The Western Powder online reloading manual, Edition 5, does not list any bullets lighter than 55 gr for TAC powder for 556 however they list a myriad of bullets lighter than 55 gr for 223.

Does anyone understand this?

Does anyone have experience using TAC with lighter than 55 gr bullets?

I am looking to duplicate XM193 point of impact so achieving a similar velocity would seem to be a significant consideration.

I am intending to use Hornady 55 gr FMJBT bullets, LC cases and CCI 450 primers.

Any chronographed data would be appreciated.

I'm confused, you say you want 5.56 load data for lighter than 55gr bullets, but then say you're seeking to load 55gr bullets to mimic m193?





The main reason there is probably no load data for lighter than 55gr bullets in the 5.56 pressure levels is because there are no standard NATO loadings in 5.56mm for anything lighter than 55gr.  The lighter weight bullets are usually varmint or match type bullets used in .223 guns.  If you want to use TAC in sub-55gr. bullet loadings, use the data in the .223 section as a starting point and work up.





As for making a m193 clone using TAC and 55gr Hornady FMJs, look at the available load data in the Ramshot manual in the 5.56 section.  Start low and work your way up in your rifle until you can get something with comparable velocity and POI in your rifle as you get with factory m193 in your rifle, of course watching for overpressure signs and being safe.





Also remember that the bullet shape and design does play a part in accuracy and POI, and since factory m193 may use a slightly different bullet design, your may not be able to achieve perfect match to POI, but I'd wager you'd get pretty close.

 

I'm assuming the part in red is a mistype.

What bullet weights are you planning on using?

Actually I did not ask for loadings for bullets lighter than 55 gr. I observed that there are there loadings for bullets 55 to 80 grains but not any loadings for bullets less than 55 gr. I do not need loadings for less than 55 gr, just wanting to know why there are none.

Curious to know why you would think that this is a mistype? As stated, I intend to use 55 gr Hornady FMJBT bullets.

I am looking to understand if there is a reason that there are no loadings listed for bullets lighter than 55 gr bullets.

Your post implies that you are trying to load bullet weights less than 55 grains in 5.56 NATO cases. This is especially true when you ask if anyone has experience loading lighter bullets with TAC, and then stating you want to duplicate the point of impact as XM193, and then asking for chronographed data.

Everything, and I mean EVERYTHING, you posted makes it appear you want to load light bullets and are asking for data.

I'm also obviously not the only one who thought this. Since you're not asking for load data for lighter weight bullets, then it seems you're actually asking two question. Your first question, it seems, is "Why is there no loading data for lighter bullets with TAC?" and your second question, which deserves it's OWN thread, is "Does anyone have load data to duplicate XM193 with TAC?"

Rethink your delivery and try again.

The 5.56 data is to duplicate (or approximate) military loads. Since the lightest military load is 55 grains, there is no 5.56 data to duplicate with lighter bullets.

Just use the .223.

This....

and this is a perfect example of how texting and internet forums comments can be taken the wrong way from everyone.

I can see how the information I give and the questions I asked may not appear to be congruent so I will elaborate.

But first I must respond to the post quoted. The Western Powder Edition 5 reloading manual publishes many, many loads for bullets that have no military analog so I assume that the 5.56 data are loadings that are within the pressure standards for 5.56 rather than attempts to duplicate military loads while the loads for 223 observe the lower commercial pressure standard.

Back to the original question. For those that have been loading for a while you know that there is some correlation between bullet weight and powder burn rate. It is not in lock step as there are other factors involved but generally, for a given cartridge, slower powders tend to be more suitable for the heavier bullets and faster powders tend to be more suitable for lighter bullets. The fact that for a given cartridge, heavier bullets tend to be limited in the maximum muzzle velocity that can be achieved with any powder and that lighter bullets can often be propelled to higher muzzle velocities and that this is achieved by using faster powders reinforces this concept somewhat. Add to that the fact that slower powders will tend to produce higher muzzle velocities with heaviest bullets, again for a given cartridge.

If one thinks of the bullet being propelled down the barrel by the burning powder charge as a resistive force or load which collectively considers all factors, not just the bullet weight, the bullet weight to powder burn rate relationship makes sense. For a more 'resistant' load which includes a heavy bullet a slower, longer push will impart the most energy to the bullet and for a less resistant load which includes a lighter bullet, a faster powder.

If one thinks of load rather than just bullet weight, then barrel twist rate becomes a consideration. For the same bullet, a faster twist will present a greater load to the burning powder charge and a slower twist will present a lesser load. Bullet construction is a consideration as well. Do you use the same powder charge for a lead jacketed bullet as for an unjacketed lead only bullet of the same shape? Do you get the same muzzle velocity? One would expect to see higher muzzle velocities when switching from a jacketed bullet to a lead bullet if using the same powder charge.

This leads to the driver for my question. The Western Powder manual data for 5.56 is collected using a 24",  7 twist barrel and no data is presented for bullets lighter than 55 gr. My two barrels are 16", 9 twist and 12 twist which could have a similar effect to using a bullet lighter than 55 gr. Since no data are listed for bullets lighter than 55 gr is there a limitation with TAC powder with lighter bullets. If so there might also be a limitation if using a 55 gr bullet and a barrel with a much slower twist. A 16" barrel might also suggest using a faster powder than one might use for a 24" barrel.

Since there are ample data for .223 using TAC and lighter bullets I would think probably not and if someone was able to share their result using TAC and lighter bullets that would alleviate my concerns.

Of the components I have selected, LC brass, CCI 450 primers, Hornady 55 gr FMJBT bullets and TAC, the powder is the one I would be most likely to change if I encountered issues.

I got an answer to part of my questions.

"25.6 grains of TAC with the 55 grain Hornady FMJ should put you at the velocity of the XM193 ammunition."

Now I have a place to start.

I opened up an American Eagle XM193 and it had 27gr. of what looked just like Tac, their .223 version had 24.2gr if memory serves correctly.

If you can verify which powder they use you can copy their round.  It is definitely hotter than any .223 ammo I've shot.

Large ammo manufacturers do not use specific cannister powders as we know it.  They buy a generic bulk powder with a formulation that approximates the performance they are looking for, then develop loads from scratch to match velocity and pressure specifications.  Each batch could use a different, but similar performing powder, so there's no telling what it is by popping a round open.

I think the 5.56 section implies military bullets in rifles with a 5.56 chamber, perhaps even military pressure levels seen in such loads with new brass and crimped primers.  

In my mind, with that orientation, and no military bullets lighter than 55 Gr for 5.56, they just felt they didn't apply to that section.





I can't help you there.  I prefer extruded powders for the light bullet .223 loads.  (H322, Varget, Benchmark, etc.)



That sounds like 5.56 data.   Personally, I don't want to replicate such a load, for they assume crimped primers and new brass (which they're harder on.)

You can do it...but there are trade-offs in terms of accuracy, safety, and brass life.

It may make sense if you're stashing ammo for zombies.  Mine is more geared toward smaller groups and prairie dogs, which dictates different bullets, and a greater accuracy requirement.