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Post by Bullshop on Apr 1, 2020 13:40:11 GMT -7
We at BS acres have accepted the task of developing loads for one of the E. A. B. model 97-d single shot rifles chambered in his 6mm Bench Rest Magnum. I am thrilled at the opportunity to work with a rifle that I have always found interesting but a bit out of my price range. Too the series of cartridges designed by Mr. Brown for single shot rifles have interested me but to say they are outside the main stream is an understatement.
The cartridge in question uses the standard 30-30 as the parent case but uses the improved Ackley body but with a 30* shoulder angle rather than the 40* common to Ackley cartridges. This one I would describe as a 6mm improved Zipper.
The rifle is very easy to like in the precision manufacture it displays. The action opens and closes with the metallic snap of a bank vault. The breach block movement is absolutely vertical so there is no camming power to push cases that are less than a perfect chamber fit into the chamber. In short if they don't free fit they don't go. The trigger is absolute perfection devoid of any movement that does not release the hammer set at perhaps in the area of 1.5 pounds.
The 24" fairly heavy contour but not extremely so barrel has an 8" twist and a factory installed break of Mr. Browns design. The break surely aids in the shooter spotting hit but for sure the same shooter better wear ear protection because the shooter gets whacked with a loud sharp crack from each shot and this even with loads of 6gn Unique for fireforming cases.
The suggested procedure for forming cases is to first run new 30-30 brass through an 7-30 Waters FL die then through the 6mm BRM FL die provided by Brown. I did not have a 7-30 available so first ran annealed new 30-30 brass partly into a 25-35 FL die then finished setting the shoulder in a 6mm PPC die that also happens to have the same 30* shoulder angle. This procedure worked nicely to produce brass that chambered freely. Since this is a rimmed case shoulder position is not critical for fireforming.
As earlier mentioned I used a charge of 6gn Unique for the fireforming load this under a Lyman design 80gn bullet. The bullet is round nose gas checked with the multi lube groove/drive band common to Loverin type bullets. So if first impressions are important mine of this very interesting little and it is little was WOW !!! this thing is going to shoot.
My first 5 shot string of these fireform loads just chewed out a single enlarged hole at 50 yards. So with 50 newly formed cases on to stage two with jacketed bullets. I figured with this case volume it should be well suited to the 16 pounds of surplus WC-842 I just recently purchased at least with the lighter weight bullets. That assumption was spot on with the only jacketed bullet tried so far the Sierra 70 gn HP-BT match. The sweet spot for this powder bullet combination was discovered at 30gn which has the same effect at 100 yards that the fireform load had at 50 yards in that after about 20 shots you have what looks like a 50 caliber hole in the target. Pleasing!
The factory indicates the rifles with the 1/8"twist are intended for bullets between 90 and 100gn so as we work our way up in bullet weight it may just keep getting better. We have a long way to go to find out as we are just barely getting started.
I have read a wee bit about chamber length in these rifles being too long for 30-30 brass and I plan to investigate the validity of that. Still I see no real problem there because first off 30-30 based brass is shooting pretty darn good. Secondly if anyone has a problem with 30-30 brass being too short for their chamber the simple fix is to form your brass from 38-55 where you have too much length so can trim for a perfect fit. I plan to cast the chamber of this rifle simply to satisfy my curiosity because there is no disappointment with accuracy.
That is all I have for now but as I said just getting started. I plan to chronical all progress on this project here on this forum so if you find this interesting please check in from time to time. I plan on working up through bullet weight all the way to the newer 100 + gn VLD type long range bullets so there is a lot of shooting to be done.
I am really up for this job as our gophers are just now popping out and there are many young critters that need to be fed. I stole away to the reapers roost this AM to squeeze off the last few rounds of the 30wc-842/70 Sierra and there stood a gopher at 225 yards and the attempted head shot was positive. Again pleasing !
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Post by Bullshop on Apr 2, 2020 11:28:02 GMT -7
Today we had the very unusual occurrence of no orders to fill so even though it is snowing and blowing I managed to work a wee bit with the 6brm. Its way too nasty to chronograph which I am anxious to do so I worked on loads for two new bullets. These bullets are the 100gn Sierra spt-bt old style with lead tip and the Nosler 95gn ballistic tip hunting. At the EAB web site they list only two loads for this cartridge and both with the same powder. These are, Speer 80gn with VV-160 - start - 36gn-- max- 40gn @ 3186 fps Lapua 90gn -- VV-160 - start - 35gn -- max - 37.5gn @ 3026 fps Since they only show loads with this one powder and I did have some on hand it is what I tried today. I started with the 100gn Sierra at 33gn and found it a bit too hot for this rifle so progressively went down in powder weight charges with poor results at each step. I decided this gun and bullet were not a good match and I didn't want to get into a lengthy force feeding to come to the same conclusion and I can live with that it just does not for whatever reason like the Sierra 100gn SBT. So with that and what we learned about powder charge with the Sierra we went to the 95gn Nosler bullet. After a few groups with a few different powder charges we settled on 32gn VV-160 as the best charge. Once we found the right seating depth the rifle showed a distinct fondness for this bullet. We did experience an anomaly in that one bullet appears to have some wobble making an oval hole on paper and clearly well out of the group. For this reason a second 3 shot group with the same load was fired which landed in the single hole made by two shots from the first group making a five shot one hole group. I will try to get Tina to post a picture of this target later. So with our second session with this rifle we are learning and some points with this rifle became clear. One of those things is that this rifle apparently just does not tolerate a cartridge length that has bullets engaging the lands. It seems not too finicky about how far off the lands it wants as .005 to .025" shoots good. The target we will show was .005" off. Another point about cartridge length has to do with the design of the rifle in that as stated previously cartridges have to be a drop in fit because the action lacks any amount of camming of the cartridge into the chamber so if it is not fully into the chamber the action will not close. This situation is somewhat compounded by the fact that there is only enough room for a single finger to guide the cartridge on a straight entry path into the chamber of the scoped rifle. Another possible design flaw is that when the breach block is opened the hammer drops with it and tucks neatly into a milled slot below flush with the receiver. The issue that this creates is that a hammer extension can not be used to make cocking the hammer easier since it is tucked closely under the scope. It was not a problem for me but I noticed when my girls fired the rifle they lacking the thumb strength had a bit of a problem cocking the hammer. Not really a big problem but just wanted to note the observation. As I said earlier the gun is on the smallish side so things seem compact to the small overall package. Still I like the package and with the accuracy it is displaying accept with the Sierra 100gn SBT bullet there is a lot to like from a single shot that theoretically should not shoot as well as a bolt action. Without changing the scope setting for the 100 yard zero for the 70gn Sierra bullet I noted that the poi shift was down apx. 2" and not up as I expected the slower bullets would be. Just goes to show nothing is set in stone. Shooting is one thing where it is safe to never say never and never say always.  |
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Post by missionary on Apr 3, 2020 6:04:24 GMT -7
This is my first to hear or read about these rifles. I was well informed about their single shot falling block pistols as I used to shoot the steel critters but with Dan Wesson revolvers. And Mr. Brown always had a large add in the Silly-wet "news print" that arrived monthly.
So I guess I will do a search and get a look at one of these rifles.
It does read as if you have a special project to test out for the coming spring time. Those 6mm slugs just may be a fine "bean field" or hillside to hillside dispatcher.
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Post by missionary on Apr 3, 2020 6:10:59 GMT -7
Found the websight. Yep it looks like Mr. Brown turned his fine falling block action into a rifle.
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Post by Bullshop on Apr 3, 2020 7:22:49 GMT -7
Yesterday PM I slipped out again to retry the 100gn Sierra spt-bt bullets. I found that with the right powder this bullet will indeed shoot well. The right powder though for this rifle cartridge combination has me a wee bit befuddled. The only powder recommended by the EAB company is VV-160 and the only bullet weights shown are 80 and 90gn.
This is puzzling to me because VV-160 is a quite slow burning powder on par with IMR-4831. It is a short cut extruded powder so allows a bit more weight in the same volume. The case volume on the other hand is moderate somewhere between the 6mm BR and the 6mm international. In my experience this type case volume usually gets best performance with slightly faster powder burn rate say between 4895 and 4320.
This seems perhaps another quirk of design dictating allowable chamber pressures. I have observed with the rifle cartridge combination that because of the lack of any camming of the cartridge into the chamber neck sizing is out and a tight fit wont chamber. On the same token the lack of any leverage for extraction means that anything approaching a warm load and the breach block will not open. There is just no way the abbreviated thumb lever used to drop the breach block can offer enough leverage to extract anything other than a case that will drop free of little more than its own weight.
So this design flaw is dictating the max allowable chamber pressure even though the action is quite strong. What I am seeing is that this rifle will easily surpass what is considered the pressure limit for conventional lever guns at roughly 40,000 psi but not equal the accepted norm of bolt action rifles on 50,000 + for standard cartridges and even up to 60,000 + for some magnums and or more modern developments.
Not having the equipment to verify my theories I will guess that extraction with this rifle can begin to become an issue somewhere around 45,000 psi but this may be somewhat variable dependent on powder burn rate and the pressure time relationship to peak pressure.
Please do not misinterpret what I am saying to mean that there are serious problems with this rifle cartridge combination because that is not my meaning all I am doing is pointing out some facts that I have observed in the small amount of testing so far done. These observations in no way detract from the quality and potential accuracy of the combination they just allow an understanding of the place to look for best performance. So it will never be the ballistic equal of the 243 but it is not intended to be.
Now back to the 100gn Sierra bullet that just would not shoot well with the VV-160 powder. Since it is the factory recommended powder for 80 to 90gn bullets perhaps a slightly slower powder burn rate to peg that pressure time curve would be more appropriate. BINGO !!! Going to a slightly slower powder in this case H-450 and the grouping with the 100gn Sierra spt-bt perked right up and turned 1.5 moa groups into .75" groups cutting the previous in half.
The curiosity for me with this rifle is why the 8" rifling twist rate. I know the current trend in target rifles especially precision built and 6mm is to the faster twist rates of 8" and even as fast as 7" but these type rifles have the ability to utilize the higher chamber pressures of bolt actions so even with fairly small case capacity such as the 6BR and even the 6 Creedmoor and a myriad of other lesser known small case 6mm cartridges they are performing extremely well at quite long ranges even well past 1000 yards.
This rifle is not in that class because with the limited allowable chamber pressures described earlier it can not compete on the same ballistic level. So what is it then a hunting rifle ? I will say yes and a darn good one. It is fairly small and light weight so easy to carry and quite compact for length because of the very short receiver. I discovered very early on in my coyote hunting that for off hand shooting a single shot has the center of balance closer to the body than does a bolt action with an equal weight/length barrel so for me was easier to steady for off hand shooting. I like that! And as earlier stated its not as good ballistically as a 243 but on the same hand it is better than some smaller cartridges in the same caliber such as the 6x45, 6x47, or 6 PPC.
For me here in the reapers roost I can attest to its effectiveness on gopher management to 300 yards. Very soon our rock chucks will begin to appear from the Red Rock bluffs beginning 700 yards out from the reapers roost and should present quite a challenge for this little hunting rifle but I feel even with its limited velocity potential with the heavier high BC bullets required for such shots it is not out of that game. Hopefully if allowed enough time we will learn just what are the range limits with this rifle cartridge combination.
So with what I have learned so far should I be disappointed ? Not even close!!! This little package is a thoroughbred and as such will perform if the user is wise enough to listen to what it asks for and not force feed what you think it should want!
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Post by missionary on Apr 3, 2020 17:20:30 GMT -7
I will eagerly await the next chapter in your fine description of a unique rifle.
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Post by Bullshop on Apr 5, 2020 13:18:45 GMT -7
Well this installment wont be much of a chapter but I do have a couple new loads to add. I don't know why but with the jacketed bullet loads I began to feel like I was under pressure to produce load data and I began to feel as if I were cramming for exams. So for that reason decided to for a bit leave the noisy high performance loads and move in the direction of fun low power loads with cast bullets.
With that in mind I had to evaluate the mere 5 6mm designs we have available and of those chose an LBT mold for Verals spitzer design at 80gn. What I was looking for is two different purpose built loads. One would be a bus load for shots to about 75 yards and the other a reapers roost load for shots to about 300 yards.
If your wondering what a bus load is its for use in the school bus we bought to move from Alaska. We have a shooting bench of sorts inside and we just swing the big rear door open and shoot from inside. You can see why we would want a very low noise load for that. The two things required for a bus load are low noise and accurate to 75 yards. Most shots from the bus are about half of the 75 yard limit but occasionally we might shoot that far.
The bus load turned out to be 5.7gn of Trail Boss powder. No idea of the velocity yet but that is not important what is important is that the load is capable of making head shots to its maximum in tended range.
The roost loads have no sound conditions but accuracy to longer range is of ultra importance. The roost load worked out to be 17.5gn of IMR 4198. Again no chrono data but with a 100 yard zero about a 1.5 gopher high hold makes hits at near 300 yards. Wind as always is a problem but manageable Shooting this AM in about a 5-6 mph cross wind required about three gopher width hold to blow into the target. This shooting is for sure more challenging that with the jacketed bullet screamer loads that pretty near always use the same center hold out to near 300 yards with a 200 yard zero. One type is more for serious gopher culling while the other is for more serious marksmanship challenge. Both are fun just different purpose.
Well now that I have a few usable loads I may turn my attention to some other guns in the rack that seem to be calling out for attention. Developing a load data book for this cartridge is something that may happen over time but to try and accomplish that at one time become more like work than fun so maybe only tolerable in small doses.
So at this point if I were to offer an evaluation of the rifle cartridge combination I will say that first yes I like both but because of the design limitations you really cant compare it to any other cartridges in the 6mm/243 caliber. It has its quirks but like all specialty firearms if allowed enough time to become familiar with those and offered developed loads of its choosing it will deliver a level of performance that is on par with custom precision rifles of any design and so doing can be a pleasure to the shooter owner. In short its a darn nice little package that shoots darn good too. What more can you ask for?
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Post by missionary on Apr 5, 2020 15:34:51 GMT -7
Just a couple well placed targets to watch the effect.
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Post by Bullshop on Apr 5, 2020 17:22:44 GMT -7
I forgot to mention that on the fifth firing I found a cracked case neck. When I started out forming cases I started with new RP 30-30 brass and annealed it before I even started the forming process. Checking the case neck diameters of fired and loaded cases I get .2724" on fired cases and .2710 on cases loaded with a cast bullet at .245" diameter. That allows .0014" clearance or case neck expansion if you prefer. A .0014" clearance is on the snug side compared to most commercial production run rifles where .004" or more is more the norm.
The die set provided by EAB Co. is a good match to the chamber not over sizing the neck or shoulder excessively. Retracting a sized case from the die has some drag on the expander ball coming through the case neck but not the two handed press arm lift that lifts the loading bench off the floor of some poorly matched sets. There is just enough drag to know it happened with no reverse sizing going on. Even so 5 shots was the limit for at least that one case I found with a cracked neck so I would suggest to anyone to re-anneal after every 4 shots which is what I plan to do hence forth.
So I have a 50 round box loaded with the 80gn LBT bullet with the 17.5gn 4198 load just waiting for a nice sunny windless day to coordinate with free time to spend in the reapers roost to burn them up in gopher control. All part of the job fellas just all part of the job !
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Post by missionary on Apr 6, 2020 5:30:22 GMT -7
Would be interesting to know if EAB reams the sizer die with the same reamer at the same cutting sequence as the chamber.
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Post by Bullshop on Apr 6, 2020 6:45:48 GMT -7
I was recently reading info from a custom barrel supplier that they are now using some sort of electro displacement technology for chambering barrels. In this system there are no reamers. Their claim is tighter tolerances and repeatable dimensions.
If the claims are true I suppose it will become standard for the industry at some point. The upside is we may see a lot of used reamers show up on eBay.
Oh too I don't know if I mentioned that the loading die sets from EAB are mixed manufacture with the seater being made by Hornady and the sizer being made by Lee.
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Post by missionary on Apr 6, 2020 15:50:45 GMT -7
Now I will need to read up on electro displacement . Interesting though about the multi-manufactured die set.
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