Problem reloading for Argentine Mauser w/ generous bore

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Mr. Farknocker

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I need some advice on how to approach a problem that I have encountered while reloading for my 7.65x53mm Argentine Mauser.

The bore of my rifle slugged at a fairly large 0.3175' so I casted a few bullets using the Lee C324-175-1R (8mm Mauser) and sized them down to 0.319". Using the Lee die set, I then made a handful of brass cases with Winchester 270 brass. The shoulder length of the Lee dies are known to be too long for the Argentine Mauser (as opposed to Belgian) but I was able to push the shoulder back sufficiently by sliding a .013" feeler gauge under the rim while resizing the case. The bolt closed with only light resistance after the brass was resized using the gauge. I then made a dummy round by seating a resized bullet in an empty case. When I attempted to chamber the round, I could not close the bolt on the round. I made several attempts using several other rounds I made in the same manner and had the results.

I then resized the bullets to .314 and seated them in the cases. Unlike the first set of test rounds I made, I was able to chamber the round and close the bolt.

I measured the OD of the neck for the cases I loaded using the .319 resized bullets that wouldn't chamber and they measured .347".

mMUm5b.jpg

I then measured the OD of the case necks for the rounds I loaded using the .314 resized bullets and they measured .345"

oVm9e6.jpg

I then looked up the case dimensions for the round and found this graph:

vrivwS.png

The specs show that the maximum neck diameter is 8.78 mm or .3456" and explains why the round with a neck diameter of .345 chambered while the one that measured .347' did not.

Apparently, the bullet sized optimally to .319" (based on a bore diameter of .3175") expands the case too much while a bullet undersized to .314" doesn't.

Under the circumstances, it seems to me that I have a few options, none of which looks appealing to me:

1. Shoot undersized bullets and hope for the best accuracy one could achieve under the circumstances;

2. Have the chamber reamed to allow for the increase in the neck using a .319 bulle with no guaranty that the accuracy of the rounds will be any better than option 1; or

3. Have the barrel relined so that the bore diameter is line with specs and allows for the use of .313 rounds as recommended.

The first option appears to be a no-brainer as it costs me nothing to try and if it ends up shooting well -- end of story. However, if it doesn't, what would you recommend that I do?
 
You could get some jacketed bullets to try and see if they shoot any better than the lead ones if those smaller lead ones do not pan out. The jacketed bullets do not usually require as tight a bore fit for fair accuracy and no fouling. Still the smaller sized lead bullets might even shoot well so that would be my first try. I might even get a LEE sizer die that is half way between those two---or get another one of the smaller sized one and slowly open up the hole and try the bullets to see how big you can go before things get tight.
 
Turning the cases may be your best bet ,before you drill out your mold you may want to powder coat and not size your boolits to find the size that works ,that's what worked for me in my 1891(made in 1893)7.65 x 53 that slugs @ .314 . The .311's with fat P.C. work for me. I have to turn cases for my 300bk. as it has a tight chamber with cast boolits.

CC
 
Wouldn't it be cheaper to simply buy new brass (I'm assuming the neck turning is necessitated by forming the brass from .270)?
 
cp1969 nailed it. If your bullet fit is fine, but your loaded cartridge case neck OD is too high, the root cause is the thickness of the case neck. Turning the case necks should fix the problem!

Have you thought about doing a cast of your chamber? You could use something like Cerrosafe to create a cast of your chamber and then measure the neck portion as this will tell you exactly how much to turn your necks down to.

Link: https://www.brownells.com/gunsmith-.../cerrosafe-chamber-casting-alloy-prod384.aspx
 
I bought one box of Norma then I found out that they could be made from .270 cases for next to nothing, now I have hundreds :) for a little more than the price of Norma 's you can get the tool and range pick up your brass .

CC
 
I bored the chamber neck of an original Remington Hepburn single shot in .40 - 2.5" Sharps Straight.

This rifle had an original paper patch chamber. When brass was turned to fit the chamber with a .408 bullet the case neck walls were like foil only .003 thick. We could not seat a bullet without crushing the neck.

The chamber was dialed to dead nuts runout in using a 4 jaw chuck and the neck was bored .004 larger than a case made with a RWS 9.3X74R case.
The barrel was an excellent shooter when reinstalled.
 
I was told that if I formed 7,63mm Mauser pistol cases by trimming and sizing longer .223/5.56 rifle cases, I would have to ream the inside of the necks because the resized necks would be too thick for standard diameter bullets. Wouldn't reaming the inside of the necks after first resizing be easier than turning the outside of the neck or rechambering the barrel? Or am I missing something?
 
Mr. Farknocker said:
Wouldn't it be cheaper to simply buy new brass (I'm assuming the neck turning is necessitated by forming the brass from .270)?
Click to expand...

I ended up purchasing some PPU Brass because that seemed to be the cheapest route. Unfortunately once the oversized bullets were seated in the PPU Brass, the bullets expanded the necks to the point where they would no longer chamber. Looks like I'm left with either trying smaller bullets or neck turning.
 
I bought 5 boxes of Norma 7.65 x 53 back in the '80s. After reloading them numerous times, I started resizing .30-06 cases. They work fine. The necks are a little shorter than the factory brass but they cause no problems. I have RCBS dies and I use Hornady .312" bullets that I think are discontinued like all the other Hornady bullets I like.
 
An alternative route (especially if you are set up with a Wilson trimmer) to turning the outside of the necks would be to send off to Wilson and
have them make you an inside neck reamer.
Just another way to go at it.

JT
 
I have a couple of Wilson reamers and they work well. You'll need the trimmer and a case holder for best results.
 
You can ream the neck and turn the necks.
A reamer is not adjustable so you might have to buy several reamers to get the exact size required. Neck turni g tools are adjustable so you can cut the brass to the thickness you want by a simple adjustment. But turning and reaming have to be done to every case.
Opening up the chamber neck is a one time operation.
In the case of the .40-70 2.5 inch sharps chamber the case necks were only .003 thick when turned to fit. The case necks were like foil. The cases were too thin to load or shoot so there was no choice but to open up the chamber neck.

Carl N. Brown said:
I was told that if I formed 7,63mm Mauser pistol cases by trimming and sizing longer .223/5.56 rifle cases, I would have to ream the inside of the necks because the resized necks would be too thick for standard diameter bullets. Wouldn't reaming the inside of the necks after first resizing be easier than turning the outside of the neck or rechambering the barrel? Or am I missing something?
Click to expand...
 
Mr. Farknocker said:
I need some advice on how to approach a problem that I have encountered while reloading for my 7.65x53mm Argentine Mauser.

The bore of my rifle slugged at a fairly large 0.3175' so I casted a few bullets using the Lee C324-175-1R (8mm Mauser) and sized them down to 0.319". Using the Lee die set, I then made a handful of brass cases with Winchester 270 brass. The shoulder length of the Lee dies are known to be too long for the Argentine Mauser (as opposed to Belgian) but I was able to push the shoulder back sufficiently by sliding a .013" feeler gauge under the rim while resizing the case. The bolt closed with only light resistance after the brass was resized using the gauge. I then made a dummy round by seating a resized bullet in an empty case. When I attempted to chamber the round, I could not close the bolt on the round. I made several attempts using several other rounds I made in the same manner and had the results.

I then resized the bullets to .314 and seated them in the cases. Unlike the first set of test rounds I made, I was able to chamber the round and close the bolt.

I measured the OD of the neck for the cases I loaded using the .319 resized bullets that wouldn't chamber and they measured .347".

View attachment 775013

I then measured the OD of the case necks for the rounds I loaded using the .314 resized bullets and they measured .345"

View attachment 775014

I then looked up the case dimensions for the round and found this graph:

View attachment 775015

The specs show that the maximum neck diameter is 8.78 mm or .3456" and explains why the round with a neck diameter of .345 chambered while the one that measured .347' did not.

Apparently, the bullet sized optimally to .319" (based on a bore diameter of .3175") expands the case too much while a bullet undersized to .314" doesn't.

Under the circumstances, it seems to me that I have a few options, none of which looks appealing to me:

1. Shoot undersized bullets and hope for the best accuracy one could achieve under the circumstances;

2. Have the chamber reamed to allow for the increase in the neck using a .319 bulle with no guaranty that the accuracy of the rounds will be any better than option 1; or

3. Have the barrel relined so that the bore diameter is line with specs and allows for the use of .313 rounds as recommended.

The first option appears to be a no-brainer as it costs me nothing to try and if it ends up shooting well -- end of story. However, if it doesn't, what would you recommend that I do?
Click to expand...

I reload for every rifle I have except that same Mauser as yours & 303 , I didn't know anyone else had such a rifle.
Not to your subject , but me & my wife tried to blue the barrel & it won't take blue, it won't even take any paint we
tried. It had a painted barrel to start with but it was scrappy.
It was left in a flood , the wood did better than the metal, the receiver blued good.
It looks solid , the barrel rifling is good.
Question, is it worth ever shooting, or even trying to dress it up ,I only have about 15 bullets for it.
 
I ended up springing for a K&M Neck Turner. I purchased the kit with the carbide cutter, steel pilot and expandiron for the .30. Neck thickness measured at .016 - 0.165 for the Argentine Brass and I turned the necks down to just a shade over 0.013. Test bullets were seated and the round chambered so it looks like my problem with the Argentine brass have been solved. I am now moving on to turning the .270 brass and will be making dummy rounds to see if the neck turning also resolves my problem.
 
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