GC retention

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  • Last Post 23 May 2019
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Ross Smith posted this 18 May 2019

Do gas checks stay on after leaving the barrel? How would I test for that?

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stevebarrett posted this 18 May 2019

Sometimes they don't - picture of imprints on chronograph sensor.

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JeffinNZ posted this 18 May 2019

Sometimes yes, sometimes no.  I have had impacts on the chrony also but likewise have recovered GCs in the berm.  Don't mind either way as long as it is consistent.

Cheers from New Zealand

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BudHyett posted this 19 May 2019

Three ways:

  • Bullet recovery box, eight foot long, two foot square, plywood box filled with oiled sawdust.
  • Digging out of the berm at 100 and 200 yards, this is after a heavy rain so the tracks were easily seen.
  • Extra holes in the targets at 25 yards or on the chronograph screens.

What is interesting on the recovered bullets is the lead captured between the gas check and the bullet base on the shank. This observation leads one to consider whether the leading edge of the gas check is scraping the lead fouling from the bore during passage.

The Marston Municipal Ballistics Testing was too absorbed in other projects to immediately follow up on this and then I moved. A structured experiment to see whether the leading edge of a gas check scrapes the bore in passing would be interesting. 

Country boy from Illinois, living in the Magical Pacific Northwest

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Ross Smith posted this 20 May 2019

I use gator gas checks and they are on pretty tight. My friend Lee wiggins homemade aluminum checks are kinda loose. That's why I asked . Once the bullet is out of the barrel, does it matter accuracy wise if the the checks come off randomly? If I get some plywood I just might make a trap. I've recovered some of my bullets from the backstop but our target stands use rubber conveyer belting as a backing plus damage in the gravel berm, so I've never seen a gc on my recoveries. Some bullets, pistol mainly won't penetrate the belting. It's full of bullets, but try to pull one out, no.

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Alstep posted this 20 May 2019

I would think that you would get elevation changes with bullets that retained gas checks vs those that lost them, due to weight change being inconsistent.  Especially in rifles over some distance.   

I've always wondered, too, about the need of keeping gas checks fully seated on the base, as the tremendous pressure impact of the powder gasses on the base of the bullet would surely seat them.

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Ross Smith posted this 21 May 2019

I shot some 115 gr 30 cal gc bullets today and none of them retained the gc after going through 7/8" thick conveyor belting and dirt. No surprise there really. Still thinking about the sawdust box.

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Ross Smith posted this 21 May 2019

Bud: Speaking of the sawdust bullet trap, Do you have to change your point of aim or can you shoot at a single bullseye?

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BudHyett posted this 21 May 2019

The input was through soft rubber fins like a box fish trap. The fins were 18 inches long, triangular, and fitted to solve the sawdust leakage problem. These fins did not interfere with the bullet and kept the sawdust in. 

The first problem was the alignment of the bore to be parallel to the centerline of the box. We ended with a cleaning rod out the muzzle and a level to get the bore parallel to the ground.

The second problem was holding the barrel back far enough to keep the muzzle blast from destroying the rubber fins. We ended with a table holding the rifle about two feet from the end and still replaced the fins several times a day.

We cut slots in the top and added targets every foot to be able to trace the bullet through the sawdust. This was an unforeseen problem since the bullet would go differing distances with the same load. The two loads that made it the full eight feet were .30-'06 National Match and .45-70 500 grain round-nose black powder equivalent loads.

This is more work than first thought. Each bullet must be retrieved individually to keep them from bumping each other. The results are outstanding. 

   

Country boy from Illinois, living in the Magical Pacific Northwest

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Coydog posted this 21 May 2019

I say alot of times if the GC is press on  the GC will fall off often  in flight then the ones that crimp on like the Hornady and the Gator. after they are going through the target it dose not matter to me if they on or not. The ones that fall off in flight is what change how the boolit is I found.

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Mike H posted this 22 May 2019

Over the years I have seen that some have come off,but most bullets that I have recovered have retained the gas check,since most bullets are not recovered,one couldn’t be 100% sure of what happens.Not long ago I had an experience with gas checks coming off,I wrote about it in the Military Bench Rest section,the post was    Who shoots the 303 British. What happened was that at 100 yards all the gas checks came off,ten shots on the target,20 holes showing,then at 200 yards,five shots fired,9 holes on the target.The question I had then was if the gas checks must have detached before 100 yards,how could they continue on to 200 yards?

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Ross Smith posted this 22 May 2019

That's weird! Why would the checks follow the bullet anyway?

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Fitzpatrick posted this 23 May 2019

Here is a picture of a recovered 38-55 bullet with a homemade check from a Pat Marlin check maker that is pressed on 

I've recovered many of both the 38-55 and 45-70 with checks in place.

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