Curious Range result - Thoughts anyone?

[Hick]

I've been working on a load for my M1 Garand. The bullet is 180 grain lead spire point, powder coated (no gas check or lube). I was looking for 1900-2000 fps using a slower powder (IMR 4895) so as to accelerate the bullet without a large pressure peak. I tried two sizes: 0.311 and 0.309. This same bullet with normal lube works very well at 0.311, but with PC chambers a little tight-- so I decided to try 0.309 also.

I missed my target velocity-- ended up too hot (2200 fps), so I was not too surprised when some of the bullets didn't work well.

Here's the curious part: the 0.309 bullets shot well-- no issues at all. NONE of the 0.311 shot good-- some keyholed and most simply never reached the target ( a little puff of smoke downrange and they were gone). All the bullets were cast in the same session with the same lead, and coated in the same session with the same powder coating, and loaded in the same session with the same powder charge. Any ideas why the larger ones self-destruct but the smaller ones don't?

[Winger Ed.]

Interesting.
Maybe the .311 ones get shaved rather than 'sized' in the first little bit of rifling.
It so, and it wasn't even, they might fly like a football with a weight on one side and not stabilize.

Looking at recovered boolits- I've had some of my garbage alloys shatter rather than smash & deform when they hit.
That may be a factor too if the .311s get carved up or crushed enough to break apart on their way out.

[popper]

Water dropped? Leading in the barrel for the 311?

[Hick]

No leading-- air dropped

[Yodogsandman]

Rather than speculate what happened, how about making up some dummy rounds with both sizes and run them through from your magazine to the chamber, looking for the underlying problem? Don't be surprised at a PC boolit shooting better when sized just over bore groove diameter.

[dale2242]

I don`t powder coat but my lubed, gas checked .309 bullets shoot as well as jacketed.
I am shooting IMR 4064 with both.
48 gr. with jacketed and 32 gr with 150 gr cast..dale

[Kraschenbirn]

My Garand also doesn't seem to like PC. The RCBS 165SIL, cast from #2 alloy, sized .310, and lubed with Carnuba Red, will easily match ball ammo for accuracy but same boolit. PC'd and sized .310, using the same powder, prints more like buckshot. Similar results with the Arsenal 309-188PC which shoots MOA from my Savage M10 .308 but will barely stay inside the 8-ring from the Garand.

Bill

[Toymaker]

Your issue is curious. Load up 8 of the larger bullets, put them in an enbloc and cycle them manually. Check the bullets to see if the PC has been chipped or scratched off. Reload the cartridges in the enbloc and shoot them. BUT after each shot check the bolt to make sure it is fully in battery. You can go so far as to give the handle a smack with a mallet while watching the bolt. If it moves in the locking lugs, it isn't in battery.

[Bama]

Just a thought, it may be that the larger bullets is holding the rifling tighter and not slipping. So it is obtaining a higher rotational speed and destructs ( comes apart) shortly after it is no longer contained by the barrel. From the same experience, that problem can be solved by the addition of copper to your alloy. It is a grain refiner which really works. Thus far I have not been able to make a bullet go to a puff of smoke if copper is added. Highest Cronoed to date is just shy of 3000fps with an 87 gr in a 1in8 barrel with no issues noted.

[rsrocket1]

I had a similar problem with my 91/30. The bore slugged at .313" so I cast at .315" and size to .314". Unfortunately, I got a Lee 7.62x54R die set and the depriming/sizing die sizes the neck for a .308" bullet (I.D. = 0.305") That was way too small for the .314" bullets and it put quite a bit of seating force on the bullets. The loads would not hit paper at 25 yards although cases sized with the Lee whack-a-mole loader were not bad (1" @ 25 yards).

When I went back to carefully watch the 0.314" bullet get seated into the 0.305" neck, I saw some getting seated with a bulge on one side or the other. At best the bullet was swaged heavily as it was seated and chances were that the run-out was pretty bad.

Your .309" bullets may be seated straight but the .311" bullets may be just a bit too wide to seat straight into the neck. 6 mils is a lot of squeezing for a lead bullet.

Check your run-out. Roll the loaded cartridges on a table and see if the tip is concentric with the case.

[truckjohn]

The "Poof" in mid-air is when the bullet disintegrates from high centrifugal force. A normal bullet may be running 250,000 rpm at 2200 FPS... That's a LOT of spin...

This is basically a sign that you are pushing them too hard. Back off your velocity some and things will calm down.

On accuracy vs size - many people find the best accuracy when the bullet matches the groove diameter. The trouble is that many people measure bore slugs wrong by 0.001"-0.003" because they smoosh the slugs. In that case - a bullet mold that "casts" a bit bigger than the (wrong) measurement turns out to be the right size.

[megasupermagnum]

The "Poof" in mid-air is when the bullet disintegrates from high centrifugal force. A normal bullet may be running 250,000 rpm at 2200 FPS... That's a LOT of spin...

This is basically a sign that you are pushing them too hard. Back off your velocity some and things will calm down.

On accuracy vs size - many people find the best accuracy when the bullet matches the groove diameter. The trouble is that many people measure bore slugs wrong by 0.001"-0.003" because they smoosh the slugs. In that case - a bullet mold that "casts" a bit bigger than the (wrong) measurement turns out to be the right size.

You have a 1 in 6.5" twist, I didn't know they made such things?:???: Being the Garand should be a 1 in 10 twist, that puts it at 158,400 RPM at 2200 fps. Both .309 and .311 would be turning the same speed, skidding doesn't slow the rotation. Why the larger one didn't shoot well, but the smaller one did is beyond me, but I know it has nothing to do with RPM or twist rate.


This does bring up a good question I've had for a while. Why is the standard 30 caliber sizing .311" anyway? Most commercial cast bullet calibers are .001" over jacketed bullet size, many private bullet casters use .001 or .002" over jacketed bullet size, unless the groove diameter dictates a different size. Myself, not intentionally either, but every cast bullet I load is .002" over jacketed size. I run .310 in 30 cal, .314 in 32 handgun, .359 in 38 cal, .412 in 41 cal, .431 in 44 cal, etc. I'd say .313, 358, .411 (or even .410), and .430 respectively are even more common. Why then is 30 caliber rifles commonly sized to .311", .003" over jacketed size?

I'll disagree though that people are wrongly measuring slugs by up to .003". Even a calipers can get you closer than that. If you look at the best cast bullet shooters, I really doubt you will find any that are sizing the same as groove size.

[Bird]

I guess the answer here is don't use PC bullets with your load and you won't have a problem.
If the PC 0.311 are chambering tight, I think it would be reasonable to believe there would be a pressure and possibly velocity increase. If you were operating at the edge of the bullets capability then that little bit extra pressure could make the difference of bullets blowing up or other inaccuracies. I think we all understand the difference, of 1/10th of a grain or more, and thus pressure, of powder can make to bullet accuracy when working up a load.
Lower the charge, and see if the problem goes away.

[Hick]

Thanks for all the good ideas. I'm going to try a slightly harder alloy and lower charge (especially lower charge, since I overshot what I wanted anyway).

[Hi-Speed]

Cast bullets in a M1 Garand...you’re more experienced than I’ll ever be. I used surplus 150 gr fmj and cases with IMR 4895 back in the 1970s. Garand is long gone sadly. Enjoy and thank you for sharing your experiences.