How to Size Lube & Gas Check / BenchRest Competition

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Wm Cook posted this 26 October 2025

I've been sizing, lubing and adding gas checks with my old orange Lyman sizer and Hornady gas checks for 30+ years.  In the past three years, the alloy being used has been about 9 to one Linotype to #2.  Carnauba Blue from White Label has been a constant.  Another specific is that the questions I have involve 190 to 230 grain borerider designs running 1650 to 1750 with a .308.

Somewhere on my shelves I have both the Lee push through sizer and the NOE gas check seater.  I also have the option of gas checking on the Lyman sizer using their gas check sizing block.  For the sake of accuracy, do you have a preferred way that you size, lube, gas check your BR competition bullets.  

I heard that with the Lee push through sizer you get a straighter final bullet since it pushes from the base and thus is a gentler sizing method.  That, as opposed to the nose first push method of the Lyman, which I have read can produce an other than straight bullet.  No data anywhere that I could find that could prove, disprove either opinion. 

If I went to a two step process could the Lee put the checks as its being push sized on or do you size first with the Lee first, then, a second step to add the gas check / lube on the Lyman.  I tried the NOE gas check seater once but at the time it didn't crimp the Hornady check in place.  Probably operator error on my part. Thanks, Bill C.

 

 

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Tom Acheson posted this 26 October 2025

I’m kinda simple.

A long time ago doing my own testing, I concluded that my Saeco lubricator/sizer produced “straighter” bullets than my RCBS unit.

That’s the only gizmo I use. Seats the gas check, sizes the bullet and adds the lube. We can make it more complicated than in most cases that it needs to be but so far, that’s what I’ve used the last 30+ years.

I will add that for my 22 BR bullets, they must be nose sized, so that’s done in a separate device. All other bullets do not need to be nose sized.

Tom

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Wm Cook posted this 26 October 2025

Tom, what method did you use to measure bullet “straightness” when you compared the SAECO vs RCBS? Bill.

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John Alexander posted this 26 October 2025

I have never detected a bent bullet. But with the soft alloy that currently works best for me, sizing first in the lubrisizer sometimes upsets the nose to a larger diameter, and sometime doesn't-- not good. So I use the Lee first, then  the RCBS. with the same diameter die for lubing.

I put the checks on the bullet by hand if I can, But most lots won't go and so I us a seater made for me by Paul Pollard to force them on. (Thanks again Paul.).

This sometimes results in a thin thread of lead shaved off the bullet, which I worried about until after shooting many groups of hand seated vs. forced on by seater and not being able to find a difference in the average group sizes.

I don't like the extra operation but sizing with the Lee goes pretty quickly.

John

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Glenn R. Latham posted this 26 October 2025

I have a number of the Lee push-thru sizers and like them for just sizing.  I have a Lyman gas check seater  LYMAN GAS CHECK SEATER - Graf & Sons

that slips under the sizing die so you can force the bullet into the GC before you size and lube it.  This seems a good way to do it because if there is a little tit from the sprue cut-off, the GC will conform to it and the bullet and GC will stay in place while sized.

Although I have not tried it, my feeble brain tells me that if the bullet is not a tight fit in the Lee die, the GC will not be forced up against the base of the bullet, and could be cocked before crimping.  Maybe I'm all wet.

Glenn

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Wm Cook posted this 26 October 2025

Just to clarify:

John uses a custom check seater that crimps, then runs them through the Lee push sizer then runs them through a lube sizer with the same size lube die (no sizing occurs, just lubes).

Glen uses the Lyman check seater, then runs them through the Lee sizer, then lubes them through a lube sizer for lubbing (same size lube die as the Lee push through).

What do you use to lube the checked bullets before you send them through the Lee push sizer?

Appreciate the help. Thanks, Bill C

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RicinYakima posted this 26 October 2025

I do it a little differently. I push the weight sorted bullets up through a 1930's Pacific die .311",, same as a Lee but better finish and less taper. They have just a touch of Imperial sizing die wax rolled on with my finger. Then to the SAECO lube and sizer to seat the gas check and lube. Since it is only sizing half a thousandths, checks seat straight. Then into an Egan nose sizer and taper die to get the top drive band the same angle as the throat. Lots of work, but they shoot well and I had all winter to get them done for the Military Nationals in June. 

 

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lotech posted this 26 October 2025

I've had very good accuracy results for many years affixing Hornady gas checks by hand then running through Redding/SAECO lubrisizer. No shaved lead, no bent bullets. I have an Eagan 30T taper die that I've never used; maybe I need to add it to the process. 

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Wilderness posted this 26 October 2025

Not bench rest, but still trying to do as thorough a job as possible.

I'm with Glenn in distrusting the Lee die for gas check seating, although it should be OK if the bullet offers enough resistance to sizing. That said, I've seen plenty pf pickup bullets on the range with gas checks just part seated and dimpled, presumably applied with Lee dies.

Given this distrust, I seat my gas checks with Lyman or RCBS lube sizer using the tool shown in Glenn's post. As regards the little tit from the sprue cutoff, that will show through the seated gas check, so I take the extra step of shaving the bullet bases to ensure the gas check is flat on the base - just the high spots, not a complete reduction. I lube the bullets as I seat the gas checks, then size the lubed bullets in the Lee dies. A disadvantage of seating gas checks this way is that it can involve some compression of the bullet nose, as indicated by variations in bullet length (vernier measurement).

As regards straightness I have noticed some irregularity on the front band when sizing #311008 down from .313" or so to .310", and for this reason alone distrust the lube sizer for sizing. For the plain base bullets I now true them up in the Lee dies (anhydrous lanolin for lube), then finish them in the lube sizer with bullet lube and no further reduction in diameter.

You are only as good as your library.

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Bud Hyett posted this 26 October 2025

Steps for .30 and 6mm caliber: 

  • Set the check on the base by hand.
  • Feel sure it sets on easily and visually check that the check looks evenly set.
  • Then through a die in Lyman sizer die .001 to .002 larger than desired finish diameter. Go in just far enough to start the seating process.
  • Then seat in the final step in a die that is the desired diameter. 

6mm die selection:

  • Lyman 450 with .245 die to start seat.
  • SAECO with .244 die for final.
  • I have an Eagan .244 taper die I want to start using. 

.30 caliber die selection:

  • Lyman 450 with ,311 die to start seat.
  • RCBS with custom .3105 or .3085 die for final. 

I have tried the NOE push-through sizing die and did not find it helped. 98% or 99% of the bases firmed up against the base but not all. This necessitated another step to check each one after sizing. That might be my experience and not yours. 

 

Farm boy from Illinois, living in the magical Pacific Northwest

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Larry Gibson posted this 26 October 2025

I use an "as cast" diameter H&I die in a Lyman 450 to seat the GCs using a Lyman GC seater.  Then the bullets are lubed only in that H&I die w/o any bullet distortion.  The final step is to push size the GC'd and lubed bullets through a Lee sizer.  I might not the "as cast" diameter of the bullets are only 001 or less diameter than the final sizing with the Lee push through.

LMG

Concealment is not cover.........

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Waleone posted this 26 October 2025

I push the gas checks on by hand then finish seating (if necessary) and crimp using the Lyman gas check seater in a RCBS Lubrasizer. If the gas checks do not snap on by hand, I expand them using the NOE gas check expander before crimping. I am not comfortable with the gas check shaving lead. For 30 caliber, I used to seat using an Eagan .30 gas check seater, but the Lyman allows crimping, and the Eagan does not.

After all the bullets I am working on have their gas checks installed and crimped, they then go back through the RCBS for sizing and lubing. To me the two separate operations helps me make sure the checks are firmly and completely pressed on the base of the bullet. I have never used the Lee sizer. No particular reason why other than my method seems to be working for me.

I have made my own taper dies but mainly use them only to allow the bullet to stay completely in the neck of the case when the cartridge is chambered. For bore riders, I adjust the bore riding diameter of the bullet (if needed) with NOE nose sizing bushings. I do not like taper sizing bore riders, sometimes the nose diameter ends up too small when the bullet is taper sized the amount I am looking for.

BTW, I have found weights of Gator gas checks to be much more consistent than Hornady checks.

Wayne

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Paul Pollard posted this 27 October 2025

For those of you who shoot .30 caliber with gas checks...

Several years ago at a national match, I talked with Dave Lee and asked him how he processed his bullets. He seemed like a good person to ask since he held several records. He said that he added a pinch of molycoat to his tumbler, added the bare bullets and then tossed in the gas checks and tumbled everything for an hour. I asked why he put the gas checks in. "Because they attach to the bullets all by themselves."

I found that hard to believe, but I tried it when I got home. I tried it with some .30 caliber bullets and gas checks. Amazingly, it worked just like he said. I tried it with 6mm and .22's, but didn't have the same degree of luck as the .30's. Doing it this way may save some time and frustration.

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John Alexander posted this 27 October 2025

Bill's question -- What do you use to lube the checked bullets before you send them through the Lee push sizer?

Nothing is needed. Lead alloys are naturally slick.

As for the question of push thru dies maybe not consistently seating the check. As cast bullets have very uniform diameters and the force needed as felt at the handle while sizing seems very uniform, more consistent than I think I can manage while seating in lubrisizer.

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Bud Hyett posted this 27 October 2025

As for the question of push thru dies maybe not consistently seating the check. As cast bullets have very uniform diameters and the force needed as felt at the handle while sizing seems very uniform, more consistent than I think I can manage while seating in lubrisizer.

I've observed that gas checks in their opening are not uniform, this can contribute to the problem. This is around one or two percent. They can be dented during formation or packaging. 

Farm boy from Illinois, living in the magical Pacific Northwest

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.22-10-45 posted this 27 October 2025

I turned up tapered gas check expanders for use in lubesizer for custom fit.  Here's another twist on gas checking:  If you have a Hoch, or Leeth type nose pour plain base...or any nose pour plain base using a plug or bottom plate by placing a gas check on plate & closing mold, you can cast gas check in place.  Accuracy is at least equal to best plain base loads.

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pat i posted this 27 October 2025

I size and seat the check in a Lee die then lube in a .001 over H&I die. Only thing different is I drill out the center of the ejection pin until there's about a 32nd or so ring around the outside. When the bullet reaches bottom I give it a little bump. This leaves a ring around the outside of the check so I know it's fully seated. When people talk about Lee dies making straighter bullets I don't think they mean bent bullets but bullets sized off center. It takes a full diameter bullet like an LBT to see it but I went to Lee dies because after sizing some LBT 45 caliber pistol bullets in a lubesizer I could see they were being sized more on one side than the other. The Lee took care of that.

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OU812 posted this 28 October 2025

I've allways squeezed my bullets from tip to base to make bullet more round and better fit to throat and bore. This also squares gas check. I've never shot competition, but I am confident I could out shoot most all of you HA HA.

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OU812 posted this 28 October 2025

BTW simply seating a bullet in case neck that is too tight can deform or enlarge softer alloy bullets.

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Tom Acheson posted this 28 October 2025

I have an old 1990’s Neco concentricity, wall thickness and run out gage tool.

Did anyone here mention the use of a “bump “ die? I did that for all of my match .30 cal. Bullets. Trues-up the OD of the bullet and sharpens up the corners of the gas check.

Today no .30 cal. Loads. Just .38-55 in a CPA (PBB) category and 40-70 Sharps Straight in a CSA Model 74.

But…..bullet fit to chamber is still the key component to accuracy, regardless of all of the crazy tools and techniques we drive ourselves nutz with. A taper inserted into a taper seems like a key.

Tom

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.22-10-45 posted this 28 October 2025

Biggest gripe I have with most commercial checks is the uneven height of sidewalls.  It seems to me that if one edge clears muzzle before the other side, muzzle blast would throw bullet off course.  If bench rest guys can buy precision based jackets..why can't we?

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