Sierra 7mm 180gr Bullet Blow Up!

[bsoutlaw32]

I decided to give the new Sierra 180gr 7mm bullets a try this weekend in my F-Class rifle at a local match. I had 3 of the 180gr bullets blow up after leaving the barrel. 1 blew up in the first relay at shot 18 (out of 25) and 2 blow in the 2nd relay on shot 23 and 24! I run a 7mm Weatherby pushing them at 3000fps. Barrel is a 1-8 twist and had 400 rounds down the tube. Barrel was very clean and the throat area is kept smooth.

Has anyone had any of the 180's come apart yet? I have been shooting the 175 sierras with no problems!

 

[model 12 toby]

i don't know about sierras but i had 162 a-maxes blow up. i backed off 3 grains and only get 60 less feet per second and no problems since. i had 8 of them blow up in a match. it's just a rem mag though. 2990 with reduced load.

 

[maxpower]

I,m running them at 3050 fps out of a 7mm WSM in 9" twist and havent YET had any blow ups. The 8" twist though spins them 12% faster than a 9" which is the same as me shooting them at 3400 fps, so I suppose it would be spinning plenty quick.
Have you tried Berger Hybrids? Did they blow up?

 

[jonbearman]

Sounds like you need to back off the charge and see what happens. If the 175's didnt have an issue,it could be the right bullet period for you. I would try bergers as they design these bullets for severe duty so to speak. I would give them a call asap and see what they suggest.They are vey helpful and nice people. You could call the tech line at sierra and others who produce bullets are always ready and willing to get you in the right direction. Hope this helps and good luck shooting.

 

[bheadboy]

At 3000fps in a 8 twist your bullet is rotating at 270,000 rpm, at 3000fps in a 9 twist the rpm is down at 240,000. you are most likely over spinning the bullet at that velocity

To slow the rpm down to equal a 9 twist you need to slowdown to 2700rps in the 8 twist. I suggest you try reducing you load gradually until the bullets hold together - also call Sierra tech line and ask the rpm capability of the 180 vxs the 175,

Bob

formula : mv fps X 12 / twist in inches X 60= RPM

 

[MrMajestic]

Can't say about that particular bullet however do not attempt to push 4000 fps with a 110 grain V-Max with a 1in10" twist .300 H&H Ackley Improved! The visual cloud at 25-30 yards is spectacular. ;D

 

[bsoutlaw32]

I have not tried the bergers! All i have used are the 175 sierra's and 190gr matrix ballistics! No problems with them! Matrix bullets i believe are made with j4 jackets so they should hold up like a berger!

 

[kyreloader]

I have shot many of the 180g SMKs out of my Shehane around 2975-2980 fps in my 1:8 twist Shilen barrel with no problems.

I have shot them over 3000 fps with RL17 and I have not lost any bullets.

My load with the 180g Hybrids are around 2950 fps, again with no issues in my 8 twist.

 

[AlanPF]

I have shot many of the 180g SMKs out of my Shehane around 2975-2980 fps in my 1:8 twist Shilen barrel with no problems.

I have shot them over 3000 fps with RL17 and I have not lost any bullets.

My load with the 180g Hybrids are around 2950 fps, again with no issues in my 8 twist.

I'm thinking of trying the RL17 in my Shehane. I'm concerned that most who try it seem to go back to 4831SC - have you found a RL17 load which is consistently good? (no need for details - just interested in your overall opinion of the powder).

 

[FroggyOne2]

In the streight .284 I was using RL17 with good results. Load was 49 grains under a SIE 175 SMK.

 

[BOBC]

Sierra is using the same jacket for their 180 7mm as they use for their 175MK. I know this for a fact because I use their jackets for all of the various calibers of bullets I make. In my opinion the only thing they did to gain that extra 5 grs. of weight is shorten the ogive length a very small amount and make it a secant which looks to be a 12cal ogive. So in my opinion that small shape change should not cause blow ups. I've been using their jackets and bullets since 1954 and have not had any blow ups. I'd maybe look at the barrel ie. small tight or rough spot in bore just ahead of the throat. Lead dia. may be slightly tight. I like my lead diameters at least .001" over bullet diameter. Hope this helps.

 

[RDavies]

I didnt reralise the 180 Sierras were secant. I have been jumping them the same as I was jumping the 175s and not getting good results. Looks like I might have to try jamming them. What is everyone else doing, jamming or jumping?

 

[kyreloader]

I have shot many of the 180g SMKs out of my Shehane around 2975-2980 fps in my 1:8 twist Shilen barrel with no problems.

I have shot them over 3000 fps with RL17 and I have not lost any bullets.

My load with the 180g Hybrids are around 2950 fps, again with no issues in my 8 twist.

I'm thinking of trying the RL17 in my Shehane. I'm concerned that most who try it seem to go back to 4831SC - have you found a RL17 load which is consistently good? (no need for details - just interested in your overall opinion of the powder).

I shoot H4831 in my Shehane. I stumbled into a load that shoots well, so I didnt mess with any other powders.

My brother however, shoots RL17 in his Shehane with good results. His ES/SD along with his vertical has been very good with 175g SMK around 3000 fps. He really hammers with it now.

 

[kyreloader]

I didnt reralise the 180 Sierras were secant. I have been jumping them the same as I was jumping the 175s and not getting good results. Looks like I might have to try jamming them. What is everyone else doing, jamming or jumping?

The 180g SMKs shoot best in my rifle approx 15-20 thous off the lands. (I tested -25 to +20 thous).

 

[LCazador]

Do you have a bore scope or access to one ? There could be an issue with the barrel that is causing your bullet integrity loss . I can't imagine overspinning as the cause . Overspinning a 120gr maybe , but a 175 ? I have had no problems shooting 175 or 180's out of my 404 Jeffery case , at 3100 plus fps , thru an 8 twist .

 

[Cakes]

Slight departure from the original thread but I put about 500 rounds thru my .284 using RL-17 and 162 A-Max's in F-Class lately. 90% of the time ES/SD was great but just couldn't get away from odd flyers and ES/SD excursions. Switched to H4831sc and ES/SD dropped to single digit consistently with very little vertical and my scores shot up into the 195-200 range. Lost about 150fps as RL-17 is a hot powder but I'll take the consistency always. Brian, I was pulling your targets on one of those strings and I believe you were clean until the blowup...tough luck for sure! EJ

 

[bsoutlaw32]

Update!! As it turns out the barrel has a manufactures defect about 10" down the bore, the bad spot was tearing up the jacket a bit! I do not believe there are any probems with the 180gr bullets! Installed new barrel same brand and twist and no problems yet!

 

[BOBC]

I was willing to bet the farm that it was a barrel bore issue causing the blow ups and not the bullet. If you blow up Sierra's bullets you had better look to some other cause rather than their bullet. Thats why I've only used their jackets and bullets since 1954. Would not consider using anything else.
Now just "Hold em, Squeeze em and Follow Through" and get some wins.

 

[LongRanger]

In working up something for my 1000y F gun, initially tried Berger 180 VLD's and 175 SMK's. Nothing worked good consistently. Bought some 7mm SMK 180's after they hit the market. Trying to get a good load with them in my 284 drove me nuts since nothing seemed to work. Finally found what MAY have been problem with mine. About 1 out of 15 or so would hang up when allowed to slowly slide (free fall with no force from me) into the same empty case which had a slightly reduced diameter case neck. Checked with a micrometer and found diameter of these to measure a few 10 thous more than the cases which slid in slowly. MAY have accounted for the many 3-in 2-out, and 4-in 1-out groups I was getting at 200y.

Got some 162 gr AMax this week. Just today got some repeatable small roundish clusters of 5 shots measuring 1/2" at 200y. Not the 3/8" I wanted, but hey. Next stop will be 600y bench then 1000y to see if they are worthy of F-Class comp.

30" Krieger 8 1/2
Barnard action
53.5 gr H4350......This is a stiff load in my rifle, about .5gr from sticky bolt...work up to it with caution.
Moly'd 162 AMax .020 into lands
Wolf LR magnum primers
2950 fps

Frank