When Shawn was working on his +P throat design, i was working on my Hybrid throat design. Neither one of us knew the other was working on either project but the outcome was extremely similar. Interestingly enough, the reasons each of us started R&D work on these throat designs were totally different, yet the end results were nearly identical.
My reason for designing my hybrid throat design was two fold.
1. I wanted the performance advantage that came with a freebore type throat but i wanted short over all length in my ammo for my repeating hunting rifles.
2. I needed a throat design that would greatly reduce the stress on the bullets jacket/core bond as we were having issues with some of the Wildcat Brand bullets being used at the extreme performance levels that my wildcats produced.
So to meet both these requirements, my hybrid throat design started with a conventional style throat with conventional 1-30-00 leade angle into the hands.
However, at the end of the conventional throat, the hybrid throat reamer reduced the depth of the rifling so that here was only very shallow grooves remaining for roughly 1/2" of bore length. After this, a secondary leade angle of 0-30-00 gradually tapered the lands of the rifling to full depth.
The design idea was that the conventional section of the throat would retain all the accuracy advantages as a standard throat design. The very shallow lands in the middle section of the hybrid throat would allow the bullet to very easily move through this section of throat yet still grasping the bullet and starting its rotational movement the instant the bullet started traveling down the bore. This would make life much easier on the bullets core/jacket bond.
The final section of the throat would transition the bullet very gently into the full depth of the lands but after the bullet had gained significant velocity.
In testing the hybrid throat as well as Shawns +P throat design offered all the performance advantages of a free bore throat design which Wby was one of the first to mass produce but these throat designs also offered the accuracy potential and consistency benefits of a conventional short throat design. They do exactly what we both designed them to do. Wby's design is nothing like what Shawn and I designed in form or function. Our designs ARE NOT, just free bore designs, much more complicated then that.
Now, why did i stop offering my APS Hybrid Throat design to the public. I had tested my Hybrid throat first on my 7mm Allen Magnum. At the time using Lilja barrels. Performance gains were +100 fps once i figured out how to adjust loads for the dramatically flattened pressure curve these throat designs produce.
Same conventional loads used in these hybrid throat designs actually will produce less velocity then when used on a conventional throat. So loads need to be adjusted. As such, loads developed for these throat designs are not safe to use on conventional throats…..
In testing my first 7m Allen Mag with my hybrid throat i was extremely happy with the performance gains and the elimination of the bullet failures in flight i was seeing previously with the 200 gr Wildcat bullets pushed to the +3400 fps level.
So much so that i ordered my hybrid throat reamers in all calibers from 257 up to 375 cal for use with most of my wildcats and conventionally chambered custom rifle order as an option.
However, i also found that after significant ballistic testing, i noticed that the throat life on my original test rifle showed significantly accelerated throat wear, especially in the second stage of the throat.
Within 200-250 rounds the very shallow lands would erode away much more quickly then conventionally throated rifles would. At 400-500 rounds, these shallow lands were basically gone.
Knowing the lilja barrels were soft and not known for the longest barrel life, i switched to a much harder, cut rifled for testing. Ordered two identical barrels, only difference was one was cut with my conventional throat and the other with my hybrid throat design.
Ran both barrels through the exact same test procedures and inspected and measured the the erosion levels every 100 rounds fired and it was clear that by 200-250 rounds even with the harder barrel, that the hybrid throat design was having more accelerated throat erosion. I pushed these two barrels to the point i started seeing either bullet failure in flight or accuracy drop off to the point the rifles could not hold moa accuracy at 500 yards. The conventional throated barrel reached roughly 800-850 rounds. The hybrid throat design hit that point at 550-600 rounds…….
Thinking this was possibly accelerated because of the shear intensity of the 7mm Allen Magnum chambering, i repeated the test, same brand of barrel, chambered in the 7-08 for that test. While the accuracy life was dramatically longer as expected, the reduction in accuracy life for the hybrid throated barrel was nearly exactly the same % as it was for the 7mm Allen Magnum…..
I then tested two more barrels, this time in 338 caliber and chambered in my 338 Allen Xpress. Results were nearly identical again with the hybrid throat design reducing usable barrel life by nearly the same. All tests showed a 25-30% barrel life reduction.
When i found these results i contacted Shawn and asked what type of results he was seeing and he said absolutely zero change in throat life……
Over time, that has been proven to be closer to the results that i found on my testing from talking with shooters that actually owned and shot their Defensive Edge rifles a significant amount.
Another thing that really baffled me was the use of N570 which is a great high energy powder producing amazing performance, but at the cost of very high flame temperatures. Something that will cause even more accelerated heat cracking and throat erosion….. one reason i dont recommend it over RL33, if the later is available.
In the end, i was not happy getting an extra 100 fps at the cost of 25-30% of a barrels useful life. Granted, MOST of the shooters out there will not shoot their rifles enough to really find the limits of these throat designs but they are certainly there and if the rifles are used enough, they will be found and i am confident from what i hear direct from shooters using these throat, that their results echo mine.
Some have stated they are perfectly fine with the abbreviated barrel life as barrels are simply disposable items and they want the performance.
However, after my testing of these throats, which i believe Shawns motivation for designing his +p throat design was to allow his 338 Edge to match the velocity of my 338 Allen Xpress which is did, kind of….
When he released his 338 terminator which is nearly idential to my 338 Allen Xpress, it was claimed it would produce nearly 3200 fps from some of his customers used in his LRKM rifles but with 30-32" class barrel lengths. Then over time these same shooters posted 3100 fps speeds stating they shot better there. Then this shooter posted claims of 3050 fps with a new barrel installed. When i asked why the new barrel with so few rounds down the barrel, there was no explanation for the velocity reduction or the new barrel…. However i suspected i knew the reason for both.
When i dropped the option of my hybrid throat, i started playing with using different types of powders especially in my 338 Allen Xpress to allow seating these rounds in conventional magazine length with relatively short Over All Lengths of 3.650" even using the 300 gr berger.
The ranshot powders proved amazing. Yes they were not QUITE as stable as the better stick powders with wide temp changes but in my 26" stalker rifles, using short conventional throat designs, they were still pushing comfortable 2950-3000 fps levels with long life throat designs.
Using longer mag lengths or in single shots where OAL was allowed to be longer, 3000-3050 fps was the norm with case life on the +8 firings per case, often +10.
Seeing this, i simply dropped my hybrid throat design option as i saw no good reason to shorten barrel life for as mentioned an extra 100 fps which most of that could be made up for using different powder types at least for running through the length limits of a repeating rifle.
While i fully agree the performance improvements are there, they come at a cost of throat life. With a conventional throat, when it becomes worn, its a simple process to take 1" off the shank, refit, rethread and rechamber and your set up with a relatively fresh throat.
That is not a possible procedure with my Hybrid or the +P throat design because of their length. Once they are done, new barrel time.
Reporting my results cause quite a bit of heat to be thrown my direction as it seemed to directly counter the results Shawn was getting. I was in no way attacking him or his results. In fact we were quite good friends and still consider him a friend and respect him tremendously. I waa just reporting my real world results on a throat design which is EXTREMELY similar to his design.
I simply made the decision to not offer that option on my rifles mainly because of the hyper performance level they were already meeting. Could not afford to loose 25-30% off a 900-1000 round barrel life if cared for properly.
Is using a chambering that will typically get 2000-3000 rounds, as mentioned, dropping 25-30% off that barrel life, most shooters to not shoot enough to ever see the end of their useful barrel life, so for that application, getting 1500-2500 rounds instead of 2000-3000 rounds will often never be noticed.
Again, was never flaming Shawn in any way, just offering my real world results after spending several thousand $$ in testing and R&D to prove what these throat designs really do in the real world. They certainly improve performance while maintaining accuracy and consistency but in my testing results, at a relatively high cost of noticeably shorter barrel life.
Just something to have read before jumping into this decision.
