Bullet modification

[royinidaho]

Shot 3 @ 610 this morning.

Temp was 5 degrees w/10 MPH wind @ ~25% value.

Shooting pad was on a little snow and it was too darn cold to achieve a good shooting position. I simply couldn't get "just right". To the extent that the third shot put a ding on the bridge of my nose. Just sayin I didn't expect a great group.

Group was a bit over 1 MOA and I held 1/4 MOA too much into the wind. None the less all shots went in the 8.5" X 11" paper.

All holes were round. Shooter called for 5.8 MOA guestimate of center group was 0.75 MOA high. However, the group didn't give great confidence thus I'll give it another go around 800. Hopefully I'll be a better shooter that day.

I'm finding seating the point to be critical. Too much point seating pressure shows a little meplat expansion.

Additionally, bullet trim length variations are easily seen after the point is seated. A few thou makes a big difference. I'm fearing that additional shock wave. . .:roll eyes:

Accuracy looks good enough, even when I shoot badly, to do some terminal testing @ distance. (as soon as it warms up a bit). Darn near got frost bite walking out to and back from 600 yards.

 

[Topshot]

Thanks for the update Roy.
Some promising results that match what I achieved with my modified SMK's. Almost time to shoot some game with them.

I don't know how you put up with the cold over there? Its almost too hot over here to go shooting. Expecting 40 deg C (104 F) here over the weekend.

 

[royinidaho]

Thanks for the update Roy.
Some promising results that match what I achieved with my modified SMK's. Almost time to shoot some game with them.

I don't know how you put up with the cold over there? Its almost too hot over here to go shooting. Expecting 40 deg C (104 F) here over the weekend.

Cancelled my shooting today. Simply too cold! -8*F at the moment. But. . . wind is 0 which makes it tempting.

 

[royinidaho]

Hmmm its been awhile.

I think I'm making a bit of progress.

Am finding it increasingly difficult to be a decent machinist. But that may be a good thing as I want to determine just how uniform a bullet needs to be to meet my accuracy desires.

As it turns out things don't need to be "perfect" at least for moderate ranges.

My efforts are running around 0.005" run out, max, for the ones I've actually shot.

I simply roll the bullets across a granite tile and measure only if I "see" wobble.

Shooting two shot groups, I'm sensitive to barrel life :roll eyes:, @ 870 yards holes were round and group size was very satisfactory. Retrieved no bullets at this distance as there was no back stop within a reasonable distance.

Next step was 1127 yards. Watching for accuracy and round bullet holes.

Wind kicked my but again as far as correcting for windage goes but group size was again very satisfactory. Groups just weren't where I thought they would be.:roll eyes:

I was shooting at a 1.5 MOA target holder, card board box, with a 6" sticky target.

Holes in the card board were again round.

Back drop was about a 20 degree up slope of about 80% moist Idaho blow sand mixed with a little sage brush residue.

I didn't expect to find any bullets as I never have before. Simply large divots.

Well, low and behold, as I looked at the first two divots, on the back divot rim I spotted a piece of brass. It was a reflection off of the base of the bullet. Ended up being the jacket without the core. Hmmmm……

Strolled back to the house, loaded two more. Compensated for the windage of the previous shots and fired too more. Guess what? As typical for me, I neglected to note the wind change. Pretty much opposite that of the previous shots. Impact was just off of the card board in the other direction. Duh!

Edges of divots were a hand width apart. Guestimated ~ 0.7 MOA with pretty much identical elevation.

A little snooping revealed another jacket about a foot and a bit right of the front of the divot. Hmmmmm again. . .

Here's what I'm thinking.

These two bullets acted very similarly to the 130 gr Sierra BTs out of my 270 Win that I shot for years. I'd get penetration almost the full length of a deer at long range with nothing but the jacket under the hide at the front of the off side hip.

Under 250 yards the 130 Sierra would ruin the front half of the deer with a broadside shoulder shot.

If this 350 SMK tipped bullet would preform similarly to the 130 at 375 AM distances I'd certainly be satisfied.

I've improved the lathe a bit for more consistent repeatability so we'll see what happens next.

Whatcha think?


Also need some advice:

Shooting non-modded SMKs Shooter inputs of 0.80 bc and 3250 MV and 2.040" line of sight over line of bore puts POI spot on out to 1200 yards.

With these bullets @ 352 grains and same velocity, POI is about 1 MOA higher @ 1127 and not quite 1 MOA higher @ 870.

To get Shooter to agree with actual I upped the velocity to 3400 FPS. These numbers are not precise but close enough for a decent "feel".

Any suggestions/help/hints/etc would be well received.

 

[Topshot]

Roy,
Thanks for the update. Interesting results that match with what I found. While my bullets were lighter, they also shot higher.
Definitely worth a try on game from these results.

 

[HarryN]

Very interesting thread, especially since I have considered doing similar things. (once I get this far)

I am not sure if you are doing this, but if you use a collet to hold your parts, this setup tends to be more accurate than holding items with the jaws.

It might seem counter intuitive, but my perception is that your biggest gain for expansion would actually be to instead bore out a hole in the base of the bullet about 50% of the diameter of the base x 50% of the bullet length. Obviously, staying clear of the edge tapered areas.

The reasoning (might be wrong) is that:
- moving the center of gravity forward will increase bullet stability (center of mass in front of center of area), so potentially improve range
- the increased velocity (from reduced mass) will improve expansion
- Slightly weakening the core will improve expansion

Of course, this is just based on what I have read and am guessing at, not on facts.