Ammo Modification Experiment

[matshock]

I know this has been tried before- but I've never seen it photo-documented. (NOW EDITED FOR BETTER IMAGE/ ADDED HORNADY .308)
http://www.gunsnet.net/photopost/data/500/medium/HP_comparison_ver_2.JPG

Left: out-of the box Privi Partisan .308 168 gr match

Left Center: modified "

Right Center: Hornady .308 168 gr match

Right: Black Hills .223 68 gr match- new brass


The stock Privi shoots about 2 MOA for me @ 200 yards.

I modified 10 rounds with a little drill bit and a hand file to open up the tip a bit.

The Black Hills is insanely accurate- I've shot cloverleaf groups with it @ 200 yards. I also have some Hornady .308 168 grain match- it's about 1 MOA ammo at 200 yards. They both seem to have larger, cleaner open tips than the stock Privi. The may also be loaded more consistently.

So, hopefully tomorrow I'm shooting 10 rounds of each for comparison and will post the results. If I shave .5 MOA off of the Privi with this mod I'd consider it a worthwhile activity.

[Schuetzenman]

No I don't think this has been tried before. Certainly I do not recall seeing it, nor have I done such myself.

IMO it won't accomplish anything notable. The reason the .223 Black Hills match is so good is the Sierra Match King bullet in it. The MK is held to +/- .1 grain tolerances and it's nice and round. Privi bullets will not be nearly as close in weight compliance and possibly not really perfectly round or .308 in diameter. Lastly as you touched on, powder charge consistency. The privi is probably not as uniform in charge. Lastly, case volume is probably not as good, consistent as a US made case. Variation in case volume will change the pressures and resulting speeds of the bullets. Match shooters will often fill cases with water and weigh them to identify and group cases by volume / weight. Oh, one other thing, uniformity of neck thickness can also impact accuracy. Benchrest shooters will neck turn thier cases inside and out to create the same "pull" or friction on each round. This is also to create as uniform as possible pressure and break away force on each projectile.

This is how these guys can shoot 5 shots inside of what looks like one ovaled bullet hole at 100 yards.

[matshock]

I saw some posts on Sniper's Hide where some guys tried this with Privi- they were testing for terminal expansion though, not accuracy and they didn't document the results very well.

It sounds like it might even make them less accurate as I doubt my method removes the same amount of material each time so the bullet weights will be even more varied.

One question though- why does a hollow tip matter at all then? Why aren't "match" bullets just tightly variance controlled FMJs or ballistic tips?

[matshock]

OK- I did shoot today but there was a 12-18 MPH S-SW wind with rounds fired heading north. From the 200 yard line with a bipod.

Black Hills .223 68 gr match:
http://www.gunsnet.net/photopost/data/500/medium/BH_223_group.JPG

3.5" was the largest spread or 1.75 MOA- if I kick out that round on the orange vertical bar the next spread would be 3.00" or 1.5 MOA. This is consistently accurate ammo for sort of a baseline. I fired this group in-between the .308 groups to let the .308 rifle cool off.



Privi .308 168 gr match stock-out-of-the-box:
http://www.gunsnet.net/photopost/data/500/medium/Privi_308_stock.JPG

I had two called fliers (me, not the ammo) and was re-using this target after a short warm-up string. 4.75" or 2.375 MOA- the group looks a little uneven I admit- it was the last string I fired.



Privi .308 168 gr match mod:
http://www.gunsnet.net/photopost/data/500/medium/Privi_308_MOD.JPG
Again 2 called flyers (my fault) and then a hair less than 4.25" or 2.125 MOA This was the first string I fired after a quick warm-up

All-in-all: I'd say inconclusive or that Schuetz is right and the mod won't really matter. I do want one more go at it- next time I will do the stock ammo string first and then the mod string. I'd also like to do it in less wind and take a full rest period of no shooting in-between strings.

At least I had some fun!

[matshock]

I had one more go today- results were about the same, no real difference. I opened up a few more rounds more aggressively and it had a small, negative impact.

After doing some more reading it appears the only purposes of a hollow point in a rifle bullet are to shift the center of gravity to the rear for various reasons and in some cases, expansion. The cosmetic appearance of the point itself has little bearing on accuracy.

[Moebrown20]

The cosmetic appearance of the point itself has little bearing on accuracy.

So what if you drilled a hole and removed about 20 grains or so and filled the tip with glue?

[deth502]

i always thought a big part of the hp on match bullets was that the hole in the leading edge created a small vortex at teh front of the bullet which, by nature, will always be centered on the mass of the projectile, negating any off-centered-ed-ness that you might get with a fmj point. even though, as it has been proven, a deformed tip will do very little to effect accuracy.

that and the shifting of the balance point of the bullet.

[matshock]

i always thought a big part of the hp on match bullets was that the hole in the leading edge created a small vortex at teh front of the bullet which, by nature, will always be centered on the mass of the projectile, negating any off-centered-ed-ness that you might get with a fmj point. even though, as it has been proven, a deformed tip will do very little to effect accuracy.

that and the shifting of the balance point of the bullet.

That's what I was thinking- but apparently not.

[az_paul]

Very interesting thread!! Thanks for sharing with us.

[l921428x]

So what if you drilled a hole and removed about 20 grains or so and filled the tip with glue?

Would it just tumble, because of the inbalance?

[romak10/63UF]

I use the same idea more simple on 22lr hollow points I normally use CCI hollow points i sit the bullet up then i use a normal ball point pen to open the hollow point up. It opens up nice an deep. I like to shoot parie dogs with a ruger 10/22 .