Sierra 180grn in 7mmWSM

[6BRinNZ]

Hi,

Is anyone having problems with Sierra 180 match kings not making it to the target at 7mm WSM velocities?

At a regional match this weekend and I know of two different rifles that had this problem.

If you are using them OK, if you can post twist and fps that would be great.

TIA

 

[RDavies]

I've tried them at around 2950 fps, no blow ups but they didn't go all that well in mine, more development needed maybe. I did get a call from a bloke who got 11 Xs in a row on our smaller ICFRA targets with them today, but this was at a lower speed again.

 

[6BRinNZ]

cr500 - thanks - what twist are you using? These are/were shooting well in both rifles...

 

[RDavies]

9" twist. Were you using an 8" twist? What speed were you pushing them.

 

[6BRinNZ]

I know one of them was an 8.5 twist and I believe it was close to 3100fps...not me shooting directly, I am asking on their behalf.....

 

[expiper]

In my experience with any of the big 7mm bullets (anything bigger than 168) the 8 twist is necessary ..no matter what the velocity....for dependable results.......Id say the bullets were NOT blowing up .....they were flying like pie plates ,,,,not enuff twist...Roger

 

[6BRinNZ]

In my experience with any of the big 7mm bullets (anything bigger than 168) the 8 twist is necessary ..no matter what the velocity....for dependable results.......Id say the bullets were NOT blowing up .....they were flying like pie plates ,,,,not enuff twist...Roger

I can recheck the twists but I am pretty confident it is 8.5. String of xs and then a 0 then more Xs on day 1. Day two same thing, this time we were looking for the vapour trail and saw the puff of copper about 70 yards out happened twice on a relay.

Absolutely no problems with accuracy in load testing, these loads were selected after discarding other loads.

 

[expiper]

That puff you are seeing is the bullet turning sideways...these big bullets will work one day at a certain temp or alt....then the next day ,,,give U grey hair......Roger

 

[6BRinNZ]

Thanks Roger - comments taken on board, it sure is a weird one. I'm sticking with my 6Br...so long as they can't ge their bullets down there I will keep winning LOL...

 

[expiper]

HI NZ,,,,hahah...I shoot a 6mm most of the time also....I cant carry a HG so I shoot something light and mild recoil......is it spring down that way....we are starting the duldrums of winter here....Roger

 

[AusFclass]

ive heard that the berger 180 VLDs come apart at 3100fps in a 1-8 twist. a 1-9 twist is ample at those velocitys. i think most would agree a puff just down range is bullet blow up due to high velocity, over spin and possibly a warm barrel. if you think they are under stabilised put a target up at say 100yd and see if the bullets cut slots insted of holes ;D

 

[Shiraz]

I have shot over 1500 of these in several different barrels and not a single "mishap". Every bullet made it to the target and it is a very accurate bullet with many different accuracy nodes.

More often than not its the barrel. All mine are Bartleins and a few Kriegers, running with 8.75 twist, some with 9 twist. All 31" and 32" long. In my opinion the 8 twist called for by Sierra is too fast. Oh, and I have run them upto 3150 in my WSM, and upto 3050 in the RSAUM, to test extremes. Very accurate in the RSAUM at 3010 and in the WSM at 3100. (4831SC)

 

[6BRinNZ]

Thanks guys - I found another thread with the same question for the same bullet., his solution was a rough spot in the barrel. I will pass on everyones comments, it is good to know that your experiences are all good.

Thanks again

HI NZ,,,,hahah...I shoot a 6mm most of the time also....I cant carry a HG so I shoot something light and mild recoil......is it spring down that way....we are starting the duldrums of winter here....Roger

First day of Summer last Thursday

 

[dennisinaz]

I'm with Shiraz, I have shot quite a number down range with great accuracy in both 7WSM and 7x300 WBY. I have pushed them to high 3100s. Both Bergers and Sierras. They don't blow up. Both barrels are 9 twist at 1300' elevation.

 

[Steve Blair]

In my experience with any of the big 7mm bullets (anything bigger than 168) the 8 twist is necessary ..no matter what the velocity....for dependable results.......Id say the bullets were NOT blowing up .....they were flying like pie plates ,,,,not enuff twist...Roger

Roger,

I sure have not seen what you describe. My .284 Shehane with 9" twist Krieger shoots 180 Hybrids, 180 VLDs and 175 XLDs better than I can hold. It shot well enough to win the 29 Palms Long Range Regional @ 75° and second in the AZ State Palma Championship @ 40°. X count ran around 40% in both events. Velocity is ~2950. During load development I was shooting sub-1/4 MOA groups. Miller's Twist Calc shows the 180 Hybrid at 1.400 @ 32°. Being a San Diego resident, I draw the line at 32°.

The Shehane is holding 1/2 MOA or less vertical at 1000 and, wind excepting, puts them where I break the shot. I also have a 9" twist straight .284 that shoots the same bullets very well around 2820.

 

[expiper]

Thanks for the info.....and OBTW...good shooting Steve......here in the Ohio valley at 600'elv.--80% RH--30*F I have had truble with the big 7mm bullets ...I realize these are not typical match conditions and only aply to my home range.....I hope to "someday" get out of the holler here and shoot at a top level match with shooters of your skill level.....I apreciate the help and hope my findings can be helpfull to others also....Thanks again.....Roger

 

[flatlander]

My 284 bbls. are all three 1:9tw. - or at least, that's what I ordered. Two are cut rifled(Bartlein & Krieger), while the first one I chambered is a 3-groove PacNor. The PacNor absolutely loves S175MKs, and shoots them noticably better than either of the cut-rifled bbls. The Bartlein & Krieger both seem to prefer Berger or JLK 180 VLDs; I've got a few boxes of the newer 180 Hybrids & S180MKs, but haven't had the opportunity to shoot either of them yet.

I seldom shoot any of the 284s at closer than 1000yds; have several good rifles chambered for 6mm & 6.5mm cartridges for 600. Have never had any of the 7mm bullets I use - incl. 162AMax, Berger & JLK 168VLDs, and the above mentioned 175/180s - give any sort of problems out of my 1:9 bbls. Elevation here is 2660' MSL; out at CRC's range N. of Byers, Co., it's around 5000'. I get 2850fps with the 180s with H4831, and a bit over 2900fps with RL17.

 

[TonyR]

My 284 bbls. are all three 1:9tw. - or at least, that's what I ordered. Two are cut rifled(Bartlein & Krieger), while the first one I chambered is a 3-groove PacNor. The PacNor absolutely loves S175MKs, and shoots them noticably better than either of the cut-rifled bbls. The Bartlein & Krieger both seem to prefer Berger or JLK 180 VLDs; I've got a few boxes of the newer 180 Hybrids & S180MKs, but haven't had the opportunity to shoot either of them yet.

I seldom shoot any of the 284s at closer than 1000yds; have several good rifles chambered for 6mm & 6.5mm cartridges for 600. Have never had any of the 7mm bullets I use - incl. 162AMax, Berger & JLK 168VLDs, and the above mentioned 175/180s - give any sort of problems out of my 1:9 bbls. Elevation here is 2660' MSL; out at CRC's range N. of Byers, Co., it's around 5000'. I get 2850fps with the 180s with H4831, and a bit over 2900fps with RL17.

Dennis.

Do you find that loads developed at 2500 feet for the 7mmWSM require adjustment when shoot at 5000 feet or is it just the external ballistics that change?
Thanks