures and it allows the barrel to completely clear the firing pin bushing when closing the barrel.
Meaning, once you have shimmed the firing pin bushing forward, you should be able to find a measureable gap of at least a couple thousandths between the end of the barrel and the firing pin bushing.
On the subject of barrel-to-frame gap, it can safely be up to about 1/8" of an inch.
While it may not be esthetically pleasing to the eye, once again, a gap substantially greater than required to clear the firing pin bushing has NO bearing on anything. For example, take the common Mauser rifle, the entire case head sticks out of the end of the barrel on average about .115" thousandths.
The counterbore in the end of a Rem. 700 bolt action rifle is .155" deep, OVER 1/8." Looking at the closed barrel and seeing brass is NOT a problem. EXCESS "SPACE" AT THE CASE "HEAD" IS A PROBLEM, and it is the space at the CASE HEAD we are concerned about, not daylight between the end of the barrel and the firing pin bushing.
nstall the required thickness of Bellm Encore Headspace Shims.
To do this, simply unscrew the socket head screw in front of the hammer, remove the screw, and push the firing pin bushing, firing pin, and firing pin return screw out the front of the breech face. Note that the firing pin return spring is cone shaped and its pointed end is oriented to the rear of the frame.
Shims must have a section cut out with scissors for the firing pin bushing to pass through.
In our example above where we need to move the firing pin bushing forward .011" to leave a .001" gap between the case head and firing pin bushing, we would install two .005" shims and one .001" shim in the recess for the firing pin bushing, then reinstall the firing pin/spring/bushing assembly.
We recommend you snug the screw down, fire the gun a few times, then retighten the screw as required.
NOTE: TOO LITTLE HEADSPACE CAN ALSO BE A PROBLEM AND CAN EASILY BE CORRECTED BY REMOVING MATERIAL FROM THE BACK SIDE OF THE FIRING PIN BUSHING, as an alternative to cutting the chamber deeper.
This would be due to the chamber being too shallow and is often indicated by not being able to cock the hammer with a round in the chamber, but being able to cock it with the barrel empty.
We have also found that the barrel hitting hard on the firing pin bushing can cause severe accuracy problems. Thus there should be some clearance. If everything else checks out ok, but accuracy is not acceptable, consider removing material from the end of the barrel to create some clearance between it and the firing pin bushing
We have corrected accuracy problems by just this simple fit adjustment.
You may also send your barrel to us to have it faced off to clear the firing pin bushing.
ALL sights and scope bases must be removed, or add $20 for us to do it for you. The barrel must be completely "slick" on top to fit in the spindle of the lathe. This is our preferred method. OR, if you prefer to leave the sights and/or scope base on, we can at no extra charge mill the end of the barrel instead. Blued barrels will be touched up with cold blue. Stainless barrels will be left as machined.
Neatly, precisely face off the end of the barrel, with shipping:
First barrel $50
Additional barrels in the same shipment $15 each.
As a standard practice on most all barrels I work on now, I take .010" off the end of the barrel for non-belted magnum chambers, .015" off of all the belted magnum chambers such as .300 Win. Mag, 7mm Rem. Mag. and others based on the H&H; case head. Sometimes as much as .020" is necessary to correct headspace. If this is the case with a given barrel, be sure to let me know, and I will remove .020."
Ship barrels ONLY (NO FRAME!) to:
-CALL FOR ADDRESS
Phone: (541) 956-6938
Call KURT BELLM to setup a work order for a complete system including sending in the frame and barrel for trigger job.
Complete guns will be billed on completion of work once final costs are determined, barrel will be sent to MIKE BELLM for facing off then returned for final install. There are many options available and costs will be determined on a case by case basis.
In summary, headspace is very easy to understand and correct following our procedures. Failure to keep headspace within a workable range is simply money down the drain!
There is no reason whatever to sell or otherwise get rid of a barrel that is not performing due to headspace issues.
The factory does not address the issue adequately in our experience and that of many others, nor do most "gunsmiths" who are not TC savvy.
We have found that when there is a headspace issue that must be corrected, you are pretty much on your own, and we are here with the solutions.
It IS what we do!
Don't fight it,
don't waste time and money sending back and forth to the factory,
don't take it to "my local gunsmith" who does not have the first clue what to do with these guns,
and don't take a loss on it!
Just Shim It! It is the only sensible thing to do.
The break-open guns are sensitive to headspace, both too little and too much. Sooner or later headspace will become an issue.
If you are not willing to take a few measurements and make the corrections yourself, quite candidly, you might as well sell the gun to someone who will.