Different Rifles Have Different Chambers

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Alas, not all rifle chambers in the same chambering measure the same.
Alas, not all rifle chambers in the same chambering measure the same.

 

Q I am reloading for two people who have .243 Winchester rifles. One is a Ruger M77 with paddle stock and stainless barrel; the other is a Howa 1500 stainless. Both are new. I have a problem when I full length resize cases for the Ruger, that the bolt handle is very tight to close on 80 percent of the reloads. Oddly, when I neck-size only they slide easily into the chamber. But when I tried the full-length sized cases in the Howa they worked perfectly. Case length is within stats. The cases have been fired two or three times so are nearly new. I tried adjusting the Lee dies to see if that solved the problem. When I reload I generally stay about 1 to 1-1/2 grains below maximum. I have enclosed two cases for your inspection. One is neck-sized only and the other full-length sized. In the 15 years I've been reloading I have never struck this problem. It occurred to me that it may have something to do with the Ruger being a new rifle,the chamber may be tight and needed to be worn in. It has probably fired 200-250 rounds and doesn't seem to be getting any easier. I'm hoping you may have an explanation as to how I can solve this problem?

Les Brew

Springfield O3-A4 vintage sniper rifle. Image US Marine Corps
Springfield O3-A4 vintage sniper rifle. Image US Marine Corps

A You are reloading for two different rifles with different chambers which vary dimensionally. Consequently, headspace measurements can also vary quite a bit. It looks as if the chamber in the Ruger M77 is tighter than the chamber in the Howa. Normally, Cases that have been full-length resized should fit easily into both chambers, which makes me think that the Ruger May have a "short" chamber e.g is more tightly headspaced. You may be able to get around this by pre-loading your full-length die, screwing it down about 1/8th to 1/4 of a turn so that it pushes the case a bit farther into the die to shorten the headspace. I have had to do this with some rifles. By the way, chambers don't "wear in", but stay the same throughout the life of the barrel. The reason why neck-sized cases go easily into the M77's chamber is that they've previously been fireformed to fit that chamber and neck-sizing only affects the neck without altering the body of the case. In other words, they don’t affect the headspace measurement. I am sure you keep the different brands of cases separated and only load one brand for each rifle. Actually Winchester cases hold about 2 grains more powder than the Federal cases. I'd also trim them all to have a minimum length of 2.035" as the Winchester case you sent me is 2.045" and the Federal is 2.043", unless my dial caliper is wrong. Every rifle is a law unto itself, not only as to the loads they'll digest, but dimensionally too. that's why each rifle has to be treated as an individual when you are reloading ammo for them. Let me know if pre-loading the die works.

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