Chamber casting issue....I'm confused

[Cranium]

I've been fighting with some leading in my Sig 226 and have it down to a minimum after starting to size at 0.357" and decreasing my load of Power Pistol to a mere 4.8 gr with my 120 gr, 12 BHN cast bullets. These are now averaging 1020 fps at a PF of 122. I suspected there was more to the equation than I was aware of which so I bought some chamber casting alloy from Rotometals.

I broke out the hotplate, cleaned out a ladle and broke out the heat gun. I also plugged my cleaned barrel with a cleaning square. I melted the alloy in the ladle on the hot plate while pre-heating the barrel with the hot air gun. Once the alloy was completely melted, I filled the plugged barrel to the top, waited for about 5 minutes and used a cleaning rod to push the slug out. There were no obvious issues visually. I waited for an hour then broke out the micrometer to measure.

Now this is the point of my confusion. I was getting a reading as high as 0.3575"! This is much larger than expected. So I figured I messed something up and cast another slug. Same thing after an hour; 0.3575"! Now I'm thinking I have to buy new bullet molds and another sizer die for my lyman or buy a new barrel.

While brainstorming, I figured why not use an actual cast bullet? So I broke out a bullet that cast to 0.358" and used a brass punch and aluminum hammer to tap it in the barrel a couple inches then tap it back out. It looked very good. I measured and I got a max of 0.356"! ***? I did another bullet the same way and got the same reading.

So I'm confused. Do I trust the bullet or do I trust the cast? If I trust the bullet, why is the cast so far off? If I trust the cast, why is the bullet so far off? [smilie=b:

Hopefully someone can help out with some good advice from experience here. This is a couple pics of my resulting slugs and bullets.

http://img849.imageshack.us/img849/2894/chambercastsm.jpg
http://img269.imageshack.us/img269/7666/chambercast1.jpg

[Doby45]

Use the boolits as cast, problem solved. That will be $5.82 and I accept most forms of payment. ;)

[MtGun44]

Calipers are +/-.001 or even .002 accurate ONLY. You really must have a .0001"
reading micrometer for this work. Look at Enco tools, they often have .0001"
Fowler brand decent quality mics for <$35.

Possibly a pure measurement issue. Or try shooting some at .358 diam.

Bill

[firefly1957]

easy to check see if casting will go back in! Trust the slugs you did of barrel that is the proper way to do it the casting is for chamber dimensions.

[44man]

I never got the right readings from a casting either. They always read higher. :groner:

[onesonek]

Cold barrel and cold slug, vs heated barrel and hot alloy??, would be my guess for the difference.
Then again, the chamber casting alloy I use, has a set time, at which you take a reading. Don't remember right off hand what it is however, seems to me it was like 20-30 mins. after.
Prior to the set time, it will read larger, after it will read smaller. But I don't know in Roto's alloy, as I haven't used it.

[harvester]

Borrow or buy a micrometer and compare your measurements of the slugs. They will probably be different.

[XWrench3]

either try a larger boolit (up to as large as what will chamber), or in stead of buying different molds, just beagle one of your molds, and shoot them as cast (measure them before you shoot them of course). you should plan on reducing the powder charge a bit due to the extra resistance of a larger boolit. all you need to beagle a mold is some aluminum tape to do that. and even if you have to buy a roll of it, it will be a lot less expensive than a new mold. but seriously, if you do not have access to aluminum tape, p.m. me with your address and i will send you some. shooting boolits that are larger than the barrel seems to be common in this hobby. in my 30-30, i have to shoot a 0.311" boolit, in a barrel that slugs out @ 0.308"! it may have to do with the microgrooved barrel, but then again, it might not. i am not a rocket scientist, but i am pretty good at experimenting. and sometimes, that is what you have to do to solve problems. as far as micrometers vs. calipers, in some cases, the other guys are right. i have seen calipers that were only good enough for "government work". but then again, i have also seen some that were as accurate as a 0.001" micrometer, i have 2 pairs of them. but a 0.0001" micrometer is the rule in this area, and i have yet to see a set of calipers that are anywhere near that accurate.

[Cranium]

Thanks for the opinions and suggestions so far.

The calipers I have are accurate to 0.0001". It is rare, I know, and Starrett no longer makes them this accurate. These were purchased about 15 years ago. But the measurements are repeatable when the same amount of pressure is applied each time to the part being measured. They probably stopped making them because the readings can vary from person to person if they are not doing it the same way. Micrometers remove this variable by having you turn the clicker to apply the same pressure for you. The reading in the picture is actually 0.3576". The reading of the boolit was 0.3559". These are readings taken at the largest diameter on the pieces and not averaged in any way. I trust the readings on the calipers within 0.0005" and usually round to this.

The barrel was > 150°F when I did the pour so there was no chance of it being too cold. I did use a fan after a couple minutes to help cool it down but don't think that would have caused an issue.

At this point, I'm tending to lean towards trusting the measurements of the bullets unless there is a reason someone could think of that this would be off. I know the bullet was up to 0.358" in spots to begin with and can't think of a reason it would not be reliable. However with the casting alloy; it is an unknown factor for me. I have to have blind trust that it will be an exact representation at 1 hour after casting.

The suggesting of beagling the mold is interesting...I've never heard of this before. How is this done?

[Doby45]

The suggesting of beagling the mold is interesting...I've never heard of this before. How is this done?

Really? A search will yield untold posts on the topic.

[fecmech]

Heating your barrel to >150 deg. would account for the casting being larger, metal expands when heated. I would trust the slug measurement myself. In the past when I wanted to see the chambers in my rifles I have used impact castings and they match my slugs for the same barrel and they dont change over time like cerrosafe.

PS. If the gun will chamber .358 I would give it a try.

[Cranium]

True enough about expanding but I didn't remove the casting until it was cooled down so it contracted and the alloy isn't going to hold back the contraction of the barrel.

I'd love to test sized .358" to see what it would do but have no way to do this without buying some custom molds and another sizer die.

I was reading the procedure on Brownell's for this and they state:

"Always melt the entire Cerrosafe ingot to make a chamber casting. For best results, never cut off, or use, just a part of the ingot."

Any ideas why this would be? I guess I could try melting the whole pound tonight to see if it yields any difference.

[Cranium]

Really? A search will yield untold posts on the topic.

hmmm....now that I've searched this, I'll have to try it. :)

Although I do not understand completely the dynamics behind it. I would tend to think it creates an oblong bullet that, when sized, is now round but whose center of gravity has changed. Any accuracy difference studies done?

[Doby45]

I have heard of no adverse effects from the beagling process. If done properly you would not even see any difference in the parting line of the mold on the boolit. I had to beagle my old 358477 and it did just fine accuracy wise.

[BABore]

True enough about expanding but I didn't remove the casting until it was cooled down so it contracted and the alloy isn't going to hold back the contraction of the barrel.

I'd love to test sized .358" to see what it would do but have no way to do this without buying some custom molds and another sizer die.

I was reading the procedure on Brownell's for this and they state:

"Always melt the entire Cerrosafe ingot to make a chamber casting. For best results, never cut off, or use, just a part of the ingot."

Any ideas why this would be? I guess I could try melting the whole pound tonight to see if it yields any difference.

Cause they sell Cerrosafe. It won't make any difference.

I too have never had a Cerrosafe casting come out to the actual throat size. I followed the directions and wait time exactly and always come out big by 0.001" or so. I got several small mold cherrys to prove it.

Calipers don't measure as accurate as a good 0.0001" resolution micrometer because of a couple reasons. One is that the measuring jaws are over an inch below the slide. Any tolerance in the slide will result in jaw canting. Second is that jaw pressure is applied with the thumb which will be variable. A micrometer anvil is in-line with the spindle and most have a rachet for repeatable pressure.

0.3574-0.3575 boolit diameter is a good place to start with alot of 9mm's. Use the largest boolit that you can chamber safely and reliablly. If it still leads, experiment with different powders assuming your already using a good, soft lube.

[MtGun44]

No accuracy issues. All boolits are out of round, only a matter of degree. Once they are
jammed into a round barrel with 30,000 psi behind them they are round - with grooves.

You are the first one I have seen with a real, live accurate set of calipers. Any other brand
but Starrett, Brown&Sharpe or Mitutoyo and I would be quite suspicious of these claims since
most calipers are, at best, +/- .001" many really .002".

Ignore the diameter difference as to pressure, no significant change in pressure due to
a couple thousandths diff on a boolit. I have the same mold, size mine to either .357 or
.358 and they all work just fine in a bunch of 9mms, including a pair of Sig225s (P6) which
I have either no slugged or I forget right now, far from home and can't check my tub of
slugs in little bags labeled for the gun it was run through.

http://castboolits.gunloads.com/picture.php?albumid=161&pictureid=2344

Exactly what lube are you using? If not NRA 50-50 of some brand, please obtain some and
try it. I use this on my version of your same boolit, same hardness, same diameter in
a couple Sigs, no sweat. I am using SP8, a Vectran French powder, not going to find it
here. I got 8 lbs in a cheap trade and it is (I know this sounds crazy, but true) only useable
for 9mm, so I use it exclusively to get benefit out of it, plus it works fine for me.

Also, try something in the W231/HP38 or Titegroup or Clays speed range (fast) and see
what you get. PP is about like Unique in speed, and Unique usually works well in this
cartridge out to full power, BUT I have never actually used PP in this caliber, but got great
results with fairly hot (IIRC 5.1 gr or similar - DO NOT trust this without verifying).

Bill

[nanuk]

I slugged a bore on my 45/70 the other day, and I found some issues that could make a difference to me.

I found resistance at one point, so I used my rod and punch to make an "Impact" slug, and it came out a bit bigger. like 5 tenths.

i too used both calipers and a mic. my calipers are repeatable to about 5 tenths and in agreement with two different micrometers

I found that it really does make a difference on where and how you measure/orient the slug.
I have to measure with the jaws perpendicular to the bore. if I measure "With" the bore, the readings differ by where you place the jaws. A mic is less prone to this as it can only measure at one spot at a time. also, the item to be measured has to be at or inside the inner half of the jaws. Outside that, the thumb wheel exerts too much pressure and like BaBore said, tolerances take their pound of flesh

[Cranium]

I'm currently using the Lyman lube that came with the sizer (super moly I believe?). I've tried Orange Magic but did not like the way it applied at all. The Lyman heater would get it too hot and it certainly was too hard to apply cold. This meant to get good application, I had to keep unplugging it and plugging it back in.

The lube I'm using is very soft and I don't really like it either. It is messy and gets all over the place when the bullets are stored in a bin for loading. I have some Thompson Bullet Lube to try next (Blue Angel & Red Angel).

I do have 3 other powders on hand that I could try but intended to get something stable with PP before moving on to something else. I guess I should rethink this. The other powders are: Titegroup, HS-6 & Unique. I have read that others have had issues with Titegroup being too fast for lead bullets and causing leading. Have others had good experience with Titegroup and lead bullets with pistols?

[Cranium]

The most accurate measurements I achieved with the calipers were with the calipers perpendicular to the bore. I measured using the flats on the calipers and rotated the bullet to find the high spots to measure. I checked multiple times to verify accuracy and consistency and had two castings and two bullets to compare against. The only change in readings I had was with one of the bullets that showed a smaller diameter. I failed to measure the bullet before testing it and suspect I happened to select one that was a bit smaller than the other.

[MtGun44]

I think any of the three would work, don't think TG is too fast. My first 9mm cast many
years ago were with Lee 105 SWC and BE, then Unique at about max in a Browning HP,
got great accy no leading.

Try 5 rds of each powder at book speed of about 1050 and unsized if it will chamber (make
up one dummy first). How much TC are you using? Some is required, excessive can down
size the boolit as it exits for very thick walled brass. Can you smear the groove full (it is a
PITA, I know) I scrape it off level with a small screwdriver side of the blade. Only useful for
VERY small quantities for testing. So if you do 15 boolits unsized and lubed with something,
each over a "book est 1050 fps" load of TG, HS6 and Unique it may be useful with a
minimal amount of work. This is a good boolit design and definitely used successfully by
a number of shooters here.

Good luck.

Bill

[OuchHot!]

I have used cerrosafe and pounded soft lead with generally similar results. In you method, you mentioned:
" While brainstorming, I figured why not use an actual cast bullet? So I broke out a bullet that cast to 0.358" and used a brass punch and aluminum hammer to tap it in the barrel a couple inches then tap it back out. It looked very good. I measured and I got a max of 0.356"! ***?"
If the bore tapers from the ball seat forward, your pounded slug will give you the minimum dimension. To slug the ball seat you need a rod from the muzzle to upset the slug against and then tap it out toward the chamber. Did that make any sense? I think both of your measurements are correct, they just measure different places.

[Cranium]

I go through the paces as I develop loads for jacketed bullets with loading them individually and trickle feeding the powder in so your suggestions just add a small step. I would have to get a different lube since the extras I have now are all too hard to smear into the groove without heating. Guess I could try to heat a small piece of it with a hot air gun though.

I use only enough TC to remove the bell, not cause any noticeable deformation on the bullet when removed, and not allow the bullet to move. Does this need tweaking as well?

So far, I have suggestions to beagle the mold, try different powders, and try not sizing the bullet. All easily doable. :)

[Cranium]

If the bore tapers from the ball seat forward, your pounded slug will give you the minimum dimension. To slug the ball seat you need a rod from the muzzle to upset the slug against and then tap it out toward the chamber. Did that make any sense? I think both of your measurements are correct, they just measure different places.

Thanks for the suggestion.

Both the casts and slugs were done on the same part of the barrel from the chamber side. I also checked and measured no difference in the diameter of the cast on the 1" or so barrel rifling on the longer of two casts. If I'm missing your point, please try to explain a little better.

[OuchHot!]

I read your method to indicate that you pushed the slugs several inches into the bore. The picture shows the very tips of the caliper blades measuring the ball seat at the very mouth of the chamber. This "ball seat" (if it exists, not all throats are so equipped) can be slightly differrent in dimension from the bore in front. To get a good measure of this area by slugging requires a rod inserted from each side to act as an anvil and the slug upset in the area of choice and drifted out through the chamber (which is larger). I am saying that you cast the ball seat and measured it to be .3575 and then found the bore further toward the muzzle to be .356. I would size to the ball seat dimension if this will chamber and feed. Did that help?

[Cranium]

I apologize if the photo was misleading. I set the calipers in that position for visual reference only. I used the flats of the calipers for measuring the diameter holding the cast perpendicular to the calipers. I mistyped in an earlier post stating parallel and realized it when reading typing this (I corrected my post). It would be quite hard to get measurements holding it parallel. :) I did not take any measurements in the direct area that transitions from the chamber to the barrel where the rifling begins (the area that the blades are at in the photo).

To better clarify the method used for using a bullet, I put the bullet in the barrel from the chamber side and then tapped it in using a brass rod about 1" (bullet was completely in the rifling area of the barrel). I then put the brass rod in the other end of the barrel and tapped it back out. The comparisons in measurements taken between the slug and cast should have been reflective of the same area in the barrel.

When you state a rod inserted from each side, are you referring to at the same time? Or as I did it? If it's different from how I stated I did it, I guess I'm still having a problem following you and I apologize.

[OuchHot!]

I did not clearly understand your procedure, it sounds to me like you do have a discrepancy in two measurements that I cannot explain. The casting media (like cerrosafe) shrinks right after casting but as time goes by, the bismuth rich intermetallic progressively crystallizes and that causes it to expand. I guess the idea is that after one hour it gets pretty close to "as cast" size. Maybe it is just expanding at a more rapid rate or possibly the preheating of the barrel did expand it a bit....normally I don't get things too hot before pouring. When I slug a chamber, I have a case with a piece of bore diameter rod in it the length of the case. I drop my slug into the chamber and insert the plugged case. Then from the muzzle, I insert a rod and wack that (pure lead does not require much) and then pop the slug and plugged case out. This gives a really firm replica of the front of the chamber and lead. I do put a slug through the bore but obviously that tends to give you the minimum dimension and doesn't really tell you over all bore variability. So given what you have measured, it seems like your slug might be more accurate than your casting......sorry for the confusion!

[Cranium]

I'm going to try another casting tonight melting the whole pound of cerrosafe and not preheating the barrel before pouring. Then I will wait 30 minutes before removing the casting; which is the point it should be at its smallest.

[williamwaco]

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While brainstorming, I figured why not use an actual cast bullet? So I broke out a bullet that cast to 0.358" and used a brass punch and aluminum hammer to tap it in the barrel a couple inches then tap it back out. It looked very good. I measured and I got a max of 0.356"! ***? I did another bullet the same way and got the same reading.

So I'm confused. Do I trust the bullet or do I trust the cast?



----------------------------------------------------------------------------------

I would trust the bullet.

I have been using soft cast bullets to slug bores and revolver chamber throats to almost 50 years. It is always repeatable and it has always solved my bullet diameter problems.

Now I am retired and have too much time so I ordered some Cerrosafe about a month ago. I have a TC .357 magnum that is giving me fits with one bullet.

I cleaned that bore and chamber until it looked like a mirror. I then degreased it like I would a new bullet mold. I then cast my chamber. I did not preheat the barrel. I was rewarded with my very first chamber cast. I was amazed at how easy and how little trouble it was. I was expecting it to look like a wrinkled bullet from a cold mold. Didn't happen. It was perfect. AND my measurements of the cast agreed exactly with my bullets slugs. .3562. Oh yes, I measured the cast exactly one hour after casting it.

If they had not agreed, I would believe the bullet measurements because years of experience have convinced me it is a good system.

[geargnasher]

If you want a chamber and throat casting that's accurate, make an "impact slug". Search is your friend, posters include members "45 2.1", "BABore", and myself to name a few. It will be accurate to the tenth.

If you want an accurate groove diameter, slug the bore like you did, partway from both ends (an inch or two) and back out, and then all the way through. This will tell you if you have a taper or restriction.

USE PURE OR NEAR-PURE LEAD FOR BARREL SLUGS. Casting some boolits from pure lead is one way, using LEAD (not zink) barrel sinkers is another. Antimonial alloys are "springy" and can come out a half-thousandth or more larger than the barrel you just drove them through. Barrels are also springy, and the harder alloys will stretch them some like a snake swallowing an egg. Also keep in mind that during a long string of rapid-fire shooting, your barrel can grow a great deal as it gets hot, and if your boolits are marginally large enough to begin with, by the third clip you might find you start to get leading. This leading might be mistaken as "cumulative", but you might be able to shoot a clip, cool the gun, shoot another, and so on all day without leading until you shoot a long enough string to heat up the barrel until the boolits no longer fit.

Gear

[Cranium]

Tonight I had success! :)

I melted the whole pound of cerrosafe and did not preheat the barrel. I also prepped the barrel of my XDM compact to cast it at the same time. Once the alloy was liquid, I poured it into the barrels. Within 5 minutes, the barrels were only warm and I easily pushed out the casts. They looked much better than the ones I did last night. The fast cooling apparently prevented crystals from forming on the surface as can be easily seen in the photo. And perhaps melting the whole pound also allowed more even, slow heating of the alloy and helped.

After about 50 minutes I measured them and they were both at about 0.354". I was worried that I was ending up at the other extreme this time but just over 10 minutes later, they were both at 0.356". And 10 minutes after that, they were at 0.357". It was amazing to see this stuff grow in such a short period of time. I know know that when using cerrosafe, timing is extremely critical if you want measurements accurate to 0.001" or better. I also now know that heating up the barrel promotes slower cooling and crystal formation and seems to cause premature growth of the alloy.

And these new casts also agree with the [good] lead bullet I put in the barrel last night so I'm all good! :)

Thanks all for your help and suggestions. Your method is the correct one, WilliamWaco.

Gear, thanks for the info on leading when shooting at a rapid rate and causing the barrel to expand. I never thought of that before but it does make sense. At some point I'm going to have to try to make that happen to see how many (or few) rounds it takes to cause this.

http://img88.imageshack.us/img88/5092/chambercast2.jpg

[geargnasher]

One thing about that barrel, it looks very well suited to cast boolits. Many throats in automatics don't transition well into the rifling, having a step rather than a taper. Both of those barrels show a nice transition, especially the one on the left in the above pic.

Gear

[williamwaco]

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Tonight I had success! :)

Your method is the correct one, WilliamWaco.



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WOW!

Would you tell that to my wife?

[Cranium]

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WOW!

Would you tell that to my wife?

Sure....but she may look at you funny forever afterwards wondering how I came to that conclusion. ;)