RCBS 7mm 145 SIL and Gas Check Issue???????

[Magnum Mike]

I have a RCBS 7mm 145 SIL mold that i recently started casting with. The boolits come out of that mold perfect, very nice mold to work with. My problem with it is...the Hornady gas checks do not really crimp in place and can be peeled off with a fingernail. I had this same problem one other time when i used the wrong check on a boolit and accuracy was terrible! Seems that the checks were departing after the boolit left the bore causing those bullets to fly everywhere. That in mind, i obtained some RCBS checks and seated them, same deal! I am sizing these boolits and checks with a Saeco .285" die, all boolits were sorted into one grain lots prior to sizing. I have yet to shoot these but cant imagine having much success given my past experiece with a check that is not firmly attached to the base.

Any advice?

[joeb33050]

The bullet GC shank may be too small. What is the diameter of the GC shank? I will check, or Hornaday GC dimensions are in the FILES at the yahoo "bulletcasting" site.
joe b.

[7br]

What alloy are you using? I have the same mould, but it is about 10 years old. Can you give us some measurements on the check shank?

[Magnum Mike]

I will have to measure them later today.

I am using straight wheel weights.

This mold is probably 10+ years old, bought it at a local shop that has a bunch of new old stock molds.

Since neither the RCBS or Hornady checks work, it must be the check shank is undersize.

[Willbird]

I know at one time I had a 7mm sil mold, it may have been an rcbs, but I had the same problem, I gave up on cast boolits in 7mm tcu pretty easily.

another poster has said that annealing gas checks makes them seat nicer and crimp on better, both if they are too tight or too loose, I bet you could float a piece of steel in your pot and set a few checks on it to anneal them and see if that helps.

Bill

[JDL]

Try annealing them by heating cherry red to make them dead soft. If that doesn't work, you may have to make the shank a little larger.-JDL

[Buckshot]

............Mike, you can open up the GC shank easily even if you don't have a lathe, and that's via a reamer. From most any of the machine tool companies like Rutland/Airgas, MSC, McMaster-Carr you can buy reamers in steps of 1 or 2 ten thousandths increments.

Using a reamer will do away with the taper on the shank. The length of the area you're opening is short, and it's not difficult.

Another way that's simple but kinda rudimentary is to use a needle nose plier and 'pinch' the GC shank. This will oval it to a degree and does a good job of getting the GC to stick.

...................Buckshot

[Captain Midnight]

Buckshot...........
Who's the Pligrim there with you and Toby?
Serious lookin' dude.
Captain

[Buckshot]

Buckshot...........
Who's the Pligrim there with you and Toby?
Serious lookin' dude.
Captain

Just one of my ole riding buddies!

............Buckshot

[azrednek]

Mike, I suggest you get on RCBS' website and send them an email. My gut feeling is RCBS will correct the situation especially if you mention using their brand of gas checks.

I had a similar problem many years ago with a 30 caliber slug. The Herter’s brand mold and the Herter’s gas checks just wouldn’t stay on. I could easily pull them off with my fingers. Over all I got great accuracy but seemed to have to many strays. I’m speculating that the strays were caused by the gas check falling off in flight or falling off all except the strays. I put a dab of Elmer’s Glue on the gas checks before running it in the sizer and the strays were almost non-existent afterwards. I never got a chance to try a different brand of gas checks. Lost most of my reloading equipment in a house fire.

The Herter’s goods I had at the time came from an estate sale. There were some cast slugs with the gas checks installed in the box of reloading goods I bought. The previous owner used some kind of red cement and I presume it was fingernail polish. I recall somebody claiming to have used Super Glue to keep gas checks in place in a post in the Yahoo cast bullet news group.

[bobthenailer]

hi i also have the 145 gr rcbs, all rcbs rifle & silhouette bullets are cast from linotype as per rcbs , all pistol bullets are from a 1 & 10 mix as per rcbs, having said that do as a previous post said aneel the hornady gas checks, i have 3 rcbs silhouette bullets and thats what i do & i dont use linotype i use a alloy + around 15 bernill hardness & water drop the bullets, i must of used at least 20,000 of these bullets.

[JSH]

Heck, I saw the problem right off the bat. Using straight WW, all of mine have had a slight curve to them.
I would do as stated above, give RCBS a holler. The 30 cal 165 SIL you got for me is a fine mold. If you run across another of the 7mm's give me a holler.
Jeff

[wcshooter]

sounds to me like your alloy may be to soft. try making it harder wich will make a larger dia. bullet. try going to .284 instead of .285. at .284 the bullet bump up from ignition should fill out your barrel and the additional compression of the grease grove may allow for a better lube pool around the bullet down the barrel. hope this helps

[beagle]

IF you don't find a check that fits tight, try lapping just the check area of the cavities. A steel bolt shank in a slow moving drill press works all right for this as it cuts very slow. Cut and try until you have it where you want it.

Another solution is to "beagle" just that part of the mould blocks.

Gas check retention is probably the biggest cause of inaccuracies in small diameter cast bullets. The smaller in daimeter you go, the worse it gets./beagle

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