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Forum Index > Rifles general discussion > Help with .280 Sendero

Help with .280 Sendero

23 May 2020
@ 04:24 am (GMT)

David Gausepohl

Yes, I built a .280 Sendero with a Shilen Stainless Select Match barrel. It's bedded in the HS Precision stock, and scoped with a SIII 6-24X50 LRMD. It was chambered with a standard PTG SAAMI spec reamer. I've gotten Speer 160gr BTSPs down to 5/8" groups with H4831sc. Velocities have been good at 2850-2900 fps depending on charge.

I'm working with the Sierra 160gr TMK now, but have not gotten groups below 1" with H4831sc and Re23. Bullet jump so far tried at .035 and .040.

Short of rechambering with the Manson reamer and it's longer throat, what else should I be trying? With the SAAMI chamber/throat is there another bullet I should be looking at? Another powder? Need more or less jump?



Replies

23 May 2020
@ 11:24 am (GMT)

Paul Leverman

Re: Help with .280 Sendero
I don't remember which book, or where in the book, but Nathan has set out the jumps for various tipped bullets. Sorry I can't be more specific, but it may be in the reloading book.
23 May 2020
@ 11:56 am (GMT)

David Gausepohl

Re: Help with .280 Sendero
Thanks Paul. I have all the books, so I'll look for it.
23 May 2020
@ 09:16 pm (GMT)

Iain

Re: Help with .280 Sendero
If you seat them at .020 off, will you still have plenty of shank in the neck, remembering that the 280 neck is quite long ?. Minimum of one calibre and I would be happy.

If you can do that, I would start at .020 off and increase jump in .015/.020 steps and see what happens.

.005 steps are going to be slow and frustrating.
24 May 2020
@ 01:45 am (GMT)

Paul Leverman

Re: Help with .280 Sendero
David, in case you hadn't found it yet, or for others that were curious, the info is on page 144 in the reloading book.
24 May 2020
@ 08:40 am (GMT)

Nathan Foster

Re: Help with .280 Sendero
Hi David, the TMK is somewhat hybridized between a secant and tangent design.

From your description, the throat design prefers a tanget style bullet and can handle some jump with this ogive shape.

The gun is also telling us that it is not quite so happy about this jump with a slightly different bullet style. You may have to come right up (10 thou) to the lands. But as you will already have discovered, the lengths of the TMK vary from bullet to bullet. They are not as uniform as Hornady bullets. To get an accurate measurement for recording, it would help to measure the max OAL at a datum point on the ogive of the bullet rather than the tip.

You will be able to obtain the max OAL using a partially neck sized case and projectile. Following this, you can use the same projectile to set up your seating die. But for the purpose of recording, it would be good to take a reading on your caliper, using a hornady tool that reads at the datum.

To recap, you can use a projectile measured at its tip to work out your max OAL and to set up your seating die. But it can help to make a record using a tool within your vernier that records the max OAL and seating depth at a datum point.

In addition to the above, you need to take note that you will most likely be seating out into the case neck. This sometimes cannot be avoided in the 7x57 and .280 Rem and AI. The risk is the formation of a donut which could act as an internal crimp later on. If you end up with a good load, but the load is sitting out in the case neck, that will be fine. Just make sure that this brass is not used with longer projectiles at a later time.

Be aware of pressure variations for the two different bullet designs and also seating depths. If for example, the rifle likes 57 grains of Short Cut with the 160gr Speer BTSP, you may have to drop as much as 4 grains to find the same sweet spot with the TMK. Just be a bit careful with this and with the ELD-X and M.

If all else fails, the 160gr Speer is a very good bullet in its own right. You are off to a very good start.

The Foster Manson reamer does not have a longer throat. But it has optimal geometry throughout in an attempt to make life easier for the hand loader. Some of the very worst .280 reamers have long throats, resulting in very finicky rifles and major donuts in brass.
24 May 2020
@ 09:42 am (GMT)

David Gausepohl

Re: Help with .280 Sendero
Thanks Nathan and All

I will apply these suggestions and report back.

David
 

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