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Headspace on older military weapons
robsguns
Member Posts: 4,581 ✭✭
I've long thought that its odd every gun I buy in a military version, seems to only pass headspace checks on the field guage. I know that the arguments on this will be diversified, but I thought this recent info. I came upon interesting, and for different reasons, I feel it may pertain to more than the Swedish Mauser. Read it and see what you think, and I'd appreciate your feedback. The pictures that should have accompanied this article will not be displayed, but thats irrelevant for the most part.6.5x55 Headspace GaugesMany owners of Swedish Mausers have dropped in American headspace gauges and been disappointed that it closed on a no-go gauge, erroneously thinking their rifle had excessive headspace. This isn't true. The simple fact is that Swedish Mausers were not chambered to American S.A.A.M.I. specifications. To top that off, there were at least two standards used inthe years the Swedish Mausers were in use (until the mid-1980's). My information comes from1948 ordnance orders specifying what the standard would be from then on. The followingbrief statements are direct translations from those 1948 ordnance orders.Bolt should close easily on gauge 3.20mm Rifle is reported if bolt closes on gauge 3.35mm Rifle is rejected if bolt closes on guage 3.45mm Rifles that have undergone major repair; the bolt should close on 3.20mm but not on 3.35mm On un-repaired rifles the bolt should close on 3.20mm but not on 3.45mm Rifles are re-barreled when headspace is over 46.80mm (3.45mm) The following is a comparison between Swedish regimental headspace gauges andcommercial American gauges. For an overview on the meaning and significance of headspace measurements see Cruffler.com.This is a set of Swedish regimental headspace gauges. The first number is the headspace length, the second number is the distance from the barrel breechto the bolt face.The sizes are:46.50mm, 3.15mm46.55mm, 3.20mm46.70mm, 3.35mm46.80mm, 3.45mmThis is a set of Forster commercial gauges:go = 1.7794"no-go = 1.785"field = 1.789"For comparative purposes only, the gauges were inserted into the breech of a new m/96 barrel and the projection measured with a dial caliper. This method proved to be accurate to under .002".Measured projections:Go = .119" 3.15mm = .123" No-go = .124" 3.20mm = .125" Field = .129" 3.35mm = .1335" 3.45mm = .135" What this means is that Swedish chambers are longer than American gauges can accurately gauge. Your rifle can fail the no-go test and be perfectly fine... by Swedish standards.I've heard many stories of rifles being handed over to gunsmiths to have the headspacere-qualified when there's nothing wrong with them. For those who do not handload there'slittle need to do anything other than shoot and enjoy. In 36 years of shooting and handloading the 6.5x55 I've not had a single problem with case life beyond normal and you probably won't either.
SSgt Ryan E. Roberts, USMC
SSgt Ryan E. Roberts, USMC