Fun with 7.62x39

[405grain]

I went target shooting last weekend and tried out something new while I was there. I've got a '93 Mauser sporter that's converted to 7.62x39 (.308 bore) Just to try it out I loaded up 50 rounds with RCBS 32-98-SWC pistol bullets. I powder coated the boolits with Smoke's signal blue and sized them to .312". I used 6.0 grains of Unique and large pistol primers. When I tried them out I ran into a slight problem: the stubby boolit with the flat meplat wouldn't allow the cartridge to feed from the magazine. It would catch on the edge of the chamber, and trying to help it into the chamber would cause the case to get ahead of the extractor. With a control round feed that's not such a good thing. I found out that to chamber the rounds I'd have to remove the bolt, place the cartridge on the bolt face, then re-insert the bolt and cartridge back into the action. This made the rifle a single shot, but it wasn't as tedious as it sounds, and in my opinion it was better than trying to force the extractor over the case rim.

I was shooting at targets 50 yards away and the diminutive little boolits were making me smile with every shot. The sound of the boolits striking the cardboard backing on the target stands was louder than the report of the rifle. There was no recoil at all. The groups were hitting about 3" high and printing onto 2" groups.(the rifle had been sighted in at 100 yards using RCBS 30-165-Sil boolits at around 1750 fps) There were some rocks on the ground downrange about the size of softballs. Hits on these rocks sent them skiddering off like they'd been kicked by a donkey. I have no idea what the velocity was, (a wild guess at 1200 fps), but I took a shot at a dusty hillside at 200 yards out to see how much the boolit dropped and was able to hear the tiny crack that told me the little boolit was going supersonic. Shooting these rounds was so much fun that I decided I'm going to load up some more and take them along on some ground squirrel hunts this Spring. I've got better varmint rifles, but these should quietly put the zap on any squirrels that are within normal 22Lr range.

[Texas by God]

That does sound like a fun load. If you're using the original extractor, you may be able to drop a cartridge in the chamber then compress the side of the extractor while closing the bolt- a two handed operation but may be doable with the smaller rim of the x39 case. That was a long sentence.

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[405grain]

Hey Texas: I tried that but trying to guide the cartridge into the chamber - fat fingers & the scope gets in the way. It was easier to just single load.

[Nobade]

Watch out using very light loads in the 7.62x39. I did the same thing with my little CZ carbine, and by the third loading the cases had gotten enough shorter that they wouldn't fire. The primer blows the case forward and increases the headspace each time it is fired and the pressure isn't enough to shove it back out. It seemed like a good idea at first...

[barkerwc4362]

I have a 1894 Brazilian receiver that was converted to 7.62x39. It has a 24" heavy sporter profile Douglass premium 1-14 twist 308 barrel with a custom chamber throated for the RCBS 168 grain bullet. I have loads for IMR 4198 and IMR 3031 for it. I mostly shoot the 3031 loads. Used to compete in the local sporting rifle shoots. Did very well competing against 223 sporters. It will also shoot 170 grain round nosed Remington 3030 bullets with RL7.
Bill

[waksupi]

It sounds like you may be treating that Mauser too gently. SLAM the bolt home, and see if they feed. Mausers react well to some brutal loading, as that is how they were designed to operate.

[TurnipEaterDown]

Integral magazine box Mauser rifles are made to feed cartridges of specific body diameter & taper of the case.

Often they will feed something close acceptably w/ spitzer bullets, or even bigger in case body with the same taper angle to shoulder, but sometimes not. Also, due to production variance, a person may often find that rounds on one side of a Mauser staggered magazine stack feed better than on the other side.

The permanent fix to this is modification of the magazine feed rails in the receiver. There is more to do with this than width, there are angle(s) intentionally formed on the bottom of the feed rails. Modification of these rails will solve the issue (generally). I would very much recommend spending time looking at it and figuring out what to try before trying. Like a carpenter: measure twice cut once... Trying the modification after Slight Alteration is much like measuring.

Last Round feed can also be a problem After ones above it do feed OK. Last round feed is affected by the angled "fin" on the follower. Changes to this for L/R placement and Angle can be mocked up by biasing the follower away from one mag box side or the other with a taped on shim. Angle change can be mocked up with appropriately place tape layers.
Look at the cartridge dimensions of what the gun was designed & built to fire, and what you are adapting. That is really The Place to start.
I read in one book or another that it is no mystery as to why the "standard" length belted magnums (6.5, 7 mm, and a Host of well designed Wildcats) have the taper they do: they were designed to feed in a '98 Mauser, because in the 50s & 60s, if you were making a new cartridge it had better feed in a 98 Mauser. Taper is a big part of feed in a Mauser, and the 7.62x39 isn't very close to a 7x57 or 8x57.

[405grain]

Hi Waksupi: (You've built enough good rifles that this is just going to be preaching to the choir.) I've got two Mauser's in 7.62x39 - an 1893 & a 1894, (plus an SKS). When I do a cartridge conversion on a Mauser (both large ring and small ring) I work on the feed rails and feed ramp until the cartridge will feed smoothly from both sides of the magazine as I move the bolt as slowly as possible. I've often heard that the solution to feeding problems with Mauser's is to work the bolt more forcefully. This advice might hold true if someone were to do something like convert a Mauser to 308 and not modify the feed rails. I've been spoiled from the onset because my first bolt action rifle from way,way back in the younger days is a pre-64 Winchester model 70 in 30-06. That rifle will feed flawlessly no matter how slowly or fast the bolt is cycled. I have used that as a benchmark for the way bolt actions are supposed to feed. With regular jacketed and cast rifle bullets there's no problems with the 7.62x39 Mauser's. This feeding issue is because of the short, flat nosed SWC pistol bullets. On any cartridge the nose of the bullet should already be entering the chamber before the base of the cartridge releases from the magazine and rides up under the extractor. With the pistol bullets the nose of the bullet just wedges against the back of the barrel and causes a jam.

Nobade: Thanks for the advise. I've got lots of good brass, but based on your advise I'll use range pick-up brass for these type of loads. After the second reload I can just throw them away. I've read about people drilling out the primer flash hole, but I'm not going to do that (too much possibility of it getting mixed in with normal brass at some point.) There's a lot of people that drive over from the Bay Area to shoot on the public lands in the Diablo Mountains where I shoot. (I just go during the week when they're not there) Those people are basically slobs. I pick up their trash on the way out. On the plus side, anywhere that a group of people have been shooting together is an absolute brass mine! I buy good brass brand new, but I've got brass that I didn't pay a penny for, and won't shed a tear tossing it out after it's been used.

[lar45]

Sounds like a cool rifle.
We need pics!

[Larry Gibson]

........Nobade: Thanks for the advise. I've got lots of good brass, but based on your advise I'll use range pick-up brass for these type of loads. After the second reload I can just throw them away. I've read about people drilling out the primer flash hole, but I'm not going to do that (too much possibility of it getting mixed in with normal brass at some point.) There's a lot of people that drive over from the Bay Area to shoot on the public lands in the Diablo Mountains where I shoot. (I just go during the week when they're not there) Those people are basically slobs. I pick up their trash on the way out. On the plus side, anywhere that a group of people have been shooting together is an absolute brass mine! I buy good brass brand new, but I've got brass that I didn't pay a penny for, and won't shed a tear tossing it out after it's been used.

You shouldn't have to throw away any of those cases. What Nobade describes is what will mostly happen with push feed actions with a plunger ejector in the bolt face. Your Mauser is a controlled round feed, thus the case headspace will only decrease to where the rim is held back by the extractor. After that the case headspace will shorten no more and if the firing pin extrusion is to spec all will continue to fire.

The better solution is to drill the flash holes out with a #30 - #28 size. It is the flash of the LR primer in the pocket that drives the case forward. Drilling out the flash hole alleviates the problem, and the case headspace will not decrease with those very light loads. The larger flash hole also improves ignition and lessens powder position sensitivity. Some will say it is dangerous to enlarge the flash holes as the pressure will increase, especially in the primer pocket. Thorough pressure testing with full power jacketed bullet loads in the 308W has shown this to be a myth.

The test information is here; https://castboolits.gunloads.com/sho...oles-dangerous I can repost the pictures if needed?

Another solution, although probably impossible these days, is to find some R-P cases with SR primer pockets. I have fired 50+ shots using a single R-P case primed with WSR primers, with 2.7 gr Bullseye under a 90 gr WC in my Mini Mk X Mauser 7.62x39 measuring the case headspace after every shot without not even .001 decrease in case headspace.

[405grain]

Thanks for the information Larry. lar45: Here's a snapshot of the rifle in question. With RCBS 30-165-Sil and a 19.5 grain charge of BLC-2 it will print around a 2" group at 100 yards.

[jaysouth]

Here is my favorite cast bullet for 7.62X39. It is a 145 gr. plain based spitzer. I have it cut in .312 for my Ruger RAR Ranch rifle.

You can get it cut for .308.

http://arsenalmolds.com/products?product_id=192

[Bloodman14]

Was looking for a picture of the boolit?

[405grain]

I shot up all the ones I had loaded, and haven't had time to load more. Here's a photo of the boolit and case.

[lar45]

405, thanks for the pics I really like the rifle, very nice.
I have an AR Pistol in 7.62x39 that I tried to shoot cast in with terrible results. I may have been trying to push them all too hard.
Do you know what velocity you are getting with your BLC2 load?
I don't know if it was the gas port cutting the base or ???
I finally gave up and switched to Barnes X and had instant sub 1" groups.

[Texas by God]

That's a good looking rifle. What kind of wood is the stock and accents? Is that a dressed knot by the front action ring?
Is that a GPC/ Numrich barrel?

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[405grain]

Texas: The stock is a straight grained walnut. The forend, grip cap and buttplate are sycamore. The knot by the front receiver ring is just a surface blemish, but I installed steel cross bolts at the receiver recoil lug and back near the trigger anyway. I capped off the cross bolts with disc's of sycamore. The barrel and "feed kit" are from Numrich.

I have a second small ring Mauser in 7.62x39: a 1894 Brazilian that I set up to use single stack AK magazines. It has barrel made from a hammer forged blank, and I chambered it using a Lapua specification reamer. I'm in the middle of putting a new scope on it and once that's done I'll see if I can get some tighter groups with it. (but that'll be another thread)

[Hueyville]

Wife shoots 100 to 200 160 grain 7.62×39 cast per week through her SKSs (massaged Tapco triggers, tritium sights, extended butt pad to fit length of pull) and 7.62×39 ARs. Load in free copper washed steel cases for the combloc rifles and commercial brass for the ARs. Didnt know the small primer R-P cases were rare as have a five gallon bucket of empties all the time in line for loading along with several thousand loaded and ready to shoot. She is recoil sensitive due to bone disease and cheap thus she really likes to shoot cast ×39 because she knows we recover majority of lead from our bullet traps so we can recycle the lead as well as the cases and now using a lot of repacked Berdan primers in our steel case reloads. Have not played with light bullets as want solid cycling of her repeaters.

[jaysouth]

Was looking for a picture of the boolit?

http://arsenalmolds.com/products?product_id=192

[lar45]

Hueyville, would you share your 160gn AR cast load details, or atleast the powder used and velocity? Thanks.