Shaving Bases of Cast Bullets

  • 569 Views
  • Last Post 3 weeks ago
Wilderness posted this 06 January 2025

Here's one for the OCD crowd.

A while ago there was a thread on shaving the bases of cast bullets, i.e removing lumpy sprues and generally flattening the bases, mainly to make a better seat for the gas check.

Generally I don't bother shaving plain base bullets. If I can see a lumpy sprue when I open the mould I just dump the bullet - I can make a new bullet in less time than it takes to clean up a lumpy one.

I do however shave/scrape the bases of #U321297HP bullets (.322") that I turn into .30-30s (.312"). Sizing down a .32 gas check to .30 results in a concave dimple in the gas check. If the bullet base is clean (shaved), the dimple will be centred. If there is a some lumpiness or cratering around the sprue the dimple may be misshapen and off centre. I shave all the bullets, not just the obvious ones. The tool is a sharp knife, and I try to get just the sprue material.

Variable sprues also feed into variable bullet weight. I sort my bullets into weight groups, although mainly I'm after the light ones that might have a hidden flaw or the heavy ones that were made with the HP pin not fully engaged.

I also use my bullet weight to confirm correct alloy, so differences from shaving if substantial would come into play.

Out of interest I weighed the material that came off a recent run of  #U321297HP. Total weight of scrapings was 27 gns off 269 bullets - 0.1 gn per bullet. Doing the weight grouping after rather than before shaving seems a viable choice.

I should say that all but a few of my sprues are pretty good to begin with, but scraping makes them better.

You are only as good as your library.

Attached Files

Order By: Standard | Newest | Votes
OU812 posted this 07 January 2025

Have you ever tried touching hot soldering iron to sprue area...it should smooth it out pretty good.

I've shortened gas check shank using drill press and sandpaper, but found that shaving .030 off top of mould worked better. I swear shorter gas check shank shoots better. Especially using the 80 grain 223 caliber Alexander bullet.

Attached Files

Shopdog posted this 07 January 2025

I take about .005" or so off bases held in a fix

Attached Files

  • Liked by
  • TRKakaCatWhisperer
Shopdog posted this 07 January 2025

Try it again.....

I take about .005" off bases in a fixture. It's stupid quick and easy.

What I've found is that even if I hold really tight tolerances on casting... they're still a couple .1's of a grain variation in weight. That's on a good day casting. Some moulds can be a whole grain variation.

Milling bases makes this all just go away. Without writing a book,it's pretty obvious with this approach,that it shows most/all of the weight issues are in the base.

Another tidbit; the space above GC on some moulds is "generously" wide,as cast. These are nice because you have a little/lot of room for fine tuning the load. But on moulds... Saeco/cough/cough there isn't any room for adjustment. IOW's,as cast taking .005" off can put the GC right up against the lowest drive band. Can not give an "absolute" on this through testing but it is NOT holding anything back that I can tell on heavy for cast,loadings.

To the point that two of my heavy hitters that utilize Saeco "no gaps" are,the bullet of choice if the metric is paper group size. One is a 6mm Rem with the Saeco 85g... the other is a .260 Rem and the Saeco 140. Both interestingly use IMR4831. The "no gap" just isn't a problem.

Can't say that it happens on every chambering,or mould. Will stop there.

Attached Files

  • Liked by
  • Wilderness
TRKakaCatWhisperer posted this 07 January 2025

I take about .005" or so off bases held in a fix
I'd love to see a picture or so of the fixture!

Attached Files

  • Liked by
  • RicinYakima
  • max503
John Alexander posted this 07 January 2025

I generally use the softer alloys and cut sprues with down hand pressure so bumps no longer appear, but I know they can appear with hard alloys and some molds. Nobody seems to love the bumps but do we have actual shooting results that show that they enlarge groups or do they  just offend our sensibilities concerning ugly bullets. Does anybody know?

Maybe worrying about them is just something to occupy the free time of us OCD sufferers as Wilderness hints. Then again, maybe not.

I won't get into the same question about  tiny variations in bullet weight mentioned above.

John

Attached Files

linoww posted this 07 January 2025

Thank you for that post, John.I deleted my previous comments because I did not want to get flamed.But they were very similar.

"if it was easy we'd let women do it" don't tell my wife I said that!

Attached Files

Wilderness posted this 07 January 2025

What I've found is that even if I hold really tight tolerances on casting... they're still a couple .1's of a grain variation in weight. That's on a good day casting. Some moulds can be a whole grain variation.

Milling bases makes this all just go away. Without writing a book,it's pretty obvious with this approach,that it shows most/all of the weight issues are in the base.

A few years ago a friend milled some of my #321297HP bullets held in V blocks. The operation didn't really reduce weight variation, and I was concerned about the side pressure being exerted in the operation, but the groups I got with full power loads were sub 2 moa. If I had the equipment myself I'd still be doing it, but instead I now scrape. It taught me the importance of clean bases.

I flatter myself that my scraping does as good a job as the milling, provided the bullet base is square to begin with. And I can do just a few at a time when I need to or when I have the time.

My post was spurred not so much as a promotion for base scraping, but as a note on the (minimal) weight reduction from the operation. I don't go after the pits in the bases as you can with milling, just the high spots that affect gas check dimpling.

You are only as good as your library.

Attached Files

  • Liked by
  • Glenn R. Latham
LeverGunner posted this 4 weeks ago

Interesting discussion. I will remove a high sprue on occasion, with the tip of a razor blade knife, being careful not to get into the edge of the base. I've never heard or thought of milling bases though.

Attached Files

pat i posted this 4 weeks ago

I went down the road of perfecty flat bases years ago as an experiment. I chucked the bullets up in a collet in my lathe and made a skim cut to get the bases perfectly flat, didn't make any difference on the target. After that I followed Veral Smith's advice of running a drill bit into the H&I dies ejector pin so there was about a .050 rim left on it so it was only contacting the outside edge of the check and gave it a little bump so you could see a ring on the check. I don't know know if it helped or not but ot didn't hurt. But then again I've never had much problem with lumps. My problem is tearing a divot for lack of patience.

Attached Files

  • Liked by
  • RicinYakima
  • John Alexander
Justin.P posted this 3 weeks ago

I've never done it or even considered it, as I have never had the problem yet. But as I was reading this thread I had a thought for those so inclined and that wanted to flatten in any quantity.

I would think a LE Wilson case trimmer could be setup to produce some really nice flat, square bases. A replacement for the case holder would be needed, and something like an adjustable top punch to index the bullet against...... maybe. And it could possibly become a hollow pointer even.

And it would be cheaper than a milling machine............

Attached Files

  • Liked by
  • MarkinEllensburg
Wilderness posted this 3 weeks ago

Justin - I have cleaned bullet bases in the Forster trimmer, but am sufficiently confident to continue scraping bases with the knife for the small numbers involved.

I found I could grip the nose of the bullet with one of the standard Forster collets. I used a flat ended cutter from my Dremel set, with the shaft shimmed up with paper. Of course it cut better on the edges than in the middle. It may even have been better if the cutter was a bit off centre and describing an elipse.

You are only as good as your library.

Attached Files

  • Liked by
  • Justin.P
Shopdog posted this 3 weeks ago

Was at this yesterday. Sorta even impressed me as I had never thought about timing this. My fixtures cut 11 bullet bases at a time.

Made a calc mistake when making the first(of 1/2 dz now) fixture and wound up with an extra hole.... and then just stayed with 11.

So here goes; 1-grab a handful of bullets. 2- don't even look at them and load 11. 3-Tighten clamp,mill.

Without hurry,it takes 50-60 seconds to do 11. Was doing RCBS 60G (drops @60,mould is their 55g) .22 for 22.250.

The issue with this is; it seems like everytime I discuss milling,folks think I'm trying to "sell them something"? Am positively NOT gonna argue about it. If you're shooting low node <2000 fps="" loads="" on="" a="" well="" cast="" bullet,keep="" at="" it.="" i="" shoot="" varmints="" with="" outstanding="" results,cast="" only="" at="" starting="" jacketed="" speeds.="" am="" nipping="" at="" the="" heels="" of="" my="" jacketed="" accuracy="" accomplishments.="" some="" of="" these="" rigs="" will="" absolutely="" shock="" folks="" into="" what's="" possible="" with="" not="" only="" typical="" "groups"="" but="" way="" more="" important="" to="" the="" hunter.....="" no="" foulers,no="" warming="" up,cold="" bore="" shots="" are="" to="" be="" included="" into="" the="" measuring.="" and="" subsequently,no="" cherry="" picking="" groups.="" this="" site="" is="" very="" difficult="" for="" my="" limited="" tech="" savvy.="" can't="" post="" pics,can't="" edit...="" i="" will="" gladly="" take="" a="" few="" pics="" and="" email="" them="" to="" you.="" send="" me="" a="" pm="" and="" i'll="" shoot="" you="" an="" address.="" fps="" loads="" on="" a="" well="" cast="" bullet,keep="" at="" it.="" i="" shoot="" varmints="" with="" outstanding="" results,cast="" only="" at="" starting="" jacketed="" speeds.="" am="" nipping="" at="" the="" heels="" of="" my="" jacketed="" accuracy="" accomplishments.="" some="" of="" these="" rigs="" will="" absolutely="" shock="" folks="" into="" what's="" possible="" with="" not="" only="" typical="" "groups"="" but="" way="" more="" important="" to="" the="" hunter.....="" no="" foulers,no="" warming="" up,cold="" bore="" shots="" are="" to="" be="" included="" into="" the="" measuring.="" and="" subsequently,no="" cherry="" picking="" groups.="" this="" site="" is="" very="" difficult="" for="" my="" limited="" tech="" savvy.="" can't="" post="" pics,can't="" edit...="" i="" will="" gladly="" take="" a="" few="" pics="" and="" email="" them="" to="" you.="" send="" me="" a="" pm="" and="" i'll="" shoot="" you="" an="" address.="">

Attached Files

Shopdog posted this 3 weeks ago

Looking up at that scrambled MESS... this is what this site does?

Ya'll carry on,wishing everyone the very best.

Attached Files

Close