Seating Concerns with Sierra Tipped MatchKing® (TMK) Bullets

Written by Sierra Bullets Ballistic Technician Rich Machholz

Now that the new Tipped MatchKing® (TMK) bullets are being shipped and shooters are putting them to use I have received several calls regarding marking on the bullets ogive from the seating stem.

3 77 gr Tipped MatchKing Bullets
The cause can be traced to one of several things.

In the 223 and especially with the long 77 grain TMK seated at 2.250” or even 2.260” most loads of Varget® and Reloder® 15 are compressed loads, sometimes heavily compressed.  This puts a great deal of pressure on the bullet through the seating stem.  The result of all this pressure is a mark of varying depth and appearance on the ogive of the bullet.

Some older seating stems might even bear against the tip of the bullet which can make a slight bulge in the jacket just below the junction of the resin tip and the copper jacket in a compressed load.  If this is the case there is not a ready fix other than calling the die manufacturer and requesting a new deeper seating stem.

If the seating stem is of proper depth the culprit most generally is a thin sharp edge on the inside taper of the seating stem.  This is an easy fix that can be accomplished by chucking  a spare 77 grain bullet in your drill, coating it with valve grinding compound or even rubbing compound or in a pinch even tooth paste.*  Remove the seating stem assembly from the seating die.  Turn the drill on and put the seating stem recess over the spinning bullet with the polishing compound to break or smooth the sharp edge that is making the offending mark.  This might take more than one application to get the proper polish depending upon what you use but the more you polish the better the blend of angles which will show up as a brightly polished ring.

Chucking A 77 gr Bullet If the above is a little more than you care to tackle you might try very fine emery cloth twisted to a point that can be inserted into the mouth to the seating stem and rotated to polish the inside to eliminate any sharp edges that might be present.

And last but certainly not least.  Actually, even though we don’t say you need additional data for the TMKs, remember you are dealing with heavily compressed loads in some cases because of the additional bullet length.  Due to the additional length of these new bullets and in the interest of gaining some room in the case you might consider trying a slightly faster extruded powder like BenchMark or the 4895s or an even more dense powder like the spherical H335®, CFE223 or TAC.  The extra room will allow for trouble free bullet seating also.

Good luck and remember we are no further away than your telephone – 1-800-223-8799.

*Wear safety glasses and follow drill manufacturers safety instructions. 

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35 Responses to Seating Concerns with Sierra Tipped MatchKing® (TMK) Bullets

  1. john zerfas says:

    Rich, thank you for keeping us up on this, I am working on load development with the 223, particularly the 69 TMK, although I’m not having this problem I appreciate the information, thank you!

    Like

  2. Pingback: Seating Concerns with Sierra Tipped MatchKing® (TMK) Bullets | Rifleman III Journal

  3. firstriverbend says:

    Look at this information for other methods to overcome this problem.
    https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwi88u25wZ3MAhXMRCYKHQjKCloQFggdMAA&url=http%3A%2F%2Fwww.uniquetek.com%2Fsite%2F696296%2Fuploaded%2FBullet_Seating_Stem_Customization.pdf&usg=AFQjCNEW6f7kRSyn638grbG7r5BEcJim-Q&cad=rja
    Not too hard to do and the hot glue gun method is reversible. Been using variation of this for decades.

    Like

    • Rich says:

      Thanks for sharing that info with us

      Liked by 1 person

      • firstriverbend says:

        And thank you very much for all the information yourself and your colleagues share with us!! It is certainly a two way street when it comes to reloading and solving reloading problems.

        Like

      • firstriverbend says:

        Forgot to add, this is just one of the reasons Sierra has been my favorite bullet manufacture since the early 70’s.

        Like

  4. Al Lawler says:

    agree, a friend showed more pronounced deformation with a different brand of quickly expanding bullets over compressed load of Varget as well..
    sure looked bad but Interestingly enough the rifle was still very accurate.
    thanks for the fix as well.

    Like

  5. Roy Parker says:

    Had same problem and with deform tips on .308 win. , change seating plunger to a .270

    Like

  6. J says:

    I am finding that a lot of factory rifles are having a hard time stabilizing these bullets due to the length of the bullet itself. Working on a .243 with a 1-9 right now and no matter what I do they will not shoot moa. No problem with with my GA built .308.

    Like

    • marty says:

      I agree 100% They are way too long and the gun which is a ruger target will not shoot them at any depth but will shoot nosler 95 grain balastic tips very well.

      Like

      • Scott Millett says:

        Physics make slow twists and long bullets a bad match. I learned that with a 40X in 222REM (1:12″) that shot even the cheapest bulk 50 gr flat-base varminters at under 1.5 MOA, but keyholed 69 grain match bullets (even SMKs) at 50 yards! If you want to keep your slower-twist barrel, live with shorter, lower-BC bullets.

        As an added challenge for us ‘gas gun’ shooters who have to fit in a magazine, better BCs usually mean longer jump to the lands at a given COAL. In my 308B-chambered LR-308, at 2.800″ the 168×308 TMKs are almost 1/8″ from the lands (!) and groups show it. SMKs with their ‘fatter’ ogives let me set jump at ten thou (2.805 in my chamber), and shoot MUCH better. I’ll donate the rest of my TMKS to one of my buddies who has a 26″ F-class bolt gun; he can hang the TMKs out past 2.900 where they’ll do great.

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  7. I had similar problems with some 45 ACP bullets I was loading. bullet seater was set up for Ball ammo… I don’t shoot much ball ammo. so I walked over to my lathe and chucked up the seater and cut it to the proper shape. tried it and no more deformed bullets. Granted this is not the fix for everyone but it is my fix. and it’s nice to be a toolmaker with machines in the garage just for such an occasion

    Like

  8. Eric Rumpel says:

    Thanx Rich-as always, good info.

    Like

  9. Thorleifur says:

    Have you have tryed a vld stem? Might that work?

    Like

    • Rich says:

      No, but one that matched the minor bore diameter would work very well I’d guess.
      I wanted to work with what I had but yours is a good suggestion. I would think that if the inside diameter was about minor bore diameter (.216″) or so it would be just about perfect. That would give absolute control over ogive to land proximity in a match rifle but an AR platform offers some unique challenges due to the magazine requirements.

      Liked by 1 person

  10. Scott Millett says:

    I commonly drill out the seater cone, using the letter/number drill that’s next smaller than the land diameter. I set the depth of drill by using that same drill in a thin piece of metal, and measuring which kind of bullet’s tip sticks out furthest. I drill the SIDE WALL of the drilled hole in the seater stem just a bit deeper than the protrusion (plus the test piece thickness). Side benefit is that jump is much more consistent because ogive variations have less effect. (Make sure to debur after drilling using the smoothing technique described by Rich Machholz!)

    Like

  11. Have for years fitted the seating punch to the actual bullet its simple. Get some Devcon Steel Putty or similar product mix it up and fill in the nose of the seating punch, make sure that the inside of the die and the bullet are well coated with release agent. Using the dummy round force the bullet into the bedding compound in the die while in the press. Once this has set up take it out and leave the bedding material in the seating punch and clean up the excess material. I also drill a hold in the seating pinch just every so slightly larger than the bullet meplat to allow for variations which normally occur in the bullet making process .

    Liked by 1 person

  12. dmr says:

    great tip! thanks

    Like

  13. JAL says:

    Thanks Rich useful info

    Like

  14. Dave Monroe says:

    Hasn’t been a problem but thanks for the info, I will archive the information.

    Like

  15. Danny East says:

    Would it be too much to ask for Sierra to start making stems that solve this problem from the get go?

    Like

  16. Rich says:

    We only make bullets Danny so I’m afraid seating stems are out of our marketing model, at least for now.
    Rich

    Liked by 1 person

    • Danny East says:

      Ah ha, “at least for now”, Some one while in the break room has mentioned that outsourcing is a possibility?

      Like

    • firstriverbend says:

      Good to know, too many company get into making/doing what they are not good at and ruin a great thing!!
      Also, this is such an easy issue to resolve as a reloader, that I do not see the merit in custom stems. If I had custom stems for all of the different bullets I have loaded over the years, I would need an additional room for them!
      Most marking on bullets by the stem are just cosmetic anyway.

      Keep the focus on make superior bullets, let someone else deal with minor issues. 🙂

      Like

  17. Steve says:

    Wish somebody would pick up on the old DPMS VLD magazine/bolt stop. I have one for my 223 AI AR, and have a TOL capability of 2.460″–no problem with either bullet and they are DEADLY to long-range on coyotes.

    Like

    • Scott Millett says:

      Sorry, Steve. I’m not familiar with “…the old DPMS VLD magazine/bolt stop”. Can you explain? Is it a bolt stop that catches the bolt a little further to the rear, and a special magazine have a super-thin rear wall, together allowing some additional COAL? Don’t see how you could gain a fifth of an inch of COAL (from 2.260 SAAMI to your 2.460) though. (??)

      Like

  18. Steve says:

    Scott, what someone did was they opened the guide ridge at the rear of the magazine so that the head of the 223 case could slide into it. They also put some plastic inserts into it that would allow for single stacking. See pg. 64 of the AR Rifleman 2017 Edition. My article’s in there on long-range shooting with the AR-15 and there’s a picture of the old DPMS VLD magazine. Works great with some tweaking. With this system even the 75 A-Max can be seated with the bottom of the bullet’s bearing surface just slightly below the neck/shoulder junction. The 69 TMK works perfectly with that setup.

    Liked by 1 person

  19. MK says:

    I agree. I haven’t seen any marks on mine running the 77g TMKs and TAC. getting awesome velocity and accuracy out of an AR. have any of the VLD seating stems been tried with any more success?

    Like

  20. Kent Sherrington says:

    Very good you give the advice. The best of it was and I use my own words here “use an appropriate amount of the right powder” 😂 👍

    Liked by 1 person

  21. Lynn Whittington says:

    If the problem is compressed load because the powder is too high in the case to adequately seat the TMK, you might read through this article from Accurate Shooter for information on how to solve that problem
    http://bulletin.accurateshooter.com/2017/04/powder-column-height-varies-with-case-filling-methods/

    Like

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