Speed limit of lead - Horrible accuracy at 1200 FPS

[Steamdonkey]

I'm fairly new to reloading (about 500 rounds so far) and I'm trying to figure out why Meister Bullets hard cast .40 cal 155 gr. work pretty well at 1000 FPS and spray all over the place at 1200 FPS. Is this normal with lead? I'm shooting these through a Glock 35 using a Storm Lake barrel. With a 5.3" barrel and a 155 gr. bullet, 1200 FPS can be achieved with standard cartridge pressures, so I'm wondering why accuracy is so bad. Is the friction melting the outer edges of the bullets as they leave the barrel or is the pressure behind them so high that the relatively soft lead gets deformed to the point that the bullets can't fly straight? I'm confused, thanks for your help.

 

[poco loco]

that should be a doable velocity, are these gas cked

bullets or plain base? And do you know your land and groove size...

Too hard a bullet that is just at bore size or a tich under will lead like heck as you get flame front blow by.

Make sure you are at least a thousandth over size and I prefer 2 with harder lead.

Might be a little too hard also as a softer bullet upsets the base on initial light off and effectively plugs the bore so no more blow by, no more leading.

.40 and 357 Sig are my next 2 pistol projects so I hope to have better answers in a couple weeks....I do cast my own though so I have the advantage of adjusting my melt and sizing. This helps a lot when there's problems....also kinda sucks as no one else to blame it on, heh.

The fun part, I have an OG Winchester mold for the 38wcf that drops at about .402, a rnfp with a fat meplat. I find it both amusing and satisfying to use a 100yo Win mold for the boolits for my Glock...heh.

 

[hartcreek]

You must not be using gas checked bullets. I cast my own and gas check but my bullets are really hard and I do not have leading problems. I do not load lead bullets for .40 but my .44 Special, 44.Magnum, .32 Winchester Special, 25-35 Winchester, 7.62 x 39, 7.62 x 54R and 30-06 are above and way above 1200fps and show no leading problems.

 

[sexybeast]

Too much pressure going around the bullet and its not engaging/being spun by the rifeling. Lead is softer than jacketed and it happens sooner/lower pressure. Happens with plated too but after lead and before jacketed.
Doesn't happen with .45 or .38 as much since its lower pressure.
Have news for you, its even worse with 9mm

 

[BigBore44]

You need to check your barrel for leading. That will give you a great place to start. And slug your barrel. ALSO, make sure your gun is completely free of copper fowling before you shoot straight lead or alloy lead.

 

[Sam1911]

Brad over at Missouri Bullet Co. has a short essay on how to figure out the right bullet hardness for your given load pressure: https://www.missouribullet.com/technical.php

Velocity isn't the problem, and 1,200 fps isn't over some magic limit for lead, but you have to have all the details right.

1) The bullet has to fit the bore, preferably about 0.001"-0.002" oversized.
2) The bullet has to be the RIGHT hardness (not too hard, not too soft) for the pressure you're putting behind it.
3) Lube, barrel condition, chamber throat size if you were shooting a revolver, etc.

 

[steve4102]

As pointed out above, the first thing you need to do is take the barrel out and remove all the lead.
Next is to remove all the copper.
Next is to slug the bore.

Your bullets should be at least .001 over bore diameter.

 

[Bert2368]

Commercial cast bullets are usually a "one size fits some" affair, and your gun or loading might not be the one they fit. Also, the bullet alloys & bullet lubes used commercially are ones that pack and ship well, rather than the best for function.

Go here & read a bit about how to make & use your own cast bullets, it's worth it.

http://castboolits.gunloads.com/sho...to-Target-A-Cast-Bullet-Guide-for-Handgunners

 

[Steamdonkey]

After reading the article from Missouri Bullet (thanks Sam1911) I'm starting to wonder if obturation is insufficient with the 'hotter' loads. I know this sounds 100% backward, but what I didn't disclose is the the 1000 FPS loads were made with fast buring Clays that were near the upper pressure limit and the 1200 FPS were made with slower buring Blue Dot with a lower pressure.

To answer some of the above questions, the bullets are not gas checked, they're 1 thousanth over size and I did not ensure my barrel was 100% free of copper fouling.

Thanks for all the helpful info guys.

 

[Sam1911]

Few folks use gas checked bullets with common service pistol cartridges. It usually doesn't take too much tinkering to come up with something workable with the much cheaper plain cast bullets.

 

[ReloaderFred]

You'll be hard pressed to find a gas checked bullet for the .40 S&W, or even 10mm. They're not really necessary in these calibers, which is why there aren't any gas check bullet molds for them, except from custom mold makers.

It's bullet to bore fit, alloy hardness and powder that determine accuracy in handgun bullets. Once you work it out, the accuracy will come back, but you might just consider staying with the load you found earlier that works in your pistol.

As for "speed limit" of lead, I shoot 420 grain cast bullets through my .45-120 Sharps at 2,200 fps and have no leading whatsoever, but it took some tweaking to get those results.

Hope this helps.

Fred

 

[Schwing]

This is probably a silly question but why do you always see this equation as:

Optimum BHN = CUPS / (1422 x .90)

instead of:

Optimum BHN = CUPS / 1279.8

??

 

[rodregier]

The other issue I've seen is seating the projectile too far away from the throat. Lead projectiles tolerate a long jump to the barrel throat much more poorly than jacketed.

Concur with the other checklist items.

 

[Don McDowell]

I'm fairly new to reloading (about 500 rounds so far) and I'm trying to figure out why Meister Bullets hard cast .40 cal 155 gr. work pretty well at 1000 FPS and spray all over the place at 1200 FPS. Is this normal with lead? I'm shooting these through a Glock 35 using a Storm Lake barrel. With a 5.3" barrel and a 155 gr. bullet, 1200 FPS can be achieved with standard cartridge pressures, so I'm wondering why accuracy is so bad. Is the friction melting the outer edges of the bullets as they leave the barrel or is the pressure behind them so high that the relatively soft lead gets deformed to the point that the bullets can't fly straight? I'm confused, thanks for your help.

No it's not uncommon to change a load and either increase or decrease the velocity and have accuracy take a sudden exit from the building.
As has been pointed out bullet fit, check the barrel for leading.
BPCR shooters run pure lead bullets at or above 1200 fps all the time and don't experience much leading, it's all in the bullet fit and using a good lube.

 

[Elkins45]

After reading the article from Missouri Bullet (thanks Sam1911) I'm starting to wonder if obturation is insufficient with the 'hotter' loads. I know this sounds 100% backward, but what I didn't disclose is the the 1000 FPS loads were made with fast buring Clays that were near the upper pressure limit and the 1200 FPS were made with slower buring Blue Dot with a lower pressure.

To answer some of the above questions, the bullets are not gas checked, they're 1 thousanth over size and I did not ensure my barrel was 100% free of copper fouling.

Thanks for all the helpful info guys.

This sounds entirely plausible to me.

 

[chris in va]

Could be powder choice.

 

[[email protected]]

You can find plain base gas checks for sale at the cast boolits sight, but you will need a sizer die to seat them onto the bullet. It sounds like you found your load limit for that bullet at 1000 fps. Is there a reason you need the extra 200 FPS? If you need more energy out of your load to reach a power factor you may be better served by using a haiver bullet that goes slower. In general (I really mean in GENERAL) it is best to look at lead bullets as plinking practice loads until you mastered the art of loading cast bullets. If you push them too hard you will have problems, if you dont push them hard enough you will have problems. The alloy, lube, powder, and bullet fit determines how fast is too fast and how slow is too slow. The bullet fit is the main key to this. I have run pure lead hollow point bullets in my storm lake barrel at full speed without any leading and acceptable accuracy.