Hi all,

Was looking at the Bellm/Shearer pressure measurement method, and was wondering if anyone's ever seen any actual verification of pressures on a load determined to be "max" by the springback method. Also was wondering if anyone has used this method on a bolt gun. Looks to me to be a valid method.

SS,

I have used the sping-back method with my 358 Bellm barrel and was quite satisfied with the results. It DOES work. It is also a boon to my confidence in developing safe loads in this particular barrel.

I had extensive correspondence with Don during my own initial use and testing of the method when developing the first loads for my barrel. It was a tremendous learning experience and quite enjoyable.

You could actually plot what was going on with a graph to reach a Redline for your load.

(Don is a real researcher possessing an excellent ability in regard to plotting, recording and verifying his results.)

While there is the possibility of this method being applied to other cartridges in other guns, the Marlin case, in the Bellm chamber dimensions, is the only true application for it at this time that has been verified within the current criteria.

To extropolate it to other cases/chamber dimensions without initial ground work may or may not be safe or at best, inconclusive. This method relies heavily on the brass case properties to be successful. Being Remington is basically the leading manufacturer of the Marlin brass, the potential for other brands getting mixed in with the criteria is little or no factor. This is not to say brass from a single brand does not differ. In the case of the Rem. Marlin brass, the differences are largely inconsequential with regard to the use of this method and surprisingly uniform. The method also calls for staying with a particular group of brass throughout the load development.

I believe Don at one time was looking into pressure verification of this method but am unsure what if any outcome became of it.

Might be worth dropping a line to him to inquire.

Regards

[ 12-06-2002, 19:20: Message edited by: Headstamp ]

Hi guys,

Yes, I am still working on the "spring-back" pressure determination method. I have written a technical paper describing the method and do hope to get it published soon. As far ar further work, I can't find anyone who has an Oehler Ballistics Lab who is willing to come sit beside me and make on-the-spot pressure measurements to use for verification. The next best thing is to compare the pressure curve from the spring-back method against a good pressure calculation method. I did that and included some of it in the technical paper. I used the Miller method which was published in a recent issue of The Varmint Hunter magazine. After looking into his method in a lot of detail I decided it is about as good as any calculation method available today. The long and short of it is that the Spring-Back method produces a pressure curve that is righ alongside the Miller calculation method.

So far the spring-back method applies only to cases reformed from R-P 444 Marlin brass (R-P is the only manufacturer of that size case). I have tried to apply it to cases based on the 30-30, but they are so thin and light weight that it doesn't work there. I am currently trying to use other heavier cases and do hope to find one that will act in a similar manner as the Marlin case.

I haven't forgotten about doing further work on the subject, but right now I'm not making much progress other than to write the paper.

Hope to have more soon.

Don Shearer

Don, as you know there have been a number of folks interested in 6.5 mm and about 4 years ago I did the one and only .260 Bellm, the .260 Rem. chamber shortened .050," case made from full length .307 Win. brass.

I do have one 6.5mm 15" barrel turned and ready to weld a lug on later this winter if you are interested in developing data for this round and gathering comparative data using .307 Win. brass.

I also plan to make .30 Alaskan barrels and have doubts about data extant for this round. It is one of the very best Contender rounds there is, but it appears the data distributed for it by your neighbor is hotter than I want to put my name to. For the benefit of all, it would be good to put this to the test also.

Working with either round, you should be able to draw some valid comparisons with results obtained from .444 Marlin brass.

If you have room on your plate and an interest in either project, let me know.

Also, I think you should have one of my Headspace Indicators. I'm taking delivery on the first production run in the morning, bluing over the weekend, and shipping Monday. Want one? Let me know.

All the best, Mike

My thanks to Don and Mike for openly sharing their efforts and information. The internet can be a great thing when used properly! When I had thoughts of applying the springback method to other cartidges, I had .308 in mind. Hadn't considered thin cartridges like the .30-30. I think the method would probably work with the .308, just need baseline data. Don, what issue of Varmint Hunter had the Miller article? I hadn't seen much on methods of calculating pressure without an Ohler setup.

Mike,

I am again interested in doing some experimental measurements regarding pressure. I think going after the 6.5 based on the 307 case might be the best next step. I have also thought about trying something in the 30-30 family using brass reformed from 375 Win brass. It seems to be a lot stronger than the regular 30-30 stuff. Possibly the 30-30 AI would be worth trying. What are your thought about that?

Sav Shooter,

I did my original comparison pressure calculations from a prepublication copy of Miller's paper, as I corresponded at length with him as he was writing the paper and while I was doing the original comparisons. His paper is quite long and so it has been separated into two parts for publication. Part 1 was published in The Varmint Hunter magazine, Issue #43, July, 2002, page 65 - 74. There is easily enough detail in part 1 to understand what he is doing and to set up to make the pressure calculations. The only drawback is that you have to make quite a few dimensional measurements of the round itself and you need the chronographed velocity. However, the calculations are straightforward and can be done with a good scientific calculator, such as the H-P.

Don Shearer

Don,
I am glad you have an interest in the .260 Bellm project. There are at least a few who are interested in the 6.5s and would likely pursue it if they knew whether a 6.5 based on .307 brass was a valid approach or not.

One thing I have never done before is obtain hardness tests for both .307 Win. and .444 Marlin brass. One of the machine shops I use here in this area has an excellent inspection room, including a hardness tester, so it will be easier to do this now.

In regard to the .375 Win. brass, I have sectioned it and .30/30, and at similar locations approaching the web of the case, I find only about .007" greater thickness in the .375 Win. brass. It is thicker, but not by a lot.

On the other hand, the .307 Win. brass is massively thicker than either .308 Win. or .444 Marlin.

If you want to pursue .30/30 Imp., it would be best done in a custom barrel, and I would be glad to work with you. It may prove quite interesting to see how it stacks up against the .308 Bellm under your controls. Likewise, a comparison on the top end with .309 JDJ under a different moniker could be quite interesting.

What I see is the value of your controls that are apparently quite "wanting" in other sectors.

I have .30 cal. barrel blanks on order, and a definitive study of .30/30 Imp., .308 Bellm, .30 Alaskan, and .309 JDJ all in the same type of blank could put to rest a lot of conjecture. This could be done in 4 different barrels, or to keep things as controlled as possible, at most two barrels. I would have to double check dimensions, but I think I can start with .30/30 Imp. and rechamber all the way through to .309 JDJ, excuse me, .30x.444 Marlin 40 degree.

The .30/30 case is a tad longer than the .307 Win. case, but not enough to make a material difference in this instance.

I am still trying to catch up on old obligations and cannot make up the .260 Bellm barrel right away, but some time probably toward the end of January, it should see light of day.

Pick what interests you most, and just let me know how you want to proceed.

Mike

Mike,

I will give the issue some serious thought over the next few days then get back to you via wmail.

Don Shearer

Rats - - the w is right next to the e

Don

Don, I can handle the w and e problem, its those magic mickey soft keys in the first row that makes whole documents disppear that tends to put a puter in a race with a bullet.

Take your time deliberating. I still have obligations to clear up before finishing out a barrel.

If it ain't fun, why do it? Let's have some fun.

Mike

Thanks Don for the Varmint Hunter reference. Looking forward to someday seeing the results of further collaborative efforts by you and Mike. Have a Merry Christmas all!