Gunsmithing 300WSM Dimensional Discrepancies

[Bugholes]

Gents-
I have spent the morning wrestling with a 300WSM that I built and had came back to the shop, customer was having trouble closing the bolt on factory loads and new unfired brass. I like to keep the headspace on the minimum side when chambering, the bolt closed on my GO gauge before it was shipped. I began to think there was a issue with the gauge, so I sent the gauge in for inspection. The gauge was found to be 1.7249 (.0001" short, see print), irrelevant in my opinion. After some digging and talking with people who are alot smarter than I, this SAAMI print was found. Please have a look at the dimensional discrepancies between MAX cartridge headspace and MIN chamber headspace. FYI, this print seems to have been pulled (removed) from the SAAMI website...

 

[3oh8er]

Re: 300WSM Dimensional Discrepancies

As far as the new brass issue, I always size and trim new brass due to manufacturing tolerances, rough handling during shipping, etc. I have yet to find a piece of new brass that did not have to be resized/trimmed when checked with my case gauge, usually Wilson. As far as factory ammo goes, yes, some factory ammo can give resistance during bolt closing. I have found that Norma uses thick brass. Additionally, today at the range my son found that his new Rem 700 was fine with Federal factory but very tight with my reloads. I checked the ammo, he was most prudent in not firing the rifle, and found land marks on the bullet. These reloads functioned fine in my Savage 99, Ruger 77, and his SA M1A. so, the lead could be an issue for the rifle you built v. the projectile seating depth of the ammo used.

 

[LRI]

Re: 300WSM Dimensional Discrepancies

Greg,

Assuming its truly HS and not a seating depth issue:

If it were me I'd first attempt to duplicate the condition. Meaning I'd source identical ammunition that the cst is using. If the condition repeats then it answers the first question: Is it really goofy?

Next. If the gauge is a tenth out then as you stated, it's meaningless. If the gauge is to spec but it still has issues with the cst ammunition choice then I'd attempt to duplicate it with other brass/ammo.

If it's isolated to the cst chosen load then it may be best to have a conversation that encourages him to change brands.

If its indeed .004" as your print illustrates then I'd almost be inclined to leave it as all it does is emulate the "pinch" at the neck/shoulder junction of an Ackley during the initial fire form. A bump with a die will certainly fix that. This is running on the assumption he's reloading. If not then . . .(skip next paragraph)

Just educate your guy that if he expects more than one/two reloads then he should ALWAYS size brass to the gun, not to SAAMI specification. Meaning just enough shoulder bump to ensure reliable function. Especially with a WSM as its not really known as a cartridge that tolerates lots of reloads anyway due to pressures/performance/brass quality. This goes really for any cartridge that's reloaded to any HS depth. As many an AR service rifle shooter has discovered failure to do so will often result in a case splitting after the 3rd/4th resize.

If he's a box ammo only kind of guy then I'd just kiss the chamber till it allows the bolt to drop.




Hope this helps and good luck,

C.

 

[Bugholes]

Re: 300WSM Dimensional Discrepancies

my issue is known to be a headspace issue, customer sent several brands of factory ammo along with the rifle and all were problematic. MY problem is solved, the purpose of this post is to notify others of a potential pitfall, and to consider actual SAAMI dimensions versus real world circumstances

 

[3oh8er]

Re: 300WSM Dimensional Discrepancies

Thanks for the update. Could save us all from some hand wringing!

 

[Burleyboy]

Re: 300WSM Dimensional Discrepancies

My new custom 300 wsm has had some chambering issues. I tried to use brass that had been fired in another rifle and then full length resized and used in this one. The bolt wouldn't quite close. If I start with new Norma brass it chambers fine and then I bump the shoulder back and get a few more loads out of it. I need to try a factory load if I can find someone who has one.

Bb

 

[turbo54]

Re: 300WSM Dimensional Discrepancies

Thanks for the update/solution/advice bugholes.

Burleyboy: it's rather common for fired/FLS'd brass to NOT fit custom rifles, which tend to have SAAMI minimum, or perhaps even SAAMI non-compliant chambers.

A small base die will usually make it go.