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Are these firing pin indentations ok?


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#1 Baltimoreed11754

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Posted 29 April 2019 - 08:50 AM

Yesterday I cleaned my Saturdays cas/ BAM match .30-06 brass and .45 brass that I had shot in my 1927a1 WH and in my .45 AR pistol. I noticed that the Thompson fired primers were unlike any that I have seen before. Im wondering if these primers are normal for these guns? My load is what Ive used for years 4.5 gr of Red Dot under a 200 gr cast or pc bullet. Here is a photo of them compared to normal primers. All of these are the same load and bullet.

Attached Files


Edited by Baltimoreed11754, 29 April 2019 - 09:59 AM.

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#2 Oldtrooper

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Posted 29 April 2019 - 09:19 AM

This is caused by over pressure ... Could be too hot a load or head space ... I'd try some factory loads to compare 


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#3 peter kohler

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Posted 29 April 2019 - 11:51 AM

I actually just went through this with a 27      I changed the firing pin and it completely eliminated the problem   mine was piercing the primers.   make sure you do some research on here about replacing the pin and filing it to fit    not a difficult thing to do.  


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#4 wh20crazy

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Posted 21 May 2019 - 09:19 AM

I got the same intentions on my WH. The replacement fitting pin fixed it. If you look at the bolt face, you'll see the slot that causes this. It's not over pressure. I got it with factory loads and my reloads, which are bottom of the scale (7.1 grains of Accurate #5 under a 230 grain plated ball). Worst part is sometimes the primer will come out of the case and cause a jam. May be getting some gas escaping to the rear when that happens too.
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#5 ppgcowboy

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Posted 21 May 2019 - 10:32 AM

When you say you have been using that recipe for years, would that be in a pistol with a 4 inch barrel?
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#6 Baltimoreed11754

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Posted 24 May 2019 - 03:06 PM

Yes sir, it works my in Detonics, Colt New Agent, blowback Olympic Arms carbines and full size 1911s. I use the same bullet [not the same powder] in my cowboy .45lc Vaquero revolvers.
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#7 ppgcowboy

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Posted 24 May 2019 - 03:12 PM

Do you have a chronograph? If you do,look for around 950fps. I think at times that people load for pistols and putting them in rifles do not aklways match up well. Just me thinking.
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#8 TSMGguy

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Posted 25 May 2019 - 09:40 AM

Overpressure will normally cause the soft primer to fill the entire primer pocket, even the chamfer. If this round is overpressure, it isn't by much.


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#9 Baltimoreed11754

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Posted 28 July 2019 - 02:44 PM

I carried my 1927 a1 WH to my cas match yesterday to show off and let one of the cowboys try it out. Well I just finished cleaning my brass from the match .45 lc [Marlin 1894], .38-40 [Colt New Service revolvers] and the .45 acp that he shot. Lo and behold I don't have the aforementioned deformation on these primers, they look normal. Same load except for the round nose bullet. The only difference in the gun is the install of shortened McMaster Carr springs and a buffer. Don’t understand but normal primer indentations are ok by me. My 10.5 bbl arrived from GPC, waiting on my sbr paperwork. It’s been five months 17 days so far.
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