Question About 7.5 X 55 Swiss Round

[FallRun]

I would like to find out how many of you guys (if any) crimp your ammo for your Swiss K-31 and why you do it (if you do) Thanx in advance, Glenn

[C A Plater]

No, just regular neck tension. Some light loads may benefit from a crimp to help keep the powder burn more consistent but full power loads have been doing just fine for me without it.

[mike in co]

no....
the factory gp 11 ammo has a machined groove that splits the two diameters of the bullet and provides a crimp groove......the rest of us aren't in battle....

[DanM]

My K31 is a smooth feeding rifle, and does not need any extra crimp. The dies I use (lee) will add extra crimp if turned down enough, but I don't even do that. If you trim your cases all even, your results will be uniform without adding crimp. This is pretty much true with all bolt guns. The Swiss surplus GP11 ammo that works so well is also used in MGs, hence the heavy crimp seen there.

[versifier]

I put a light Factory Crimp on them. I started testing with soupcans, which my rifle won't shoot well at all, and experimented with varying degrees of crimp to see if it helped. It did, a little, but not enough to matter. I continued to put a light crimp as I worked up through heavier boolits figuring it couldn't hurt. I'll try some without it to see if it really helps or not with the 180's I'm testing now.

[felix]

Ignition speed can compensate for crimp, compression, boolit/bullet seat, in almost all situations. ... felix

[Bob S]

Never EVER ....

Resp'y,
Bob S.

[DanM]

I haven't tried real boolits in my K31 yet, just JBs, and it shoots those SMKs like nobody's business. My loads with SMKs are real short and stubby looking to clear the rifling due to the chamber being cut for those VLD profile GP11 bullets. Fatter profile cast boolits seated real deep, and the fast twist might be difficult to deal with. Just wondering if others have had success with cast in a K31?

[jonk]

Not with cast bullets, no. Just enough to take the flare out from the M die.

With jacketed, yes, mild crimp.

[MtGun44]

DanM,

The problem with your (and everybody else) needing to seat the MKs
deep isn't "VLD profile", but the fact that the Swiss bullet is a two
diameter design. Fwd of the crimp groove it is .300" and aft it is
.308", so no need for them to cut any throat whatsoever.

Bill

[garandsrus]

DanM,

Quite a few folks have had success with cast boolits in a K-31. I have shot several different boolits and they worked well. I size to .310 without any problems. You do need to test the boolit fit when seating to make sure the bolt will close. If not, seat the boolit a little deeper and try again.

I especially like the shape of the 311413 in the K-31.

John

[JDL]

Preliminary testing with NEI 154311 and Lyman 311466 has shoned extraordinary accuracy from a iron sighted rifle and my old eyes. These were sized .311" but, will try some sized .309" for next test. -JDL

[jonk]

MtGun44:

For the K-31 I agree. The older guns though- G 1911, 1889, K11, etc., have generous throats by comparison.

[DanM]

Bill...
I have read that the Swiss GP11 bullet was the first military use of a VLD bullet. I am pretty sure that is true. The throat is so short because it was designed for the narrow VLD profile. Maybe I just don't understand your comment. BTW, I don't remember seeing a crimp groove in the GP11 bullet I pulled. Working from memory here, which means I could be wrong.

Here is a link to a nice illustration of K31 and K11 chambers and bullets (about half way down the page) on SwissRifles.com.

http://p083.ezboard.com/Bullet-seating-depth/ftheswissriflesdotcommessageboardfrm11.showMessage ?topicID=2.topic

[mike in co]

the gp11 bullet has a long boat tail , a cut groove that splits the two dia of the bullet and all of this results in a very short full dia bearing length with the nose tapering forward to the point.
bullet is a fmj bt open base
oal 1.37
frt dia .303( please note there is no cylinder section, its a constant curve)
rear dia .308( ok it was .30799)
bt length aprx .27
bearing length aprx .2
crimp groove width .04
leaves the pointy end length of 0.86

i suppose its ok to say its not a dual dia....its just that the crimp groove does split the two dia's....there is no straight/cylinder forward of the crimp groove.

[FallRun]

Thanx Guys

[frugal]

I was having probs with 311291U being loose after seating so I ended up reducing the size of the expander so the bullet was tight. The 311291U I have casts at .3075 with ww. A crimp could have had the same effect, but I think it may reduce the life of the brass a bit.

Frugal

[MtGun44]

I stand corrected, my micrometer shows .303" just
ahead of the cannelure on the GP11 ammo I have
just measured, and .308" behind it. My K31 needs 168
and 175 MKs seated VERY deep to avoid failures to close
and misfiring.

I did measure one GP11 bullet last year when I started
shooting my K31 and I distinctly remember that one
bullet measuring .300" ahead of the cannelure.
However, the one I just measured is .303", so
maybe the first one was off standard, or perhaps
I misremember. (Say it ain't so!) ;-)

In any case, it is .005" smaller in front of the cannelure
and this means the K31 throat is nearly non-existant,
and you will need to seat normal one-diameter bullets
deep enough to properly chamber, which is quite
deep for my K31.

I don't shoot GP11 anymore as I couldn't get good
groups. I have several friends that shoot extremely
well with GP11, but my two K31s will not shoot GP11
better than about 3" at 100, while my handload does
under 1" at 100 yds. Weird but true.

Bill

[FallRun]

Mt
Thats good to know, Thanx