HELP!! With 6mm superX

[Raptor]

I just had my 6XC rechambered to Roberts 6mm superX,or 243XC)and I am having trouble with loosing primer pockets!! I started off with N160 and H4831SC and H4350. All my loads were in the 42 to 44gr range with the 107 Sierras.

The H4350 and the N160 shot the best but I was blowing primers at 44grs with H4350 and getting loose primer pockets after one firing with 42grs fire forming the cases. I was getting loose pockets at 42grs with N160 and blowing primers @ 43grs with 107s.

I have read where you guys are shooting up to 45grs with these powders so what is my problem??? I am using new WW brass. Any thoughts would be appreciated!!! Thanks guys!!

 

[Kodiak99317]

Do you have enough neck clerence? Is it a tight neck'd chamber? Sounds like you are getting extra pressure from somewhere and I'm just tossing out ideas.

 

[Raptor]

Kodiak,
Its a .273 neck because I lightly turn my necks to clean them up. When Dave made the reamer he recommended the .273 because I do turn the necks and thats what I went with.

I too thought this was my problem, so I went back and turned all the necks again. My loaded rounds are right at .270 so, no, I don't belive thats the problem now, if it ever was. I can push a bullet into the empty fired case with out much pressure. I was not sure how much clearance I needed and asked on here and was told that if I could push the bullet into a empty case I should have enough clearance.

I also thought that maybe I had to much neck tension because the bullets seated tighter than I like so I put an expander ball on my die to bring the necks back out and that didn't seem to help either.

The rifle seems to really shoot well. It will shoot 5 shot groups in the .3s to .5s and 3 shot groups in the .2s I am happy with everything but the primer issue. I have not cronographed it so I have no idea of my speed. I wanted to be in the 3000+ to 3100fps range with the 107s for now.

I shot two groups at 40grs of H4350 yesterday in the cold and they were both in the low .4s so the gun wants to shoot. If I can just keep the primer pockets in the brass!!! Thanks!!

 

[rcw3]

Raptor

Your loads are too hot and with the loads you mention of H4350 and N160, your bullet velocities are probably way up there,at least they would be in my barrels based on the testing I have done).

44 gr of H4350 with a 107 Sierra is way hot no matter if you are shooting plain or moly bullets. If you put that on a chrono I bet you are going around 3200+ fps with that load. I would not shoot that in any of my barrels.

You are also not giving enough info to make an accurate assessment of the situation.

Are you shooting moly or plain bullets?

What free bore length and throat angle did you put on your reamer?

I now have 5 different barrels chambered in the cartridge three of them 7.5 twist, one 7.8 twist and one 8 twist and I have not had the issue you are presenting except with very hot loads.

Hopefully you also don't have a 1:7" twist barrel. If so, I would say it's your barrel twist is part of the problem.

H4350 is also a little on the fast side for that cartridge.

With N160 you should max out around 43 gr with a 107 gr moly bullet and that should be going around 3150+ fps.

Until you put it on a chrono and see what your bullets are doing speed wise you are blind.

Robert Whitley

 

[Raptor]

Thanks Robert!! I am shooting naked bullets and I belive the freebore is 104,If memory serves me correctly). I have the drawing here at work and there is a reference on it that is marked as 1deg.-30 if that means anything to you.

What is a good load and powder for the naked 107s, in your opinion, with a 1-8 twist Kreiger 26" barrel??? I would like to be in the 3000+ to 3100fps range if possible.

As far as the reamer goes I just called Dave an told him what I wanted for a caliber and he said he was very familiar with the 243XC or 243BR and like I said he recommended that I go with a .273 since I always "Clean" my necks anyway. I did not spec the reamer in anyway, it was what he thought it should be I guess. He asked about bullets and if I turned my necks.

 

[rcw3]

Raptor

That should be a real nice set up with a .104" free bore and a 1 1/2 degree throat angle and a 1:8" twist barrel.

Looking at some of my chrono tapes from a while back, here are some loads to try:

Barrel one 1:7.8" twist:

43.8 gr H4831SC w/ naked 107 Sierra, Russian Primer, .015" in the lands, 3048 MV, ES 15, SD 6

43.5 H4831SC w/ naked Berger 108 gr BT, Russian Primer, .015" in the lands, 3027 MV, ES 20, SD 8

Barrel two 1:8" twist:

44 gr H4831SC w/ naked 107 Sierra, BR-2 primer, .015" jump, 3073 MV, ES 15, SD 7

45 gr H4831SC w/ naked 107 Sierra, BR-2 primer, .015" jump, 3120 MV, ES14, SD 6,on the hot side)

47.5 H1000 w/ naked 107 Sierra, BR-2 primer, .010" jump, 3008 MV, ES 27, SD 9

45 gr IMR 7828 SSC w/ naked 107 Sierras, BR-2 primer, .010" jump, 3075 fps,chrono had a problem picking up shots - very dark day)


N165 is also a good powder to try, probably in 45 - 46 gr range should get you going well with a 107 Sierra. I only did some testing with 115's and N165.

3000 fps is easy out of this cartridge with the 107 Sierras.

Start with something like 43 gr of H4831SC and see where you go. N160 should be a good powder, but it might be a little bit fast in the burn rate dept.

If I were going to "hot rod" this I would try double based powders like RL22 or RL 25, maybe N560.

Robert Whitley

 

[Raptor]

Robert,
Thank you so much for the help, I love your cartridge!! I was curious though as to why you are using H4831SC but then think that N160 is to fast??? Isn't N160 slower than H4831SC or am I missing something here??? What type of accuracy are you getting with your loads??? Thanks again to all who offered advice!!

 

[rcw3]

Raptor

I guess there may be a fair bit of variance out there in the burn rate of the powders and various lots of powder. I load about 1 to 2 gr more of H4831 SC to get the same velocity out of a load than I do with N160 so to me the N160 I have is definitely burning faster than my H4831SC.

When you ask what type of accuracy I am getting from my loads, my response is this:

The cartridge is definitely an inherently accurate cartridge and easy to load for.

The loads I posted were loads I had from chrono tapes, to give you some idea of what powder charges give certain velocities. My final loads are made up with the particular powder and bullet I am shooting. I don't usually push what I am shooting to the max mainly because in the prone shooting I do, accuracy and consistency needs to be maintained over a long string of fire, and I find the loads that run the best over a long string are those that I back off a bit. When I made up the cartridge I was looking to run a bullet like a naked 6mm 115 gr bullet 3000 fps without working the cartridge hard - I have that in the 6mm Super X.

I am a prone shooter and I only do all my load testing shooting prone with a sling and a scope at 100 yards with the slow prone target,x ring = 1 MOA). Shooting off a bench is a waste of time for me because I would spend a lot of time at a bench working up loads and lose the practice time that is just as valuable as having a tight shooting load. A load that's good is a load where I can lay down and run a string of 22+ shots in a row,that's the minimum of what we need to shoot) and if I can hold them, every one should come up an x,particularly the last 10 shots of the string when the barrel is hot and the gun is dirty). When I have that, it tells me I have found a load that is running about .25 MOA or better the whole way because I have .5 to .75 MOA of body movement and pulse built into my group. The key is the last 10 shots, if I am holding x ring, every one needs to come up an x. There are plenty of hot loads that shoot great for 10 or 15 rounds but they'll fall apart at the back end of a long string - seen this many times with loads - that's no good - the load has to make it all the way - if it makes it 15 shots but not 22 or more, it generally is too hot and needs to be backed off more. The tight shooting loads also run much better in the winds too.

Be careful of bench rest shooter postings as many of them only shoot a five shot group plus some sighters and that won't be helpful to someone who has to run 22+ shots in a row. Just my opinion, but many of the bench rest guys can run much hotter loads and stay tight because their string is much shorter and they can clean their rifle at the match too.

My first 3x600 with the 6mm Super X netted me a perfect 600 score at 600 yards and that's the first one of them I ever shot, so the accuracy and performance is there for me.

Robert Whitley

 

[Raptor]

Robert,
Once again thank you for your learned advice!! You are also correct that N160 is faster than H4831. I was talking 4831 but thinking 4350 becasue this is the powder that was shooting the best for me.

I will keep playing with my rifle and with REDUCED loads. I once again thank you for all your help and for advice on a great cartridge!!

 

[Rtheurer]

Raptor and all

I have included my Spread sheet of my Load testing over the last two months.

Rifle Specs

Trued 700
Kiff Coned, Fluted,bolt with Sako Extractor
Tannel Firing pin and spring and Shroud
Ellisio B1 stock
Satern 5 groove .236 1:8twist Stainless 30" Palma Countour

274 Neck

Lapua Brass
Loaded Rounds .272

Please Please remeber this is safe in My rifle and load accordingly by working up!!!!!!!! Dont be stupid.

The 107's shot steller in my gun, They were even Sierra Factory seconds!!! I was firforming brass too.

Russ T

 

[Rtheurer]

Like Robert said this Case has alot of horse powere if you want it but it iddles those 115's real nice at 3000fps+.

I also shot a 3X600 with my set up shooting 105 berger VLD's
197- 199-199= 595/600.

I hope to shoot it again at 1000 at the end of the month. Im expecting a 197 to 200 out of this gun at 1000yards if the wind isnt a hurricane.

RussT

 

[Raptor]

Russ,
What powder did you find worked the best for you?? Did you ever bench your gun or are you testing with a sling all the time too?? Thanks for the data that really helps!!!

 

[Rtheurer]

Raptor

All my load testing is done off the Bench with a scope. Now Im going to warn you Im not very good at shooting off the bench, butt I think i get a better idea of how my load development is going weather it be good or bad.
Also this particular rifle is a TUBE gun and it really is the,SH*&) to shoot off the rest. It rolls around like a bore pig in a new mud puddle. Not the best for shooting groups im sure. So when Im getting them into the High two's and mid Three's im pretty happy about it. As far as best powders Ill have to ask with what bullet are you refering too?

I really need to get the rest of the MOA data entered onto that spead sheet.

Also I would like to note that some of the groups on here were re tested checking bullet seating depth and may have ended up being the top dog when the ES came way down.

 

[Raptor]

Russ,
I am shooting mainly 107 SMKs right now. I plan on trying some 115 Bergers because I hear they are easier to get to shoot than the 115 SMKs are.

I tried 44 and 45grs of H4831SC and I get mixed results with it. One time it will shoot in the .5s then maybe out into the .7s or .8s. The 4831 just won't group as tight as the other powders have.

I don't shoot off the bench a lot either. I do tactical style shooting so my bench shooting leaves a lot to be desired. I have found so far that N160 and H4350 has given me the best groups.

I also need to load to mag. length so I can feed from the mag. so this limits me on seating depth. My reamer has a 104 freebore.

I did try 47.5grs of H1000 last night,Picked it up on the way home) and also 42grs of N160 with the 107s. The first group of N160 shot .525 with 4 in .295 I was very happy with that until I shot the 2nd group an it went into a .7 with 4 in a .5 I don't know if its me or the brass or something else.

The H1000 shot into a .395 with 4 in a .240 and that was the only group I had with the H1000. I shot a couple of groups of 4350 that had shot in the .4s the last time out and they both shot like crap!! SOooo...I am pulling my hair out right now. I just can't get any consistancy out of me or the loads. I may just pick one and start shooting at 400 on out to see what it does.

I hope to get some more testing with H1000 this weekend. If it continues to shoot well I will go with it and N160 to test at long range. Thanks again for your advice and info!!!

 

[Rtheurer]

OK Raptor I updated my Spread sheet and loaded all the groupsizes into the sheet.

Some not to shabby groups in there for shooting a Peace of pipe off a rest.

RussT

 

[Rtheurer]

Raptor

How does the seating of the bullet feel, are they consitant on every bullet from case to case when seating the bullets? Just a thought.

I like the idea of taking them out to 400 yards now that you a have an idea of what to work with. I would shoot the N160 unless the extreme Spread was real high,,like over 30fps). Make sure its a real nice calm day.

Good luck

RussT

 

[rcw3]

Raptor

Whenever you have a rifle not shooting to your expectations it's always frustrating because the options of what can be causing the diminished accuracy are endless, is it the scope, the barrel, bedding of the action, the action itself, the load, the brass, the cartridge, the bullet, or something else?

Years ago I used to shoot the 107 Sierras almost exclusively. If all your testing is with 107 Sierras my suggestion is to try another bullet. I really don't shoot them too much anymore because sometimes you get a good batch of them, sometimes not. Ask this - how many bench rest shooters shoot Sierra 107's in longer range bench rest matches?,Answer - almost none!) Why? I think you will find that most bench rest shooters don't shoot Sierra 107's because their accuracy and consistency can leave something to be desired - at least that's the response I got when I asked around to some bench rest shooters. At 600 yards I never shot a clean with the Sierra 107's, but I have shot a lot of cleans with other bullets,Bergers, Lapuas, JLK's). Now some shooters are passionate about the Sierra 107's and think they're great, and if that's the case I won't argue with them, but that won't change my shooting choices either. Just a thought.

It does not seem like you have tried any milder loads for group. If you get four shots that go .4 but the 5th puts you at .7 - why don't you drop the load 1 grain of powder further down and 2 grains further down, and try it again? You still may not know what your barrel is doing velocity wise and whether your barrel cannot handle hotter loads,some barrels can and some cannot).

Robert Whitley

 

[Raptor]

Russ & Robert,
I got a chance to get out and shoot some lighter loads and I cronographed them also.

I am not real sure if my cronograph is accurate but I tried it anyway. I started off with 43grs of H4831SC and that was right at 3000fps with the naked 107s. I then went to a load of 39grs of H4350 and it was 2984fps. The next load was 41grs of N160 and it was in the 3040fps range. The last load was 46grs of H1000 and this load was in the 3050+ range. It seems like all the loads had around 30 to 40+ for ES and in the teens for SD.

The H4350 load shot a .177 group for 5 shots!! But the 2nd group was a .5 with 4 in the low .4s. Most of the groups are in the .4 to .6 range on average with a few really good ones in the .3s. The one thing I did notice yesterday was that on my last group its point of impact was nearly 3/4" to the left of the first group fired with the same load. I had nearly 60rds through the rifle by this time so that may have had something to do with it or it may be walking after it warms up. I have noticed some horzontal stringing in my groups but not enough to say this is a problem because sometimes I will have some vertical also. Like I said my bench technique probably leaves a lot to be desired.

The rifle is a Remington 700, steel bedded into a H&S VS stock and has a 26" Kreiger 1-8 twist heavy barrel, straight taper .930 on the end. The scope is a 4.5x14 Leupold Mk4 tactical with mildots. Everything is tight and checked after each cleaning.

Russ,
I plan on getting out again to do the longrange testing but I wanted to take advantage of the sun to cronograph this weekend. I "WISH" I could wait for a calm day but I live in South Dak. and we only have about 2 or 3 of those a year!!,HA) I will keep you posted when I get out to shoot. I will only be shooting 3 shot groups though for my long range testing. I feel that tells me what I need to know and it saves on the barrel. Thanks again you guys for all your help!!!!