Hi all, I'm just getting into gun building and I'm wondering about proof loads. I've read in the British standards that they use one round of 30% over max pressure or when that is not availible, then a max load with 110% bullet weight. It would seem that 10% more bullet weight wouldn't give you 30% more pressure. Any thoughts here? I suppose I could get that quick load program to estimate a pressure.
Thoughts???

The US gov't proof round for the .30/06 Springfield rifles developed in the neighborhood of 75,000 PSI for a service load developing 50,000. I believe these were loaded with a non-canistered powder, and the advice given in the old days was "proof loads?? Don't try this at home"!!

Are you building your own actions that will require proofing, or just barreling actions that have already been proofed by someone? Trying to estimate how much of a pressure increase you will get by increasing the charge weight of some particular powder or by increasing the weight of a projectile with a fixed amount of some particular powder is a very dangerous practice. The reason for this is the posssiblity of pressure spikes when you reach the crossover point for a particular powder, since you probably don't know where this point is in the pressure increase curve. If you are building actions, you should acquire a pressure measuring system so you can work up a safe proof load from a standard load. If you are able to build an action, you surely have the skill to build a pressure gun. Rocky Gibbs made himself one for testing the Gibbs line of wildcat cartridges.

[ 06-15-2003, 18:32: Message edited by: eldeguello ]

SAAMI Specifications
The following list represents the maximum pressure levels (psi)
recommended for each cartridge by SAAMI (Sporting Arms and
Ammunition Institute).

Rifle
6mm Rem 65,000
7mm Mauser 51,000
7mm Rem Mag 61,000
7mm Wby Mag 65,000
7mm-08 Rem 61,000
7-30 Waters 45,000
7.62 x 39 45,000
8mm Mauser 35,000
8mm Rem Mag 65,000
22-250 Rem 65,000
222 Rem 50,000
223 Rem 55,000
243 Winchester 60,000
25-06 Rem 63,000
257 Rob 54,000
264 Win Mag 64,000
270 Win 65,000
280 Rem 60,000
284 Win 56,000
30 Carbine 40,000
30-06 Sprg 60,000
30-30 Win 42,000
300 Sav 47,000
300 Wby Mag 65,000
300 Win Mag 64,000
303 Brit 49,000
308 Win 62,000
32 Win Spl 42,000
338 Win Mag 64,000
35 Rem 33,500
375 H&H 62,000
416 Rem Mag 65,000
44 Rem Mag 36,000
444 Marlin 42,000
45-70 Govt 28,000

Handgun
380 Auto 21,500
25 Auto 25,000
9mm Luger 35,000
9mm Luger +P 38,500
32 S&W Long 15,000
38 Auto 26,500
38 S&W 14,500
38 Special 17,000
38 Special +P 18,500
38 Super Auto +P 36,500
357 Mag 35,000
357 Rem Max 40,000
40 S&W 35,000
41 Rem Mag 35,000
44 Rem Mag 36,000
44 S&W Spl 15,500
45 Auto 21,000
45 Auto +P 23,000
45 Colt 14,000

11 Mile Hill Road
Newtown, CT 06470-2359



Multiply Max Average Working pressure by
Cartridge Class

Minimum Proof Maximum Proof

Shotshell


1.55


1.70

Centerfire Rifle


1.30


1.40
Centerfire Pistol 15,000 psi or less 1.40 1.55

Centerfire Pistol 15,100 - 18,000 psi


1.35


1.50

Centerfire Pistol 18,100 - 21,000 psi


1.30


1.45

Centerfire Pistol 21,100 psi or greater


1.30


1.40

Rimfire


1.25


1.40

And I ask myself how those CZ52 surplus pistols got in the country without a proof test, and it is obvious, that no standard for pressure exists in the US for 7.62x25mm. But they should have been proofed with ~1.35X 42 k c.u.p.
That would have blown them up, and maybe the load books would not be saying that the CZ52 is stronger than the Tokarev.

[ 06-15-2003, 21:29: Message edited by: Clark ]

That SAAMI information is very misleading, because it is predicated upon the supposed strength of a particular action design, rather than the relative strength of a cartridge case, which is the weak link in the system. For example, are we to believe the 7X57mm Mauser case is so much stronger than the 8X57mm Mauser case that the former will safely stand 51K psi vs 35K psi for the 8mm? I think not!! The difference is because of the 8mm Gew. 88! Both of these cases, and the .257 Roberts, can be loaded as hot as the 6mm Remington, which is essentially the same brass, in guns of equal strength! I contend that ANY bottleneck HP rifle case of current manufacture in the Mauser 57mm/.308 Win./Springfield .30/'06 family can safely be loaded to the same pressure levels, if they are to be fired in rifles having actions and barrels of equal strength!! The same applies to a lot of other case designs as well. The determining factor is the strength of the brass, and this varies between manufacturers even within a given individual caliber.

[ 06-15-2003, 23:56: Message edited by: eldeguello ]

Makeing my own falling blocks from lumps of 4140. I've thought of building a pressure gun and useing a piezio strain gauge, it just hasn't come up on the list to do yet.

Also converting a double shotgun to 470NE and want to reproof it before final assembly and shooting next to my face.

Lar45,
Have you read the Meuller book?
http://www.realguns.com/books/review55.htm

That book has more information per page than most books have in the whole book.

I hadn't seen that one, but I'm ordering a copy today.
Thanks.

1894,

You might be surprised, most all of them I've tested with the Oehler 43 usually only show signs at over 70-72kpsi and usually takes two grains, sometimes only one, but someties three or more to drop back below 65kpsi... just depends. If you're running on the edge of hard extraction and seeing slight ejector marks... you're running about 70kpsi would be my edjucated guess. We ran some 6.5 WSM loads with 140gr smk's to 3400 fps and 75-81kpsi the other day with RL25, that's what a switch in lot# can do. They were running at 67kpsi with a grain more than that, as you can see, dropping back just one grain wsn't even close to enough when changing lot#'s!! After three rounds, it wasn't a fluke! They all got pulled apart at home and dropped down, they'll be worked up from way low this time.