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Old June 18, 2000, 05:04 PM   #1
Big Bunny
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Join Date: August 9, 1999
Location: New South Wales - Australia
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Out of 70 auto rounds fired yesterday I found 22 with an upper chamber made dent near the top caused by "over-jumping" of the loaded round out of the magazine or off the ramp.
This is a new pistol and all rounds chambered and fired OK without malfunction.

Could it be the new mag springs or maybe my 'new'(most successful accuracy-wise) trial double hand position - IE not using the trigger guard serated grip for the first time?

I have loaded up the 12 round mags and left them to stand (as suggested by a club member)to get the newness out of them, as they are VERY stiff still.

Any suggestions welcome on this random and puzzling brass marking problem.

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A thought from 'Big Bunny'...."The sword does not kill, it is a tool in the hands of the killer".... Seneca 'the younger' (circa AD 35)
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Old June 18, 2000, 09:57 PM   #2
Bud Helms
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"... near the top ..." Near the case mouth?

By upper chamber, I assume you mean the top of the chamber mouth? How do you know that?

"... all rounds chambered and fired OK without malfunction. ..." If they all fired, then the dent is probably related to ejection, not chambering, don't you think ...? Firing cycle pressure usually irons out dents and dings in the case walls.

If the rounds are tipping up too far during the transition from magazine to chamber, maybe you could run the bullet out a little farther (don't seat quite so deep) to give it more front weight.



[This message has been edited by sensop (edited June 18, 2000).]
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Old June 18, 2000, 11:42 PM   #3
Big Bunny
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Thanks Sensop for replying, but the marks are too shallow to be pressed out by the firing pressores I use, I feel. They are around 1/4"below the case mouth on one side on the 40S&W case, with 155gn SWCs and 6.7gn of W540.

I feel that they are caused by the mag spring "flip" ,as that is where I have had my 2 first(and last?) round reloading "jams" due to my not allowing the slide to go forward fast enough on a full 12 round magazine. The marks are identical and in the same place (but far worse in these cases), but I "cured" it by reducing OAL to 1.13" or I thought I had...I do remember a sight hesitation to load a few times. I fired 6 mags of 10 each and 2 with 5 each...perhaps the first two of each had the problem but not the rest?

Possibly if I smoothed out the mag followers(plastic) and gave them both a good clean(only 120 rounds fired so far, but W540 is a bit dirty)it could work. I have loaded 200 more as I thought I had the right formula

I now will have to think again.



------------------
A thought from 'Big Bunny'...."The sword does not kill, it is a tool in the hands of the killer".... Seneca 'the younger' (circa AD 35)
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Old June 19, 2000, 03:21 AM   #4
Bud Helms
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Any where around the rear (entry area) of the barrel got any "sharp" edges?

Another possibility. If the Hi Cap mags are new, I'd give'em a good cleaning on the inside and leave a very slight film of lube. Inside of the mag body can cause too much drag on the brass if it's dirty.

Have you gotten your springs out to inspect them yet and make sure they maintain the proper form when relaxed completely? Straight and not a big coiled arc.

If your right and it's the top two rounds out of the mag, it may be that the follower isn't maintaining even pressure when it's full. I'd clean hell out of 'em, inspect the springs and run an oil damp rag down in the mag body then follow with a clean mop. I'd pay particular attention to any dirt or powder deposits, deformations or rough spots on the sides of the follower where it contacts the mag body. (I just reread and see where you thought of this already.)

Good Luck. Post again after you find out the problem.
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Old June 19, 2000, 05:20 PM   #5
Big Bunny
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Thanks again sensop, I really appreciate your help here, as it is my first high cap CF auto-loader and I am 'feeling' my way forward.I see other auto owning club members infrequently - due to the scarcity of private S/A high power/capacity pistol owners over here in OZ!
I have carried out what you suggested as regards cleaning, as I am/was a S/A rifle owner(now almost completely banned here after 1997) and mags are important I know, and I even trimmed two mould-marks(plastic spots) from the orange follower on one mag.
All looks AOK in this deparpment now, as well as the spring tension(too much!) and their shape too. After 2 days left with a full mag the loading ease/operation is slightly better too. Thanks for the tips.
Further to this, I did a loading cycle by hand and noted that as I had not taper-crimped, there was a roughness of the leading edge of the case leading to jumping on the (standard CZ)polished ramp.
Now I have mildly taper-crimped 50 shells last night and the potential 'problem' disappeared, but field-testing on targets is indicated this weekend...(!!!). I will inform you of the results.

I did not need to taper-crimp to chamber etc on my LEE carbide dies, and following the Lyman's directions, which I trust, I thought if it was not needed - why do it? It works the brass slightly harder and gives a less positive chamber/headspace, I reasoned.It might have a cleaning function....!

I didn't realise that ramp problems with SWC could occcur on a % of cases with rough mouths. Usually, I trim/chamfer my brass but with the new pistola it was verboten I was told, as the .40 S&W case is rimless...all my other CF pistols are revolvers - so I followed this advice carefully.
On looking through a X5 magnifier some of my reloads still had little residual "bells" on them. The factory rounds did not and were mildly taper-crimped. So I have now done the same for 50 trial shells but over 300 are waiting still un-modifies until I know the brass-denting "culprit"(brass is $25AUD per 100 here, but all mine are cleaned/polished range droppies).

My best wishes and thanks sensop. FL for ever! BB

------------------
A thought from 'Big Bunny'...."The sword does not kill, it is a tool in the hands of the killer".... Seneca 'the younger' (circa AD 35)
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Old June 19, 2000, 06:40 PM   #6
Bud Helms
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Yes, taper crimping is a VERY good idea. You might have it!

Best of luck.
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Old June 25, 2000, 09:28 PM   #7
Big Bunny
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Yes sensop -the taper crimp worked well over the weekend and no more brass dents with the CZ-75 in 40S&W - albeit under some 'pressure'.
The fellow next to me was busy demolishing part of a single brick wall he had brought with him to the range, with a Desert Eagle in 44MAG at 25M range!!
By the time he had finished the bricks were powder.
At least we didn't get our cases mixed up.

Thanks again everyone for your help, all sincerely appreciated this side of the world

------------------
A thought from 'Big Bunny'...."The sword does not kill, it is a tool in the hands of the killer".... Seneca 'the younger' (circa AD 35)
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