Chilean Modelo 1912-61 rifle and Carbine Chambers

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Rapidrob
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Chilean Modelo 1912-61 rifle and Carbine Chambers

#1 Post by Rapidrob » Fri Jul 14, 2017 8:10 pm

I have a few of these rifles/carbines and have noticed the fired brass is larger than normal when fired. Not,dangerous nor hour-glass shaped,just larger than any US fired brass I have seen.
The Israeli chambers are very tight.
The model of these converted rifles are 1912,converted in 1961. The Chilean climate is close to ours here in the US. I have been there several times in the Navy.
I'm wondering if they increased the chamber size to allow a slightly lower operating pressure when the rifles were fired? Increase volume, lower chamber pressure.
I'm going to be shooting with one of my clubs members this Sunday and he will have his 1912-61 rifles as well. I will check his fired brass and see if his brass is also oversized as well.
Yes,I realize they are military chambers and some can be a little large,especially the MG's. I'm thinking these modified rifles were originally in 7x57 Mauser. A cartridge with less chamber pressure. The 7.62x51 NATO is a much "hotter" cartridge with a higher chamber pressure and Proof load.
If the Chileans did increase the volume of the chamber a little,it would lower the max chamber pressure. How much is anyone's calculations?
The quality of the conversions are first rate,not a rush job done by the apes at Century Arms. The rifles I have in my collection are all well thought out and the conversion executed with great care.
I did an article on the converted rifles years ago going into great detail on the two types of conversions to the rifles and K-type conversions of their barrels.
I'm more interested in these rifles chambers,not how their were made.
Thanks.
Tin Can Sailor
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President New Mexico Military Surplus Rifle Pistol Shooters

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Re: Chilean Modelo 1912-61 rifle and Carbine Chambers

#2 Post by Rapidrob » Sun Jul 16, 2017 7:27 pm

OK, here are the results. An unfired round and cases fired out of my rifle and Jorge rifle.
Unfired- base .468
One inch up from base .458
My rifle- Base- .474
One inch up from base - .467

Jorge;s rifle
Base-.472
One inch up from base- .467
Tin Can Sailor
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Re: Chilean Modelo 1912-61 rifle and Carbine Chambers

#3 Post by LEP » Fri Jul 21, 2017 10:23 am

Haven't checked mine, but possible it's a typical, loose, military chamber?

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Re: Chilean Modelo 1912-61 rifle and Carbine Chambers

#4 Post by Rapidrob » Fri Jul 21, 2017 6:16 pm

I'm sure they are,but it is just a military chamber,or was it done to control max pressure?
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Re: Chilean Modelo 1912-61 rifle and Carbine Chambers

#5 Post by LEP » Sat Jul 22, 2017 11:13 am

Pressure control for the 1895 conversions would make sense. M1912, Hmmmm.....?

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Re: Chilean Modelo 1912-61 rifle and Carbine Chambers

#6 Post by LEP » Sat Jul 22, 2017 11:14 am

Pressure control for the 1895 conversions would make sense. For M1912 conversions, Hmmmm.....?

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