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7.55 swiss 175smk?

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arky65
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7.55 swiss 175smk?

#1 Post by arky65 » Tue Feb 12, 2019 1:34 pm

I have not shot this rifle in over 10 years, and I can't find my old notes and load data. So looked in the Sierra manual found some load data and this is what I loaded:
175smk 48.5 H4831, coal 3.051. using resized and fire formed .284 brass.
I painted the ogive to get in idea of where I am at. When I inspected the round found I was in the rifling. Seated it down to 2.75 and am just in rifling. How close is safe with these rifles?

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Re: 7.55 swiss 175smk?

#2 Post by arky65 » Tue Feb 12, 2019 9:05 pm

So, shot 3" group at 100yrds. I have not shot Iron Sights in a loooong time so I am happy with the Group. Tried some 168smk's 4' group the sun was going down. I'll shoot some more tomorrow.

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Re: 7.55 swiss 175smk?

#3 Post by ammolab » Tue Feb 12, 2019 9:22 pm

You don’t want to jam the bullet into the throat. Most bullets will have to be seated quite deeply in the 7.5x55. Back 20 thousands off contact.

Note sleek Very low drag bullets may seat to mag length without contact...that is what I found with Nosler 175 RDF bullets.

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Re: 7.55 swiss 175smk?

#4 Post by arky65 » Thu Feb 14, 2019 10:38 am

Ammolab, thanks for the input. Without the proper modified case, I ran a Swiss case through the expander of a 7.62X39 to open the mouth up and allow a bullet to move with some resistance. Chambered this modified and smoked cartridge and took measurements till the faintest rifling marks on bullet. Loaded 20 rounds, backed off 15K, they chamber and no rifling marks on the bullets. Switched to IMR 4064 powder shot three, 4 shot groups with increasing charge weight by 3 tenth. These held at 4"-5" all groups had at least 2 shots 1" and 2 flyers. I am sure a lot of this is my bad technique, I have not shot rifle irons in 10+ years and a 63 my eyes ain't so good.

Before I read you post, loaded 20 rounds with the charge weight that gave best group and set them 15K off, weather permitting I will shoot these today.

"Note sleek Very low drag bullets may seat to mag length without contact...that is what I found with Nosler 175 RDF bullets."

Ran across a youtube that discussed this very thing, gave me a lot of insight. GP11 projectile measures .302 to the cannelure then .306 from cannelure to the beginning of the boattail. Makes for a very very low drag projectile.

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Re: 7.55 swiss 175smk?

#5 Post by ammolab » Thu Feb 14, 2019 6:36 pm

How find bullet “contact” distance,

Take a fired un sized case from your rifle that allows your selected bullet to be a slip fit. A case that will chamber. Put a ‘ring’ of jell super glue in the neck of that case.

Drop your bullet (works best with boat tails) into the chamber (rifle muzzle down)...it falls to the origin of the rifling.

Chamber your glue laden case and close the bolt. Store rifle muzzle down for a few hours. Extract your length gauge round. You then have a bullet locked into that case gently touching the lands. Use this to make reloads at your desired length.

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Re: 7.55 swiss 175smk?

#6 Post by arky65 » Thu Feb 14, 2019 9:13 pm

Thanks again, I'll try that with other bullets I want to test.

I, shot, 2, 5 shot groups today of the 20 loaded earlier, shot a 3" and 2.5" group. Then I screwed the pooch, tried the St.Marie accurizing trick of balancing or optimizing the tang screw torque. Next ten shots barely stayed on a sheet of copy paper I used as a target. The load I worked up at least was holding consistent when I did my part. So, I will loosen the receiver screw and tang screw tomorrow and try and find the sweet spot again. I did index the screws for reference.
At least I enjoy this stuff.

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Re: 7.55 swiss 175smk?

#7 Post by Smokey » Fri Feb 22, 2019 8:36 am

I've gotten good accuracy with WW760 and 180gr Sierra BT HP bullets. Put all six into a 1 inch cluster at 100 yards.
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Re: 7.55 swiss 175smk?

#8 Post by arky65 » Fri Feb 22, 2019 9:59 am

Thanks, Smokey for the reply.

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Re: 7.55 swiss 175smk?

#9 Post by Rapidrob » Sat Feb 23, 2019 7:22 pm

My long range load is a Sierra Match King 175 grain or the surplus M-118 175 grain bullet over 44.0 grains of Relolader-15. This load matches the sights on my rifle and is dead bolts on the target at 800 yards. It bucks the wind very well and groups right around 1 MOA.
I use Swiss military brass and Berdan primers. I seat to .002 off of the lands ( not a low drag bullet as the GP11 is).
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Re: 7.55 swiss 175smk?

#10 Post by Ned Christiansen » Sun Feb 24, 2019 12:00 am

I love pulling the GP11 bullets and dropping in a 175 SMK...… from good to better, instantly.

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