Reloading 7.62x39 for Mini-30


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Ray P
August 4, 2013, 06:57 PM
What is a good/optimum bullet diameter for a 0.3103 barrel? When my current batch of 0.3095D bullets are done, should I get more of the nominal .310, or should I try some .312 FMJs? (I think only Sierra has .311 bullets in the mid-120 grain range, and they're hunting projectiles.) In other words, should land to land diameter match bullet diameter (e.g.; .308 to .308 for a .30 caliber barrel), should the bullet be slightly smaller, or slightly larger than L2L bore?

Some background on how I got to this question:

Any attempt to reload 7.62x39 for a Ruger Mini-30 has to start with the rifle. Rumor has it that Ruger sold two different-sized barrels for the Mini-30 over time; one with a land-to-land diameter of .308, and the other with a .310 or .311 barrel... depending on the writer. Since my Mini-30 is an older edition, I assumed (yeah, I know) the barrel was made for .308 bullets. And that's how I reloaded. I used the smaller diameter sizing button when full-sizing brass, & used .308 bullets. I got OK groups, but the point of impact at 100 yds was about 6-8" lower than Winchester or FC commercial hunting ammo. (Groups with commercial were about as good as the .308 reloads.)

So back in Aught-Nine, I decided I needed to slug the Mini-30's barrel. Starting with a .36 Hornady round ball, I hammer-swaged it down the bore. Land-to-land diameter miked to 0.3103; definitely bigger than .308. And that is where things stopped for a while.

Last month I decided to break the Mini-30 out of her protracted closet stay, and to try reloading with bigger diameter bullets. I found some 123 grain .310 FMJ bullets from Mid-South (Thank you, Jessica!), and loaded 50 of them in once-fired Winchester cases over IMR 4198 powder and Federal LR primers. Cases were full length resized using the larger button. I could not get good neck tension. Without a crimp, the bullets would push into the case the slightest thumb pressure. With a moderate seating die crimp, bullets would spin in the case on the cannelure. Finally had to use a factory crimp die to hold the pieces together against movement. Groups were definitely so-so. I think I was just recycling the brass for the next attempt.

When I got back from the range, I miked both the large button and bullet diameters. The large button averaged out to .3097 (three readings), and the bullets averaged .3095 at the base and .3093 just forward of the cannelure. Think I see the problem.


Next, I measured the smaller button. (My die set came with both.) It miked at .3064 D. For S&G, I attempted a couple of dummy assemblies today using the .3095 bullets; plenty of neck tension and no little ring of gilding metal. I can build cartridges for this gun using the smaller button and the larger bullets.

But looking past the next 100 rounds, is it worthwhile to try reloading with the large button and 312 bullets?

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steve4102
August 4, 2013, 10:35 PM
Sierra has .311 bullets in the mid-120 grain range, and they're hunting projectiles.

The Sierra 311 dia. bullet is a Pro Hunter Hunting bullet. It is also designed for m,uch higher veloccities than the 7.62 x 39 can deliver. I contacted Sierra several years ago and asked if this bullet would perform well on Whitetail deer at x 39 velocities. I was told it is to hard and would most likely just "pencil through" at 100 yards or more.

Ray P
August 4, 2013, 10:43 PM
Steve4102: Good info! I guess most .311 and .312 rifle bullets are intended for .303B & 7.62x54R.

Marlin 45 carbine
August 5, 2013, 03:24 PM
earlier than 189 series were the long throat - smaller bore M30s.
my Lee die set came w/2 neck stems one .308 the other .310.
I've had good luck with the Speer 150gr .308 sp in my 189. unfortunately have'nt yet recovered a slug from a deer all pass throughs.
I'm doubtful of the ability of the 125gr Win and Rem sp .310 on larger whitetail beyond 125 or so yds and muleys, elk, etc altho a quick follow up shot would help.
one of the Win 123gr sp I recovered from a large doe - I've taken 2 useing this slug - the jacket shucked off the core on a quartering away shot at about 100yds.

Ray P
August 7, 2013, 11:00 AM
I did catch an error in my original post; what I measured on the slug was groove to groove, not land to land. so the bullet is slightly larger in diameter than land to land distance, but not quite as large as groove to groove. I was wondering from accuracy point of view if it would be better to fill the grooves completely. But since it appears the only way to test that would be with cast bullets, I think I'll work with what I got.

Marlin 45 Carbine: You called it; mine is a Series 189. Lapped & torqued gas block, and a trigger job by Gundoc from the perfectunion board.

Since the .311 choices are limited, and what is available isn't suitable for my use, I guess I'll quit worrying about whether the bullet needs to fill the grooves or not.

HOWARD J
August 7, 2013, 08:43 PM
I use Hornady .310 bullets in my Mini 30
The boxes are marked .311---I called Hornady & they said boxes got marked by mistake--whatever
These are 123 gr bullet soft nose--I have had no problem reloading them using a RCBS resizing die with the decaper rod removed---I use a RCBS decaping only die with a 30 carbine decaping rod in the die & I seat the bullet with a Hornady 7.62 x 39 seat die.
This makes the neck nice & tight--WORKS GREAT

Jesse Heywood
August 7, 2013, 10:32 PM
From the Sierra website
The 125 grain #2305 Spitzer Pro-Hunter bullet was designed as a hunting bullet for the Russian 7.62x39mm cartridge. It is also very useful as a light game or varmint bullet in the larger .311 diameter cartridges, such as the 303 British, 7.65 Mauser and 7.7 Japanese. This bullet adds some much needed versatility to these often overlooked but very capable cartridges for hunting. Positive feed characteristics are required for all semi-automatic rifles using the 7.62x39mm cartridge, and Sierra's profiled ogive point shape provides flawless functioning. They have excellent accuracy, together with deep penetration and excellent expansion on medium and large game. The Spitzer shape provides a flat trajectory and high energy delivered downrange.
https://www.sierrabullets.com/store/product.cfm/sn/2305/311-dia-125-gr-SPT

Ray P
August 8, 2013, 12:38 AM
Howard J; Good trick!

Jesse Heywood; Looks like Wideners has them. Thanks for the tip! (not currently in stock at Natchez, Midway, Midsouth or Graf)
Edited to add: Too late! OOS at Widener's, too.

Jesse Heywood
August 8, 2013, 03:32 AM
I didn't say you could find them! :banghead: Put in requests for notification. For my SKS I found some #2300, 150 gr. Still working on loads with AA-1680, but it looks promising. Had a 1" group at 50 yards before my scope came loose. Built a cheek riser, got a 2" butt pad, loc-tite on scope base threads and loaded some rounds to sight in. Now I need to get to the range and start over.

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