450 Bushmaster Head spacing ?

I have my barrel from apache and all the tools I need to change my barrel on the way. I am working with a 110 action SF , I have owned the rifle for sometime.

My question is about the head spacing of this caliber seems to have some issues from all the post I have read in this forum. First, the 4D rental gauges may give .009 head spacing and they have two types, one works the other will not. So are they reliable and should I get standard or AR?
Second, If I did use them could I tighten the barrel till it touches the go gauge, then load a factory round and see if it will tighten more. I would assume if it tightened a small amount at all the gauge would not give me proper head space.


This will be my first barrel change and I just want make sure that I go about it correctly.

I'm not sure what you are talking about. Why would one guage work and one not? And what does go standard AR mean??It is simply a straight wall case, so things headspace of the case mouth, like most every auto pistol cartridge on the planet. Here is a similar thread that you may like.

http://www.savageshooters.com/showth...-factory-round

I have some concerns about your choice of donor rifles. I have done quite a few of the 450BM conversions and can tell you from experience the SF models do not work well. SF's will not feed the 450BM from the magazine. I suggest you try a center feed short action. Maybe sell what you have and get a SF SA with .308 bolt face. It will still require some magazine and feeding ramp tweaking, but I think you'll come out better off in the long run.

Thanks darkker, I have read that post and it is pretty straight forward, but I have read a few others that muddy waters for me. There was another on here I couldn't find again, but stating the gauges gave him .009 head spacing. I figured as you are that use the gauges and be done with it, but these other post gave me so doubts about that.


http://www.savageshooters.com/showth...450+bushmaster

I am no expert but .002-.003 seems where it should be. Just enough to prevent the brass from latching onto the rifling. But not too much as to allow for light strikes to the primer.

I think the early short mag actions with controlled feed would be the cats pajamas on a short straight walled cartridge.

Whether you are setting headspace for .308 .243 or, .223 or 450BM (it does not matter), I would expect the go gauge to give you a little more headspace than the actual factory ammo you are, ultimately, intending to use. If that wasn't the case, you would likely find some factory ammo that would not fit when closing the bolt. Headspace needs to be set neither too tight nor too loose. If you wanted, you could set it to match your customized ammo, but then it might be too tight for the next guy who is using factory ammo. Therefore, back to Darkker's point, if the go-gauge is wrong, don't use it. It's a bad gage. If it's right, don't mess with it. If you have read something here to the contrary, I would be suspect of it, no matter the source.

This reminds me of the 6.5 Grendel "multi throat/lead/chamber?" debacle.

Leave it to the "AR" guys to screw up 100 years of accepted firearms standardization. Since the "gauges" are the "holy grail" of setting headspace, "how can there be 2 of them for the same chambering"? And how can the firearms industry and patrons, like sheep, just follow along and accept this "dilution of excellence"?

I have been fighting off the urge to do a 450BM build. If I go through with it, I will only do so knowing I can acquire reload components, and or, factory loads. If I find 2 boxes of factory loads that I intend to use, I will measure all of them from the base to the case mouth, pull the bullet from the "longest" one, and set my headspace to it. This allows me to shoot what I have and likely whatever I get in the future.


Many will say that this could confuse a new builder, but I contend it is less confusing than "allowing" 2 standard chamber gauges to exist for the same chambering.

Rant Over...Thanks...Jim :-)


This stuff "can" be straightened out. You see how quick Savage was to drop the name "Edge".

Thanks for the help guys. I will rent the gauges and set the head space with them.