Where can I find chamber pressure data for 7.62x54R?

[BHuij]

Hey all--

I've checked every reloading manual I can easily get my hands on (including the Lyman Cast Bullets 4th Ed.), and Googled pretty extensively. Everywhere I can find load data for 7.62x54R, it will give me velocities for min and max loads, but pressure info seems to be nonexistant.

I'm getting ready to start developing an accurate high velocity cast load for my Mosin, and want to find the optimal BHN and alloy to use for my bullets so I can push them up to at least 2500 FPS. Hard to do that if I don't even have a shot in the dark for chamber pressure information.

Does anyone know where I can find these figures?

Failing that, do you think using COWW alloy, heat treated to around the 22 BHN would be a decent starting point? I think with some dedication I could probably get my COWW alloy up to around 29 BHN, but that might be overkill for a 185 grain bullet...

[LAGS]

I shoot Lyman #2 or lino out of my Mosins, and have never had a leading issue with the loading data available.
But I think you are expecting too much hardness out of your COWW and heat treating.
I have switched to powder coated boolits, and can use softer lead without leading.
My accuracy goes south past 2000 to 2200 FPS with cast.
But if you want to try going to 2500 FPS with cast, then You better start with Lino , not some alloy that is Iffy being heat treated.
More consistency in the long run.

[17nut]

CIP data: https://www.google.com/url?sa=t&rct=...V-z7ncIadQboHi

Pmax. 3900bar

[BHuij]

So upper limits on the round are about 56k PSI, but is there a way for me to calculate the pressure given a specific load? No access to Quickload here unfortunately

[ShooterAZ]

Iv'e been working with the MN recently. The chosen alloy so far has been Lyman #2, WD. Best accuracy for me has been 1850-1950fps. You should easily be able to attain 2500fps, but to do so with any kind of accuracy is going to take a lot of work on your behalf.

[17nut]

So upper limits on the round are about 56k PSI, but is there a way for me to calculate the pressure given a specific load? No access to Quickload here unfortunately

In short: No!
Rely on published loads ans ask for QL calculations.

For that we need:
COL
Bullet used
Barrel length
Powder

From that we can supply a chart like this:

[Outpost75]

http://www.cip-bobp.org/homologation...idge_type_id=2
Name______Date_______Rev__________Country___TDCC__ ____Annexe__M___Ptmax__PK___PE___EE
7,62 x 54 R_1984-06-14__2014-05-20___USSR_____ FR EN DE__FR EN DE_25__3900___4485_4875_3960

M-location of transducer from breech
Ptmax - Maximum sample average pressure (Bar)
PK - Statistical maximum individual pressure (1.15xPmax)
PE - Mean Proof Pressure (Bar)(1.25xPmax)
EE - Proof Kinetic Energy (Joule)

3900 Bar = 56564.72 psi

[Larry Gibson]

I have actually measured the psi of 8 different milsurp 7.62x54R cartridges, 3 factory jacketed loads and numerous reloads both with jacketed and cast bullets. The psi's were measured via the Oehler m43 PBL and a Sako Finn M39.

As already pointed out the C.I.P. Pmax is 56,500 psi. The milsurp/factory psi's are under or close to (+/-) that Pmax. I have loaded ternary alloyed cast bullets up to 40,000 psi while maintaining accuracy equivalent to milsurp but at velocities in the 1800 to 2100 fps range. The best accuracy is going to be in the 1800 t0 1900 fps range with ternary cast bullets in the MN.

To be honest with you and to save you time, expense and aggravation I will tell you up front that a ternary cast bullet at 2500 fps out of a MN with it's 10" twist with any accuracy beyond 50 yards is pretty close to improbable if not impossible. However, with harder alloys reasonable loads can and have been developed with velocities into the 2300 - 2400 fps range. To do that requires an appropriate cast bullet design, the use of slow burning powders and a harder alloy. For the alloy I suggest researching those alloys that have Cu in them, are heat treated in ovens and are PC'd.

[BHuij]

How does one get a measurement of chamber pressure? I was under the impression you had to drill a hole in the chamber and plug it with copper to get CUP. Obviously I don't want to make any such permanent modifications to my rifle

I may just need to ask some of you good folks with QuickLoad to help me out.

At this stage I'm planning on using the Lee .312 185gr RN GC over IMR 4895, set to a COAL of 2.850"

Rifle is a 91/30, so 28 3/4" barrel length.

[Outpost75]

Conformal ballistic sensors measure true gun chamber pressure directly through the cartridge case. The diaphragm of the conformal sensor is contoured to match a specific chamber diameter. An alignment guide and spacers help the user to install the sensor flush with the gun chamber walls. The conformal ballistic sensor, when correctly installed, has a proven life expectancy of hundreds of thousands of rounds, outlasting many test barrels. Rapid-fire testing is possible since there are no cartridges to drill and align, no diaphragm ablatives to apply, and no gas passages to clean. The conformal sensor does not affect operation of the test barrel, nor change the measurement process. Developed in cooperation with members of SAAMI to provide an accurate rapid-fire electronic production test method to replace the mechanical “copper crusher,” the conformal sensor has experienced 20 years of proven performance.
Attachment 219388Attachment 219389Attachment 219390

[Outpost75]

Larry has given you great advice.

In my own Finn M39 and M28/30 I get very good accuracy to 300m, much better than milsurp ammo and equal to good Euro commercial softpoints using the NOE clone of #314299 cast of 50-50 wheelweights and linotype, sized .314" and lubed with 50-50 Alox-beexwax, and loaded in Norma cases with Federal 210 primers with 36 grs. of either IMR4064, RL15 or Varget, using a weighed 1.0 grain tuft of Dacron polyester fiber tucked loosely into the case neck before seating the bullet, to help occupy some of the frere airspace. Velocity is about 1850-2000 fps. depending upon barrel length and powder used.

When the PU scope on the M39 is caibrated to match the Sierra .311" diameter 174-grain Matchking at 300m with either 44 grains of Varget or 52 grs. of IMR4350, the cast load is then "on" at 100m. I use the 400m setting on the PU elevation drum for 200m and the 500m setting for 300m.

[Larry Gibson]

BHuij

How does one get a measurement of chamber pressure? I was under the impression you had to drill a hole in the chamber and plug it with copper to get CUP. Obviously I don't want to make any such permanent modifications to my rifle

The Oehler M43 PBL is a computerized program that measures the psi via strain gauge permanently affixed over the chamber. Comprehensive test by Dr. Oehler demonstrates very comparable psi readings to those taken by peizo-transducers. I affix the strain gauge over the SAAMI prescribed location for the transducer measurement. I also use reference type factory ammunition of known psi measurement to "calibrate" (actually nothing in the equipment is physically adjusted with reference ammunition. You just get an offset pressure measurement and adjust the measured readings accordingly. With most properly applied strain gauges used with the Oehler M43 I have found the measurements quite close [usually within test to test variation] so the offset is not used.

I may just need to ask some of you good folks with QuickLoad to help me out.

Quickload can be very close but it is only a "guestimate" based on the information inputted. Insufficient data or incorrect data can greatly alter the Guestimated psi. If you use that method then get as much of the requested data as you can and be precise in measuring it. Keep in mind there are some things that can cause pressure to vary that Quickload does not take into consideration.

At this stage I'm planning on using the Lee .312 185gr RN GC over IMR 4895, set to a COAL of 2.850" Rifle is a 91/30, so 28 3/4" barrel length.

That is an excellent bullet for the MN if the groove diameter isn't over .313. I suggest a 3/4 - 1 gr Dacron filler with that load for improved accuracy and internal ballistics. You might also try 28 to 31 gr with the Dacron filler. The velocity will be 1800 - 1980 fps depending on whether the Dacron filler is used and the powder charge used. The pressure will be from 22,000 psi to 27,000 psi +/-.

• Lee's "new" C312-185-1R

05-14-2016, 01:31 PM
Many years ago, back in the mid '70s I picked up a Lee C312-185-1R from a sporting good store going out of business in then Baker, Oregon. I recall paying $5.95 for the single cavity moulds, I also got my Lee C457-500-FN at the same time for the same price but that mould is another story for another time. The C312-185-1R served me well for many years using bullets cast from it in a Finn M91 and a M91/28 I had. I also used it in several M911 and M1909 7.65 Argentines that were going through my hands at the time and an occasional 7.7 jap and SMLE .303 that came along. It was a very good bullet in all but the occasional oversized 7.7 and .303s. In the Finn M91 (I subsequently traded for a pristine M91 Argentine) and M91/28 (Bring back from SEA war games) the Lee bullet excelled. I shot many a load with that bullet over 28 gr of various 4895s with a Dacron filler w/o much load development. When I picked up an Ishevsk M91/30 sniper and then the Finn M39 I also picked up a single cavity 311299 which also shot okay in both those but not well in the M91/28. Point is after you get used to 2, 4 and 6 cavity moulds using a single cavity is about like watching slugs race........I got a CBF group buy C314291 and it is a good mould. I also got a new Lyman 314299 and it does extremely well in the Finn M39 and M91/30 sniper. Still I longed for the old Lee 185 which ad done so well so while placing a Midway order a couple months ago I saw the double cavity C312-185-1R was in stock so I got one.

I really like the new design of Lee's double cavity moulds. The bottom now fits the slot in the Lyman Mag 20 mould guide perfectly. Wasn't long before I pulled the Lee mould out, disassembled it, deburred it, cleaned it thoroughly, lubed it and re-assembled it. While doing that a Mag20 pot of #2 alloy was "brewing". I cast up a bunch and WQ'd them. Using the mould was a dream, I encountered no problems what so ever. The bullets dropped out in excellent condition 2 after 2 after 2 after...........First thing I noticed while doing a visual cull was the new bullet was different than the original. The original had a long GC shank and a shorter nose with longer bearing surface. You can see that on the old cull original C312-185-1R which is the top bullet in the photo. I was somewhat concerned the new bullet wouldn't shoot well. I shouldn't have been concerned. I could find no dimensional difference between bullets out of either cavity nor was there any weight discrepancy. For practical purposes the bullets from each cavity were identical........doesn't get any better than that.
Attachment 219401

Still not being certain about the performance of the "new" C312-185-1Rs I did not weight sort the bullets as I had never weight sorted the "original's" either. I loaded 4 test strings over 28 - 31 gr milsurp IMR4895 with a 3/4 gr Dacron filler. Testing in the Finn M39 with the Weaver T-6 scope did not let me down. The accuracy of all 4 test loads is excellent with the 29, 30 and 31 gr loads in need of further testing at 200 yards. All 3 would have scored 100 on the CBA 100/600 target. I was very pleased with the new bullet and will be doing more testing in the Finn M39 and the M91/30 sniper.

Larry Gibson

Attachment 219402

[303Guy]

The Hodgdon reloading site has all the load data with pressure.
http://www.hodgdonreloading.com/data/rifle

[Clark]

I have converted mosins to 223, 30-30, 45/70, 7mmRemMag, and 300 Win Mag.
The most pressure I have ever done is with an M39 stock chamber that pinched the neck. I could barely get the bolt open.

[Multigunner]

I have converted mosins to 223, 30-30, 45/70, 7mmRemMag, and 300 Win Mag.
The most pressure I have ever done is with an M39 stock chamber that pinched the neck. I could barely get the bolt open.

I had high pressure signs with a .303 once. I realized the chamber neck was way too tight.
That being unlikely to be normal with a milspec chamber I made a scraper from brass tubing by cutting saw tooth notches in one end.
After soaking the chamber with solvent I ran the scraper in a few times turning by hand, then repeated the process spreading the teeth a bit each time till I could feel the teeth slide on steel. Huge amounts of old hardened carbon was scraped out in strips and granules like pencil lead shavings. They actually looked exactly like pencil lead.
After finishing up with a chamber brush made by cutting the ratchet off a Garand chamber brush and threading it into a length of old cleaning rod which I turned with a hand cranked drill the chamber was as clean as one could possibly get and no more pressure signs.