trimming the bullet meplay for better BC

[*WyoWhisper*]

Jeff,

I must admit I often wondered about the inconsistencies. But I am not areo expert so I figured it must be no big deal cause these guys are shooting tiny groups at 1K...

So Jeff where does a guy get a tool like the one you mentioned???


and I thought I was anal when I debur the flashhole from both sides and bevel both the inside and outside edges of them.

 

[a.JR]

WyoWhisper,I understand Your own Dave Tooley sells a unit to trim meplats but i have not seen one so i don't know how his cuts or if it changes the point dia..If his 1K groups are enough proof i'd say it's a beauty...I don't think u need to be an Aero expert to want to change things,i started in trying to make my life a bit simpler in having bullets nearly all the same length...When u see the points after doing this the meplats all look different so i made a cutter to even them,sort of evolution...1 of the true brains of L/R bench shooting is Henry Childs in your country and he went another way and instead of cutting the point he repoints it with a die ..I am presently makeing one for my 187 BIBs as we speak,will let it be known if it's a better "mouse trap"..JR..Jeff Rogers

 

[Guest]

We're testing the Tooley tool to uniform meplats on a number of bullets at the USAMU. So far any loss in BC is miniscule -- all we're doing is uniforming the points and bullet overall length.

We've tried it on 7mm Remington Short Mags, 6.5 x 284, and both 80 and 90 grain 5.56mm bullets.

We machine rest test all ammo at 300 and 600 yards. We're moving our 1,000 yard concrete block and will get our 1,000 yard machine rest capability back in February.

Groups are indeed shrinking slightly, and I think it's because the bullets are now more consistent length- and point-wise.

 

[a.JR]

G'day From Aust Dave,Your machine rest has got my interest...Have you tried checking the bearing surface lengths??,i have found this area to be the most productive in reducing the vertical dispersion from a conventional rifle ....With Full cartridge preparation i can hold V.D. of less than 2.0 ins at 1K in fine shooting conditions with my present gun...Do you find that a ballisticly inferior projectile will perform better after meplat modification than a unit with a higher bc proportionately speaking???...How do you uniform the points after the length classifying is done??...JR...Jeff Rogers

 

[Vern Harrison]

Hi guys,

I have been doing this for a few weeks now, after reading the post at BR.com, I had Dave send me one. All I can say is it works.

I guess old Two Shoes at SH would have a field day with this one. LOL but it does work.

By the way droped the whistle pig but it's still me.

Good luck, Vern

 

[Steve Shelp]

Brent,
Again sorry for the delay. Below are my attempts to answer your questions as accurately as possible.

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Have you guys experimented with cutting the tips way back, or just enough so they all clean up square vs. the wild uneven ones etc.<HR></BLOCKQUOTE>
So far, I don't see the numbers saying that cutting them back to far has any deterimental effect, but I'm sure at some point it has to have some affect on the negative side.
We have only cut back enough to cleanup the tip only when shooting across the M43.
One guy that shot in these tests with us, definitely cuts his tips back a lot further than the rest of us. But on paper he hasn't lost anything except for some BC loss. That's an experiement for the future and it would take a lot of rounds to statisitcally prove or disprove this and I'm not sure we have enough guns, barrels, bullets, and setup to tell anyway.

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Have you played with boring the HP out larger and it's effects either?<HR></BLOCKQUOTE>
We haven't specifically bored out the HP per say but after cutting the tip flat we all clean up the burr using different methods.
Myself, I use my dremel tool with a wire wheel attchement that rounds the inside and outside edges very nicely. I do deburr the inside of the HP on the 338 bullets with a small number drill first before putting the wire wheel to it.

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Do the really wildly uneven tip always reduce BC by a certain amount?<HR></BLOCKQUOTE>
There is a reduction, but I don't have the hard numbers calculated to give them to you. We not worried about the loss only about the consistantcy and that's what our tests have been concentrating on.

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Have you all established a baseline BC ES for the squared tiped bullets and compared them to the ES of random selected out of the box bullets?<HR></BLOCKQUOTE>
Yes. but, I don't have a lot of the raw data fully compiled due to work restraints right now. But during these tests we would take 1 rifle, same lot# of bullets, powder, primers etc and fire strings of unaltered, trimmed, and tipped bullets for comparison. This same test was fired for 4 different calibers between 6 to 8 different proven BR rifles/barrels.

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>I'm curious, do you guys leave the acoustic target set up, or use a stand for it that is always a set distance from the bench? I don't have this type of permanent setup, it's a real PITA to get accurate measurements without this.<HR></BLOCKQUOTE>
Unfortunetly we can't leave it setup. So all of our numbers are comparable within that particular test for BC comparison. But it's not that critical being we're only looking for relative changes within and not what the actual true BC. Though we do take out time to setup as accuractly as possible so that we are pretty close.

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>As I'm sure you're aware of, the distance is very critical for absolute BC numbers, relative ones for tests like you're doing would be easier, if that's all you were after.<HR></BLOCKQUOTE>
Oh yea... afterward we went in a plugged in some different numbers, jsut changing a distance here or there by fractions of an inch and it would definietly affect the number in a big way.

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Do you guys use a seperate frame for the acoustic target just ahead of another target frame to icsolate the sound traveling through the frame. It does travel faster through the wood than it does through the air, and often the target backer material will transfer this noise to the sensor before the mach wave reaches it.
The sensor will sometimes trigger too soon in this case.<HR></BLOCKQUOTE>
I'm trying to think exactly how these were setup the last time we did this. We did see a couple of the 338 bullets give obviously wild numbers for TOF but the velocity readings on the chrono and proof screen said everything was fine so we suspected something with the acoustic setup. We also has a slight rain come and go that morning so there were many variables to consider.

hope this answered some of your questions. BTW: I don't hear you bragging about how nice the weather is up there this year as compared to last winter!

I was chilly enough that I had to throw on a flannel shirt the other day to go to work. But we haven't had a frost yet.

I've got pictures of the trimmer and stuff coming shortly.

Steve

 

[Steve Shelp]

Here's some images of the actual tool and some of the actual bulets I fired through my LG rifle during this test session of unaltered, trimmered, and tipped bullets.

Dave Tooley's trimmer (L -&gt;R) cutting head with stop coller that sets the amount of cutting depth, next is the body that the cutter rotates in and has a plastic collar pressed into the opposite end that is cut like a throat would be in your rifle. This is the stop that the bullet seats against while being trimmed. Last is the bullet itself.

Next is how I hold it while trimming. The cutter sticking out the right side is turned by hand or can be chucked up in a drill for power if your doing a large batch.

next is a picture of 30 rounds of ammo for my LG just before firing, showing the unaltered meplats, trimmed meplats, and plastic tipped meplats.

Steve

[ 11-29-2003: Message edited by: Steve Shelp ]

 

[Vern Harrison]

Steve,

Did you get my e-mail?


Thanks, Vern

 

[Brent]

Steve,

Thanks much.

It's been cold here for the last three weeks or there abouts, below zero or in the single digits, not much fun. No bare ground like last year either. The warm winds will come and be sure to melt it all off soon, that much is a given. Snow just doesn't stay long here in this valley like it does elsewhere, iceland is a good way to describe it.

Farmers almanac calls for heavy snowfalls this year so we'll see.

Any conclusions on the polymer tips, if they're worth using or not? Where do you buy those at seperately? I wonder how they'd work in the X bullet for LR work.

 

[a.JR]

Thanks Steve Shelp,The pics of Dave's cutter are a big help...At least i know what/how is being done on the other side of the world...I have nearly finished the point up die as per Henry Childs set up and will test as soon as it rains...Where could i purchase the plasttic tips like the ones in your pic ..JR..Jeff Rogers

 

[Steve Shelp]

Brent & Jeff,
Those tips were supplied by a bullet company that I'm not sure I'm at liberty to say at the present. Like I've mentioned before this has been an ongoing experiement over a period of time and data is continually being fed back to "the source". I'm not playing oppossum with you, but I was asked to keep quite.... so I must honor that request at the expense of not being able to tell ya'll the whole story. If I was given the go ahead to say who, what, when, where, why, and how.... I'm pretty sure even I couldn't buy them myself at this time.

Now about the tips and how they work.... obviously it makes your BC go up and keeps the BC uniformand that's a good thing. That tip on a 300gr MK is an awesome looking bullet. I gained about a 12-16" of elevation at 1000yds using them. This is the reason for cutting the meplat to begin with... was to prove or disprove if uniform meplats make a difference. The end result was to eventually install plastic tips. The cutting of the meplats was merely a cheap easy test to the end means of uniform plastic tips.
The cutter allows you to uniform already existing bullets (loaded or unloaded) and enjoy the benefits of meplat uniformity without going all out to install the tips. The last batch I made up at Dave's shop was 86 bullets and it took well over an hour. Eventually my thrist for a beer overcame my desire for more plastic tipped bullets and the lathe was shutdown for the night.

The true test I beleive now lies with the USAMU testing the Dave L. mentioned above. They have the means to truely test, with some statistical certainty the thousands of rounds over different ranges and to get some true repeatable hard numbers. I don't think anyone in our little group has/had any grand allusions of our tests standing up to hard scientific scruntiny. I think we were trying to show that, "hey there's something here and here's rough data".... will someone pick up the ball and make it happen. In that sense the testing to date has been a success and the wheels are definetly turning in more places than NC on this subject.

Jeff,
You couldn't do much better than to have Henry as a reference. I've shot at many matches with him and he usually sets up next to Dave and I. Henry is a walking calculator/encylopedia of internal and external ballistics/mathematics. Henry even shot aluminum tipped bullets at one time that he made himself. That was an interesting experiement with some drawbacks that were encountered.

Steve

 

[a.JR]

Steve ,Infos been great,looks like i might have to make some tips to try out,reckon i know the right plastic to use it machines up nice.Brent ,i don't get cabin fever with the heaters and overcoats , At this time of year i get, Hide in the airconditioner type fever...It's warming up now, be bloody hot soon today's not bad it's 92deg F because of the low cloud cover, back to over a 100 in a coupla days..JR..Jeff Rogers

 

[GPWEAPON]

a question for the knowelagable people on this board from a newbie, since the vertical stringing question is addressed here. I always woundered how much effect extreme spread had on vertical stringing. I look at hornady balistic manual and 100 fps at long range seems to have a great impact on vertical shot to shot. I know this is extreme considering most calibers being used but 25 fps from my M1A @ 600 is relistic for me. Is it theory or reality? thanks

 

[Brent]

Jeff,
That's too funny!

I take the cold "much" better than the heat, getting out shooting is much easier when it's warmer than it is now tho. At least it isn't -20 to -40 deg F or colder, that I'm thankfull for.

GPW,
I think you're asking if it does have an effect with lower extreme spreads? If so, the answer is absolutely. If BC, wind, BP and every other variable, including the rifle capable of bughole groups, the slower shot will always be lower than the faster shot, 5, 10, 15 fps or whatever, time of flight will be different and so will trajectory.

A ballistic program is the easiest way to see what effect a shot with a different MV will produce in vertical error.

This is one of the important goals in load development, not just tiny groups. 10-15 fps MV ES is what I shoot for, although some loads I have refuse to go below a solid 20-25 fps ES. Knowing the probable grouping limitation of the load is important, what ever ES you use. If the ES says vertical could be 16" at 1000 yards, and you shoot many groups with the load that go under 10", be prepared for the eventual 16" group or larger because it will happen and you can't count on the 10" groups.

POI shifts between trips to the range or field:

A more temp stable powders will also help you reduce large vertical errors from mild temp swings, very much a positive step that should be taken when shooting LR. ES should be noted at different temps for the load too, it may be quite different at one extreme or the other.

A swing in BP will also shift POI considerably at LR. Ballistic programs are usefull to understand what to expect ahead of time here too. Using the exact BP and MV on the drop chart will help in big ways at LR. This is where a ballistic program on PDA, along with a wind meter/ weather meter can give you an edge by using real time data.
Once you have established your known drops at a known BP, temp, MV and BC, matching these come ups in the ballistic program, and then modifying them with it makes things pretty simple and accurate in the field.

How close do you want POI to be to POA in the field? Well, the closer you know you can keep them to each other, and the smaller you know you can keep it grouping, these will largely determine your accurate effective range.

[ 12-01-2003: Message edited by: Brent ]