Best/Biggest 30 cal

[Norm]

a 300 something was given a bit of "look the other way" dispensation regarding his muzzle break and allowed to compete in 1000 yard BR. Tony

Tony,
Muzzle brakes are permitted in 1000 yard benchrest. It is within the rules!

[johnk]

True, but the guys I've met who use them come prepared with ply baffles that they fit each side of their rifle.

[DenisA]

Hi Guys,

I started shooting my .300wsm using 230g Hybrids. I couldn't get them to do what i wanted and I'm having much better results with 215g Hybrids.

I know some of you are looking for them and I have 6 x un-opened boxes of 50 (300) that I'd be happy to off load. Lot#4536.

PM me if your interested.

Interestingly, using my ballistics app, I coulnd't get these to meet Millers 1.4 Sg in a 10 twist barrel. They were close at 1.31. I wonder if thats why myself and some others haven't got the greatest results with them.
A 9 twist barrel seems to suit them better. I think its the long OAL, long ogive and short bearing surface of the Hybrid that causes it to want a faster twist........... not specifically the weight.

These images tell a different story to what you have found. Maybe you need a little more load development.



Image from Berger Bullets website with my data and the bullet looks stable from a 10 twist to me!



Recent results from a load tune up for the SA Queens with my 300WM and the 230gr hybrids.

Ian

Hi Ian,

Thanks for the input.
You've input 1.64" as the bullet length. I used 1.69" as thats the average length of batch that I've measured.
I changed my input data to match yours and got the same result as you with my program, however, thats not their length.... at least not of my batch.

Changing the length in the ballistics program from 1.64 to 1.69 is enough to drop it down to 1.32 Sg.
Bergers twist rate calculator also agrees but I'm not sure how to copy and paste it as you have.

I also developed at 100 yards and have a consistant .3 moa load at that range. I was running them at 2750 fps with AR2213sc. They didnt hold very good vertical at the longs.
I spent a lot of time with them blaming my self, ie technique, windreading, etc. Then I tryed the 215s and instantly had much better results.

Do yours measure 1.64" or is that info you've sourced from a publication?

Nice group.

I suppose the other consideration is "actual twist rate" of a barrel V's "specified twist rate.. I haven't checked mine, though I'm lead to believe that often twist rates can be a little different to what they are claimed to be. That alone could give different barrels very different results with the same bullets. Especially where the bullet/barrel combination is close close to the Sg limit.

Cheers.

[DenisA]

I now see that 1.64" is straight out of the Berger reloading manual.

Again, "actual values" V's "specified values". Difference between batches, etc.

[Seddo]

seddo,
you might be able to get bulk discount on barrels.
bruce.

I don't shoot the same rifle enough for it to be an issue.

[bruce moulds]

in the real world, 1.32 is still ok stability.
keep safe,
bruce.

[AlanF]

... I strongly believe that if you cant shoot it without a muzzle break then it shouldnt be allowed on the mound IN F CLASS.
I wouldnt hold that position for a "try it"/one off occurence, but as far as being a regular competitor in F Class then i am totally against muzzle breaks being allowed. It seems that the rules that govern F Class competition internationally agree !
Tony

This one is a dilemma. On the one hand we have F-Class rules here and internationally disallowing muzzle brakes - and that is a perfectly understandable position. On the other, we have large numbers of potential members (much-needed) in Australia who want to use muzzle brakes. I think the best way of satisfying both parties is to keep the braked shooting separate by having it at different times. We desperately need more members to keep our NRAA affiliated ranges from closing, and F-Class is not growing enough to do that.

Alan

[IanP]

I now see that 1.64" is straight out of the Berger reloading manual.

Again, "actual values" V's "specified values". Difference between batches, etc.

Dennis, I think you are better off with the 215s for your 300WSM as I dont think the case has enough boiler room for the 230s. I'm sure the 10T barrel is more than adequate to stabilise both bullets otherwise I would could not be shooting high X counts at long range. The 300WM and the load I am using have the ability to group well at all distances otherwise I would not be considering it to shoot in the upcoming State Champs.

Berger quote average values which they use to provide a barrel twist recommendation for all their bullets, printed on the labels. Its up to the individual to determine what barrel they want to buy, but Berger are not fools and dont make recommendations that would have their bullets shoot inaccurately. Berger recommend a 10T barrel or faster to launch their 230s and looking at my results I am not going to suggest anything different.

Berger also quote average G7 BCs for their bullets and again I see no reason to question this method of representing an accurate value to use to determine their ballistics. During load development I have experienced groups opening and closing but did not jump to the conclusion that it was because of marginal stability. There is a lot to consider before thinking that Berger may have their recommended twist rate wrong.

Ian

[IanP]

... I strongly believe that if you cant shoot it without a muzzle break then it shouldnt be allowed on the mound IN F CLASS.
I wouldnt hold that position for a "try it"/one off occurence, but as far as being a regular competitor in F Class then i am totally against muzzle breaks being allowed. It seems that the rules that govern F Class competition internationally agree !
Tony

This one is a dilemma. On the one hand we have F-Class rules here and internationally disallowing muzzle brakes - and that is a perfectly understandable position. On the other, we have large numbers of potential members (much-needed) in Australia who want to use muzzle brakes. I think the best way of satisfying both parties is to keep the braked shooting separate by having it at different times. We desperately need more members to keep our NRAA affiliated ranges from closing, and F-Class is not growing enough to do that.

Alan

I agree Alan! I also think and have said before on this forum that sound moderators are a great option to consider. They are legal in NZ and would help eliminate the high db sound we are subject to in shooting.

Its not going to happen in my lifetime as OHS at rifle ranges is countered by public misconception that sound moderators are somehow criminal. We shoot to the rules we have and if we dont like them then we need to organise a change to them through the NRAA.

Goodluck with that for muzzle brakes which dont only make just as much noise as open barrels but also direct the muzzle blast back onto adjoining shooters on the mound.

Ian

[DenisA]

I agree Ian.

Bergers recommendation is a 10 twist "or faster", I'm not suggesting anything different either.

I'm certainly not suggesting that Berger have their twist rate wrong. I'm identifying that the 230's in a 10 twist are at the lower recommended limit of Millers stability which is still .4 Sg above stabilisation.

I'm querying whether they would be more easily tuned and/or offer more consistent results with a 9 twist barrel.

I'm not disputing that you and others are using them very successfully. Paul J has them shooting well in a 300wsm.

Maybe more speed than I've been pushing them at is required, but as I'm sure you know, more M.V affects the Sg far less than more spin.
My calculations using 2730fps and 59 deg F results with Sg 1.3. Increasing MV input to 2930 only brings the Sg up to 1.33.

I'm not jumping to conclusions. I've been shooting the 230's for a while and started looking at myself intently before anything else. This is just a questionable area that I've identified.
The fact that I have them shooting one hole at 100 and have poor vertical at the longs, suggests to me that it may be an external ballistic issue which is what got me looking down this path.

I'm sorry you've taken me as being a smart ass that's challenging the best ballistician in the world. It seems that you have me and my point all wrong.

[IanP]

I agree Ian.

Bergers recommendation is a 10 twist "or faster", I'm not suggesting anything different either.

I'm certainly not suggesting that Berger have their twist rate wrong. I'm identifying that the 230's in a 10 twist are at the lower recommended limit of Millers stability which is still .4 Sg above stabilisation.

I'm querying whether they would be more easily tuned and/or offer more consistent results with a 9 twist barrel.

I'm not disputing that you and others are using them very successfully. Paul J has them shooting well in a 300wsm.

Maybe more speed than I've been pushing them at is required, but as I'm sure you know, more M.V affects the Sg far less than more spin.
My calculations using 2730fps and 59 deg F results with Sg 1.3. Increasing MV input to 2930 only brings the Sg up to 1.33.

I'm not jumping to conclusions. I've been shooting the 230's for a while and started looking at myself intently before anything else. This is just a questionable area that I've identified.
The fact that I have them shooting one hole at 100 and have poor vertical at the longs, suggests to me that it may be an external ballistic issue which is what got me looking down this path.

I'm sorry you've taken me as being a smart ass that's challenging the best ballistician in the world. It seems that you have me and my point all wrong.

Denis, a lot to think about in your post and I'll have a go at getting you onside this time instead of offside.

Please dont think me a smart arse, as I have never thought that your posts suggested you were. I will just add some technical detail as I uderstand it and maybe able to show why I question your comment about marginal stability. You are not alone in your assumption that a Sg of 1.4 is some magic number that must be achieved.

1. The person who suggests a Sg of 1.4 or better is Bryan Litz. He qualifies this suggested value in his book in the "Bullet Stability", (Chapter 10) section. He qualifies the 0.4 safety margin by saying it is for general use as in all types of shooting. He goes onto say that if using high quality components as in BR, (like in F-Open) then the safety margin can be safely reduced to 0.3. It is my understanding then that for F-Open a 0.3, (Sg = 1.3) safety margin is adequate.

2. You said that you thought marginal stability may have contributed to your vertical spread at longer ranges. I would be looking at the SD of your load as a primary contributor to this effect and not stability.

3. Marginal stability would result in a loss of BC through increased drag caused by the bullet's less than point forward optimal position. You could easily check this on the longer ranges by measuring bullet drop and checking to see if it corresponds to your ballistic program.

Bullet stability increases considerably at long ranges, (as long as supersonic) as the bullet velocity drops away considerably faster than the spin rate. Its all explained in Litz's book.

4. I'm suggesting that a 300WM is better suited to the 230gr Hybrids simply because a little higher velocity than the 300WSM can launch them, gives them the edge over the 7mm, 180gr Hybrids. I'm not suggesting that the higher velocity is needed to stabalise the 230s in a 10T barrel.

As a final bit of useless info I would like to add that when I was in Canberra for the Australian Team F-Class tryouts, a F T/R shooter was launching 230gr Hybrids from a 308W case. Daryl was shooting them off at the 900m target and Alan Seaman was the wind coach. Alan Seaman was amazed by the accuracy of these slow moving bullets, (guessing at 2400fps) launched from a 308W in a 10T barrel. The load backed out a few primers so didn't make it as a desired load.

Ian

PS If you want to clip screen shots to post as pictures, etc, then use a program called Snipping Tool. Its included in MS Win 7 and higher and is great to use for stuff like what I did with the Berger twist rate calculator!

[DenisA]

Ian, my apologies for getting defensive. I really appreciate your advice and knowledge.
I'll go back to my records and check the MV's and SD.

I have been to a couple of shoots with Daryl at Belmont when he was trialling the 230's. I can't quote the exact figure as I don't specifically remember but I was very surprised at how close his MV was to mine considering the cartridge difference. Honestly I didn't believe his results until he showed me his test targets and chrono results.
We had a couple of conversations regarding brass life and why I don't take full advantage of the wsm and beef up the MV.

[Norm]

Denis,
I’ve had a bit of experience with shooting very large, high BC bullets and they can be a bit sensitive to vertical. Apart from neck tension etc. A couple of things that I have found are…..

Bullet shape variation.
Batching seems to be important to reduce vertical at long range. G7 drag values can decay at a higher velocity than what most people think. If your bullets have not been batched then slight changes in bullet shape result in vertical as this decay will take place at different distances. A stability factor of 1.3 at the muzzle sounds fine and should improve as velocity reduces. But if one bullets BC drops lower than another at long range, then it will hit lower on the target no matter what its stability factor is.

Not sure if your load is doing this as it should still be going quite fast at 1000 yards. But batching may help. When I batch large bullets for long range, I do it by bearing surface and bullet length. I am looking to maintain a consistent BC from one bullet to the next.

Powder temp/primer selection.
The slow powders that are required to drive heavy bullets can be effected by cold temperatures. Below 10 degrees C they will have a higher ES than on a day when it is warmer. Ignition becomes a problem in cold weather so primer selection for these conditions is also important. You may need a hotter primer on cold days or when shooting first up in a comp that starts in the morning. Or you can keep them warm.
I have even used a hot water bottle next to my ammo to keep them nice and warm. With some loads using slow powder, this has given excellent results.

[IanP]

Norm, where did you buy your pin adjustable Barrett rings from?

Ian

[Barry Davies]

My take on Muzzle brakes --
If the recoil is causing you problems ( without a brake ) don't fire it.