Inspecting Gas Checks

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  • Last Post 04 January 2017
OU812 posted this 10 November 2016

 I think that “equal skirt length” of gas check is very important for great accuracy. Equal skirt length also equals even thickness of skirt for better bullet concentricity after sizing. So recently I started using my dial calipers to check for equal length. For example one .223 gas check skirt can vary as muck as .001-.004 in length (one side longer than other). One box of my Hornaday checks only had about 500 that were near perfect. 

The shape of base can sometimes vary also. Most were more flat and uniform, but a small few were more rounded and thrown out.

I once sanded skirts evenly, but this does not cure the wide thickness variation of skirt. Also seems that the checks with sanded skirts fell off easier in flight?

Little details like this along with a more perfect snug fitting cast bullet can improve accuracy .

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John Alexander posted this 11 November 2016

It would be interesting to see what you found if instead of throwing away those gas checks with more rounded bases you used them and shot them in alternative groups with the flat bottomed ones to see how much they affect accuracy.    Same for the gas checks with uneven heights.  Is .002” variation enough to matter or only the ones that vary around .004"?

Maybe you have already done this comparison shooting.  If so the results would be interesting.

John

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David Reiss posted this 11 November 2016

Several years ago, I tested the theory of the flat & rounded gas checks when working up some practice loads for my 7mm TCU & .30 Herrett. In my tests I found that with the 7mm TCU it seemed to make no difference. But accuracy did improve some with the flat bottom GCs in the .30 Herrett. However it only improved with RCBS 308-165-SIL bullets. With the LEE C309-160R it seemed to make no difference at all. 

David Reiss - NRA Life Member & PSC Range Member Retired Police Firearms Instructor/Armorer
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OU812 posted this 11 November 2016

John Alexander wrote: It would be interesting to see what you found if instead of throwing away those gas checks with more rounded bases you used them and shot them in alternative groups with the flat bottomed ones to see how much they affect accuracy.    Same for the gas checks with uneven heights.  Is .002” variation enough to matter or only the ones that vary around .004"?

Maybe you have already done this comparison shooting.  If so the results would be interesting.

John

No comparison so far, but I will compare the culled gas checks with the so called good ones to see if it makes a difference.

I know my shortened gas check shank requires a gas check with a shorter skirt. This was the biggest reason I inspected skirt length. 

I also re throated my factory Remington using the 5.56 NATO chamber reamer. The lead is now .2265 diameter, lead length .0566, less steep 1-13 degree throat angle. Bullets are sized .226 for a good snug fit. Bullet is pushed back deeper into case when chambered. No testing so far...but soon will.

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John Alexander posted this 11 November 2016

Good to hear about your planned testing. I will look forward to seeing the results. John

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OU812 posted this 17 November 2016

Top target is the first 10 shots from squeaky clean barrel (two fouling shots fired before test). These cast bullets have the “sorted gas checks” attached. Bullet bases inspected for a smooth level sprue plate cut. Bottom target is the second 10 shot group fired from a dirtier barrel (bore snake pulled thru barrel in between groups). These bullets have the "culled checks” attached. Bullet bases were not inspected. 45-45-10 lube used.

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OU812 posted this 18 November 2016

223 Recipe:

Soft 10-11 bhn alloy. Antimony and lead lets you cast hot without worry of loosing tin content. Softer alloy also conforms well to throat when fired. https://rotometals.com/antimonial-lead-ingot-3-5-antimony-lead/>https://rotometals.com/antimonial-lead-ingot-3-5-antimony-lead/

Bore ride section must engrave rifling slightly when chambered. I have enlarged the cavities slightly to allow for eroding throat.

Clean barrel! Lead can be difficult to remove from barrel, but must be done. Excessive cleaning can also enlarge throat. So you must enlarge bullet diameter (bore ride section)overtime.

Tite Group powder...per Mr. Alexander

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OU812 posted this 19 November 2016

Powder charges were thrown using RCBS Uniflow with smaller pistol powder insert...this may be the reason for small vertical dispersion. Next test will involve hand weighed powder charges (6.8 grains) and CCI Bench Rest primers. I have been using Winchester small rifle primers.

These are the same bullets but, cast using 20-1 alloy (Alexander 80 grain bullet with shortened gas check shank) :)

I have requested over 3 months ago for NOE to make 6mm, 6.5mm, 7mm, 30 calibers versions of this bullet...but NOOOOOOOOOOOO. This bullet design just makes perfect sense and will out shoot everything else NOE sells...maybe this is the reason for me being ignored?http://noebulletmolds.com/smf/index.php/topic,1569.0.html

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mtngun posted this 19 November 2016

Hard to say why a manufacturer won't introduce a particular product but regardless of how they spin it, it usually boils down to profits or capability.   

Most bullet mold sales are for plinking applications, not for CBA-style target shooting.     Dig bullets out of the berm at your local range -- mostly 9mm, 45acp, 357, 44, etc..   That's what sells, and those types of molds are easier to manufacture, anyway.

CBA target shooting, like jacketed benchrest, is worthwhile in that it pushes the technology forward and ultimately benefits the casual shooter.   I've yet to compete in either cast or jacketed benchrest, but I am nonetheless fascinated by the technology.  

Thanks for posting your target results, by the way.

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.22-10-45 posted this 19 November 2016

I too became discusted with uneven heights and wavy bases on gas checks. I tried annealing & pressing flat with a simple punch & base set-up for my 45 & 450 Lyman sizers..only with mixed improvement..this was mostly with .22 caliber. So, I decided if I couldn't remove the imperfect base..to remove it! I had Corbin make up a reloading press type punch & die to punch out center of .22 gas check..leaving about .03” of original base on sides. I really need to put more time in testing this design as results are to mixed to say this was a real improvement or not. One thing I do know that will improve accuracy of a gas-checked bullet..again this is with .22 caliber, is a swaging die and pre-lubed/gas checked bullets sized .001” under die dia. & swaged up to .226"..check base is perfectly flat & square with bullet sides..Although it's easy enough to apply pressure to bring edge of check to a sharp corner..better accuracy is had by leaving a very small radius. I am using Lyman Super Moly//stiffened up a bit using beeswax & lanolin. Best accuracy so far has been with the Saeco #22 swaged using a tapered flat point nose punch (same shape as original 49gr. Lyman 225415). In a Ruger No.1 .222 Rem. this can equal best jacketed match bullet accuracy at 100yds. (7/16"). Next most accurate is the Eagan MX reformed using a round nose punch..bullet comes out looking just like the Remington .22 rimfire Yellow Jacket bullet.

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billwnr posted this 20 November 2016

If you want to get squared edges on gas checks just run your bullets thru a bump die.

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OU812 posted this 21 November 2016

Consistently uniform edges...round or flat will work, but all must match equally.

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OU812 posted this 23 November 2016

OU812 wrote: 223 Recipe:

Bore ride section must engrave rifling slightly when chambered. I have enlarged the cavities slightly to allow for eroding throat.

Clean barrel! Lead can be difficult to remove from barrel, but must be done. Excessive cleaning can also enlarge throat. So you must enlarge bullet diameter (bore ride section)overtime.

Tite Group powder...per Mr. Alexander

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Misinformation: I stated that the Bore ride section must engrave rifling slightly when chambered. A bullet that chambers easily and leaves marks on bullet in a clean barrel may not chamber in a dirty barrel. So please allow for fouling build up in throat.

I discovered that some of my cast bullets bore ride section was too fat and bullets were being pushed back into case when chambered. These bullets chambered easily in the clean barrel, but would not in the dirty barrel (poor accuracy). Good accuracy returned when I switched back to the smaller .220 diameter versions. The .220 versions also have a good snug slip fit into muzzle end of barrel.

For some reason the CCI BR primers did poorly and had 3 misfires. I believe excessive case shoulder head space caused this. I now full length resize all my brass to push shoulder forward for tighter head space.

Today I was back to shooting some very good groups after correcting these problems...Winchester primers were used without failure.

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OU812 posted this 23 November 2016

John, My rifle does shoot a little more accurately after re throating to NATO specs. Your 80 grain bullet now fits like a glove when sized to a fatter .2265 diameter...grease groove now holds a little more lube.

The easy to apply 45-45-10 lube also performs VERY well, but I will need to shoot longer strings against other lubes to prove if it is better or not. IMO wet lube should break down and reduce hard fouling just ahead of throat area in bore. The dried 45-45-10 lube may make fouling worse in this area (fatter bullets not chambering)?

BTW my other box of Hornaday gas checks have a more uniform shape (skirts have a more equal length)

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OU812 posted this 24 November 2016

These bullets were lubed and dried using  45-45-10 lube. Casting fins on bullet tips were removed with thumbnail and 0000 steel wool before coating.

Bullets sized and gas check seated nose first thru the RCBS Lube-A- Matic using NOE flat punch and sizing die opened to .2265. I think nose first thru the full length RCBS sizing die aligns the bullet better before sizing.

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John Alexander posted this 25 November 2016

OU812, You have a good shooting combination so I hope you will follow through with a test of 45-45-10 vs. other lubes.  Mtngun's tests are excellent but the conclusions for 3,000 fps may not be the same as the best lube at more conventional CB velocities. John

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OU812 posted this 25 November 2016

I will try LBT Blue Soft against the 45-45-10...about 20 shots using each lube should do it.

Yesterday I shot a 1/2” group with 6.5 grains of Tite Group and 45-45-10 lube. These bullets were aged 3 months and I have more to test lube with.

Have you ever went to the range and shot excellent groups one day, then go back to the range days later with same load and shot terrible groups? I believe age hardening of cast bullets causes this. What causes age hardening...arsenic? Will a cast lead bullet harden over time if it does not have arsenic mixed in?

Age hardening may have been another reason my new fatter bullets did not chamber days later. I will switch back to the 20-1 alloy for easier chambering of fatter bullets and to maybe prevent age hardening.

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45 2.1 posted this 25 November 2016

OU812 wrote: Have you ever went to the range and shot excellent groups one day, then go back to the range days later with same load and shot terrible groups? I believe age hardening of cast bullets causes this. What causes age hardening...arsenic? Yes, in trace amounts along with antimony. Will a cast lead bullet harden over time if it does not have arsenic mixed in? As long as you have antimony in the mix, that will happen. These items have been in print a long time about what happens and when. Research some and you'll find it.

Age hardening may have been another reason my new fatter bullets did not chamber days later. Age hardening and it's hardness cycle until it somewhat stabilizes are contributing factors. Let your freshly cast bullets stabilize in hardness before you shoot them. Cut down the antimony percentage to about 2% and about 0.25% tin and let them age a little over two weeks. I will switch back to the 20-1 alloy for easier chambering of fatter bullets and to maybe prevent age hardening. Milton farrow wrote about this in the age of black powder. He cautioned people to only use freshly loaded ammunition as he had the same problem with lead/tin alloys. It doesn't take but a trace amount to mess up your alloy and introduce age hardening into the cycle.

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OU812 posted this 25 November 2016

45 2.1, Thank you for this good refresher coarse.

Today the range was very crowded because of holidays...no tables available. I may go back after lunch.

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OU812 posted this 26 December 2016

I depleted my old lot of Tite group powder and had to go out and buy more of a different lot. Seems the new lot is a little different and not as accurate, so back to load development. Seems to be lots of variability in everything you buy now days...every lot is not the same.

I also purchased some Gator gas checks. This lot of gator checks is .001 thicker than my current lot of Hornadays. The Gators are a different animal than the Hornadays.

BTW all future testing will be done using 45-45-10 tumble lube.

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pat i. posted this 26 December 2016

I chased that gas check demon around for a while when I was involved and came to the conclusion it wasn't worth the effort. Learning to read the conditions and bench technique will pay much bigger dividends.

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SierraHunter posted this 26 December 2016

Seems like a lot of work for little gain.

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OU812 posted this 04 January 2017

My last lot of Gator checks from NOE have a consistent .055 skirt length and are thicker than Hornaday. I did a comparison between the two and the Gators were slightly more accurate. Thicker may be better.

The 80gr SP bullet likes to be pushed faster in the slower 1-12 barrel. Next I will try slower burning powders to achieve higher velocities with less bullet deformation. I did a brief test using Unique and 4759 powder and was impressed by grouping. The 45-45-10 tumble lube performed well also.

It is too windy today to go test.

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