Load Data Lead vs Jacketed?

S

steve4102

New member
This question is about Rifle load data, specifically the 7.62x39.

I have a bunch of cast Lee .312 155gr bullets that I coated with HI-TEK and applied gas checks. They have been sized down to .309.

I originally made these for my son's Blackout, but I decided to give them a try in my Ruger Mini-30.

My Ruger will not cycle the action with jacketed bullets and fast powders like 2400, so I'm pretty sure it will not cycle with Lead bullets and these fast powders.

That leaves me with slower powders like 2230, R-7, 4198, 1680 etc.

My Lyman #4 has data for this bullet using R-7 and 2230, but I would like to try other powders I have in stock.

I can't find any data for Lead bullets other than what is in my Lyman.

So, time to experiment, Is there a general rule of thumb or a guideline used when converting Jacketed Data and using a Lead bullet?

My Lyman lists 27gr Max using 2230, Accurate 28.9gr 2230 for 150gr jacketed. That's about two grain or about 7% less than jacketed.

Would this 7% reduction in powder charge be a good safe rule of thumb?

I tried using Quickload, but wow, QL and lead rifle bullets just doesn't jive with any published data and I don't know how to tweak it.

Thanks
 
Unfortunately there's nothing quite that simple. One problem is cast bullet shooters are used to speaking in terms of the maximum velocity you can get, but it's actually pressure barrel twist and alloy hardness that determine when you'll start to get bullet stripping by the lands. So this really needs to be determined for your gun and bullets.

Richard Lee's Modern Reloading 2nd Edition has his system of allowing for alloy hardness. It's unusual but is one way to make it work and he gets good results. You might want to get hold of a copy and read through that for ideas.

Getting a rifle to cycle depends on the gas impulse your load generates. This is pressure multiplied by the time the gas port it exposed to it. So if you are wanting get the same impulse from a lower gas pressure, having the bullet take as long as possible to get from the gas port location to the muzzle will increase the impulse, and that means using the heaviest bullet you can stabilize with your twist rate. That greater bullet weight will also let you use a slower powder that holds pressure up better as you get beyond the first few inches of the barrel.
 
Go back to your QuickLoad, load the bullets from Lee. I don't shoot AKs but I use cast bullets in most of my other 30 cal rifles.

I just checked and it looks like Lee's .309, 120, LEE C309-120-R, might fit the AK.

You just need to play and find a happy medium between pressure to work the action, and accuracy without leading the barrel.

Look at 5744 powder. I found it makes and excellent cast bullet load.

4198 is another.
 
kraigwy said:
Go back to your QuickLoad, load the bullets from Lee. I don't shoot AKs but I use cast bullets in most of my other 30 cal rifles.

I just checked and it looks like Lee's .309, 120, LEE C309-120-R, might fit the AK.
Click to expand...

Here is an example of how QL compares to actual pressure tested data.

From Lyman #4.

Lee C312-155-2R bullet with Gas Check
Barrel Length 20 inches
Bullet sized to .310
Powder: Accurate 2230
Start = 19.0gr--1479fps--18,300 CUP
Max = 27.0gr--2085fps--42,300 CUP

Plug all this into QL

Cartridge : 7.62 x 39 (M43) Russ.
Bullet : .312, 155, LEE C312-155-2R
Cartridge O.A.L. L6: 2.155 inch or 54.74 mm
Barrel Length : 20.0 inch or 508.0 mm
Powder : Accurate 2230

19.00gr = 1264fps 9700 PSI
27.00gr = 1890fps 27900 PSI

That's 200fps difference between Lyman and QL.

SAAMI MAP for the 7.62 x 39 is 50K CUP and 45K psi.

Lyman is only 7,700 CUP below max while QL is 17,100 psi below max or a whopping 38% below MAP.

That just doesn't seem right to me.

Lyman data using R-7 and QL data yields similar results.

When using QL with other Lead bullets and cartridges it does not jive with Lyman at all.

Cartridge : .30-06 Spring. (SAAMI)
Bullet : .309, 150, LEE C309-150-F
Cartridge O.A.L. L6: 3.340 inch or 84.84 mm
Barrel Length : 24.0 inch or 609.6 mm
Powder : Alliant Reloder-7

Lyman lists a Max charge of 36.5gr 2508fps at 43,600 PSI

QL list this 36.5gr at 2339fps at 28,073 PSI

That's a huge difference in pressure ratings for the same load, 15,527 psi to be exact.
 
Last edited:
Lyman Cast bullet manual #4 had a starting load of 15.0 gr. @1350 fps. & 20.3 grs. Max. @2004 fps. using IMR-4198 an the Lee .312" 155 gr. GC bullet.

Just thinking out load here as you plan on using that bullet sized to .309" in a Mini 30. Does it have the .308" or .310" groove bore. I shoot cast lead in 155,160 an 185 grs. using Reloader #7,2400 an H4895 but out of a couple different SKS rifles with a different gas system and they cycle with no issues. As mentioned slower powders and heavier bullets will better cycling reliability.

The Mini 30 has the same barrel twist rate 1:10 as the SKS and Mosin so basically with your standard lead and lube GC bullet your going to be around the 1900 fps. velocity limit depending on bullet weight & length before accuracy goes south,a couple hundred fps. slower may prove more accurate and you targets want know the difference. Coated bullets may give you some added advantage on the velocity limits but I don't know since I haven't done any experiments with coated rifle bullets and HV as of yet. Coated or not they still have to fit properly to seal the bore and shoot accurately.
 
Steve4102,

One of the first things I notice is that Lyman has the 27 grain load of 2230 marked as being a compressed load, where QuickLOAD shows that load filling the case only 91%. This suggests Lyman's Winchester case was tighter than the default case capacity (probably for a steel case). Also note that both QuickLOAD powder data and Lyman's test data come from actual lots of powder. Canister grade powder typically varies about 6% in burn rate. If I lower the case capacity to 32 grains overflow capacity, I get a 3% compressed load. If I also raise the powder burn rate 6% to 0.5544/bar-s, then at that burn rate in that smaller case, I get 42,326 psi and 2100 fps. Fairly close to Lyman's numbers.

Unfortunately, when your data sources are dealing with purchased powder samples rather than known mean value data powder lots, you just have to allow the real data could have been taken at the slow or fast end of the powder burn rate range and try it out ±6% to see if you get a match. Actual case capacities obviously matter, too.
 
There has been a lot of experimentation by the cast bullet crowd to get cast loads to work effectively in gas operated guns. One approach hs been to use a reduced load of very slow powder to generate sufficient gas volume to work the action. For example, I'm currently shooting 40 grains of IMR 4831 with a 200 grain cast lead bullet in my M1 Garand. Normally 4831 would be way too slow for the Garand and would be an op rod bender for sure, but reducing the charge by such a significant amount seems to give just enough gas to cycle but not enough to break anything. In fact, at 38 grains I don't get 100% cycling. I have to jump up to 40 just to make enough gas to drive it all the way to the rear reliably.

Accuracy is as good as would be expected. Might be an approach to consider.
 
You must log in or register to reply here.
Back
Top