More range testing with 338 Allen Magnum XHS rifle....

[Fiftydriver]

To all interested,

I was shooting my new lightweight 338 AM Xtreme Heavy Sporter(XHS) a bit more this weekend finishing up the barrel break in and ran into some interesting things that I wanted to pass onto those interested in this wildcat.

Here is a pic of the rifle. I gave a review of it on the Long Range Hunting section but I feel this is a more appropriate area to post about it.

I was using some of my original cases that I have been using since I have started shooting the 338 Allen Magnum in my heavy rifle. Some of these cases have well over 10 firings on them. To be honest, lost count on the firings per case.

Most have pretty loose primer pockets but still have enough to hold a primer in place.

I started working loads up while doing the barrel break in and quickly ran into a problem. Once I reached aroung 140 to 142.0 gr H-50BMG under the 300 gr SMK, I was getting sticky extraction. The bolt lift was very smooth and easy on the BAT receiver, but when the mechanical cam on the bolt contacted the cam surface on the receiver, I needed to pop the bolt handle with the palm of my hand, pretty stoutly to open the bolt. Once it opened, the cases extracted effortlessly.

When I increased to 144.0 gr the bolt had to be tapped open at the top of its stroke with a non marring mallet to open the bolt. NO GOOD!!!

I decided there were several things that may have been causing this problem but the easiest to test was that the cases were simply to old and that I should try some new freshly formed cases and see how they performed.

Yesterday I formed up a small batch of cases, only five of them, just got this test. I loaded them all up over 144.0 gr H-50BMG with the 300 gr SMK. Again, remember this load needed the bolt handle tapped open with a mallet with the old cases.

I took the rifle out with some customer rifles to range accuracy test and shot three of the round. The group below was the result of the 100 yard three shot group. I think this little rifle will be a decent shooter!!!

As listed on the target the average velocity was 3344 fps with an extreme spread well under 10 fps. If I recall correctly it was 8 fps.

Just as importantly, the bolt opened like there was no case in the chamber at all!!!

I wanted to test this farther and find out at what point in the case life did this start to be a problem with extraction characteristics?

This morning I took one of those new formed case that had one high pressure firing on them. After sizing the case was reduced in size roughly 0.0006" at the expansion
ring just ahead of the solid case head. I loaded up the case again with 144.0 gr H-50BMG and fired the round again, extraction was picture perfect, just like the first high pressure firing. I then repeated the loadings and firing.

3rd high pressure loading and firing
diameter reduced 0.0005" after FL sizing
Extraction again perfect

4th high pressure loading and firing
Diameter reduced 0.0005" afer FL sizing
Extraction again perfect

5th high pressure loading and firing
Diameter reduced 0.0003" after sizing
Extraction had just the slightest resistance at the top of the bolt travel, hardly noticable however.

6th high pressure loading and firing
Diameter reduced 0.0002" after FL sizing
Extraction had a noticable resistance at top of bolt stroke, roughly twice that of the 5th firing. Still fully acceptable but noticable

7th high pressure loading and firing
Diameter reduced only 0.00015 after FL sizing
Extraction had heavier resistance at top of bolt stroke. Had to pop with the palm of my hand to open the bolt all the way. Excessive in my opinion.

After seeing this, I believe this is simply a case issue. The cases simply seem to become heat tempered as the case is fired a certain amount of time and once this happens, there is really no way to move the heavy case wall
just ahead of the solid case head, it simply springs back after it is released by the FL sizing die.

I also wanted to see if the number of rounds that each case would handle with good extraction was effected by the level at which the round was loaded to. I had tested my 7mm AM and it really did not make a significant difference how hard I loaded the round, in about 6-7 firings, I was seeing
the same thing and it was time for new brass.

As such, I took another freshly formed case and repeated the entire test using 135.0 gr of H-50BMG, a very mild load producing roughly 3150 fps with the 300 gr SMK.

I was able to get only one more firing with this low pressure level loading before extraction resistance got to the point where I felt it was excessive needing me to pop the bolt handle with the palm of my hand.

On the other end of the performance scale, I wanted to test with higher Pressure loads as well. I loaded up 146.0 gr and repeated the entire test. The results were extremely similiar to the original 144.0 gr load test. On the
6th firing however, there was slightly more force needed to open the bolt but not excessive in my opinion. On the 7th firing it was definately excessive force needed to open the bolt. By the way. 146.0 gr averaged 3371 fps.

I took things one step farther. I loaded up 148.0 gr and repeated the test with the last freshly formed case. This load was cooking along at an average 3395 fps with a couple firings over 3400 fps!!

First firing extracted perfectly. There was a noticable and well defined ejector mark however. Second firing extracted fine but there was definate resistance on
the bolt at the top of the stroke, not excessive however. Third firing was stiff on the upper end of the bolt stroke and on the four firing I would call it definately excessive force needed to open the bolt.

Keep in mind however, this load showed well defined ejector mark on all firings so it is certainly a higher pressure load then I would ever recommend should be used.

As far as primer pocket tightness, the 144.0 gr load maintained a very snug primer pocket fit to the 5th firing. Firings #6 and #7 were noticably looser but still perfectly usible with no chance of any gas leakage.

The 146.0 gr load held snug primer pockets to the 3rd firing but again remained adiquate to prevent any gas leakage until the 7th firing although the 6th and 7th loading did have a noticably looser primer pocket.

The 148.0 gr load had noticable primer pocket loosening right from the get go. It remained adiquate to prevent any gas leakage until the 3rd firing
but the 4th was looser then I like to see and there was a hint of gas leakage on that 4th firing but again, this load is hotter then I would ever recommend.

From looking at all the results, it seems pretty clear that the cases simply heat temper at a certain point and with loads in the comfortable working ranges of the round, it really is not effected much but the level at which you load to resulting in only a difference of two firings from very low end pressure to top working load pressures.

It is my opinion from this test that cases should be used to a max of 7 firings. In most cases I believe that 6 firings will be about max with upper end loadings and that once you start feeling the slight resistance on the top of the bolt stroke, its time to retire the brass and start with a fresh batch.

I was frankly suprised at the level of performance that was possible with this barrel length, nearly 3400 fps!!

Personally, if one can get at least 6 firings per case, thats fully acceptable to me. With 100 cases, thats 600 rounds and well over 1/2 the accuracy life of a barrel with this chambering and even if we pay $2.50 per case. That comes out to just shy of 42 cents per firing for case cost.
More then acceptable in my opinion for this type of rifle and this level of performance.

If we were talking about a chambering that would offer 2000 rounds of accuracy barrel life, my opinion may be a bit different but still getting 6 full pressure loadings with each given piece or brass is as good as you will see with any case other then perhaps the 338 Lapua and the wildcats based on it depending on the amount of case taper in their design.

I know for a fact if you load a RUM case up to 65,000 psi, your primer pockets will be loose by the time you hit 5 to 6 firings on a given case. My numbers are based on studies representing velocity for givien tested pressure ranges and I feel that 65,000 psi is about max for the RUM case.

For the 338 AM, I would estimate that 68,000 psi is about max and I would imagine these 146.0 gr loads are in that range from the length of the case life.

Just wanted to offer this information to those that already have the 338 AM or those that may be interested in it.

Basically, if you buy 200 cases, you will get enough shooting out of those cases to cover the projected accuracy life of the barrel even if you take EXTREMELY good care of that barrel.

I do not feel this should be a detractor of the 338 Allen Magnum in any way. I just wanted to offer the information to you so that you can gain even more knowledge about the round in the event you decide you want to play with one of the highest performing rounds out there today. Knowing the limits of a wildcat are just as important and anything else.

I am very happy with the results I have tested and found with my wildcat.

Now if I could just get some 265 gr Aluminum tipped Wildcat Bullets, we may be able to push near 3500 fps with even higher BC numbers then the 300 gr SMK!!!! /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif

Have a good memorial day weekend to all,

Kirby Allen(50)

 

[Buffalobob]

That is still a fine looking rifle.


Very interesting report on case life and good for a person to know.

For me a major hunting trip costs about $2K to $5K and when I am depending upon a rifle to deliver premium down range performance, I do not try to save a few pennies trying to prolong case life.

 

[jwp475]

[ QUOTE ]
That is still a fine looking rifle.


Very interesting report on case life and good for a person to know.

For me a major hunting trip costs about $2K to $5K and when I am depending upon a rifle to deliver premium down range performance, I do not try to save a few pennies trying to prolong case life.

[/ QUOTE ]

Here,Here

 

[ol mike]

Nice report Kirby.

My favorite is still the heavy gun -black w/red .

 

[Black Diamond 408]

Kirby,

I did almost the same test saturday, i used four cases as i was checking to see where the top load started to show pressure signs. I also checked the TTI brass vs Jamison.
I started with 138 bmg50 ended up at 144, the brass ejected easy but just a hint of ejector marks on the TTI brass. Both TTI and Jamison extracted easy and went through the sizer die very good. Velocity ran from 3050 starting load of 138grns to 3295fps with the top load of 144.

I tried some US869, i checked my log book and seen where i used 143grns in my personal rifle so i loaded up 4 of these. Ejector marks, on the heavy side, opened easy. (Speed was only 3150fps) I pulled the bullets on the other 3 cases.

I also used some WC872, 143grns, they also worked fine, no ejector marks, speed was 3185fps.

I shot the BMG50 loads and the WC872 loads with another round only this time i used some Moly coated 300smk bullets, the speeds dropped 60fps on average across the board. I did not increase the powder charges to try and reach the same levels as plain 300smk bullets.

This customers gun has a 30" carbon barrel, i was happy to see i can get to 3300fps, but i would say this is about the top load for this barrel length.

I also am waiting for some of the 266 grn wildcat bullets, out of the 30" tube they should really fly! I think the US 869 powder is a bit faster burning than the BMG50, should work better with a lighter bullet.

I reloaded the same cases 5 times. They size and fit into the chamber with ease. I had some of the Horneber cases, they last much longer than either TTI or Jamison. I have noticed that Jamison's primer pockets are looser than TTI brass from the start, however the primers do seal fine.

I am going to do more testing tomorrow, i set up a row of milk jugs out in my bean field, 500-700yards, it should be fun! It will give me a good chance to check the click chart i made for the rifle. It has a Nightforce NXS 5.5-22x56 R2 redical...40moa base. I set the sighting at 100yd zero.

~Dave

 

[Festus]

Good report Kirby. I like the way you put tape over your flier. I will have to try that /ubbthreads/images/graemlins/laugh.gif. Heck of a group there.

Festus

 

[Eaglet]

Kirby,
Amazing!

 

[Fiftydriver]

Dave,

From the Carbon Wrapped barrels I have built on, it seems they tend to run pretty quick as far as velocity potential compared to other barrels.

To be honest, I will admit that Lilja barrels are probably about the slowest barrels out there I have built on but some of the most accurate as well. That is why I am fine to give up some top end velocity potential for accuracy.

I suspect that is why you are seeing the velocity you are getting in that very short barrel. If that were a Lilja barrel you would probably be running a full 75 to 100 fps less then what your seeing but I am sure accuracy would be great.

I have been thinking about getting a wrapped barrel for another lightweight project. I have 7 on order right now for customer rifles if they ever show up and then I will be able to provide definate velocity comparision numbers between the two but in all my testing of different barrels, the wrapped barrels are running around 75 to 100 fps more then what the same lenght Lilja will get with same pressures.

I would suspect that a carbon wrapped barrel of 33" on this rifle would be producing 3400 fps easily without any ejector marks of any kind.

I do not see any ejector marks until I hit 146.0 gr of H-50BMG. And those are very faint. At 148.0 gr they are more defined. Not as heavy as I have seen with some handloads used by other shooters on a regular basis but more then I like to see in one of my rifles or that I would recommend to a customer.

For now, 3350 to 3370 fps is plenty for me at comfortable, long case life pressures.

As far as your powder testing. I have found similiar results. US-869, at least the lots I have is much more similiar to Retumbo in burn rate then H-50BMG. In fact its far to fast in burn rate for my needs with my 338 Allen Magnum except perhaps with 250 gr bullet weights.

That is just my lots of powder however but I have been hearing similiar reports from my customers using this powder in my other more conventional Allen Magnums. For heavy weight bullets, in my opinion, a bit slow in burn rate and not apporiate in my Allen Magnums for the most part. It works but there are better choices out there.

As far as WC872 is concerned. It is a great burn rate for any bullet in the 338 Allen Magnum over 300 grains. It has a relatively narrow pressure window where it works well. On the bottom end you can see some hangfires. On the upper end it works very well but can be temp change sensitive. I do like this powder however and all of my lots of WC872 has been measureable slower in burn rate then H-50BMG. Generally taking 3-4 gains more powder to match muzzle velocity as H-50BMG in most cases.

With the 266 gr tipped Wildcat Bullets, I think you will be much better served still using H-50BMG. When I tested these bullets I used 145.0 gr and that was a very mild load in my heavy rifle which shows pressure signs dramatically sooner then my lightweight Heavy Sporter Xtreme rifle seems to.

I personally feel that H-50BMG will offer about the perfect burn rate for this bullet when you take into consideration that the baring surface is similiar to the 300 gr SMK but the overall length is longer then the SMK and the weight is 44 grains less.

As such, you need a slightly quicker burn rate powder then would be optimum for the 300 gr SMK but not significantly faster like you would get with US869.

In my testing with this bullet, I suspect that in my HSX 338 AM I will top out at around 150-151 grains under this bullet which when using H-50BMG will give me right around 98-99% load density, what more could you ask for???

WIth US869, again I would predict there will be around 5 grains less powder used when you reach top pressures, at least from what I am seeing with my lot of powder.

Combine this with the much denser powder column produced by the ball powder, you will have much lower load densities which is not the best thing with a ball powder.

In spite of what has been advertised about US869, it is no better in changing temps then any other ball powder I have tested, at least not in my small to medium bore Allen Magnums and Allen Xpress rounds.

The advertisements are all for the results Hodgdon got testing with the 50 BMG so to be fair to them, this powder may have a totally different personallity in the big 1/2" bore but it is still sensitive to temp changes in smaller bore, large capacity round.

I think you will see from your tests that H-50BMG will be THE best powder for the new lighterweight 266 gr bullet from Wildcat. You will get the most velocity with the tightest velocity spreads and should be the most stable under temp changes.

When I get my big order of 266 gr pills, H-50BMG will be the only powder I test unless it does not offer me what I have already seen with this powder and this bullet.

In my lightweight 338 AM HSX I suspect that I will be pushing 3500 fps very hard with this bullet!!!

More to come soon.

Kirby Allen(50)

 

[Fiftydriver]

Festus,

I know you were probably joking with your comments about the flier but those are the statements that start rumors about ones honesty reporting accuracy results.

I thought it was obvious that that covered bullet hole was a 30 cal hole instead of a 338 cal hole but just to clear things up, here is a pic with my calipers measuring that covered bullet hole.

It is pretty clear that the hole measures 0.2915" which is about right for a 308 cal bullet. A bit tight for a 338 cal.

Just wanted to clear that up before some one else started accusing me of being selective in my group measurements!!

By the way, the long tears on the target to the right and down from the covered bullet hole are prototype 311 grain Aluminum tipped 338 Cal Wildcat Bullets that I obviously did not have enough twist for and they landed full profile. Not to bad of a group though at 100 yards, one hole group making an "X"!!! /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif

Kirby Allen(50)

 

[Black Diamond 408]

Kirby,
I agree the BMG50 powder is the best overall! My personal gun loves the WC872, 145.5 grns = 3350fps 33" barrel, Lawton 11.25" twist. The BMG50 also shoots just as good, but $$$ wise the 872 is nice, bit dirty however.

I haven't had to much to compare the carbon barrels to, my Lawton is the only other barrel i have used to date. The Rock bbls and ABS/Rock seem to shoot about 70fps slower than the Lawton, but they have all been the 9.4 twist barrels.

Any where from 3200 up to 3400 is just amazing as to the power these guns have.

Good shootin

Dave

 

[Festus]

Kirby,

I'm glad you recognized my comment about the "flier" as total tongue in cheek. To be honest I had not considered the possibility of anyone interpreting it as a challenge of your integrity. I appologize for that. I thought the graemlin would have tagged my comment as tugging on your leg. Your integrity and honesty has never been in question to me. Just wanted to clear that up for anyone reading this post.

Festus

 

[Fiftydriver]

Festus,

From our dealings in the past, I knew exactly where your comments were coming from and that they were only ment in good natured ribbing. I certainly have no problem with that!!!

I just wanted to make the point for those that do not know either of use much and may read your post and not know you were joking and then take that to another board and start spouting off. I am sorry to say it would not be the first time things have been taken out of context from LRH and posted on other chat rooms and used as fodder against us here.

My comments were not really directed at you in any way, just covering our rears here on LRH from those snakes that may be lurking. Unfortunately there are more then we realize!!!

Nothing negative even considered by your comments. Good shooting as always!!! /ubbthreads/images/graemlins/grin.gif

Kirby Allen(50)

 

[Festus]

Kirby,

Thanks for the insight, I'll try to remember that before I post in the future.

On the subject of barrel life, and maybe you've addressed this in the past, have you found that sherical double-based (hotter but less abrasive) or extruded (cooler but more abrasive) powders effect throat erosion to a greater degree? In other words, does one erode the throat faster than the other?

Festus

 

[Fiftydriver]

Festus,

You put near 150 grains of any powder in a 338 bore and you will be looking at 1000 rounds of accurate barrel life at most. I have not seen a real difference between the two in this chambering.

H-50BMG makes it alot easier to get tighter extreme spreads for what this round is designed for that is probably my preferred powder for most applications.

Most critical thing to barrel life in this round is not shooting more then three shots without letting the barrel cool completely before shooting again. That is as far as bench shooting.

The occasional longer string will not destroy a barrel in 10 shots but those that feel only 5 shot groups tell you anything about the accuracy of a rifle will be getting new barrels sooner then later!! /ubbthreads/images/graemlins/grin.gif

My 375 AM version will be much more barrel friendly but bullet selection is the key there.

Kirby Allen(50)