Blown primers

[Blueheeler 0]

11.5 grains imr4227, 40 grain vmax or sierra bullet, mixed commercial cases, cci small rifle primers, IMI carbine, and I'm blowing primers out -any thoughts or recommendations?

[eb in oregon 0]

That's a perfectly normal load so I'm perplexed. Are you using .223 or .224 bullets? I'd stick with .223 diameter. You may need check head space, slug the bore, and look closely at the firing pin and bolt face. That's all I got.

[Blueheeler 0]

Thanks,I am stumped too. I guess I'll do a chamber casting , then maybe rent some headspace guages if that does not indicate any issues.

[eb in oregon 0]

4 hours ago, Blueheeler said:

Thanks,I am stumped too. I guess I'll do a chamber casting , then maybe rent some headspace guages if that does not indicate any issues.

PM sent.

[Ed Johnson 0]

I am concerned with the most obvious problem....excess pressure. I would suggest that you do NOT fire the carbine again until this mystery is solved.

EB has given you a starting suggestion of dropping from .224 to .223. Yes, that will help. He's on the right track if you don't have the necessary tools or a friendly local gunsmith. But, when you CAN, please try to:

1) Measure the inside barrel bore, and then   

2) Measure the bullet.

See where you are with that, when you can. Let us know the readings. Then we'll take it from there with you.

[Blueheeler 0]

Thanks, I have the problem with 223 bullets as well. I will be checking headspace and making a chamber cast in the near future and will report my findings.

[Blueheeler 0]

Chamber cast is done. 223 barrel reading. Outside neck diameter is .257 and neck length is .22 so I think the neck is ok.  Primers will blow with a .223 40 grain bullet. Next step I guess is to check headspace.

 

[eb in oregon 0]

It looks a little short to me, but without actually measuring that's simply my thinking. The head space gages will tell the story.

[Blueheeler 0]

Well, the guages arrived and the bad news, stripped bolt closes easily on both go and no go. Tried two other bolts, same result. Any advice welcome as to what to do next.

[eb in oregon 0]

The real bad news is there are only three things that can repair a deep chamber. The first is to pull the barrel, set it back one turn, and re-chamber. I don't know if that can be done to a carbine without screwing something else up, but I'm thinking no. The other is to pull the barrel, drill it out and re-line it and re-chamber it. I have no idea if anyone is making .22 caliber liners of the correct twist. The third and final option it to find a replacement barrel. All not cheap. I guess we now know why it was for sale. And I suppose you're stuck with it.

https://www.trackofthewolf.com/List/Item.aspx/637/1

https://www.shootingtimes.com/editorial/gunsmithing_st_barrelliner_200810/99249

[Ed Johnson 0]

It sounds like the cartridge is slightly "loose" in the chamber and the primer would be the easiest "give point" to be affected by the chamber pressure. If you do turn the barrel back one turn per EB's comments, the gas port assembly goes back the same distance, so I'm wondering if that might affect any timing of the unlocking. If not, you are already in a mess, so EB's suggestion is perhaps the easiest and least expensive way to proceed. Hopefully, the stock bedding would still be ok. And from what you describe, including the reduction to .223 having no effect on the problem, it suggests you don't have a major bore size issue, which is a relief. But you could try a reduced powder load to 10 gr from the 11.5 to see if that has any effect.  ej

Edited July 2, 2023 by Ed Johnson
add technical comment

[Blueheeler 0]

Thanks for all the help. I'm going to take step back and pause on the gun for a bit while I consider my options. One possibility is to just rebarrel this one to 30 carbine, and look for another 5.7. There's a couple of plainfield sporter 5.7s on gunbroker right now, but I'm a bit leary of those particular guns.

 

https://www.gunbroker.com/item/995848215

 

https://www.gunbroker.com/item/995846099

 

 

[eb in oregon 0]

I have owned two Plainfield carbines, both work as well as any surplus carbine. My brother has one he has had for 45 years, and a friend about the same. Both of those work swell also. However I did swap out the aluminum trigger housing in both of mine for one in steel.

[Ed Johnson 0]

Most of our new Spitfires that I had assembled in RI had new cast receivers built by Plainfield. They themselves also sold 5.7s and their new barrels came from Wilson in CT, same as mine. They used surplus trigger housings and mechanisms. So did I. EB is correct. Our main difference was feed ramp (in the early models) and nicer custom stocks. Iver Johnson bought Plainfield, so there wouldn't be much change there. The most recent Mfr was AIA circa 2002 to 2003 or so, but I was told of quality issues. The barrels were not too bad.  ej