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38SC bulge how much?


kineteks

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So, as recommended in a 38/9mm reloading thread I'm looking for feedback on the amount of case bulge considered acceptable for 38 Super/SC loaded to major in an open gun. The pistol's a brand new Razorcat w/KKM barrel & I'm loading new Starline 38SC brass w/8.2 N350, MG 124 HP, 1.245" OAL, 172 PF. I'm getting about a .009/.010" increase in diameter max maybe 270-300 degrees around the case. The gun runs fine though not as flat and a little more snappy than I expected. I am still working up a load for it and expect to find something that works well. I'll gauge the chamber sometime later this weekend & add that info. It's been suggested that the chamber is out of spec or has been opened up excessively. I didn't think the bulging was a big deal but have been wrong once or twice before...

post-36911-0-12350800-1345299720_thumb.j

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That doesn't look too bad.

Mine has a slight bulge like yours too but not as visible (maybe because of the photo?).

One of the guys I shoot with has a Razorcat in 38SC, I'll see what his brass looks like.

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...chamber plugs at .3885" at the case shoulder to .3890" about where the bulge is on the case. Max dia. on selection of brass measures .3888-.3892"....roughly :)

I suspect that you're within the normal range of bulge size. I just measured some Remington cases that had been fired in a Kart barrel with standard pressure loads. They measured .387-.388.

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The bulge doesn't make a full a full 360 as indicated in the original post 270-300 degrees, though some look more even than others. Inspected closely there are rarely more than 45 degrees without some bulge, the picture is a little misleading as I was trying to show max bulge. I'm having trouble finding specs for 38 Super chamber diameter, does the .388-.389" number come in on the big side?

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SAAMI chamber specs are .3887 +.004 which should run .3927 maximum, if I'm reading SAAMI's specs correctly.

Edited to add that I never see a uniform bulge all the way around my brass. It's always lopsided.

Edited by superdude
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As another data point - my cases expand to about .388-.390 out of both my current .38 supers, (wilson barrel and bar-sto barrel). The expansion is pretty uniform around the circumference, and they resize back down to about .382 with either a lee undersize or EGW undersize die. Using an RCBS or Dillon resizer they resize back to about .384-ish.

BTW - If you don't have a case gauge I strongly recommend that you get one. I use either an EGW 7 hole case gauge which is sized at about .387 or an old midway case gauge which is sized at .386. Both of these case gauges will only pass cases which will fit the diameter of my chambers. The only problem I have had with the case gauge is that if I get someone else's brass and it has a huge bulge then the u-dies will size it down and the case can grow in length to about .908"+. Anything over about .907 case length and my main blaster won't go into battery all the way. I've gotten to the point where I can tell while resizing that the case is taking more effort so I'll pull it from that station before I prime (Dillon 550) and check the case OAL...anything longer than about .906 gets tossed.

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If you really like your 124s try a MG 124 with about 8.0 grains of IMR 4756 and work your way up from there. OAL at 1.245. 4756 is also about $10 cheaper a pound where I live, is slow burning and fairly clean.

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That doesn't look too bad.

Mine has a slight bulge like yours too but not as visible (maybe because of the photo?).

One of the guys I shoot with has a Razorcat in 38SC, I'll see what his brass looks like.

I checked the brass fired from the Razorcat today and his brass seem fine and no noticeable bulge.

And his loads do make Major.

Edited by HI5-O
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"And his loads do make Major." No bulge at all? ...any chance you could find out what his load is? I'll be trying some 3N38 this week and will get some N105 & 4756 ordered up. BTW, thanks for all the input, it's much appreciated.

...I have 13K MG 124s so I'll work with them for the time being...

Edited by kineteks
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"And his loads do make Major." No bulge at all? ...any chance you could find out what his load is? I'll be trying some 3N38 this week and will get some N105 & 4756 ordered up. BTW, thanks for all the input, it's much appreciated.

...I have 13K MG 124s so I'll work with them for the time being...

N350 is a little snappy IMO. The Razorcat has a few barrel ports right? I don't think the 4756 is going to work. In addition, 4756 varies lot to lot.

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IMHO... Theres a lot of awesome support on these forums but since your gun is a brand new Limcat... Have you talked to the smith about the bulge?

Personally I'd also be after load recommendations from the person that built it :)

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...have not talked to them about the bulge but wasn't too worried about it as others seem to find the same thing with multiple gun/barrel types. I am using JL recommended load info:

Powder: 8.4gr Vihta Vuori N350

Bullet: Montana Gold .355 JHP/CMJ

Primer: Winchester Small Rifle / CCI Small Rifle

OAL Range: 1.240" - 1.250"

Powder: 9.6gr Vihta Vuori 3N38

Bullet: Montana Gold .355 JHP/CMJ

Primer: Winchester Small Rifle / CCI Small Rifle

OAL Range: 1.240" - 1.250"

7.9 N350 still gives ~1355 fps on my ProChrono w/MG124

...will get to the 3N38 this week

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...a few, yes. I'll start with the 3N38 and then try the N105. Not enough gas with 4756?

I think you will be filling the case with 4756. It is a good powder if one's barrel does not have porting.

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