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I had a R700 re-barreled to .280 Ackley by one of the barrel manufacturers. Been doing load testing. Cases are measuring .4772 at the expansion ring just ahead of the web. Saami drawing show .4710 all dia. +.002. I have another .280 AI That measures .472 fired and is very easy full length sizeing. Case life is long. These cases take quite a bit more effort to size and I am worried the case life will suffer. Not what I expected and looking for opinions , expertise on the subject.

I'd be calling whoever barreled it to inform them that they owe me a barrel and the cost of a rebarrel.

Considering fired brass springs back .002" to .003" that chamber is worse than you think. This is why I never recommend letting a barrel maker chamber or fit anything. Most use cnc machines programmed to the low side on the threads so they will fit any receiver and the reamers are held rigidly so it's not uncommon for them to cut oversized chambers. Additionally if using cnc machines they use carbide reamers. Those are production grade meaning that when new they can be up to .002" oversized on the body to allow more resharpenings. If you want a carbide min spec you have to special order it. Then factor in the guy running the cnc has no actual gunsmith training and after 15 minutes of instruction he is expected to fit 4 or more barrels an hour or go back to his broom.

You are right about case life. Sizing that much I would expect the body to split at about 4 firings. If they don't make it right you can make it work. Neck sizing only will extend the life and you could hone a sizing die specifically for this chamber if it came down to it.

I remeasured with a dial Micrometer and they are running right at .477. My son in laws Fired cases measure .471 and My other .280 AI measures .4698-.470. That makes sense with spring back as you pointed out. So it seems to be over sized to me. They look a little pregnant, not good. I will call them tomorrow. To me if its that far off the Saami spec it should be taken care of. I will see what they say. I unfortunately did not figure this out until it was finished. I guess better than never. Shoots good groups but that is only part of the deal. Its a hunting rifle.

mw

I sent the barreled action back to the shop. Waiting for their response. I had hoped to get an idea what some of the gunsmiths and experts out there think Min and Max should be on chamber dimensions. I have had only two other rifles with what I considered oversize chambers. One .270 Win factory barreled and one 7mm08 chambered by a local Gunsmith. Both wore out brass fast usually a case lasted about three firings. This is with full length sizing for hunting. I know I can neck size and get more case life out a borderline chamber but would rather not for hunting. It seems like the SAAMI standard would be an absolute maximum. A couple of thousandths ought to be plenty of clearance for extraction and sizing. Thoughts?

If I produced a chamber which was over .471 (and I'm not saying I never have), I would assume I had done something wrong. When you consider that most brass is .467 or less, a 471 chamber is certainly plenty big. GD

The company contacted me. Agreed the chamber was out of spec. Micrometers are funny that way. They are replacing the barrel, new CeraKote job etc. No problem other than the inconvenience and delay of shooting this summer.

That sounds like good customer service, to me!

Would you share the company name with us? For those of us looking to have a rifle rebarreled it would be nice to know who they can depend on.

Ed

I have reamer prints for almost every chamber reamer I own. When I'm Chambering if the chamber does not come out the same size as the reamer I know I messed up. A reamer is a form tool, If your setup is not correct and you try to cut that chamber your going to get an oversized chamber, It might be concentric but it will be oversized. Lots of ways to mess it up and lots of ways to cut it right, but knowing the difference is the biggest battle.

E R Shaw

ER Shaw is good people.. Everyone screws up sometimes if they are trying hard enough...