Sierra 39 Blitz King

[pre64win]

Today I went to the range with some 204 Ruger handloads with 25.2 gr of RL10X, CCI450 primer, Win cases, and Sierra 39BK bullets. I had several groups of 5 where only 3 made it to the target. On one shot I saw a grey cloud about 10 yards out of the muzzle. Has anyone else had trouble with these bullets blowing apart in flight? These loads chronograph 3759 muzzle velocity.

[Silverfox]

How many rounds have you shot through this barrel? Is it possible there are some rough spots in the throat that tear the bullet's jacket. Do any other bullets fail to make it to the target? Check your muzzle to see if you have a defect there.

[jo191145]

Many years ago I had that problem. With some testing I discovered the tips were releasing from the jacket. At 200 yards I found a few tips stuck in the plywood backer I used along with witnessing the keyholed tip holes in the paper. Some bullets never made it to the target, some were fine, some keyholed, some turned to dust.
Only theory I could come up with was somehow the core was pushing its way forward in the jacket and forcing the jacket to open allowing the tip to release. The little nylon tails on the tips were intact by the way.
Clean the barrel to death thinking it was a build up of carbon and it still persisted.
Never figured out exactly why it was happening. FWIW sierras hade the thinnest jacket of any 204 offerings at that time.

Another shooter on this forum at the time had the same problem. He also had a borescope. He witnessed silverish grey streaks in his throat along with a nasty buildup of carbon. He was using 10x which I have a long dislike of for that very reason. I’ve always quipped it burns like diesel fuel. Many have good luck with it and I’ve seen good accuracy potential myself. Fouls the barrel fast ruining accuracy in my experience.
He and I surmised the streaks were molten lead. No idea if we were really right.

[varget204]

if you have shot other bullets w/ no problems,weigh the bullets,the first 3 boxes i purchased had 7 with copper jacket, ballistic tip,NO LEAD CORE.they weighed 6-7 grains each.you can also ckeck bullet ogive length.If you have bore scope check for copper/carbon ring at back of throat. if you have burr or ruff spot in throat or barrel it should efffect every bullet.i have had the 39"s key hole in the past .one day i had shot 5 -3 shot groups ;5 key holed 5 never hit 16" sqare target.they normally shoot .15 to.3 moa.i contacted sierra ,fisrt they suggested i had burr in barrel,it wasn"t possible ,the next day after the keyhole miss day i shot a.062 group.Sent them a bunch of targets that had .2 moa groups w,5 different powders.sent them bullets ;they cant explain why.every once in awhile you get some that keyhole etc.i tried to make them keyhole,miss,etc.could not,tried cases w small split in neck,cases w a crease line in neck. that did split on fireing,short cases,long cases,bullets that rolled on loading bench that looked like eggs rolling end to end,round that were off .005-.006.It seemed to happen w/short OAL bullets w large ogive differences.some bullets are .010-.020 difference in length.i had a some that had up to .023 difference in ogive length.you can also check your twist rate of your barrel.put a patch on w,piece of tape on rod and one on stock and measure distance of one turn.i weigh and check OGIVE length on every bullet.If nothing else you can wait and shoot them on 4th of july

[pre64win]

I gave the 204 a thorough cleaning last night and went back to the range today. I shot three loads--Hornady 32 ZMAX shot a group less than 1 inch, the Nosler Varmageddon 32 gr hollow point the same as the ZMAX, with the Sierra 39 BK only 2 of 5 made it to the target and impact was about 2 inches apart.
I think I will go to 32 grain bullets.
Thanks to all who offered suggestions or information.

[Bill K]

Interesting find and information pre64win, on your rifle and the 39 grain Sierra. Most rifles like that bullet along with the 32's. You rifle does have either a 1/12 or 1/11 twist, does it not ? That twist usually works very well with those. Sure would be interesting to find out why, yours will not shoot the 39's. But you will be well served with the 32's and with grouping as you found, no problem hitting varmint/critters. Bill K

[bloc]

This is a conundrum.

3700 ain't that fast for a 39SBK in a .204 and it shouldn't disintegrate (which suggests too fast a twist). On the other hand, you say it key-holes (suggesting it's under stabilized due to too slow a twist). (My pet load is the 39SBK @ 3800fps in a 1:12 barrel.) But you say the 32s work really well, which means the rate of twist can't be too fast, else they (presumably much flying faster) would disintegrate too!

So IMO you're dealing with two mutually exclusive phenomena.

Why not give Sierra a call and ask them what they think?

[slickshot223]

Have a 17 Rem that is a very good shooter! 1-9 T Thought the 30 gr Bergers would be a good long range bullet for groundhogs! Started load workup, bullets weren't getting to the target!! Berger advised twist would need to be 1-7 to stabilize the 30 gr!! Scraped that idea!!
That said, all 3 of my 204's shoot the same 39 gr Sierra load into bugeye groups! They are all 1-12 T!
Your issue is interesting to say the least!!

[slickshot223]

Have a 17 Rem that is a very good shooter! 1-9 T Thought the 30 gr Bergers would be a good long range bullet for groundhogs! Started load workup, bullets weren't getting to the target!! Berger advised twist would need to be 1-7 to stabilize the 30 gr!! Scraped that idea!!
That said, all 3 of my 204's shoot the same 39 gr Sierra load into bugeye groups! They are all 1-12 T!
Your issue is interesting to say the least!!

[pre64win]

The 204 Ruger is a Howa 1500 with a factory 12 twist varmint weight barrel. It has had several hundred rounds through it but should not be shot out. I have loaded some Nosler 40 BT, just to see how they behave, but have not had time to shoot them.

[jo191145]

The 204 Ruger is a Howa 1500 with a factory 12 twist varmint weight barrel. It has had several hundred rounds through it but should not be shot out. I have loaded some Nosler 40 BT, just to see how they behave, but have not had time to shoot them.

My first Sav tube had at least 4000 rounds thru it before I had to concede it was toast. Of course no two barrels are the same and different powders give different lives.
When they’re really done you can notice an orange hue to the fouling by looking in the muzzle. Jackets are vaporizing on the alligatored throat.
In contrast my third Sav barrel was toast from the factory. By simple visual inspection when new it was quite apparent the lands were extremely shallow. Cutter plug that had been resharpened too many times? Don’t know. Most accurate barrel I’ve ever seen. First three shots of any charge and any bullet were always at least touching at 100yds. Then all accuracy disappeared and it began to run wild. Couldn’t tame it.

As for the 39’s I think much of it comes down to lot #. I have shot different lots out of that first barrel with no problems. Either that or it smoothed up enough. I just stuck with the Bergers. Accurate and dependable.