I have a particular 338 WM, new this year, producing some once-fired cases that hold 87.8 to 88 grains of water. (measured without primers, using masking tape on primer pocket).
The 338 WM is typically rated at 86 grains of water and some new WW cases hold 85-85.6.
Also, the area immediately in front of the belt of the once fired cases mics at .5156-.5164" after firing, which is big in my opinion.
Current 'new' WW cases mic .508, while the SAAMI spec at that point is .513.

So is a chamber that produces once-fired cases with 87.8--88 grains water capacity, and .516" diameter on the body shaft at the belt, too large?

Should I consider sending it back to its factory/importer, or just load for it as a 'wildcat', with a slightly larger capacity than 338WM?

Fortunately, the chamber is fairly concentric and the once-fired cases give variance like .5156-.5163 or .5157-.5164 for a case. Rifle seems accurate, sub-MOA capable, though we're still in the load development stage and yet to reach 100 rounds.

It's easy enough to limit this gun to neck-sizing and special loads that may use 2-3 of grains of powder more than expected or than my other 338s.

In confirmation of the above, most of the loads with various bullet weights chronograph about 100 fps slower than expected and slower than other 338s I own. This would seem to support the idea that the chamber is a bit larger than typical.

So any advice, opinion?

I would just shoot it.

quote:

Originally posted by 416Tanzan:
So is a chamber that produces once-fired cases with 87.8--88 grains water capacity, and .516" diameter on the body shaft at the belt, too large?

You ever watch a kid being born? As long as the brass isn't tearing and gas isn't escaping you should be fine. Actually that's fairly typical of what passes through the manufacturers doors these days.

quote:

Originally posted by 416Tanzan:
In confirmation of the above, most of the loads with various bullet weights chronograph about 100 fps slower than expected and slower than other 338s I own. This would seem to support the idea that the chamber is a bit larger than typical.

Good news, there's more room for more powder. Seriously, if it were mine, and the brass looked good otherwise, I would neck size and shoot it.

So, is there a chance the brass is thicker, thinner in various locations along the length? accounting for the variation in water weight? Any signs of excessive pressure? Difficulty opening the bolt-assuming a bolt action?
As butchlambert replied, just shoot as it is, a .338 WM. I feel you will be just fine.

Stephen

It's not a brass, issue, this is the same for Nosler brass and Winchester brass.
And cartridges slide out slick as going in.
No high pressure signs.
But the cases measure .5164" at the beginning of the body just past the belt. A nice bulge that can be felt with the fingernail.

And I will continue shooting as is for the time being, but wonder if it out of spec to the point that a company should replace?

quote:

But the cases measure .5164" at the beginning of the body just past the belt. A nice bulge that can be felt with the fingernail.

You say you have a nice factory rifle that shoots submoa. As to out of spec not sure you have the right numbers. The case will have a spec range the chamber will as well. If you have brass on the small side and chamber at the larger side you will get a bulge. Sorry but I don't have the exact numbers. It won't hurt a thing.

If you are going to try for a rebarrel sooner vs later. However if I had a factory rifle that shoots submoa the last thing I would do is try and have them stick a new barrel on it. So the next one is in perfect spec no bulge and shoots 2" groups. You are talking about putting a lot at risk with NO POTENTIAL GAIN.

In a physical world, man producing man-made products there is no such thing as "perfect". Well (+,-)! If it shoots keep o shooting it.

Do spend your time worrying about "perfect" just shoot more.

I just checked my figures and it was 1.8-2.5 grains of extra R17 powder needed to match the slower rifle to another 338 of mine, depending on the day.
One example, the 'bulged' chamber used 70.8 R17 with 225 TTSX for 2805fps average and .75" at 100 yards. With a 160 TTSX and 76 it produced 3135 but .8" group and at 78.6 grains R17 it clocked 3275 with 1.1" inch. Needs more testing, of course. Maybe a little more powder.

I just need to keep bullets loaded for one 338 separate from the other 338. Maybe I'll keep one using Winchester cases only and the other using Nosler cases only.

I suspect all you all are right. If it's bulged but not broke, don't fix it. For the record, we're talking about a Tikka. Good gun for the money.

I have real concerns with upping loads to match other rifle velocities or trying to reach book velocity. As an example 70.8gr os RL17 behind a 225TTSX is going to be around 5+grs above a book max. Alliant doesn't list a charge for the TTSX but does for the Speer 225bt of 67.4. Looking at some other data I have TTSX bullet max is often 2+ grs lower than a lead base bullet.

Looking at the Barnes site they don't list RL17 for the 225 but using their max load for IMR 4350 QL claculates 2809 vs their 2753 with a pressure of 62668. Not exact but in the ballpark. Using RL17 and adjusting the load to give equal pressure as the max 4350 load I get a load of 65.8 being max.

Yes these are calculations every gun is different but in my opinion going 7-8% above book max trying to simply match a velocity from another rifle or load manual is asking for trouble. You bulge might simply be PRESSURE.

Just my opinion. That an $$ will buy you a cup of coffee.

It's not pressure. The buldge occurs at starting loads, too.

I appreciate your concerns, I've been slowly testing up the scale. I use outside expectations to limit the max if no pressure signs show up along the way. QL isn't quite stable yet on R-17. It also helps to check to older reload books.

quote:

Originally posted by 416Tanzan:
It's not pressure. The buldge occurs at starting loads, too.

I appreciate your concerns, I've been slowly testing up the scale. I use outside expectations to limit the max if no pressure signs show up along the way. QL isn't quite stable yet on R-17. It also helps to check to older reload books.

Is your chamber oversized or is your brass undersized?

I had the same "bulge" W/WW brass in an 8mm-06 Ackley Improved.

W/Norma brass, that was right spang on the .473" head diameter spec, I had no bulge.

The WW brass was about .003" smaller than spec so in that case it was a brass issue, not a chamber issue.

well, the bulge is in WW and Nosler cases.
The lower velocity in both new and necksized loads also supports the chamber view.

quote:

I use outside expectations to limit the max if no pressure signs show up along the way. QL isn't quite stable yet on R-17.

quote:

I appreciate your concerns, I've been slowly testing up the scale. I use outside expectations to limit the max if no pressure signs show up along the way. QL isn't quite stable yet on R-17. It also helps to check to older reload books.

Alliant calls max with the speer 225BTSP as 67.5 and 2831 QL calculates 2813 for the same load. That load looks pretty darn stable.

Maybe I misread you. I will go past a book max(specially a new manual) watching pressure. What I read was you were simply trying to match velocity.

As everyone has said you have an accurate rifle leave well enough alone work up loads for it and enjoy.

quote:

Alliant calls max with the speer 225BTSP as 67.5 and 2831 QL calculates 2813 for the same load. That load looks pretty darn stable.

Neither of my current 338s can dream or get close to 2831 with 67.5 of R17. My 'bulged' 338 uses 70.8 for 2805 and I'm happy to leave it there, though I will check out higher loads, cautiously next month to see if I can flatten a primer, etc, or decide to stop along the way. Everything slowly and carefully, grouped, repeated and chrono-ed.

My other 338 does 2800 with 69 grains R17, and is happy in hot climes. No stickiness, flat primers, craters, nada. Second 338 does .5143" above the belt.

Probably the barrel. None of them chrono exactly the same.
Butch