SmallCaliberCentral

Hi

Anyone know what sort of muzzle velocity I can expect to get with .204 20” barrel, IMR 4895 and 39g.SBK. Had pretty much the same size groups with 27.4, 27.6, 27.8 and 28g. With 27.6 was slightly the best group. Can’t imagine there is much MV difference with 0.6g of variation. Want to get the load shooting as flat as possible. Pressure signs all good, scope for higher load but maxed out on case volume pretty much.

I wrote the above yesterday but didn’t post it. So today I loaded up 50 rounds at 27.6g of IMR 4895. With the following results each a three round group with one factory round too with a clean rifle.

200y 55mm 2” low
250y 140mm 5.5” Low
300y 220mm 8.5” Low
350y 380mm 15” low.

All grouped well and at each distance I tried a factory Hornady 40g which dropped lower than my new load. Feeling disappointed with the performance. Had hoped they would be flatter. Once finished I put my pulsar n355 back on. Zeroed it at 100y and then things got weird. Went back to 250y and hit bang on, hardly no drop. (red 4” circle on Hardox plate). Should of been about 5.5”. Then went a little further back to 270y and still bang on pretty much. (Hard to get a consistent poi with pulsar but best I could) No idea what has happened there. Pictute shows the 270y shots with pulsar. If anyone knows how to work out my MV I’d be grateful.

Cheers.

I don't do guessing in regard to muzzle velocity, never have. Why not invest a paltry $125 and buy yourself a Shooting Chrony? Done, no guessing any more. Cheap, will last for years and you'll be able to make drop charts based on YOUR load in YOUR rifle. One of the best investments I've made.

Done it myself, very glad I did.

What Rick said. One can take two different rifles manufactured side-by-side and the odds of them shooting the same are subjective at best because there is just too many variables.

The other thing with load data from a book and reality is the atmosphere conditions and elevation.

HTH,

Thanks for the replies. I don’t do guessing either, was hoping someone new of some software. I usually physically measure the drop of my loads, not often concerned with MV as long as the bullet is permforming as expectet. Hard to measure with a NV on for bullet drop, no accurate poi. Chronys are quite expensive in the UK, more like $250 for a basic one.

The difference in bullet drop from day sight to night vision may in part be due to scope hight differences, NV mounted an inch higher.

Cheers.

So today I finally had time to try out some 10x. Started off Loading up 5 lots of four rounds seated at 2.260 with the following loads and groups:-
24.5g .507
24.7g .643
24.9g .752
25.1g. .744 with pulled shot/ without . 317
25.3g .745
I was pleased with the groups. A few hole in holes.

I then picked the best groups not just on group tightness but there group pattern and loaded another batch of the two best loads both with different seating depths with the following groups:-

4 rounds at 24.5g seated at 2.260 .646
4 rounds at 24.5g seated at 2.280 .420
4 rounds at 25.1g seated at 2.260 .731
4 rounds at 25.1g seated at 2.280 .584

Interestingly the slightly longer seated bullets both gave a tighter group. All four groups I think if I could of steadied the rifle better would of all gone through the same hole. Not the best weather, a lot of mirage after lunch. But I settled on 25.1g at 2.280.

Next was the long range drop measurements. I did three shots and took the average drop. At 250y got a hole in hole! All groups were 1 MOA or just under.
200y drop 1”
250y drop 4.5 in
300y drop 7.5 in

Put this data into my ballistic AE app and by trueing the MV it gave me a MV of 3762. I don’t expect that’s what it actually is. Probably slightly less. So a busy day but very happy with the out come. Last job was to put the NV back on rifle and zero. Zeroed 3/4 high, mainly because it’s hard to zero and that was near enough. The NV hight is 2.5” from centre of the chamber to centre of the NV body. With that data inputted into my app it give me a drop of only 2.69” out to 300y. That is very pleasing to me! Job done.

I didn't see whether this rifle has a custom or factory chamber or if it's a repeater or single shot. If it's a single shot then the OAL won't matter but if it's a repeater it could very well.

Using your data, I would test at 24.4 & 24.6 grains to see how they group. The reason for this is to allow for deviations with scales, powder throws, dispensers and so on. Furthermore, a .1 to .2 grains can make a difference in small cases. Anyway, If all three are good then I will make 3-4 groups of 5-shots each and test for repeatability. Now remember, don't shoot them all back to back. Ideally, you would test the group in the same environment as if you were using it in the field.

Hope this helps