- This topic is empty.
-
Topic
-
Larry Gibson
I’ve just completed a test of the NOE 30 XCB bullet in 10” and 12” rifles. Was it a complete test? No. Did I seek the best accuracy? No. What I did was push the XCB to high velocity while maintaining acceptable accuracy where most all other cast bullets lose accuracy. Before we get into the test results let me explain the test parameters.
The rifles: the 10” twist rifle is a M1909 Argentine made M98 action with a 24” Adams & Bennet barrel having a 10” twist and chambered in .308W. The barreled action is bedded in a wood sporter stock (Churchill Arms, England). The action has not been trued. The chamber was finish reamed to minimum headspace with a Clymer M118 Match reamer. The rifle shoots right around 1 moa (10 shot groups) with selected match loads using 168 or 175 Sierra MKs. The rifle has an old original Weaver K-10 scope on it.
The 12” twist rifle is a M70 Heavy Varmint rifle with a 26” factory barrel on it. It has been pillar bedded and a rail put in the fore end for a hand stop. It is a very accurate rifle and shoots ½ moa with 175 MKs. I’ve “cleaned the 600 yard line several times with it and the 1000 yard line a couple. For testing it has a Redfield Ultimate 4×12 scope on it.
The 30 XCBs were cast of Lyman #2 alloy and WQ’d out of the 4 cavity aluminum NOE mould. The BHN runs 22 – 24. They drop at .3105. The bullets were visually inspected and any visible defect rejected the bullet. The visually passed bullets were then weight sorted to +/- .1 gr. Hornady GCs were crimped on using a .311 H&I die in a Lyman 450 with the GC seater used. They were then light lubed with a spray lanolin lube and pushed through a Lee .311 sizer to fully crimp the GC on. The GC’d bullets were then lubed in the .311 H&I in the 450 lubrasizer and lubed with 2500+ lube. Fully dressed the bullets weighed 164.7 gr.
Cases were match prepped LC Match. Primers were WLRs. Cases were fire formed and neck sized with a Redding Bushing die to give just a slip fit over the NOE M die expander (a very neat tool BTW) for Lee case mouth expander die.
Already knowing which powders gave the best high velocity accuracy with the Lyman 311466 and the LBT 30-160-SP bullets in both rifles I chose to use the same powders under the NOE 30 XCB bullet. That would give a good comparison. Thinking the NOE 30 XCB should withstand a bit higher acceleration each powder was loaded over the point where the Lyman and LBTs went over the RPM Threshold and lost accuracy.
That brings up “accuracy”. The objective of this test and the other XCB tests was to push to the highest velocity possible while maintaining 2 moa or less accuracy with linear expansion at 200 and 300 yards or further for 10 shot groups. Why 2 moa? Because that is the useable accuracy criteria those of us running these tests chose. The 2 moa criteria has been the high power standard for many years. You can kill deer, coyotes and such all day long with a 2 moa rifle. Some have a hard time with “useable” and seem to grasp “reasonable” as a good measure. The two mean the same. That criteria was chosen because the primary objective is high velocity with accuracy. Once we find out the upper end of velocity with one set of components that maintain 2 moa or less then we can tweak the load and components for best accuracy, if we want to.
All velocities (muzzle) were measured with the Oehler M43 PBL. For each shot the screened velocity was recorded along with a “proof”, a pressure trace was recorded and the peak pressure and associated Area and Rise of the pressure were recorded. The averages of velocity and the pressures along with their SD & ES were computed. The screened velocity was converted to muzzle velocity. On the data sheet for each test string I traced the bullet holes, measured group size (ctc) for record and computed the RPM. Most of the test strings are of 10 shots but 3 have 9 shots (out of 20 test strings). I also tracked each shots location on the target and numbered each bullet hole on the data sheet accordingly. This gives a very clear understanding of what is happening during the internal ballistic phase. This test produced 20 data sheets (both rifles) so I will not post them all. I will post the pertinent ones that show the top end capabilities of the NOE 30 XCB as tested in each rifle.
For those enamored with 5 shot groups it is interesting to note that in tracking the shots on target in 7 of the 20 test groups the first 5 shots went into less than 1 moa (1 in the 10” twist and 6 in the 12” twist). Thus, based on 5 shot groups, we could claim that 35% of our groups were “sub moa” and thus our loads were. However in doing that we would only be fooling ourselves.
I have often stated the RPM Threshold (120,000 – 140,000 RPM) is not a “limit” but could be pushed up. I have said two of the prerogatives for doing so is to use a slower burning powder to slow the acceleration rate and to use a properly designed cast bullet of appropriate alloy to with stand that acceleration rate. The NOE 30 XCB bullet was design expressly for high velocity. It is succeeding exceedingly well at 2600 – 2800+ fps in 14” twist barrels. Let us see how well it does at higher velocity and RPM in the 10 and 12” twist rifles.
The 10” twist rifle (24” barrel) results;
I chose two powders to test under the NOE 30 XCB bullet in the .308W rifle with 10” twist; RL19 and RL22. Both of those powders gave the best accuracy out of this rifle with the Lyman 311466 and LBT 30-160-SP cast bullets. Both of those bullets began going over the RPM Threshold at about 2300 fps/165,000 RPM with RL19 and about 2350 fps/169,000 RPM with RL22. Note how both of those bullets and powders have pushed up the RPM Threshold over the incorrectly assumed “limit” of 140,000 RPM. Both of those bullets held under 2 moa accuracy with linear expansion at 200 yards. Thus with that baseline to measure against I loaded test strings of 38, 40, 42, 44 and 46 gr of each powder to test the NOE 30 XCB bullet.
The 38 gr load of RL19 gave 1938 fps, 139,536 RPM at 28,100 psi(M43). The group size for 9 rounds was 1.2” (I excluded the 1st shot out of the cold clean barrel which always drops low out of the group). Shots 2 through 6 went into .85”. The ES was 146 indicating that RL19 does not ignite and burn efficiently at this pressure. A dacron filler probably would have helped that but no filler was used.
The 40 gr load of RL19 gave 2075 fps, 149,400 RPM at 31,100 psi(M43). The group size was 1.5”. The ES immediately tightened up to where it should be. In fact this test strings ES or 37 fps and SD of 11 fps were excellent.
The 42 gr load of RL19 gave 2194 fps, 157,968 RPM at 35,000 psi(M43). The group size was 1.65”
The 44 gr load of RL19 gave 2313 fps, 166,536 RPM at 38,900 psi(M43). The group size was 1.55”. Again an excellent ES of 30 fps with the SD at 9 FPS. The Pressure ES was 1,200 psi with an SD of 400 psi which is excellent and demonstrating excellent ignition and uniform burn.
The 46 gr load of RL19 gave 2434 fps, 175,248 RPM at 43,700 psi(M43). As with the much slower 14” twist rifle I am finding the psi of 41,000+ to be very hard on cast bullets of this alloy. We see while the group size is 1.9” there are 2 and probably 3 flyers telling us that this load is exceeding the RPM Threshold or, at least those 3 shots were. Dropping the load to 45 gr would probably give close to 2400 fps at 41,000 or less psi and still give us the 1.5 +/- accuracy level we’ve achieved with the other loads. That is a 100 fps +/- increase over the Lyman 311466 and the LBT 30-160-FN bullets in this rifle with RL19. That is indicating the NOE 30 XCB bullet is indeed holding up better under the high rate of acceleration and RPM generated in this 10” twist rifle.
Larry Gibson
-
Replies
-
Moving on to the RL22 results; the 38 gr load of RL22 gave 1944 fps, 139,968 RPM at 27,800 psi(M43). The group size was 1.5”. The ES and SD were still high at 80 and 26 indicating the RL22 was not burning efficiently at this psi.
The 40 gr RL22 load gave 2037 fps, 146,664 RPM at 30,000 psi. The group size also was 1.5”. Again the ES and SD were high at 94 fps and 27 fps.
The 43 gr RL22 load gave 2132 fps, 153,504 RPM at 32,600 psi(M43). The group size was 1.45” and the ES and SD tightened up to 44 fps and 17 fps. This indicates the RL22 is burning efficiently at this psi.
The 44 gr RL22 load gave 2267 fps, 163,224 RPM at 37,300 psi(M43). The group size was 1.3”. The ES and SD remained low at 57 fps and 19 fps. The 46 gr RL22 load gave 2381 fps, 171,432 RPM at 41,800 psi(M43). Again the ES and SD remained constant at 62 fps and 20 fps. This load might be increased to 47 gr with a 2400+ fps velocity and remain under the RPM Threshold. If accuracy holds at 1.3 – 1.5” moa and remains linear at 200 and 300 yards it would be a very useable load for a 10” twist .308W. as it is the 44 and 46 gr loads are both quite useable. Might even do a bit better in a larger capacity 30-06.
Oehler M43 PBL data sheets for the 44 and 46 gr RL22 loads;
With the M70 with 26” barrel with 12” twist I selected I selected 3 powders that worked very well with the Lyman 311466 and LBT 30-160-SP; AA4350, H4831SC and RL22. I also decided on one load (a SWAG) with LeveRevolution powder based on it’s success in the 14” twist Palma rifle. The attained velocities were about 50 fps less than expected across the board. The psi also never reached 40,000. Thus this bullet could be pushed a little harder in this 12” twist rifle.
The 43 gr load of AA4350 gave 2316 fps, 138,960 RPM at 32,200 psi(M43). The 1st shot out of the cold clean barrel went low out of the group as expected. The next 5 shots (2 – 6) went into .85”. The 9 shot group size was 1.15”The ES and SD indicated ignition and burn is borderline efficient.
The 44 gr AA4350 load gave 2384 fps, 143,040 RPM at 34,100 psi(M43). The group size was 1.3”. The ES and SD was down to the expected norm.
The 45 gr AA4350 load gave 2433 fps, 145,980 RPM at 35,700 psi(M43). The 1st five shots went into .63” and the 10 shot group was 1.35”. The ES and SD were very good. I need to test this powder at 46 and 47 gr in this rifle. The Oehler M43 PBL for the 45 gr AA4350 load;
The 43 gr H4831SC load gave 2159 fps, 129,540 RPM at 27,100 psi(M43). Nothing spectacular at 1.8” group.
The 45 gr H4831SC load gave 2289 fps, 137,340 RPM at 30,800 psi(M43). Another ho-hum group at 2”.
Now the 47 gr H4831SC load was getting there at 2415 fps, 144,900 RPM and 34,500 psi(M43). The 1st five shots went into .7” with the 10 shot group at 1.34”. The ES and SD were very good at 33 fps and 11 fps. This powder also needs to be tested at 48 and 49 gr in this M70 12” twist rifle. The Oehler M43 PBL for the 47 gr H4831SC load;
The 43 gr RL22 load gave 2153 fps, 129,180 RPM at 26,800 psi(M43). The 1st five shots went into .93” with the 10 shot group at 1.7”
The 45 gr RL22 load gave 2273 fps, 136,380 RPM at 30,200 psi(M43). The group was 1.4”
The 47 gr RL22 load gave 2398 fps, 143,880 RPM at 34,100 psi(M43). The 1st five shots went into .55” with the 10 shot group in 1.6”. This powder also needs to be tested at 48 and 49 gr in this rifle. The Oehler M43 PBL for the 47 gr RL22 load;
The last test was just 1 load with LeveRevolution powder. I took a guess and figured 40 gr with a .3 gr Dacron filler should give around 2500 fps. I came pretty darn close! The 40 gr load gave 2510 fps, 150,600 RPM at 31,900 psi(M43). The 1st five shots went into .8” with the 10 shot group at 1.5”. The ES and SD were outstanding at 21 fps and 7 fps.
So there it is, you can push the RPM Threshold up just as I’ve said with faster twist rifles. There is a plethora of 10 and 12” twist .30 caliber rifles out there. They are “regular” rifles. So if anyone wants to shoot higher velocities with them and maintain useable/reasonable it isn’t that difficult as I’ve shown. First of all you and your rifle need to be capable of the accuracy you want. You must know how to cast quality bullets of proper alloy. You need to use appropriate slow burning powders and you need a cast bullet designed for that purpose. The NOE 30 XCB is the bullet for the job.
Someone has mentioned (on another forum) the 30 XCB is a “one trick pony”. Well, to the contrary, The NOE 30 XCB has proven itself at high velocity in numerous rifles chambered for different cartridges. A one trick pony…….no, more likely a Triple Crown winner.
Larry Gibson
sgt.mike
bjornborud
tommeboy
darrinwright
timmalcolm
Larry, very impressive. You leave nothing to the imagination.
Thank you for contributing so strongly to the project!!!
I notice that you were actually well within your parameters of 2MOA. Do you plan to push further just to see where you break 2MOA, or is this test complete?
Again, simply fantastic posts. Your results speak for themselves.
sgt.mike
bjornborud
tommeboy
darrinwright
timmalcolm
SwedeNelson- You must be logged in to reply to this topic.