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> Vertical/horizontal group spread
Vertical/horizontal group spread
@ 04:26 am (GMT) |
Alvaro PiquerasHello!!Im an avid reader of Nathan´s knowledge base and i have join today to post a question. First of all, thank you very much for yuor really good input!! One of the best sites on the net! I´m from Spain, so hope you will forgive my english! ;) I´m working up a load for a 222rem bolt rifle. It´s a CZ 527, with a 24 inch sporter barrel. I´m loading 50 grains VMAX, using vectan SP7 powder. This is a double base spherical powder, with a burn rate probably similar to IMR4320, norma 140 or HODGON Varget (i´m not sure of this, there are lot of differences in the burning rates comparison tables) Till today, i have get a max speed of 3286fps, with no over-pressure signs. Speed was get with a RCBS ammomaster chrono. The load was 24,8 grains The fact was that i get a load wich spread "looks like" vertical (0,42MOA, three shot group at 100 meters, 3272fps average, 25 fps max. difference). With 0.2 grains less, the group was 0,49MOA (3203fps average, 34fps max difference) but the spread was horizontal. Of course, it could be just caused by me. I´m shooting with a turret and a sand bag. But, maybe it could be caused by the rifle or the load. Maybe the armonics or another thing. I will reload more ammo and will try to see what happens. But, in case it was caused by the rifle/load... what will be better? The vertical spread or the horizontal (maybe no one, and it´s better to try a "triangle" shape...) Junst cutious on that! Hope someone could help! Now, i willl try to post images of the groups... Thanks al in advance! Regards! (I have problems with my photobucket account... Nathan i willl try to email you the photos. Maybe you are able to post it) |
Replies
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@ 04:32 am (GMT) |
Alvaro PiquerasRe: Vertical/horizontal group spreadNathan;I have mailed you the photos. Hope can help this weeckend to the "wound database" with a good roe deer!! |
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@ 07:57 am (GMT) |
Nathan FosterRe: Vertical/horizontal group spread
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@ 08:31 am (GMT) |
Nathan FosterRe: Vertical/horizontal group spreadHi Alvaro, first, thanks for your kind comments, I am glad you are enjoying the site. Your English is quite clear, easy to read.With the CZ, although the stock fit is usually quite good, it does pay to bed these rifles. Your groups are already very small, under a half inch / 12mm at 100 meters so hopefully taking care of such variables will help fine tune the rifle. In list form: Bedding, epoxy resin. Study bore- study how it is fouling at the muzzle, any rough lands that need lapping. Bolt locking lugs, apply vivid marker pen to the rear of the lugs, work the the action, then remove the bolt and study lug contact. If only one lug is touching, lugs will need lapping. Bullet jump experimentation with hand loads. Once you have done as much as you can with incremental (.2 grain) powder charges, work on seating depths. Try .2mm bullet jump, then try .5mm bullet jump, then try 1mm bullet jump. Sometimes you will find that after doing bullet jump experiments, a little bit more experimentation will be required with the powder charges to settle extreme velocity spreads. It can be frustrating to work through all of this but usually it all finally comes together within a half grain either side of the initial sweet spot. Also, by this stage,you will find that you now know the rifle inside and out, you can see trends, see the difference between fluke groups and consistent results. Neck tension of hand loads. Sometimes, all it takes to get the loads (and ES) down that last little bit is increased neck tension. But the trouble is, if the necks are very tight, there is a risk that copper will be shaved off the projectile during seating operations which is why expander buttons tend to be on the large side. If sanding/polishing an expander button down to increase neck tension, it is important to understand that after case trimming operations and following chamfering, the case mouths need to be polished smooth in order to stop copper shaving. Shooting technique- sand bags both at the front and the rear. Make the rear sand bag work for you, make sure the bags are aligning the rifle to help remove human errors. Tight fore hand, loose rear hand, firm sling tension. Trigger set to 1.5lb if possible. I don't like set triggers for target work as they tend to be too light and release before there is even a measure of feel on the trigger; the shooter cannot rest the finger on the trigger and instead has to keep the finger off the trigger and then 'touch' the trigger which requires too much movement in the 'touch'. In cold weather where finger sensitivity is low, trigger control with set triggers can be very poor. That should give you plenty to work on for now! Hope it helps. |
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@ 06:29 am (GMT) |
Alvaro PiquerasRe: Vertical/horizontal group spreadHello Nathan;Thank you very much for the input! Yes, that´s right, i have plenty of work! I have no luck with roe deers. Just see a red fox very early, and we decided not to shoot, because we don´t want to make noise. We where all morning trying to locate deers but there was no chance! When we´re walking back to the car, found a group of magpies. I decided to try the load and i get one at 128 meters, so the rifle Work, at least, when i do my part! ;) Hope I can help to the wounding data base soon! Talking about you “work list”, I can make this comments… I will bed the rifle. I like to bed and free float my rifles. In fact, I am thinking in open a new thread, to get your opinión when bedding a Wood stock with crossbolt (as some mausers 98). The CZ stock fit is good, and the stress caused by the small 222rem. is small, but i hope this will improve accuracy. Of course, it will give more consistency when the weather changes (humidity, rain, etc) I will try to analyze bore, muzzle rifling etc… but i´m not sure i will be capable to see if it´s OK or not. There must be a big problem or i will not see nothing. I will check the locking lugs… Will lap its if just one contacts, or if there are few contacta rea (even if both contact). I think that lapping the bolt face will be another good idea, even if i will try different seating depths later, so i will find the “new” sweet depth. That´s all abput the rifle. With the handloads, i will try different seating depths, refine poder loads and will get a few more neck tension. I was surprised when you tell that, because when i do this loads i thinkk myself that the bullets get too easy in the brass. I allways take much care with case mouth preparation. I chambfer and deburr, first clockwise (cutting) and thes counter-clockwise (this action “seats” Sharp edges). After this, I poolish de mouth with a Lee case turning and steelwool. I think this will be enough to prevent Cooper shaving. The trigger is more or less as you described, and I will try to do my best at the range! Thank you very much, I will keep posted my results, so maybe someone will find it useful. |
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