Does using jacketed bullets before monoliths affect group size?

[Jelen]

That may seem like a daft question. But I recently fired a proven Barnes TTSX load after 2 groups of B/Tip (10 shots). The barrel was scrubbed clean before I started the session. The B/Tips performed as expected. I let the barrel go cold between each group. Everything else was exactly the same. The MV of the TTSx was as expected. SD was 8 (consistent). But at 100m the group size was 2"!! Evenly spread.
This same TTSX load has been constantly sub 1.75" at 210m from a cold clean barrel. The rifle groups the B/Tips through one ragged hole at 100m from a cold clean barrel.
The only variable I can see is firing the B/Tips before the TTSX without cleaning.
Anyone got any ideas?

 

[palmer_mike]

Copper fouling from the btip?

 

[Alantoo]

Curious...it was always the early (pre TSX) Barnes which were said to deposit lots of copper, this is the other way around.

I invariably shoot a mixture of bullets when at the range, some jacketed and some monolithic and have not noticed a pattern...

What is the sample size of the groups that you are thinking of as normal?

Have you read the excellent Fuller article about the randomness of group sizes? Well worth getting you head around even if it is slightly depressing!

Small-bore Shooting - Group diagnosis - by W.H. Fuller

Historic Arms Resource Centre facility for British and Commonwealth Enfield and other Miniature calibre training and small-bore TARGET RIFLES (BSA- Birmingham Small Arms Co.), conversion units and accessories with representation of other nations' training rifles, plus Postal League competitions...

www.rifleman.org.uk

Alan

 

[Selous]

I have never seen this happen but that doesn’t mean the fouling is not causing problems. Try shooting the TTSX first next time

 

[Jelen]

Many thanks for your replies. The rifle (M12) has a barrel that is easy to clean and I have not noticed any excess copper from the TTSX. No different to the B/Tips in that respect.
When developing a load I always start the session with a clean barrel and use a chrono. I try to shoot when the weather conditions are identical, near as. Shooting from bench with bags.
This load grouped at 1.25" and 1.5" at 210m on the previous 2 sessions (not brilliant but OK). Velocity 2905 and 2925fps. SD of 7.9 and 8.
On the 3rd session I just wanted to confirm the TTSX POI at 100m, So I fired the two 4 shot B/Tip loads first at the 210m tgt. They did as expected.
The TTSX group doubled in size to 3" (just measured it) at half the range. That's the puzzle!

 

[finnbear270]

I have always been sticking to the rule clean to the Nth degree before shooting mono's after standard bullets.

More a hang over from using Original Barnes no groove bullets.

 

[njc110381]

I used to shoot two loads out of my 6.5x55, the Barnes TTSX for deer and also Hornady 95gr V-Max for foxing. I got rather frustrated with it for the same reason and ended up using SST's and V-Max in the end because I couldn't figure it out. Shots were always minute of fox/deer but the groups weren't as I'd usually expect. When I changed to SST/V-Max the problems went away.

So I've had the problem, but I'm afraid I can't offer any advice to solve it unfortunately!

 

[Steff]

There are some exceptions, but generally this is not a matter of monos or jacketed. Both the jackets and the monos basically consist of the same material, which is a copper alloy. The hardness of these alloys vary from bullet to bullet, but this applies to jacketed and monos. Consequently there may be an influence on any bullet passing through a bore subsequent to another bullet with a different alloy.

 

[Jelen]

Interesting replies. I figured there might possibly be a slight affect but not to this extent. If I'd shot the session in reverse - B/Tips at 100m then TTSX at 210m - the TTSX group would have grouped 6"!!
In fact I might just try that and bugger the expense. A box of 50 doesn't go far when developing a load!

 

[finnbear270]

Barnes actually uses pure copper in the X Bullets. Before they changed the design to include the banding on the bearing surface, they were notorious for copper fouling because of the purity of the copper. They are the only one that uses pure copper in their monolithic bullets.

Nosler and Hornady use gilding metal in their lead free bullets. Gilding metal is an alloy of copper and zinc (technically a type of brass) and is the same thing used to make bullet jackets. It is a little bit harder than pure copper but more importantly it doesn't gall like pure copper does and won't foul the bore nearly as badly. Borrowed this.

 

[Steff]

Barnes actually uses pure copper in the X Bullets. Before they changed the design to include the banding on the bearing surface, they were notorious for copper fouling because of the purity of the copper. ...

The exception I was talking about above.

 

[njc110381]

Barnes actually uses pure copper in the X Bullets. Before they changed the design to include the banding on the bearing surface, they were notorious for copper fouling because of the purity of the copper. They are the only one that uses pure copper in their monolithic bullets.

Nosler and Hornady use gilding metal in their lead free bullets. Gilding metal is an alloy of copper and zinc (technically a type of brass) and is the same thing used to make bullet jackets. It is a little bit harder than pure copper but more importantly it doesn't gall like pure copper does and won't foul the bore nearly as badly. Borrowed this.

I guess the softer pure copper aids expansion a little perhaps? Or would it be a cost thing?

 

[Steff]

I guess the softer pure copper aids expansion a little perhaps? Or would it be a cost thing?

No, has nothing to do with expansion. The X-bullets did didn't have guiding bands. So the whole of the bullet had to be compressed in order to fit through the rifling. The same happens with a jacketed bullet. It's lead core is soft enough for this.
On banded monos this compression is limited to the bands.

 

[njc110381]

No, has nothing to do with expansion. The X-bullets did didn't have guiding bands. So the whole of the bullet had to be compressed in order to fit through the rifling. The same happens with a jacketed bullet. It's lead core is soft enough for this.
On banded monos this compression is limited to the bands.

I've read that Barnes adopted the bands to reduce the fouling and give the displaced copper somewhere to go. Makes sense. I just wonder why if gilding metal is better as far as fouling is concerned, why don't Barnes use it? I assumed that a harder gilding metal would be slower to open up on impact than soft copper?

 

[Steff]

I've read that Barnes adopted the bands to reduce the fouling and give the displaced copper somewhere to go. Makes sense. I just wonder why if gilding metal is better as far as fouling is concerned, why don't Barnes use it? I assumed that a harder gilding metal would be slower to open up on impact than soft copper?

There is a learning curve to everything. Not sure, when Barnes introduced the X-bullets, but it is a while ago, even before there was any public lead free discussion going on. In the meantime they have become wiser.
I was just checking. The TSX/TTSX are indeed still made of 100% copper. I can only speculate on the reasons. The Hornady GMX is one of the hardest monos on the market and some rifles don't like it for this very reason and render poor accuracy as a result. I've heard it said that Hornady claims that out of a perfect barrel this would give the best possible accuracy and knock-down power. Maybe Barnes is simply taking the opposite approach.

 

[Alantoo]

The only variable I can see is firing the B/Tips before the TTSX without cleaning.
Anyone got any ideas?

Maybe the "problem" is developing your loads with too clean a rifle?

Pre-lockdown I was going to the range twice a month and most sessions would include 5-shot groups of my hunting TTSX (Copper) hunting round and a group of V-MAX (Gilding Metal jacket) and either S&B or HPS FMJ target rounds (Gilding Metal jacket) I also did some load development with Fox (Brass) MPG (Gilding Metal jacket) and Peregrine. So always a mix of metals in a session.

We get back around midnight so the cleaning regime has been limited to a couple of pull throughs with a dry Hoppes bore snake followed by a pull through with CLP loaded Hoppes Viper bore snake. The dry one is pulled through to remove CLP and any loosened crud at the range before the next session.

Over the year it was around 400 rounds, I chemically cleaned the barrel in the December and again 200 rounds later in June when the TTSX suddenly shot a 2.0" group...The 5-shot groups from all the bullets have averaged around 0.85" and have been occasionally down below the 0.50" and up to just over the inch.

Any change to the normal range of results and I give it a chemical clean.

Alan

 

[Alantoo]

I assumed that a harder gilding metal would be slower to open up on impact than soft copper?

It depends what state the metals are in as to whether they are harder or softer...the yield point of copper and brass overlap depending on whether they are work hardened or annealed...so an annealed brass can be softer than a work hardened copper...