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Rifle Magazine
December - January 2000
Volume 35, Number 6
ISSN: 0017-7393
Number 208
On the cover...
This issue is only available on CD-ROM.The Winchester Model 70 and Browning A-Bolt are chambered for the new .300 WSM. Purchase the CD-ROM here
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Forster Products Match Headspace Gauge Set

R.H. VanDenburg, Jr.

One of the older companies manufacturing equipment for the handloader and gunsmith is Forster Products of Lanark, Illinois. It is difficult to imagine anyone who has been at the game for any length of time not having several items on his bench with this venerable company’s mark on them.

This is in mind when I make up my short list of companies I must visit at each year’s SHOT Show. It was no different this year, and as I made my way to the Forster booth, there was Bob Ruch, Forster’s vice president of finance and point man for shows like this. Bob was quick to point out a few new items the company was introducing this year. I was equally as quick to request a sample for review.

One of the items that struck my fancy was its new Match Headspace Gauge Set. Normally, when we think of headspace gauges, we think of instruments or tools that measure the limits of cartridge case movement in a chamber once the action is closed. Each gauge is a piece of hardened steel shaped much like a cartridge case and turned to very precise dimensions. Each gauge is inserted into the chamber as measurements are determined.

In a rimless (or rebated rim) bottlenecked cartridge, this measurement is taken from the bolt (or breech) face to a datum line on the chamber shoulder. In a rimmed (or semi-rimmed) cartridge, it’s from the bolt (or breech) face to a shoulder cut into the chamber to stop the front of the rim from moving forward. Likewise, in a belted cartridge, the measurement is from the bolt (or breech) face to a shoulder cut into the chamber to stop the front of the belt. All specific headspace dimensions, and gauge dimensions, for factory cartridges are industry standards set by SAAMI.

Also, normally, headspace gauges come in sets of three: A GO gauge is the shortest. If the action will not close on this gauge when it is inserted into the chamber, the chamber is too short to reliably accept standardized factory ammunition. If the action will close, the chamber should accept all industry standard ammunition.

A NOGO gauge is the middle length. In theory, an action should not close on the gauge. If an action will close on the GO gauge and not on the NOGO gauge, the chamber is within ideal specs and should accept all factory ammunition. Some actions, however, will close on a NOGO gauge and further checking must be done.

A FIELD gauge is the longest. No action should ever close on a FIELD gauge. If one does the gun should not be fired until checked by a competent gunsmith. The theory here is simple. If the chamber is too long, the firing pin may slam the case forward resulting in no ignition, or poor or erratic ignition. The former means the gun won’t fire, the latter two   will guarantee poor accuracy when the gun does fire. Perhaps worse, the extractor may hold the case back against or near the bolt face, ensuring ignition, but the case will expand to fill a chamber that is too long, stretching and weakening the case. At best case life will be reduced. At worst, a case separation may occur at firing. The hot, pressurized gases will always follow the path of least resistance, and with a separated case that path may be back into the action, or the shooter. Serious damage to the gun or injury to the shooter or a bystander could result.

One of the things that attracted me to the Match Headspace Gauge Set is that each set consists of 11 different gauges. Being a match set, cartridge selection is limited to three choices: the .223 Remington (5.56 NATO), the .308 Winchester (7.62 NATO) and the .30-06. The .308 set is also correct for derivative cartridges such as the .243 Winchester, the 7mm-08 Remington and .358 Winchester. The .30-06 set will handle other cartridges as well: the .25-06 Remington, the .270 Winchester, the .35 Whelen and also the 6.5-06 and 8mm-06, according to Forster literature. I selected the .308 set for review.

Each of the 11 gauges was clearly marked and housed in a separate tube. The tubes, and an instruction sheet, resided in a well-made plastic container. The top was hinged and had two locking points. The instruction sheet was written for the three-gauge set and should be rewritten, but anyone getting this far would have no trouble understanding how to use the larger set.

For the .308 set, the minimum gauge, the GO gauge, measures 1.630 inches. Each gauge increases in length by .001 inch with the 11th measuring 1.640 inches. The NOGO gauge measures 1.634 inches; the FIELD gauge, 1.638 inches.

When I checked a .308 Winchester, I got exactly what one should. The action closed on the GO (1.630) gauge with no resistance. The action would not close on the NOGO (1.634) gauge. There was no need to go further for the chamber was cut as it should have been. Further review did determine that the action would close on a 1.633 gauge. I should have no problems with factory ammunition or handloads, assuming I do my part, nor have I.

A .243 Winchester, however, was another matter. This rifle was the real reason I chose this set as I’ve always felt there were things going on I didn’t quite understand. No problems, really, it’s just that this rifle has always behaved differently than others of the same make.

When the GO gauge was tried, the action closed without a hitch. It also did the same thing with the NOGO gauge (1.634) in place. Hmmm. Fortunately, the action would not close on the FIELD gauge (1.638). As I worked backward through the gauges, I was able to determine the action would close on the 1.635 gauge but not on the 1.636. If we assume the maximum desirable length is .001 inch less than the NOGO gauge, or 1.633 inches, then this chamber is between .002 and .003 inch too long. Or to put it another way, the rifle’s headspace is excessive by the same amount. Not bad, not dangerous, certainly, but well worth knowing.

As I thought back over the rifle’s history, I recalled that when I got it, 20 years or so earlier, only one locking lug mated with its recess in the receiver. It took quite a bit of lapping to get both lugs to seat evenly. Accuracy improved immediately. It may well be that the lapping is the cause for the now slightly excessive headspace. However, several thousand rounds have been sent down this barrel, and normal wear may have contributed. Anyway, the rifle is still accurate, and I’d just as soon leave it alone. Also, in all those rounds, almost exclusively handloads, I’ve never had a case failure. I’ve retired a few with loosening primer pockets and the odd split neck, but no separations of any kind. I attribute this good case life to being careful never to set the case shoulder back unless I mean to, and then only enough to ensure easy chambering.

In summing up, I learned something about two of my rifles. I wish I had a set for each rifle in the house, but I won’t, at least not a match set. Availability aside, the match sets come pretty dear. A standard Forster three-gauge set is quite reasonable at under $60. The 11-gauge set, on the other hand, will set you back a suggested retail price of $175. All is not lost, though. Gunsmiths need headspace gauges and builders of match rifles in the above calibers need these match sets. An enterprising shooter should be able to locate        a gunsmith with the appropriate gauges, or, barring that, might persuade his gunsmith to lay out the cash for a match set and help pay for it too by having his guns checked. Can’t hurt, and knowledge is a good thing.

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