Pressure question ?

TX Hunter · August 16, 2011, 12:41 PM

I am loading 39 grains of IMR 4895 and firing a 147 grain boat tail full metal jacket bullet for my 1916 Spanish Mauser 7.62 with 20 inch barrel. Im using .308 brass. The recoil is mild and the accuracy is good, but i want to know the pressure of this load as i am trying to be safe with this old rifle.

Jim Watson · August 16, 2011, 12:56 PM

I don't think there is any reasonable way to know the chamber pressure of a load picked out of the air or off the internet, or even out of most manuals.

But to get you in the ballpark, that is a full grain BELOW the Lyman STARTING load for a 150 JSP at 32,000 CUP.

So I am betting you are well below the pressure of the 7mm the gun was originally built for and have a safety margin even with Spanish gunsmithing.

TX Hunter · August 16, 2011, 01:21 PM

Thats what i was trying for, the Cases look great after firing also.

**Unclenick** · August 16, 2011, 02:15 PM

I thought the Spanish conversions had 21" barrels, but my memory plays tricks on me now and again.

QuickLOAD thinks you'll have about 31,800 psi with a large case like a Winchester and about 35,700 psi with a tight case like an IMI. This is with mild primers and the bullet seated one caliber into the case neck. With a 20" barrel, it estimates 2325 and 2400 fps for those pressures, respectively. With all the variations in bores and chambers it could be a good bit different. Actual measured velocities would make a better estimate possible.

The same program suggests about 37 grains of IMR 3031 would fill the case just as well or better and would give you maybe just 500 psi more pressures, but, being faster, would burn more cleanly and completely and would get you another 50 fps or so of velocity.

TX Hunter · August 16, 2011, 03:00 PM

i think your right about 21 inch barrel. If this is a Safe load im happy with it. I would like to load a 150 grain soft point in it also for short range hunting as well. Will probably use the same 39 grain powder charge with a 150 grain Round nose. Thanks for the help guys. PS I forgot to mention that i am using CCI standard large rifle primers.

August 16, 2011, 12:41 PM	#1
TX Hunter Senior Member Join Date: February 11, 2010 Location: East Texas USA Posts: 1,805	Pressure question ? I am loading 39 grains of IMR 4895 and firing a 147 grain boat tail full metal jacket bullet for my 1916 Spanish Mauser 7.62 with 20 inch barrel. Im using .308 brass. The recoil is mild and the accuracy is good, but i want to know the pressure of this load as i am trying to be safe with this old rifle.

August 16, 2011, 01:21 PM	#3
TX Hunter Senior Member Join Date: February 11, 2010 Location: East Texas USA Posts: 1,805	thanks Thats what i was trying for, the Cases look great after firing also.

August 16, 2011, 02:15 PM	#4
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,057	I thought the Spanish conversions had 21" barrels, but my memory plays tricks on me now and again. QuickLOAD thinks you'll have about 31,800 psi with a large case like a Winchester and about 35,700 psi with a tight case like an IMI. This is with mild primers and the bullet seated one caliber into the case neck. With a 20" barrel, it estimates 2325 and 2400 fps for those pressures, respectively. With all the variations in bores and chambers it could be a good bit different. Actual measured velocities would make a better estimate possible. The same program suggests about 37 grains of IMR 3031 would fill the case just as well or better and would give you maybe just 500 psi more pressures, but, being faster, would burn more cleanly and completely and would get you another 50 fps or so of velocity. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; August 16, 2011 at 02:54 PM.

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August 16, 2011, 12:56 PM	#2
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,532	I don't think there is any reasonable way to know the chamber pressure of a load picked out of the air or off the internet, or even out of most manuals. But to get you in the ballpark, that is a full grain BELOW the Lyman STARTING load for a 150 JSP at 32,000 CUP. So I am betting you are well below the pressure of the 7mm the gun was originally built for and have a safety margin even with Spanish gunsmithing.

August 16, 2011, 03:00 PM	#5
TX Hunter Senior Member Join Date: February 11, 2010 Location: East Texas USA Posts: 1,805	i think your right about 21 inch barrel. If this is a Safe load im happy with it. I would like to load a 150 grain soft point in it also for short range hunting as well. Will probably use the same 39 grain powder charge with a 150 grain Round nose. Thanks for the help guys. PS I forgot to mention that i am using CCI standard large rifle primers.