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Discussion Starter · #1 ·
I've been loading for over 20 years and haven't seen this one yet.

I have several brass at home that have signs of gas "blow by" all the way to the head into the extraction grove as thought the necks are not expanding far enough to seal. Happens about 20% of the time.

This issue has occurred in a custom build .300 Win Mag and factory .30-06. I have used Nosler and Winchester brass in the .300 Win Mag and Remington in the .30-06. All brass are no more than their second firing and I full length resize in RCBS and Redding dies.

I use Hornady one shot lube and tumble my cases before and after all prep is complete. I have loaded hundreds of .308 for another rifle in the exact same way and have never had this problem with that firearm.

A can't figure out what I might be doing wrong. Any thoughts?
 

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What do you mean by "full length resize". Do you screw your sizing die down to where it touches the shell holder? What powder and how much were in the case when this happen?
Need more information to give you a informed opinion of what is wrong if anything.
 

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Yes, I'm wondering too about that full length resize..... personally, once a case is fire formed to a rifles chamber, I readjust the dies so that they just touch the shoulder, and then that brass spends it life only being reloaded for that specific rifle. You may well do the same, but thats my only thought here. I wouldnt go pushing that shoulder back every loading.
 

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Chambers a bit on the large side for manufacturer tolerances? Resizing issues? Low pressure issues(powder charge on the low side)? Brass all the same headstamp? Like posted above, could use a little more info.
 

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Discussion Starter · #5 ·
Yes, I run the die down until it touches the shell holder. I do this because I don't want a case to not function in the gun when I need it too. I may try just pushing the shoulder back, but it concerns me a little for function.

Here are the loads.

.300 Win Mag - 200Gr SMK in Winchester and Nosler Brass, 71 gr H4831SC.
.30-06 - 150 gr Sierra Game King in Remington Brass, 48 gr of H 4895
I believe they should both be "hot" enough to expand the necks.

Thanks
 

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Your loads seem "hot" enough for good case expansion. I would stop having the sizing die touching the shell holder and see if that helps. Another reason for not touching the shell holder is that you are setting up the case for a head separation especially with the 300 mag.
After first firing, I set my sizing die to where it just sizes down to the junction of the neck and shoulder and I do not have to worry about "brass flow" to the point the rim of the shell separate from the case body during firing.
You can color the case neck with a felt pen, apply lube and size turning the sizing die down until the line just kisses the neck-should junction. You should have no problems with that case if firing it in the same rifle.
If doing this does not work, you may have to make a chamber cast of your rifle chambers to see if they are in spec. Also I would try another brand of dies for the 30-06 and 300 mag just in case the dies are out of specs.
 

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Yes, I'm wondering too about that full length resize..... personally, once a case is fire formed to a rifles chamber, I readjust the dies so that they just touch the shoulder, and then that brass spends it life only being reloaded for that specific rifle. You may well do the same, but thats my only thought here. I wouldnt go pushing that shoulder back every loading.
Yup! For typical bolt action rifles chambered for 'bottleneck' cartridges, one only needs to touch the shoulder with the sizing die. This works the case much less than full-length sizing, which means much better case life. I have never experienced chambering difficulty with my Remington bolt action rifle with my handloads. Also, most bolt actions have extreme camming force potential that can allow chambering of a slightly oversized case.
 

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I full length resize every time and always have except for using in a couple calibers neck sizing dies. I have tried in the past the trick of backing off the full length die and encountered a host of other difficulties. I cannot recommend that practice. If I do not want to full length the I use the neck sizer die. I have multiple rifles in most calibers and I mostly use the same make of brass but when it hits the tumbler it all gets mixed. I have never had a case separation but I do check for this using the inside case check method. I get very good case life.

I am principally a hunter and I want my cases to feed through the action as slick as a Vaseline coated minnow.
 

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I full length resize every time and always have except for using in a couple calibers neck sizing dies. I have tried in the past the trick of backing off the full length die and encountered a host of other difficulties. I cannot recommend that practice. If I do not want to full length the I use the neck sizer die. I have multiple rifles in most calibers and I mostly use the same make of brass but when it hits the tumbler it all gets mixed. I have never had a case separation but I do check for this using the inside case check method. I get very good case life.

I am principally a hunter and I want my cases to feed through the action as slick as a Vaseline coated minnow.

much the same for us .... we've been reloading 30 caliber (30-30, 308, 30-06, & 300 WBY MAG) for over 40 years .... the 308 and 30-06 rounds are fired from various rifles, the 30-30 and 300 WBY are only fired from one rifle .... all are hunted with and spend considerable time punching paper .... all cases are full length resized and we have never had a case separation .... when we do have a case go bad, its from a crack in the neck
 

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Discussion Starter · #11 ·
I trim to spec every time. I guess what makes me believe I am doing something wrong with my loads is that this is happening with two different rifles. Could just be bad luck though.

During other conversations with folks I remember this happening before with the 30-06 years ago using 150 gr bullets, but then it was a problem with me seating the bullets out too far looking for better accuracy. I do not have this problem with the 30-06 when using 180 gr bullets. Maybe it has excessive free bore and the 150 are exiting the neck before engaging the lands?? The .300 is another problem though. I am definitely going to check the specs on my chambers.
 

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Anyone that full length resizes every rifle case every time and has no problem with case life is lucky. Their rifles have perfect or nearly perfect head spacing.

Many years ago, my grandfather gave me a Remington 600 in 6MM, along with a set of reloading dies. Using the normal method of lowering the full length resizing die to touch the shell holder, I had case separations in two to three loadings. I reset the die to just allow chambering (using a case that was not fired in my rifle and was oversize) and then screwed it down another 1/4 turn. Bingo! my brass now lasted 10 or more firing without failure.

Was it the chamber or the dies causing the problem? I don't know, but the end result is the same.

This is especially important with belted cases.....even though they are designed to headspace on the belt, doing it that way can cause the same problems. I set all my belted case dies to headspace on the shoulder instead.
 

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I suspect the problem is too little powder or not enough crimp. My pet load for my 270 is 56 gr of 4831 and that shoots to 3/4". A load of 55 gr shot to 5/8" but was getting blow by so went with the 56 gr load as I figured there could be some inconsistency. The bullet was not obdurating enough to seal off for consistent ignition of the powder.
 

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Unless you are running a semi-auto (which I doubt these are), stop full length resizing. Get a neck sizer die. Save a hell of a lot of wear and tear on your brass. The only time I FL resize is for range pickups and once about 15 loads when I start getting sticking (not where they don't come out but when I feel resistance in bolt operation) cases in the chamber.

I have 300wm brass that has 20+ loads on it and still in great shape with only a single annealing at about 15 loads. I am running 190g Nosler CC over 75.2g 7828SSC and WLRMs. My COAL is out about 60/1000ths over SAMI which puts me about 40/1000ths off the lands (but you need to check that on YOUR rifle). I get great groups (recent comp I got a perfect 100 score at 600yd with 9 out of 10 Xs).

For 30-06 hunting, I top those with Hornady SST 150g over 47.50g IMR 8208 XBR and CCI 200's. Those too are neck only sized. I am out 35/1000ths past SAMI on COAL. Stacked a 1.5" group at 200yd.

I use Redding Competition dies which use neck sizing only using bushings.

I get no blowback off either load. 300wm is shot in a Barrett MRAD and the 30-06 is shot in a 1943 1903a3 sporterized.
 

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Discussion Starter · #15 ·
Thanks to all for your feedback. I am at the point were I am going to start experimenting by changing one thing at a time as folks suggested. Crimping, neck sizing, changing loading components, seating bullet a little deeper etc.... I have done a little looking into things and I have some theories so I will leave them with you for now and after experimenting and "solving" this problem will provide my potential findings.

I am using Win brass and think that combined with the moderate powder charge the pressures may be on the low side, but should still be in normal range. The 30-06 seems to have a fare bit of free bore which I hope to get more accurate measurements on latter, but my crude measurements show that I may have as little as .008 of neck engagement left by the time the bullet starts to engage the rifling (150gr SGK). I do not have this problem with 180 gr SGK?

The custom gun maker who built my .300 WM just re-chambered the rifle to try and remedy my problem with it. Starting from scratch there, but hope the problem was solved. If not at least I will be able to tell you who not to have a rifle built by.
 

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I 'm coming to the party late, but I full length size new brass and trim max length -0.001" and only neck size from then on. When the brass starts chambering with effort I use the full length die with a shim between it and the press to get the desired shoulder set back for easier chambering. I use 7/8" arbor shims rather than resetting the dies .
As a side note I have only used Winchester brass and load .30'06 and .300 Winchester magnum as well as others.
 
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