.17 Rem casings shrinking .004' to .005' after test firing

[Silverfox]

I had some "shrinking casings" when testing loads in my .17 Remington this morning. This is really a puzzler to me. I have never had casings get shorter after firing, but I had that happen to four casings this morning. I was shooting a charges of 23.6 gr. and 23.7 gr. of Varget with the 25 gr. V-Max bullet seated about .010" off the lands. My barrel is a stainless steel super match grade Pac-Nor with a 1 in 9" twist and 3 grooves. The chamber has a .1945" neck and my casing necks are turned so that the diameter of my loaded rounds measures between .1915" to .1918". All the casings were trimmed to 1.7865" for length before loading. I was using SPL on the bullets--first time I have ever used this stuff.

The fourth casing I shot with the 23.6 gr. load measured 1.7825" and the other four were right at or just .0005" longer than 1.7865". With the load of 23.7 gr. of Varget the casing from shot #1 measured 1.7815" and the casings from shot #s 4 and 5 both measured 1.7825". So, I had three casings get .004" shorter after firing and one casing became .005" shorter after firing.

I'd be very grateful if anyone could tell me what caused these casings to shrink???? THANK YOU IN ADVANCE!!!!

 

[Silverfox]

gunamonth--This brass was once-fired brass that I full-length resized, then neck turned and then fire formed in my .1945" necked Pac-Nor barreled rifle. So, the brass had been fired two times, but only one time in my rifle.

 

[Silverfox]

These casings had been fire formed and then fired again in the same rifle with only neck sizing after the fire forming. As for headspace, I use a Wilson Case Gauge and the casings check out just fine.

I guess this will remain a mystery, at least for a little while longer. Thanks for putting in some time to help me solve this little problem.

 

[McKay]

With new remington cases my 17 rem is doing the same thing. Mine is a Cooper with a generous chamber that has an estimated neck of around .200. I had to send both my Wilson Seater & Neck die to be opened up because of the generous chamber, so I have not had a chance try neck sizing only some fired cases to see if they keep shringing? Are you using 204 brass you form? I think it was you I read that you were doing to get necks thick enough for you to turn in your chamber?

Mac

 

[Silverfox]

Mac--I'm using neck-turned .17 Remington brass in this Pac-Nor barreled rifle because the chamber has a .1945" neck. My loaded rounds measure .1915" to .1918" I had about 1,000 once-fired .17 Rem casings and I mic'd the neck thickness on about 800 of them and found only 540 of them that had necks that were .00985" thick or thicker all the way around. That's what I turn the neck wall thickness to on these casings. I went through the FL sizing, ran them over the K&M expandiron and turned the necks on all 540 of them. I don't think I'd want to turn necks on casings formed from .204 Ruger brass. That brass is way thicker in the neck than .17 Remington brass.

I also bought 100 brand new .17 Remington casings this past winter to turn for this Pac-Nor barreled rifle. I think I only found one casing out of the 101 that were in the bag that had neck thicknesses that were .00985" or thicker all the way around. I did turn the necks on those casings just to see how they would perform in this rifle. I haven't fire formed them yet and probably won't mess with them until next summer. I have over 350 of my neck turned casings already fire formed and the fire forming loads have performed great. Accuracy has been outstanding.

The WW .204 Ruger brass I was forming down to .17 Remington will be used in my Lilja barreled .17 Remington. When I measure the diameter of a fired casing from that chamber, I get .201" on most of the casings, so the chamber neck probably measures .2015" to .202". I've never done a cast of the chamber to find out for sure. Anyway, the .204 Ruger brass formed down to .17 Rem brass really doesn't need any neck turning to fit my Lilja barrel's chamber, but I might just skim a wee bit off the high spots. I haven't gotten into forming many casings yet. Too many prairie dogs to shoot this time of the year. I'll probably get into the forming process this winter though. My loaded rounds using Remington brass only measure .196", so there's some slop in the .202" necked chamber. The loaded rounds using formed WW .204 Ruger brass measure .198". Maybe that's not enough difference to make it worth going through the work of forming the brass, but I'm willing to try it to see if it does. I'll do some of that testing yet this summer and maybe prep 15 or 20 casings that way and shoot them just to see what happens.

 

[McKay]

I bought 300 remington brass for my cooper around 2 months ago from Midway. I did not have as thin of necks on this newer brass as some. I was able to turn them to about .0104 and have the necks cleaned up almost 100%. I would like to try forming some 204 brass because of my large chamber to see how I like that. Is the process very involved?
Mac

 

[Silverfox]

Mac--I don't think the process of forming .204 Ruger brass to .17 Rem is very complicated. Here's what I did:

Before I started forming Winchester .204 Ruger brass to .17 Remington, I purchased a Redding .17 Remington #1 Form die,this is an expensive little dude--I think it was around $50 or so). Some fellows say they get by without this die and only run the .204 Ruger brass into their seating die and then into a .17 Rem FL sizing die, but I chose to use the Redding .17 Rem #1 form die in my process.

Before beginning this forming process, make sure you have the inside of your dies cleaned and polished. I think you can use Flitz or JB to do the polishing. Then make sure you clean out the inside of the dies thoroughly again. You want the inside of the dies as smooth as a baby's bottom

Step #1: Lube the casings properly,DO NOT PUT TOO MUCH LUBE ON THEM, or you'll wind up with lots of dents in the casings. DO NOT ask me how I know this will happen!!!) and run them into the #1 Form die.

Step #2: Next, I run the casings up into a .17 Remington trim die.

Step #3: I don't know if this is necessary or not, but I trim the OAL to 1.810" before going to Step #4.

Step #4: I lube the inside of the neck with Imperial dry lube and run them through my Forster .17 Rem FL die and then trim them to a length of about 1.795". I trim them to near max length because sometimes the casing may get a wee bit shorter when fire forming them.

Step #5: Load them up and take them hunting to fire form them.

Step #6: Check for length and decide whether you'll have to trim them or not.

If you get little dents in the shoulder or sides of the casings when forming them, you can still use them. These dents will disappear when you fire form the casings, so don't worry about them.

The casings I form using the steps above will usually wind up with a neck OD between .1965" and .197" and when I seat a bullet in the casing, the OD is usually about .198".