Tight throat


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stubbicatt
December 8, 2012, 09:49 AM
Sorry if I don't articulate my concerns here very well, but my concerns are still sort of half baked anyways, just mulling this over.

I purchased an old (nearly as old as me!) Mannlicher Schoenaur rifle a few months back, as I always wanted one, and there it was in 243, a caliber I also wanted. The rifle has been a learning curve in many ways, but I really like it and feel lucky that I found one after all these years.

Have shot 40 rounds through it, 20 of the Winchester 100 grain bullets, 20 Federal 80 grain loads. Shot amazingly well with the factory stuff, so being a handloader I have been laying in supplies to load with.

Generally when I start to load for a firearm, I try to find the stand off distance from the lands and grooves by taking a fired case, pinching the case mouth with a needle nosed pliars, hand seating a bullet, and chambering and removing this dummy cartridge, and measuring with a comparator to find the point of engagement.

I did this with a Winchester case, fired in the rifle, and all is swell. So one day I'm futzing about and I take a Federal case fired in this rifle, and the fired neck was so tight that the bullet was somewhat difficult to hand seat in that neck. This freaked me out, as the 243 is a relatively high pressure cartridge, this is a really tight neck, and so I began to look for other pressure signs on the Federal spent cases, and then compared them to the WW cases.

Other than the tight neck, I found no other signs of high pressure on the Federal cases, but the WW had significant swelling at the fire ring, and a slightly cratered primer. One or two had signs of gas leaks around the primers as well, and this was factory ammunition!

The Fed cases weighed more empty than do the WW cases.

I don't think I will attempt to reload the Federal cases. Anybody here have suggestions or input? I think maybe I see an issue where there is none, but I wonder whether I should have a gunsmith maybe re-ream this chamber to open that neck a little bit more. I suppose the easy thing is to avoid Federal altogether, which should be easy as I purchased 100 Lapua cases for the thing, though I haven't shot any of them nor seen how thick their necks are.

Again apologies if it seems like a rant, but the tight necks scare me, as I have always read that the neck should expand sufficiently to completely release the bullet, and I guess I wonder if I should be scared. I mean a day may come where, as I have done before since I am an old duffer now, I forget my ammo at home when going on a hunt and have to buy factory ammo, and I would worry about shooting said ammo in this rifle.

Thanks in advance.

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Walkalong
December 8, 2012, 10:21 AM
Do a chamber cast. Then will will know the diameter of the neck of the chamber. This way you can be absolutely sure of the loaded rounds ability to expand enough to release the bullet.

In my .262 neck 6 PPC, I loaded rounds from .261 to .2615, depending on the set of brass and bullet, but that is for a small set of meticulously prepped brass.

For your circumstance I would recommend a minimum .005 extra space. That would still only be .0025 on each side. This would take carefully measuring every case in a batch and every loaded round to ensure safety.

The good news is with a tight neck and thick brass you can turn the necks to be more uniform and not have excessive clearance, which defeats the purpose of turning necks.

thump_rrr
December 8, 2012, 10:22 AM
How much did the inside of the neck of the Federal case expand over bullet diameter after firing?
That will tell you if the bullet will release.
Also check if the case is longer than maximum allowable length.
I've seen factory ammo have brass that was on the longish side.

tightgroup tiger
December 8, 2012, 10:38 AM
So one day I'm futzing about and I take a Federal case fired in this rifle, and the fired neck was so tight that the bullet was somewhat difficult to hand seat in that neck. /

Are you talking about before or after you resized the case?

When you shoot these are they sticking going into battery? or being ejected?

Are speaking of as fired factory loads or have you reloaded the Federals, then found this?

And if you have already reloaded these and then discovered this, are you trimming your cases?


Something else, If you have reloaded these several times they may be work hardening and the necks are loosing their elasticity. That would be normal.

I think I would take the gun to a trusted gun smith and if the headspacing and chamber dimensions are good, then you will be able to sleep at night. If the gun checks out, I would look harder at the way I'm loading for this particular rifle.
You may find the same issues with the Lapua brass and discovered you just payed a fortune for it when you didn't need to. Then again, the gun smith may find a problem that the former owner didn't know he had.

There is only one way to find out.

stubbicatt
December 8, 2012, 09:35 PM
How much did the inside of the neck of the Federal case expand over bullet diameter after firing?
That will tell you if the bullet will release.
Also check if the case is longer than maximum allowable length.
I've seen factory ammo have brass that was on the longish side.
This is on once fired, factory loaded, store bought, cartridge brass. I cannot finger seat a bullet in the necks of the fired Federal brass. The WW opens up so that a bullet freely passes through.

I loaded up a half dozen Lapua cases with the bullets .015" from the lands as measured with a comparator in half grain increments starting down from max load to gage pressure. The necks with a bullet seated gage at .273" on brand new, unfired, Lapua brass. The fired Federal and Winchester brass both measure .277" So there appears to be .005" of room for the necks on this Lapua brass to expand.

Fed fired brass measures 2.036" in length. WW brass 2.040" long. This is one piece of brass each, they are fairly representative of the amount of bullet room in the as fired neck, so I feel comfortable concluding that the Federal "tight" necks are not due to excessive length. The Fed with the tight necks is shorter than the WW which opens enough to allow a bullet to pass freely.

I am concluding for now that the Fed just has really thick brass necks, and I won't buy any more of that brass. If I buy factory ammunition, it will be something other than Federal.

The COAL of the handloads is 2.697" in length, and these do fit readily in the magazine. I am excited to get load development underway. Since IMR 4350 is considered the powder of choice for this cartridge, I have settled on this powder to begin with. I will likely attempt a ball powder of some sort, as even with the Harrell powder measure the variance in powder charges is pretty significant.

Oh well, fun fun fun!

243winxb
December 9, 2012, 12:09 AM
Maximum neck diameter of a loaded round is .276" http://www.saami.org/PubResources/CC_Drawings/Rifle/243%20Winchester.pdf

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