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View Full Version : Experiment in progress--flash hole size reduction



bluechip
02-14-2016, 12:29 PM
I'm currently trying an experiment with a .17 hornet. I noticed my 6mm ppc Lapua cases (actually 220 Russian) had a smaller flash hole (.062") than my .17 hornet (.079") even though the hornet has one third the powder charge and they both use the same primer. I am reaming the flash holes and inserting brass bushings that are then drilled to a smaller size. A simple straight bushing, after firing, is oddly gone from the flash hole and seems to be vaporized, even though it is a very tight press. The new concept is shown in the pictures where a brass insert is pressed in with a tapered head like a flat head screw, into a case that has been machined to the same dimensions. The hornet has a flash hole that is .079 and I'll be trying .055 and .035 in the near future and will post results. It looks like the best way to go would be acquire cases that weren't drilled, just blank.
17399 17400 17401

Dusty Stevens
02-14-2016, 01:14 PM
I just gotta wonder if itll be worth it- i mean will it get lost in the noise of brass quality and bullet quality that youre dealing with

B.Larson
02-14-2016, 01:25 PM
I think your idea is a good one........ That is the only way we find out is trying something...... awaiting your results.........
bill larson

rogn
02-14-2016, 01:49 PM
<0.035" may be a tiny decapping punch. Any sort of adhesive , Locktite, methacrylates, low temp solder(*?) ? Rivetting inside case.?

Boyd Allen
02-14-2016, 02:23 PM
I wonder how it would work to look at how low your primers sit, and if you could cut your pockets a little deeper, using both dimensions to come up with the thickness of a disk to sit under the primer, possibly made from something like stainless steel, to be drilled with whatever size hole that you want. All that it would have to last for is a single firing. It would come out with the fired primer, and be replaced before the next one was seated.

bluechip
02-14-2016, 03:28 PM
I wonder how it would work to look at how low your primers sit, and if you could cut your pockets a little deeper, using both dimensions to come up with the thickness of a disk to sit under the primer, possibly made from something like stainless steel, to be drilled with whatever size hole that you want. All that it would have to last for is a single firing. It would come out with the fired primer, and be replaced before the next one was seated.

Boyd, the disc idea you mentioned was the direction I started off in and I have a punch in the mail that will form discs a few thou smaller that primer pocket minus the hole. I got impatient waiting for the punch and headed off in this direction so I could start right away. One thing I have learned is that conditions inside the case on combustion are extreme, destroying pretty much everything I have tried on first shot. The hole in the disc will probably be wildly enlarged I'm thinking but possibly after it has done it's job. Of course it will be a 'one use' item, but that's okay. I have a sheet of .006 stainless shim stock that I'll try first after deepening the primer pocket. I'll post the results soon. Btw, the press-in pieces I have tried so far have a .003-.004 press and go in hard. I loaded five rounds, shot them, removed the primers to find three of the five were missing the inserts completely. The group I shot was three shots in one slightly larger hole and two moderate flyers, but I don't know which cases in the group lost their inserts.

Wilbur
02-14-2016, 03:43 PM
What average group size does the rifle shoot with regular ol' cases?

alinwa
02-14-2016, 05:01 PM
Awesome work, thank you for doing this :)

Wilbur
02-14-2016, 05:23 PM
Awesome work, thank you for doing this :)

I'll second that....!

rogn
02-14-2016, 07:36 PM
would it be possible to "peen" the base of the pocket in the manner that the so called "case savers" displace metal in the head to tighten the pocket. Could this same type of displacement close the flash hole to the point it could be drilled to a discrete smaller size? this could avoid sending bits of metal down the bore.

JerrySharrett
02-14-2016, 09:28 PM
The early 2000 Lapua 220 Russian cases had a 1.5 mm flash hole (0.059") which stuck our small primer punch which was 0.060". They later changed the hole to 1/16" (0.062"). Didn't seem to make a difference in accuracy, but, some drilled the 1.5 mm hole to the normal US flash hole of 0.080". This did degrade accuracy of the PPC..

.

jackie schmidt
02-15-2016, 08:39 AM
A number of years ago, a shooter named Michael Turner shot a 30-30 in short range group. The Rifle was very accurate.

One of his tricks was that he made a set of staging tools to closet the flash hole in the 30-30 case down so he could red rill to .060.

I tried looking up some of his old post, but can't find them.

I am sure many of you who have participated on this Forum since the '90's remember this.

glynn angle
02-15-2016, 12:46 PM
When shooting .22 Hornet I have always had the best success when using pistol primers. This may be worth a try for your .17 Hornet (which I have no experience with). Good luck with your experiment!

Dusty Stevens
02-15-2016, 01:39 PM
A number of years ago, a shooter named Michael Turner shot a 30-30 in short range group. The Rifle was very accurate.

One of his tricks was that he made a set of staging tools to closet the flash hole in the 30-30 case down so he could red rill to .060.

I tried looking up some of his old post, but can't find them.

I am sure many of you who have participated on this Forum since the '90's remember this.

I met him at the crawfish down at hub city. He had a titanium action shooting 30-30 at that time. Very nice guy and talented machinist.

Wilbur
02-15-2016, 02:38 PM
I think his username was mturner - got several hits when I searched....seemed like the right one.

RJM
02-15-2016, 03:09 PM
I think his username was mturner - got several hits when I searched....seemed like the right one.

The name is correct. He offered to send people drawings of his flash hole reduction tool. I responded, but never received them - just reporting what happened.

He also turned the rims to uniform thickness & headspaced on the rim.

Regards,
Ron

RJM
02-15-2016, 03:41 PM
I found a PDF I had saved of one of the threads on the 30-30:

Ron

bluechip
02-16-2016, 08:43 AM
The reason I was working on reducing the flash hole was I experienced a loss of accuracy accompanied by flyers. Although I feel there is some value in tuning the flash hole size to the particular rifle, caliber, load, etc, I found my problem when working with my cases. After several firings I should have noticed that the pin I use for cleaning the flash hole went in awful easy. After measuring several, I found that some were as much as 26% bigger the original cases, resulting in poor accuracy. From now on when the pin goes in easy, the case will be discarded.

Dick Grosbier
02-16-2016, 02:13 PM
Very interesting experiment.
That being said I suspect the accuracy gain (if any) will not justify the work.

Good Luck
Dick

tazzman
02-16-2016, 10:40 PM
http://benchrest.com/showthread.php?65983-30-30s-in-benchrest-Aussie-question

Phil aka tazzman

Butch Lambert
02-17-2016, 07:36 PM
If you decide to experiment with the BR brass, I have 2 cases of new BR brass without flash holes.