9mm diagnosis please?

[gamestalker]

I agree with others on the FP strike being so far off center, that isn't right.

I would send that one back again, this time be insistent about the problem. I would also send a couple pieces of spent cases in with it, so they can see how far out of spec it is. I wouldn't mention anything about reloading though. Most firearm manufacturers frown on reloading, and will often times use it as an excuse to void the warantee. So on that note, make sure you send factory spent casings, not one's you've reloaded.

GS

 

[Walkalong]

It fires factory ammo fine, so the main problem is the reloads, and almost surely how the primers are seated.

 

[judgedelta]

I don't know any other way to seat the primers. I have seated them until the rod leaves an impression on the face of the primer. I have changed the primers and powder and the problem hasn't completely gone away. Still getting primers wanting to pierce. I found some different bullets (Xtreme) which I believe measure .355. I will try some with the 231 and report back. They are hollow point, so I'll have to pull the barrel and shorten 'em up until they plunk.

 

[judgedelta]

It appears that the problem has gone away. Thick plated bullets, tight chamber and high pressure powder seem to have caused my discomfort. Loaded 10 with 4 grns of 231 and all had uniform, reasonably good primer strikes with minimum cratering. I have learned a lot. Thank you all for your contributions. JD

P.S.: I am going to try to bump powder up to 4.2 and going to try to get a stronger mainspring to improve hammer strike.

 

[lauderdale]

A softer plaiting.

 

[Dudedog]

From Hodgdon
125 GR. SIE FMJ Winchester AutoComp .355" 1.090" Start 4.7 1055 28,900 PSI MAX 5.2 1120 33,300 PSI

5.2 is thier listed MAX
Maybe back off the Autocomp a little?


My 9mms don't seem to like Autocomp as well as some other powders but others report it works well for them.

I don't have any issues with the RMR 124 FN 9mm bullets, they shoot well for me.
Different bullets, different charge, different primer different OAL can all result in increased/excessive pressure.
Autocomp is no higher pressure than other 9mm powders, pressure is set by SAAMI, but a listed MAX load of Autocomp may be over the MAX for your firearm while the MAX charge of powder X might not be.
Glad you seem to have it solved.

Here are some chrono numbers form my tets of the RMR 124s with Autocomp. Springfeild 9mm 1911 5"
Autocomp 4.5gr 1.065
1081
1065
1084
1052
1060
AVG 1068.40
SD 13.72
PF 132.48
ES 32

Autocomp 4.7gr 1.065 OAL
1095
1080
1077
1088
1075
AVG 1083.00
SD 8.34
PF 134.29
ES 20
(Tested shorter 1.065 OAL as it was requested by a THR member, I normally load that bullet to 1.10)

 

[judgedelta]

Thanks. Hodgen shows (on my computer) the 124 gr. Berry plated at 5.4 max. The load was kind of hot at any rate. The manuf. said to shoot it a little hot for break-in. Anyway, if I go back to Autocomp, I'll load it lighter and with smaller bullets. Thanks for the data.

 

[rfwobbly]

It fires factory ammo fine, so the main problem is the reloads, and almost surely how the primers are seated.

I think the other end of the cartridge is the issue.

Thick plated bullets, tight chamber and high pressure powder seem to have caused my discomfort.

IMHO you've not seen the end of this. You've simply masked the issue in something you've done.

You say you have a "tight chamber", so exactly what do you mean by that? Are you referring to the chamber itself or the freebore ? If freebore, what allowances have you made for your barrel characteristics in your bullet and OAL selection? What is the diameter of the case mouth on a typical finished cartridge?