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Consistent Crimp Test - Finalized - Pic Heavy and Long!!

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This is test #3 of the Consistent Crimp Tool. Previously I reported on it's application in a 223 SPS Varmint and a 243 BDL sporter. This one falls in to the BR activities on the board, notice the board name? I felt that my interest in prairie dog elimination and the need to find out if the "el cheapo" AR I built in the summer of '09 could shoot well enough for DCM reduced range matches that are shot at 200 yards.

The kit was purchased from AR15 Kits as I had built one of them for my 84 year old Father-in-law earlier that year and they looked like they would do fine. Nothing special really. A basic CAR kit with a heavy barrel. Standard carry handle upper. LPK was Double Star. The barrel is a Wilson according to the supplier. 1:9 CM non-chromed. I had fired about 100 rounds through it breaking in the barrel and just general function checks with 100% reliability. I knew that the trigger, even after the 15 Minute Trigger Job, would not be conducive to maximum testing of the CC Tool so I grabbed a lower I had built for a 6 PPC. This one has a Timney 3 pound drop in trigger and an ACE stock. The basic iron sights while great for some guys were a detriment so I mounted up my 24 X Leupold on a carry handle mount and headed for the range. The rifle looked like a dime store cowboy rendition of a fighting tool but it will revert back to it's normal state this week.

 

 

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The ammunition for this test was the same batch I had used in my first go around with the Consistent Crimp Tool. I had loaded two batches at the time anticipating doing two rounds of testing on the first rifle. I had settled on a load of 25.1 grains of X-Terminator powder and all loads were thrown using an RCBS Uniflo. Cases were all once fired Winchester commercial sized to 0.000 SAAMI specs and trimmed to 1.750, primers were Remington 7 1/2's and the COL was set at 2.255. All testing was done shooting off a concrete bench with the use of a very cheap front rest and some plastic bean filled rear bags.

Targets were from MY TARGETS as they provided an excellent vertical and lateral alignment with the cross hairs. Anyone that has shot a round hand guarded AR off the bags can appreciate the issues in being consistent.

Chronograph data was through a CED Millennium set at 10 feet for the first three crimp levels but moved back to 15 feet for the remainder because of shade from the shooting shed. There was a slight drop in recorded velocities but inconsequential to the test.

Testing was done over two sessions with the ambient air temperature being a balmy 68 on the first day and 74 on the second. Quite typical for Arizona winter here in Phoenix. The procedure was to load the test ammunition up with five rounds per magazine with a throw away factory round on top of each to settle the bolt. I had found that the testing would take about 16 hours if I allowed the barrel to cool back completely to ambient temperature. I had also found that barrel heating was pretty slow if you gave it a rest between five shot group so went with that as I had observed no noticeable changes in results on the previous two tests. If you look at the chronograph tables you will see ambient air and the barrel temperature at the beginning of each five shot string AFTER the throw away round was fired.

Each level of crimp pressure from zero though fifty FT/LBS was shot in two groups of five except for the fifty FT/LBS level. The best of the two groups was scanned and displayed here. I am no bench rest master and am afraid that the groups are not those nice little round things that most guys post. As you look them over you will see that I have, once again, stuck to my old routine of getting four good shots out of five and making it look terrible with one round. Because of this I study best four of five normally when I am evaluating my loads. A bullet that is 3/4 to 1 1/2 " outside a group of four is , more than likely, my fault not the rifle or the ammunition. I know when I pull that shot nine times out of ten so I feel OK in doing this. I also know that when I see a general smattering of bullets over two groups that it really is the ammunition.

As I mentioned the weather was good though I did have some wind gusting with variable mirage on the second outing. I think the numbers reflect well and give some indication of how this tool can impact the performance of a given load.

So here we go with the targets and chronograph data:

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One Factory Load for Baseline.

 

 

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Chronograph Compilation

 

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Lots of holes to look at and enough numbers to cogitate over for about any of us!! :wink:

Looking at the entire array of targets in front of me I feel there may be some subtle movements in group location. Without reshooting these tests several times I can only put forward my assessment. I hope anyone reading this will make their own deductions with the data presented and either support my assessment or will present their own evaluations for the rest of us to examine.

Using the zero crimp target as my baseline the group is 1 1/2" right and 3 1/2' above target center with a general round appearance discounting that one pesky dropped round. As the pressure of the crimp increases the groups appear to be moving from the baseline. Five FT/LBS shows a 1/4" drop with again a nice rounded look. Ten Ft/LBS almost 1/2 inch drop from baseline but this target shows a lateral component that, at times, may indicate poor shooter interface with the stock but in this instance it was repeated at the twenty FT/LBS level also. This indicates to me that it was, in fact, due to pressure variation in the crimp. The fifteen FT/LBS is again 1/2" low with a drift to the left of approximately 1/2" but has started getting tighter. Twenty FT/LBS showed the lateral dispersion again with a return to the original baseline elevation. Twenty five FT/LBS showed a drop in grouping but a rounding up again. Thirty FT/LBS showed a return to the original baseline impact area. Groups are tightening up at this point. Thirty five FT/LBS shows a drop of 1/2" and a left movement of 1/2". Forty FT/LBS moved the group up 1/2" and right about 1/4". Forty five FT/LBS shows the grouping drop a full 1/2" but no lateral variation from the last. The fifty FT/LBS moves another 1/2" but jumps moves the group center a full 1 1/2" higher from the forty five FT/LBS level.

All this movement indicates to me that there is some effect on barrel harmonics as the crimp pressure varies. A normal load development is usually done at one crimp level and varying of the powder charge will often times see the same results on the target.

Baseline group size for the five shot group was 1.577 with a best four showing 1.041 with zero crimp pressure applied. The round out of the four shots was more than likely a product of the shooter. That leaves a four shot spread of slightly less than an MOA. Right off the top this would be an "acceptable" level of accuracy for this style of rifle given the generic level of the barrel not being noted for cutting edge accuracy.

Application of five FT/LBS of crimp tighten the four shot spread to 0.761 with the spoiler coming in to play.

At 10 FT/LBS the group was a lateral spread of 1.14 with a nice four shots falling in to 0.777.

The fifteen FT/LB was more round at 1.06 and still a sub-MOA four shots of 0.933.

Twenty FT/LBS yielded the worst groupings in the entire test with both exceeding two inches. At 2.377 for five and a four shot spread of 1.106 the rifle spoke its' displeasure at this medium point of pressure.

Twenty five FT/LBS got the groups back on track with more rounding and a 1.335 best with four back in to 0.795 for a bit of redemption.

From here on out the pressure applications seemed to make a huge difference in performance. Four shot groups started tightening up dramatically and the my expectations were exceeded quickly.

At thirty FT/LBS I finally got it together momentarily and manged an honest 0.924 for five shots and the four shot spread dropped dramatically to 0.576.

Thirty five FT/LBS was not to disappoint as a 1.852 with a huge pulled shot still yielded a four shot group of 0.435. It can't be better than that!! Once again the rifle proved me wrong and laid down an honest sub-MOA of 1.023 at forty FT/LBS. I put the calipers on the four shot group three times and came up with a 0.333 for this one. I do believe I have a winner here.

NOT!!!!

The forty five FT/LBS group was not very promising after the first shot. I knew I had flat jerked it out of alignment as the trigger broke. At this point I got up and took a big breath and a drink of water. The next shot went in with what I felt a proper squeeze. Shot number three didn't look any worse and I put everything I had in to the last two rounds. It looked good but only the calipers would tell. On inspection I had a huge 1.439 five shot but nestled in like a cheat sheet on the SAT's was a cluster that yielded only a 0.19 center to center measurement. At this point I know I have a winner.

The last group shot on day two was the fifty FT/LB set up. This is a huge amount of crimp pressure and I felt it would not do well. I was right on this one as I saw a carefully shot 1.895 develop with a best of for showing 0.917. A far cry from the group with only five FT/LBS less pressure.

Now that all the numbers and group descriptions have been laid out the number crunching really starts. Group averages are a big deal in the shooting world. Shooting ten or twelve groups on a given load with no change in load specs is a great way to tell how that load shoots. If only one factor i.e. crimp pressure is changed then the results can well be a moot point. As you can see a fellow could wear out a barrel looking for "THE " load. I, myself, would rather put those bullets down the tube at more than a piece of paper and enjoy the great outdoors doing it!! So here are some numbers for your consideration.

The baseline group with zero crimp pressure ran 1.577 with a four shot best of 1.041. This is not bad for a basic AR as most of us recognize. A bit more care might have got that fifth round in to the sub-MOA four shooter. Looking at the combined eleven levels from zero through fifty FT/LBS of crimp pressure shows an average five shot spread of 1.501. A minute and one half AR is still not bad considering this is a basic kit build and the bullet selected was only a 50 grain pill. Given a 1:9 twist the rifle should shoot this weight OK but would more than likely shine at a heavier level of 62 or 69 with the nod given, generally, to a 69 grain bullet.

Looking at the five shot baseline of 1.577 I find that of the eleven groups shot there were three that exceeded this level. The best percent decrease in five shot group was at 30 FT/LBS. This group ran 0.924. A reduction of 42%. When compared to the average of all eleven groups a reduction of 39% is seen.

The proof of the Consistent Crimp system, to me is to eliminate the shooter error as much as possible which involves a bit of faith. Eliminating the worst shot of a group is not the absolute best way to present results but knowing that even the best bench rest shooters toss one at times it does let me feel like my failures are not isolated. This is what I see using the "Ayoob" method of evaluation. Baseline best of four was 1.041 a sub-MOA that would tickle many shooters out there. Over the eleven shot series including the baseline I found an average of 0.715. A decrease of 32%. Now when we look at the comparison of the baseline with the best four shot group that was produced at forty five FT/LBS at 0.190 a reduction from baseline of 82%. Not bad for a jerky trigger finger!! While a group like this might well be an anomaly an average of the best five groups of four that recorded at .761, .576, .435, .333 and .19 shows an average of .459. This would be a reduction of 56% over the baseline or 36% over the eleven best of four groups.

One thing I did as a whim at the end of the day was to fire one ten shot group using Winchester White box 55 grain FMJ ammunition. Nothing fancy just run of the mill canon fodder. I did not put everything I had in to this group but shot it at a pace that I was comfortable with. This one showed a nine shot group of 1.958 with the best eight of that down to 1.902. The far right round was a major malfunction of the shooter and I called Mulligan on it and threw it out of the mix. I included this to illustrate that a basic AR with a basic barrel that shows so so results with a pretty pedestrian ammunition choice may well be a shooter if you can coax it along and feed it what it needs.

I will mention the SD's on this hand loaded ammunition and the velocity spread. . Remember these were all thrown charges and I made no attempt other than to check the charge weight about every twenty five throws. I had loaded a total of 220 rounds of this mix last fall in preparation for the CC test using the previously mentioned SPS Varmint . Standard deviation for all elev levels ran an average of 37.50. Much higher than the average gun writer shows with his reloads. My chronograph showed a high SD of 56 at zero crimp and a low SD of 25.4 at , oddly enough, at five FT/LBS. The best group shot at 0.19 showed an SD of 25.05 for that single five shot target. One wonders what it would shoot if a single digit number had been obtained. Day in day out I have never found an SD to be the determining factor on group size at 100 yards. It may well become involved at three hundred yards but my field use has never shown me a big difference in down range results that was repeatable at my skill level. Velocity average was 3040 for all recorded rounds with a high of 3155 and a low of 2900. High velocity was in a group at 40 FT/LBS and low velocity was in the zero crimp pressure baseline group.

The data present in this test was out of an 16" barrel CAR at ambient temperature of 68 and 74 degrees on the test days with the average, as stated , of 3040. If you refer back, links below, to my previous testing with this same ammunition last fall I had an average velocity of 3377. Temperatures for that series of test days ranged from 90 to 107 degrees with the bulk being fired at around 97. The two tests reflect a velocity drop of 337 FPS in the short 16" barrel vs the 26" barrel on the SPS. Of course temperature effects must be factored in and they are never a straight line in increase or decrease. This powder seemed to show about a one degree change in temperature would mean about 1-2 FPS velocity change in the longer barrel. Given that assumption on the effect of heat on velocities I see a decrease in velocity of about 33 FPS per inch of barrel loose. This falls pretty much in line with generally accepted theory.

What I learned from this test was that I had a load that would work very well on either paper or warm targets. I will be shooting this rifle in some reduced 200 yard courses with the bullet tested and feel that if I do my part the Gold shouldn't be far away. Application to our rifle types and choices is clearly present. Obviously not all rifles will respond but I have no doubt in my mind that crimp pressure of any given load can and does effect the down range performance of that load. The practical application of this is that rather than look for the "best" load with a bullet using six different powder charges at four different levels a shooter could, reasonably, select a powder and a bullet with a charge weight that should yield an acceptable velocity and go to the range and not have to track a multitude of variables. Using one powder and one bullet with just a little added attention to detail with the Lee FCD and the Consistent Crimp Tool could well turn that run of the mill rifle in to the proverbial wolf in sheep's clothing.

I am including links to my first two Consistent Crimp tests. Test #1 was with the aforementioned 223 SPS and Test #2 was done with a beat up old 243 BDL. Look them over and please feel free to give me any feedback regarding the results or if you question why I did or didn't do something chime in.

First Test: CC TEST #1 Second Test: CC TEST #2

I've enjoyed doing this exercise and hope that it is of benefit to all on the board.

Greg

Edited by GLShooter

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Wow, great review Greg! :thumb:

 

 

And it is only about 50% done!! LOL

 

Greg

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That 45 ft/lb target makes me jealous. I am seriously impressed :cool:

 

These 3 tests you've done on the CC tool have convinced me of one thing, I must have one :D

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That 45 ft/lb target makes me jealous. I am seriously impressed :cool:

 

These 3 tests you've done on the CC tool have convinced me of one thing, I must have one :D

 

I am afraid what the results could show with a good shooter on the trigger. I am just a hack compared to some of the guys on here. The groups are all guts and feathers so those pulled shots at least prove my normalcy. It does make me realize that those PD's that escape my bullet might be betting on my ability to keep them safe when they stay around for another try at them!! :nt:

 

Greg

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I am afraid what the results could show with a good shooter on the trigger. I am just a hack compared to some of the guys on here. The groups are all guts and feathers so those pulled shots at least prove my normalcy. It does make me realize that those PD's that escape my bullet might be betting on my ability to keep them safe when they stay around for another try at them!! :nt:

 

Greg

 

 

I've ruined more groups than I claim by pulling shots, especially lately after laying off the precision stuff for a few years. I'm happy to plant 3 rounds in a 1/2" group, but four into less than 1/4"................... :hail2:

 

ETA: Lee FC dies in 223 and 308 are ordered as of 0830 this morning from Midway, going to give precision accuracy a call tomorrow morning and get a setup on the way for my RockCrusher :thumb:

Edited by THESPECIALIST

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I've ruined more groups than I claim by pulling shots, especially lately after laying off the precision stuff for a few years. I'm happy to plant 3 rounds in a 1/2" group, but four into less than 1/4"................... :hail2:

 

ETA: Lee FC dies in 223 and 308 are ordered as of 0830 this morning from Midway, going to give precision accuracy a call tomorrow morning and get a setup on the way for my RockCrusher :thumb:

 

Please tell Scott I sent you.

 

Greg

 

PS: Good decision on your part. Odd that I can many times shoot groups with a 308 precision rifle off a bipod that rival these under pressure. Maybe the pressure is the key? :nt: Or is it the Warden with $10.00 riding on the group betting His nurse can kick their snipers butt? :ZAB:

 

PPS: What kind of RockCrusher you running? My little Rock Chucker wants to hide in that little pile. :wink:

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Please tell Scott I sent you.

 

Greg

 

PS: Good decision on your part. Odd that I can many times shoot groups with a 308 precision rifle off a bipod that rival these under pressure. Maybe the pressure is the key? :nt: Or is it the Warden with $10.00 riding on the group betting His nurse can kick their snipers butt? :ZAB:

 

PPS: What kind of RockCrusher you running? My little Rock Chucker wants to hide in that little pile. :wink:

 

:laugh: I do that more than I like to admit too. I know darn well it's a Rock Chucker, why I keep saying Crusher I don't know

 

And stores sell me reloading supplies :blink: :laugh:

 

ETA: It's the Rock Chucker II........hey, I got it right that time :laugh:

Edited by THESPECIALIST

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:laugh: I do that more than I like to admit too. I know darn well it's a Rock Chucker, why I keep saying Crusher I don't know

 

And stores sell me reloading supplies :blink: :laugh:

 

ETA: It's the Rock Chucker II........hey, I got it right that time :laugh:

 

 

I got a RC Supreme last fall. I just need to get it out of the box. :flea:

 

Greg

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Color me jealous. Nice groups.

 

I think you have, once again, shown that the Consistent Crimp product benefits the reloader. While I looking at the pictures I was thinking, "Ok, the 10-15 ft-lb groups are nice." That was until i got to see your 45 ft-lb grouping. I think you malign your shooting abilities a little too much. You are a shooter.

 

Sean

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Wow, Greg,

 

You have been hard at work!

 

Things really started tightening up at 35 ftlbs for this load and rifle!

 

I am jealous of your groups but still more your weather. We are still looking out of our house windows at 12 degrees right now.

 

Right about now I would take the groups you shot from 5-30 ft lbs if I could only have an end to this winter wonderland for a while. :blink:

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Wow, Greg,

 

You have been hard at work!

 

Things really started tightening up at 35 ftlbs for this load and rifle!

 

I am jealous of your groups but still more your weather. We are still looking out of our house windows at 12 degrees right now.

 

Right about now I would take the groups you shot from 5-30 ft lbs if I could only have an end to this winter wonderland for a while. :blink:

 

 

Well I try to squeeze the shooting in but in two months it will be around 100 and I'll have my blood thinned down enough that I'll hit my stride. I'm like an iguana and don't move to good until it hits the 80's. It was 88 today. :nt:

 

I'm still writing this up and will be doing the hard core number comparisons tomorrow if it all works out.

 

Greg

 

PS: Thank you all for the compliments. I hope I contribute a little to the sport.

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OK guys, it is finished and ready for review. Thought pro and con are welcome. I hope some value is seen in the effort.

 

Greg

 

PS: Thank goodness for spell check!!! :eekout:

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Very well written, heck, even I understood it. You laid out the points well. I cant thank you enough for the effort you put into this. It is a great reference for us all.

 

Sean

Edited by Seanhagerty

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Very well written, heck, even I understood it. You laid out the points well. I cant thank you enough for the effort you put into this. It is a great reference for us all.

 

Sean

 

 

Thanks. I'm still cleaning it up but it is finished 99.9%.

 

Greg

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