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help with 7.5x55 load data

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/10/2005 at 02:52
happy124 View Drop Down
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can anyone share some published loading data for the swiss round? im using 165g sierra spbt bullets and i have h4350 and h4895 powders. thanx in advance.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/10/2005 at 07:16
cheaptrick View Drop Down
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http://www.reloadersnest.com/

 

Hope it helps.

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/10/2005 at 12:29
happy124 View Drop Down
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thanx cheaptrick thats a very intresting site but alas, the information i seek isnt there. my K- 31 is begging for me to feed it some decent ammo.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/10/2005 at 14:37
David View Drop Down
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Q. What is the correct trim length when reloading 7.5x55.

 
A. Most sources give a figure of 2.185", plus or minus a few thousandths. Sometimes if an error is repeated often enough it acquires a semblance of truth. It seems to me the 2.185" trim length falls into this category. From what I've seen of 7.5x55 chambers, this figure is pretty short.



The image above shows a chamber cast from a K-31 and a fired case exactly 2.185" long. They are aligned at the shoulder. The chamber neck is .050" longer than the case. For this rifle the correct trim length would be 2.225" - .010" less than the chamber length. Trimming cases shorter than this will simply lead to increased erosion and possibly decreased accuracy.

This doesn't mean 2.225" is the correct trim length for a different rifle but does show why it's useful to measure your own chamber. All the 7.5x55 chambers I've measured were at least 2.220" long.

You can easily measure your own chamber length by setting a slightly oversize lead ball (#0 buckshot is good for .30 calibers) on a case mouth. Slide this little assembly into the chamber then close the bolt smartly. The mouth of the chamber will leave a distinct mark on the ball. Measure from the case head to the mark and you have your rifle's maximum case length. Trim-to length is normally .010" less.



The upper case and ball was chambered in a 96/11. Note that the chamber is about .020" longer than the lower one from a K-31. Naturally this difference only applies to these two individual rifles - not all 96/11's and K-31's.
 

Q. My reloading dies don't size cases properly when I follow the manufacturer's adjusting instructions. My sized cases are too long. [or]  My sized cares are so short I am getting head separations.
 
A.Your dies are designed to work with any 7.5x55 chamber, the super-tight to the way-loose. Your chamber is somewhere in between and that is where you have to adjust your dies.

Use your rifle as a gauge to set up the sizing die. Put the firing pin on "half-safe" so you're not fighting the mainspring when you close the bolt. Size a case with the die backed off a bit. Try it in the rifle. If the bolt won't close easily, screw the die in little and try again. If the bolt closes 100% easily, back the die off a quarter turn and try it again with another fresh case.

The objective is to size your cases so you can feel just a little resistance as the bolt cams shut the last few degrees. This is easy with a turnbolt action and harder to feel through the straight-pull mechanism but it is possible!

Once you have the die where needed so the bolt closes snugly on your sized case, try the same thing with a fresh fired case. You'll probably find some fine-tuning is needed because a fresh case puts more stress on the press than the one you were experimenting with.

If you change lube, case lot/brand, or anneal your cases, you have to go through the setup process again. Same thing if you load for a different rifle. Once you learn how to do this, it simply becomes part of your loading routine. You may eventually learn to re-set the sizing die to the rifle every time you load a batch of cases. It's easy once you have some experience at it.

Some folks use feeler gauges between the die and shellholder once they've determined the optimum clearance using the rifle as a gauge.
 

Q. What is the correct overall length for handloaded 7.5x55 ammunition?
 
A.  I can't tell you exactly. Bullet shapes vary and so do rifle chambers. This is something you normally have to find out for yourself by seating a bullet until it will just chamber easily and then seating little farther so it will clear the rifling lands by about .010" - or farther if necessary to fit into the magazine. Your rifle is an essential tool when setting up the seater die. Here are two 150 grain bullets seated for firm contact with the lands in the same K31 -


The upper bullet is a Winchester FMJBT with a sharper ogive than the Sierra HPBT below. If I told you the overall length for a 150 grain spitzer should be 2.995" and you used that length for the Sierra, your loaded rounds would be about .070" too long because 2.995" is correct only for the Winchester. Furthermore, it is only "correct" in my individual rifle, with this particular lot of bullets.
 
Factory loads are made to fit all rifles tested, but only a few sources of reloading data have tested their loads in enough rifles to give an overall length that will work in all. Many published manuals use lengths tested only in the 1911 chamber, which has a substantially longer throat than the K-31 chamber. Shown here are chamber casts of the 1911 and K-31 chambers. The biggest differences are the length of the leade (the unrifled space before the groove begins) and the shoulder diameter.
 
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/10/2005 at 17:26
happy124 View Drop Down
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wow that is awesome information, may i ask where you got it?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/11/2005 at 12:50
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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/11/2005 at 13:49
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The SR is pretty easy to convert to .308.  If you want to leave it as is, you can get surplus ammo in 60 round packs from Century.  Norma still makes a commercial loading if you can find it.

 

ranburr

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/11/2005 at 17:36
happy124 View Drop Down
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i found new manufacture ammo on grafs (prvi partizan). i would love to converty it into .308 win (ammo is super cheap) but my K-31 is pretty dang accurate so i dont think i want to touch it.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: June/15/2005 at 02:06
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www.swissrifles.com/ammo

http://members.nuvox.net/~on.melchar/75swiss/

you can also search through milsurp collector forums, I recall asking there when I first started with my K31

www.milsurpshooter.net

www.gunboards.com


Ilya

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