Dasher Posted March 14, 2015 Report Share Posted March 14, 2015 Please be gentle with me as I'm new to the 17hmr. I have a 17hmr CZ452, 20" barrel with a synthetic stock, now having never owned a synthetic stock before I was surprised at how much the fore end flexes and thus touches the barrel. Having shot it of a bipod the POI is 2" high @ 100yrds, is this amount usual. Most of the time it is shot of a bean bag or rested across the pickup's passenger seat's back rest when the seat is tipped forward (hopefully that makes sense), the gun is sighted in from a bean bag @ 100yrds. How hold sensitive do other people find this round or is it the case that the bullet has cleared the barrel before any recoil can affect the barrel position? Regards Dasher Quote Link to comment Share on other sites More sharing options...
turbo33 Posted March 14, 2015 Report Share Posted March 14, 2015 I have the same rifle Dasher, but with the 16" barrel. I expect you will have loads of replies about the barrel touching the forend being the cause etc. Personally, I have found the HMR a bit of a weird calibre. The first one I had was all over the place. This one is much more accurate. However, I can be consistent sub 1 moa all day long at 100 yards with the same rifle in .22, with the HMR, not so. I have no idea why? Off a bag, off a bipod...makes no difference. In theory, it would seem your barrel may be getting a lift upwards from the weight of it on the forend/bipod, and certainly this could be true. However, the silhouette is such a light rifle. I just can't see there being that degree of flex in the barrel. Maybe its harmonics? Your question as to the hold sensitivity is a very reasonable one and unfortunately, I seem to have similar experiences on occasions, so feel your frustration. I'm sure there will be lots of theories to follow. Out of curiosity, if you do a run on the bipod, what are the groups like in comparison to off the bag? I do think rifles behave very differently depending on how they are supported, ie on a bag or bipod. Even air rifles to a degree. Quote Link to comment Share on other sites More sharing options...
casts_by_fly Posted March 14, 2015 Report Share Posted March 14, 2015 It is the forend flex, not the cartridge that is the issue. I could move poi by 4" on my last synthetic whether i pressed forward or relaxed back on the stock. Either stiffen the stock or find a consistent position that works for you. Rick Quote Link to comment Share on other sites More sharing options...
Old farrier Posted March 14, 2015 Report Share Posted March 14, 2015 Hi dasher Very good advice given by experienced people above You may find either shoot and zero from the bipod Or Shoot and zero from the bag Is best You will proberably find the rest point on bag or seat back is 2 or 3 inches back from bipod point this may cause the flex altering your point of impact Hope this helps All the best Of Ps what ammo ? Heavy or standard barrel ? May help others to help you Quote Link to comment Share on other sites More sharing options...
Dasher Posted March 15, 2015 Author Report Share Posted March 15, 2015 Hi all, thanks for the replys. The action/barrel is a nickeled "American", guess it is what was sold as a "Style". The barrel having not seen anything else in the 452 range looks like a standard barrel. The only ammo used is 17gn Hornady, but from what I under stand all the 17gn HMR ammo is made in the same factory and just rebadged for each company. As I said this caliber is still new to me and so far I have only put about 50 rounds through it. I was quite surprised at the amount of muzzle flip I can feel on firing, I have a Wildcat Reflexed moderator on it which I thought may help counteract the flip. Shot groups are better off the bag than the bipod, but that could just be my poor shooting. I think you may have a point Old Farrier about the position of rest which would be stiffer of the bag than the forward point on the bipod. How do people stiffen stocks - sounds expensive. Thanks Dasher Quote Link to comment Share on other sites More sharing options...
wymberley Posted March 15, 2015 Report Share Posted March 15, 2015 . How do people stiffen stocks - sounds expensive. Thanks Dasher Buy wooden ones. Not being facetious as they can have problems should they warp and touch the barrel but this is easily fixed if/when it becomes necessary. I zero three different calibres on a bipod and shoot Bren Gun style and when using a bag from the truck window shoot in the same fashion simply resting the stock on the bag as it stands on the bipod with no change in zero. Quote Link to comment Share on other sites More sharing options...
turbo33 Posted March 15, 2015 Report Share Posted March 15, 2015 I'm still not convinced of this floating barrel theory on the HMR. CZ aren't inexperienced, and the Silhouette/style is manufactured with no barrel clearance. I still think its possibly the way the rifle reacts differently on a bipod to a bag, observed in part by Old Farriers comments. If you want to try a little experiment you could do this. The action is held onto the stock with 2 screws. Remove the action and make a couple of shims up, thin plastic, (Milk bottle?)pop a hole through and bolt the action back into the rifle using the shims to just lift the action a bit. Depending on how thick the plastic is, you are looking to get a bank note to slide between the barrel and the forend indicating clearance. Re test as before. Zero on your bag, then pop the bipod on. Check you have clearance when its full weight is on the bipod. Do some groups and see what you have. If the POI is the same as with the bag, then clearly it is a clearance issue. You can remedy this with a drum sander to remove a nats of material from the barrel channel to produce enough clearance for the barrel not to touch the forend. If however, your results are the same as before, you will know its the different behaviour between a bag rest and a bipod. Hope this helps. Quote Link to comment Share on other sites More sharing options...
matone Posted March 15, 2015 Report Share Posted March 15, 2015 I have a wood stocked American .17 hmr and it shoots exactly the same off a bipod as it does without it. Quote Link to comment Share on other sites More sharing options...
Velocette Posted March 15, 2015 Report Share Posted March 15, 2015 I had a similar problem with my .22 Silhouette. I opened the barrel channel to give 0.50mm clearance all the way along it and moved the bi-pod stud about 2" back towards the action where the plastic stock was a bit thicker. I shot it "Bren Gun " style at 100yds at Bisley and it was spot on. Quote Link to comment Share on other sites More sharing options...
Dasher Posted March 16, 2015 Author Report Share Posted March 16, 2015 Thanks for all the info, just need to wait for some dry calm weather to have a bit more of a play before I post my findings back. Dasher Quote Link to comment Share on other sites More sharing options...
walt1980 Posted March 16, 2015 Report Share Posted March 16, 2015 I've got an Anschutz hmr and when it was new it was all over the place, after about 50 or so shots it settled in. It's great now, pretty flat out to 120 yds. As far as I understand it CZs with synthetic stocks flex a bit, personally I use wooden stock and make sure the barrel has clearance, not a fan of the synthetic ones for this reason. Having said that I'm sure plenty of people love theirs and don't have a problem!!! Quote Link to comment Share on other sites More sharing options...
drut Posted March 16, 2015 Report Share Posted March 16, 2015 I had a similar problem with my .22 Silhouette. I opened the barrel channel to give 0.50mm clearance all the way along it and moved the bi-pod stud about 2" back towards the action where the plastic stock was a bit thicker. I shot it "Bren Gun " style at 100yds at Bisley and it was spot on. As above:plastic sands out easily to allow large gap & if you lean heavily on bipod you can put extra stud for mounting bipod halfway been magazine & existing stud or a thin washer under front mounting may be enough. Quote Link to comment Share on other sites More sharing options...
peek-at Posted March 18, 2015 Report Share Posted March 18, 2015 (edited) I've got an Anschutz hmr and when it was new it was all over the place, after about 50 or so shots it settled in. It's great now, pretty flat out to 120 yds. As far as I understand it CZs with synthetic stocks flex a bit, personally I use wooden stock and make sure the barrel has clearance, not a fan of the synthetic ones for this reason. Having said that I'm sure plenty of people love theirs and don't have a problem!!! I have the CZ 452 style (synthetic stocks) in .22 & .17hmr Both are zeroed on the bipod and stay spot on when resting on a gate post or similar..... Is your eye position consistant when prone on the bipod compared to the bag? just wondering if a slightly different body/eye position might be causing you to aim a little high.... Just had a look at my hmr...... sitting on the bipod you can see a slight flex in the stock when you take the rifles weight half way down the stock.....Possibly this is causing your problem if you dont have sufficient clearance and it touches the barrel. If you usually shoot off a bipod make sure you re-zero it on the bipod, or as previously said you may need to widen the barrel channel in the stock. Edited March 18, 2015 by peek-at Quote Link to comment Share on other sites More sharing options...
hyflier Posted March 18, 2015 Report Share Posted March 18, 2015 I have the CZ 452 American wooden stock, it is a "tack driver" superbly accurate off a bipod or beanbag, firing "laser guided bunny seeking missiles"............. unless I clean it too thoroughly! A few clean dry patches have always proved best and it holds zero nicely. Scrub the bore with a phosphor bronze brush and the zero is all over the place for at least half a dozen rounds. I like the Hornady rounds particularly, I tried some Remington and couldn't group these at all; strange really as I understand they are all loaded by CCI. Quote Link to comment Share on other sites More sharing options...
2sledge Posted March 26, 2015 Report Share Posted March 26, 2015 i have the cz American .17 hmr 18 inch barrel wooden stock was all the place when i bought it free floated the barrel as it was touching on the forend now 3/4 inch at 120 yds on a good day i would say make sure the barrel is free when you have the weight on the forend Quote Link to comment Share on other sites More sharing options...
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